tag:theconversation.com,2011:/us/topics/invasive-plants-39605/articlesInvasive plants – The Conversation2024-01-25T20:46:32Ztag:theconversation.com,2011:article/2206532024-01-25T20:46:32Z2024-01-25T20:46:32ZThe botanical imperialism of weeds and crops: how alien plant species on the First Fleet changed Australia<figure><img src="https://images.theconversation.com/files/570269/original/file-20240119-22-lcj7rr.jpg?ixlib=rb-1.1.0&rect=34%2C22%2C7618%2C3774&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://collection.sl.nsw.gov.au/record/Ydma46R9/8pg0LrwplLmxJ">Dixson Library, State Library of New South Wales</a></span></figcaption></figure><p>Locally grown produce fills Australian shops, but almost all of these species were imported, as native as cane toads. Icons of Australian agriculture, like the Big Banana and Big Pineapple, proudly display the regions’ crops, but these are newcomers to the continent.</p>
<p>British ships carrying plants and seeds from around the world arrived in Botany Bay on <a href="https://firstfleetfellowship.org.au/ships/the-voyage/">January 20 1788</a>. This story is overshadowed by convict ships and Royal Navy vessels, but the cargo on board also had a lasting impact. Colonists, convicts and Indigenous Australians were all affected when new species transformed the landscape.</p>
<p>British colonists introduced plants as foreign as the people who carried them. Some of these plants, ranging from <a href="https://firstfleetfellowship.org.au/wp-content/uploads/2013/11/PLANTS-AND-SEEDS-FROM-RIO-DE-JANEIRO-pdf.pdf">bananas to wheat</a>, were food sources, promoting self-sufficiency. Others were attempts to expand the British Empire. Could the new territory be exploited as a tropical plantation? </p>
<h2>Botanical imperialism</h2>
<p>In the parliamentary debate over destinations for convict transportation, Sir Joseph Banks and James Matra, both members of James Cook’s 1770 expedition, spruiked the potential of the new colony as an extension of the empire. </p>
<p><a href="https://www.google.com.au/books/edition/Historical_Records_of_New_South_Wales_pa/ML4NAAAAYAAJ?hl=en&gbpv=1">Matra claimed</a> the colony was “fitted for production” of “sugar-cane, tea, coffee, silk, cotton, indigo and tobacco”. </p>
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<a href="https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=898&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=898&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=898&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1129&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1129&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570273/original/file-20240119-27-gv172q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1129&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Sir Joseph Banks.</span>
<span class="attribution"><a class="source" href="https://victoriancollections.net.au/items/64a215525a416af5117dd67e">Victorian Collections</a></span>
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<p><a href="https://australian.museum/learn/first-nations/unsettled/recognising-invasions/plans-for-a-colony/">Banks claimed</a> Botany Bay was an “advantageous” site, with fertile soil – and virtually no inhabitants. </p>
<p>Two plants carried by the First Fleet stand out as examples of botanical imperialism: prickly pear cactus (Opuntia) and sugarcane. Banks, as head of the Royal Society of London, selected these species as experiments to compete with European trade rivals. </p>
<p>His goal was to break a Spanish monopoly in producing fabric dye and to expand British cultivation of sugar outside the West Indies.</p>
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Read more:
<a href="https://theconversation.com/from-captain-cook-to-the-first-fleet-how-botany-bay-was-chosen-over-africa-as-a-new-british-penal-colony-128002">From Captain Cook to the First Fleet: how Botany Bay was chosen over Africa as a new British penal colony</a>
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<h2>The secret of the colour scarlet</h2>
<p>Prickly pear cactus was imported because it is the preferred food of the cochineal insect. Dried <a href="https://www.webexhibits.org/causesofcolor/7.html#google_vignette">cochineal</a> were crushed to make a vibrant, colourfast scarlet dye for textiles. Discovered in the New World by Spanish colonists, cochineal replaced kermes, another insect that had provided red dye since antiquity. </p>
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<a href="https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Black and White Photo" src="https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=805&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=805&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=805&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1012&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1012&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570260/original/file-20240118-19-o7bfu4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1012&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Man standing in an invasive prickly pear forest in Queensland, 1935.</span>
<span class="attribution"><a class="source" href="https://www.archivessearch.qld.gov.au/items/ITM1143347">Queensland State Archives</a></span>
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<p>Cochineal dye was ten times stronger than kermes or vegetable dyes. From cardinals’ capes to British officers’ red coats, cochineal was a product for elite consumers signifying power, wealth and prestige.</p>
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<a href="https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Black and white photo, looks like a haystack" src="https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=945&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=945&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=945&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1187&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1187&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570265/original/file-20240118-21-557i3j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1187&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">2,200,000 eggs of cactus moth, collected to combat the invasive prickly pear in 1928.</span>
<span class="attribution"><a class="source" href="https://onesearch.slq.qld.gov.au/permalink/61SLQ_INST/1dejkfd/alma99183712416402061">State Library of Queensland</a></span>
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<p>New Spain, based in Mexico, had a monopoly on cochineal. Banks wanted to break the stranglehold on the scarlet dye by establishing production in New South Wales. Plants infested with the precious insects were imported from Brazil in 1788. </p>
<p>The project soon failed when the cochineal died, but the cacti survived. Colonists used cacti as natural fences and drought-resistant animal fodder. Without insects to feed on them the plants spread, uncontrolled, to cover more than <a href="https://www.nma.gov.au/defining-moments/resources/prickly-pear-eradication">60 million acres</a> of eastern Australia by the 1920s. Poison, crushing and fire failed to stop the cactus.</p>
<p>In 1926, a moth species from Argentina was introduced to eradicate the plants, but Opuntia cacti remain an environmental hazard. Trade in the plants, classified as <a href="https://weeds.dpi.nsw.gov.au/WeedListPublics/CategoryResults?showImages=True&categoryId=1&pageTitle=Weeds%20of%20National%20Significance">weeds of national significance</a>, is banned in most states.</p>
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Read more:
<a href="https://theconversation.com/exposing-australias-online-trade-in-pest-plants-weve-found-thousands-of-illegal-advertisements-212647">Exposing Australia's online trade in pest plants – we've found thousands of illegal advertisements</a>
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<h2>The first sugar grown in Australia</h2>
<p>Sugarcane was imported from the Cape Colony, now South Africa. Before sugar was planted in Queensland, or even Port Macquarie, in the 19th century, sugar was grown in a small garden plot in Sydney and as an experimental crop on Norfolk Island in 1788.</p>
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<a href="https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration of a house on Sydney Harbour" src="https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=501&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=501&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=501&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=630&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=630&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570266/original/file-20240118-15-dz0fjv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=630&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Sugarcane was first grown in garden plots in Sydney.</span>
<span class="attribution"><a class="source" href="https://archival.sl.nsw.gov.au/Details/archive/110316551">Mitchell Library, State Library of New South Wales</a></span>
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<p>The Royal Navy targeted Norfolk Island as a source of flax and timber, but it also served as an agricultural laboratory, testing tropical crops like sugar and coffee for Banks.</p>
<p>Philip Gidley King, lieutenant-governor of Norfolk Island, reported in his correspondence with Banks in 1790 that his four canes had multiplied into more than 100 plants. Within a few years he sent <a href="https://transcripts.sl.nsw.gov.au/page/letter-received-banks-philip-gidley-king-8-may-1792-series-39004-no-0004">samples</a> of sugar, rum and molasses to Sydney. By 1798, the cane was declared “prolific” and Norfolk Island was in “a state of cultivation equal to the West Indies”.</p>
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<a href="https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Black and white photo" src="https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570262/original/file-20240118-17-iojl9b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">South Sea Islander workers standing in a sugarcane field in Queensland.</span>
<span class="attribution"><a class="source" href="https://onesearch.slq.qld.gov.au/permalink/61SLQ_INST/tqqf2h/alma99183799211402061">State Library of Queensland</a></span>
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<p>This favourable comparison with the West Indies ignores the use of convict labour in producing sugar, and foreshadows the advent of “<a href="https://theconversation.com/from-the-caribbean-to-queensland-re-examining-australias-blackbirding-past-and-its-roots-in-the-global-slave-trade-158530">blackbirding</a>”, a euphemism for the abduction or coercion of Melanesian workers. Blackbirding was introduced in Queensland canefields in <a href="https://www.nma.gov.au/defining-moments/resources/islander-labourers">1863</a> as penal transportation ended and cheap convict labour became unavailable. </p>
<p>Once essential to the sugar industry, in 1901 Pacific Islanders in Australia were deemed undesirable, competing unfairly with white workers. As part of the White Australia Policy, many were deported under the <a href="https://humanrights.gov.au/our-work/race-discrimination/publications/australian-south-sea-islanders-century-race">Pacific Island Labourers Act 1901</a>.</p>
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Read more:
<a href="https://theconversation.com/from-the-caribbean-to-queensland-re-examining-australias-blackbirding-past-and-its-roots-in-the-global-slave-trade-158530">From the Caribbean to Queensland: re-examining Australia's 'blackbirding' past and its roots in the global slave trade</a>
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<h2>The fruits of empire</h2>
<p>Reconsidering the impact of alien plant species on Australia gives us additional insight into the process of colonisation. </p>
<p>Transplanting species from around the world to create a new environment was a major endeavour in the 18th century, and a manifestation of imperial power and control. </p>
<p>Indigenous connections with Country were disrupted when foreign botanical landscapes displaced native species. The roots of these early imperial projects are deeply embedded in Australian culture and history, with an enduring legacy.</p><img src="https://counter.theconversation.com/content/220653/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Garritt C. Van Dyk does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It wasn’t just colonists and convicts who invaded Australia in 1788 – invasive plant species arrived too.Garritt C. Van Dyk, Lecturer in History, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2171312023-11-07T16:51:30Z2023-11-07T16:51:30ZExtreme weather may help invasive species outcompete native animals – new study<figure><img src="https://images.theconversation.com/files/558037/original/file-20231107-22-7023v6.jpg?ixlib=rb-1.1.0&rect=4%2C0%2C2998%2C1994&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Invasive species can capitalise on disturbances like this. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/forest-fire-pinus-pinaster-guadalajara-spain-1065315416">FJAH / shutterstock</a></span></figcaption></figure><p>Non-native species appear to be better able to resist extreme weather, threatening native plants and animals and potentially creating more favourable conditions for invasive species under climate change. That’s the conclusion of a new study in the scientific journal <a href="https://www.nature.com/articles/s41559-023-02235-1">Nature Ecology and Evolution</a>.</p>
<p>Wildfires, droughts, heavy rainfall and storms are all <a href="https://www.nature.com/articles/nclimate1452">increasing</a>, and predicted to become more frequent throughout the <a href="https://www.nature.com/articles/s43247-023-00826-1">next century</a> due to human-driven climate change. </p>
<p>At the same time, humans are transporting <a href="https://www.nature.com/articles/ncomms14435/">more species</a> into new areas, despite concerted global efforts to increase <a href="https://www.sciencedirect.com/science/article/pii/S1462901119311669">biosecurity across borders</a> and to target the <a href="https://www.nature.com/articles/s41598-022-14982-5">eradication of specific species</a>. Some of these non-native species can go on to become invasive, damaging native <a href="https://zenodo.org/records/10004329">ecosystems</a>. </p>
<h2>Capitalising on opportunities</h2>
<p>Invasive species introduced by humans often possess traits that help them survive or even thrive when ecosystems are disturbed (perhaps by wildfire, a storm or human buildings). </p>
<p>Invasive plants are <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1461-0248.2009.01418.x">generally fast-growing</a>, for instance, allowing them to quickly fill gaps before native species can recover from disturbances. They are also often very good at dispersing their seeds, allowing them to quickly colonise disturbed areas.</p>
<p>This is why scientists have long suspected that extreme weather and the success of non-native species could be <a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/110137?casa_token=4_TVjhddeUAAAAAA%3AIAHZQqTWf7Q3F1-LY6-R2HiVHW5qwsdtkW1aumwAXtc3aYDdGJf9wuhkTzmH1TlP6xxqnuBdqtCWMoud">linked</a>. </p>
<p>If extreme weather removes native plants and animals, that increases the availability of resources such as water and space. Non-native species can then capitalise on these new resources to establish themselves.</p>
<p>Even more concerning is the potential for extreme weather and non-native species to interact, exacerbating their effect on native biodiversity. For instance, in a recent <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/ele.13974">field experiment in the US</a>, scientists deliberately started a fire which killed about 10% of the longleaf pine trees in the area studied. </p>
<p>But in areas where an invasive grass – <a href="https://theconversation.com/invasive-grasses-are-fueling-wildfires-across-the-us-126574">cogongrass, an Asian native</a> – was allowed to establish itself alongside the pines, the fires had more fuel and were larger, hotter and burned for longer. </p>
<p>Where the scientists had added rain shelters to simulate drought conditions, the grass dried out further and the fires became much more lethal. A combination of drought and the invasive species meant longleaf pine mortality soared to 44%.</p>
<p>Similarly, on the small Macquarie Island in the south west Pacific, a combination of extreme rainfall and the presence of invasive European rabbits reduced the breeding success of nesting <a href="https://www.nature.com/articles/s41598-020-64662-5">black-browed albatrosses</a>. Heavy grazing by the invasive rabbits reduced plant cover, exposing the albatross chicks to the harsh weather conditions. </p>
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<a href="https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Penguins on grassy surface, sea in background" src="https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558038/original/file-20231107-17-yrnh31.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Macquarie’s grass makes excellent bird nests – and rabbit food.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/gentoo-penguins-macquarie-islands-australia-111279710">BMJ / shutterstock</a></span>
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</figure>
<p>This relationship between extreme weather and invasive species – two human-driven drivers of global change – threatens native plants and animals and could cost countries <a href="https://enveurope.springeropen.com/articles/10.1186/s12302-023-00750-3">billions of dollars</a> in coming decades. Ecologists must identify priority areas and species that can be targeted in efforts to minimise costs and prevent the loss of native biodiversity.</p>
<h2>Bad weather, good for non-natives</h2>
<p>To better understand how native and non-native species respond to extreme weather events, the scientists behind the new study reanalysed information from 443 peer-reviewed studies on how species responded to wildfires, droughts and storms. In all, they gathered data on 187 non-native species and 1,852 native species from all major animal groups.</p>
<p>Their results suggest that native and non-native species may indeed respond differently to extreme weather. Across all studies, a total of 24.8% of non-native species benefited from extreme weather events compared to only 12.7% of native species.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="'attention invasive plant' sign" src="https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558048/original/file-20231107-29-vra3jw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Japanese knotweed is an invasive species in much of Europe and North America. Like many invasive plants, it grows quickly and can handle extreme weather.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/attention-sign-invasive-plant-japanese-knotweed-1777590785">Leon_Brouwer / shutterstock</a></span>
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<p>For example, while native species in both freshwater and land-based ecosystems were harmed by droughts, their non-native counterparts showed no significant response. Notably, marine ecosystems were comparatively more resistant to extreme weather events, with fewer differences between native and non-native species. </p>
<p>The authors did find marine heatwaves harmed native coral species, however, a relationship that has been documented in other <a href="https://www.nature.com/articles/s41586-018-0041-2">scientific studies</a>.</p>
<h2>Identifying global hotspots</h2>
<p>The authors took this information and combined it with known global hotspots of extreme weather, to identify areas where native species may be particularly vulnerable to the combination of extreme weather and invasive species.</p>
<p>They found high latitude areas such as northern US and Europe, for instance, are both vulnerable to extreme cold spells and possess non-native species that benefit from cold spells. Alternatively, areas of the western Amazon in Brazil and east Asia were identified as vulnerable to flooding and possessing flood-resistant non-native species. </p>
<p>In these regions, non-native species could benefit from increasing cold spells or flooding respectively, posing a greater threat to native plants and animals.</p>
<p>Studies like this are very useful. Regions that are identified as vulnerable can be targeted with early preventative measures to stop the spread of invasive species, or with measures to help native biodiversity cope with climate change.</p>
<p>This research could also allow targeted restoration to remove <a href="https://www.nature.com/articles/s41598-022-14982-5">non-native species</a> and produce <a href="https://www.nature.com/articles/s42003-023-05485-8">invasion-resistant native communities</a> that could better withstand future conditions. This is what happened on Macquarie Island, where invasive rabbits and rats were eventually eliminated and the <a href="https://www.theguardian.com/environment/2022/aug/10/rats-and-rabbits-invasive-species-macquarie-island-southern-ocean-aoe">whole ecosystem soon bounced back</a>. </p>
<p>Such action could be critical as we adapt to a changing climate and a greater mixing of the world’s plants and animals. </p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<p class="fine-print"><em><span>Harry Shepherd receives funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme. </span></em></p>Non-native species tend to be better at exploiting the disturbance caused by storms, fires or droughts.Harry Shepherd, Postdoctoral Research Associate, King's College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2137782023-09-21T12:03:56Z2023-09-21T12:03:56ZInvasive alien species are a serious threat to the planet: 4 key messages for Africa<p>Climate change has negatively – and irreversibly, in some cases – affected ecosystems around the globe. Sadly, though, it is not the only phenomenon that’s altering our natural world.</p>
<p>In 2019, the Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services (IPBES) Global Assessment Report <a href="https://www.ipbes.net/sites/default/files/inline/files/ipbes_global_assessment_report_summary_for_policymakers.pdf">confirmed</a> invasive alien species as one of the five most important direct drivers of biodiversity loss. The others were climate change, land and sea use, direct exploitation of species, and pollution. </p>
<p><a href="https://www.ipbes.net/">IPBES</a>, an independent intergovernmental body, was established in 2012. It now has 144 member countries; Somalia, the newest member, joined in mid-September. Its major objective is to strengthen the interface between science and policy to conserve and sustainably use biodiversity. </p>
<p>The 2019 assessment found that more than 37,000 alien species had been introduced by many human activities to regions and biomes around the world, most in the past 100 years. A <a href="https://www.ipbes.net/IASmediarelease">new report</a> by the organisation, focused on alien invasive species, suggests this number is rising fast, with new alien species being recorded at an unprecedented rate of approximately 200 annually. It also reveals that the global economic cost of invasive alien species exceeded US$423 billion annually. Costs have at least quadrupled every decade since 1970.</p>
<p>But the new report doesn’t just concentrate on problems. It also offers solutions. It outlines key responses and policy options that governments may take for prevention, early detection and effective control of invasive alien species. Doing so will help to safeguard nature and its contributions to people. This will ensure a better quality of life for all.</p>
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Read more:
<a href="https://theconversation.com/the-true-damage-of-invasive-alien-species-was-just-revealed-in-a-landmark-report-heres-how-we-must-act-211893">The true damage of invasive alien species was just revealed in a landmark report. Here's how we must act</a>
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<p>I am an invasion biologist whose <a href="https://www.ru.ac.za/centreforbiologicalcontrol/people/researchstaff/juliecoetzee/">research</a> focuses on the ecology and management of invasive aquatic plants. Here, I elaborate on the four key messages highlighted by the report that African countries should heed if the continent is to successfully tackle the threats posed by invasive species.</p>
<h2>Key messages</h2>
<p><em><strong>1: Invasive alien species are a major threat to nature, its contributions to people, and good quality of life.</strong></em></p>
<p>In Africa, invasive species threaten food security by negatively affecting fish production, agricultural productivity, grazing and water supplies. </p>
<p>The introduction of the Nile perch, <em>Lates niloticus</em>, into East Africa’s Lake Victoria in 1954 is one of the most extreme examples. Predation by this species caused the extinction of approximately 200 species of cichlids from the lake. It <a href="https://www.jstor.org/stable/2386700">is considered</a> to represent the largest extinction event among vertebrates during the 20th century. </p>
<p>The invasion also resulted in the shallow lake becoming enriched with nutrients as people came to fish for Nile perch. This resulted in the widespread invasion of the lake by water hyacinth. The plant restricted access to the lake, which prevented transport and fishing. </p>
<p><em><strong>2: Globally, invasive alien species and their impacts are increasing rapidly and are predicted to continue rising in the future. Accurate data is crucial.</strong></em></p>
<p>A <a href="https://www.sciencedirect.com/science/article/pii/S0048969721003041">2021 research study</a> highlighted that the reported economic costs of invasive aquatic species were unevenly distributed across geographic regions. Africa, the Oceania-Pacific Islands and the Antarctic-Subantarctic, combined, accounted for only 0.6% of the US$345 billion global estimate. That’s not because the costs are really that low. The data simply isn’t being recorded, so we’re not getting the full picture. </p>
<p>African countries need to <a href="https://healthtimes.co.zw/2023/09/19/zim-scales-up-efforts-to-control-invasive-alien-species/">partner with their neighbours</a> in better quantifying the situation. </p>
<p><em><strong>3: Invasive alien species and their negative impact can only be prevented and mitigated through effective management.</strong></em></p>
<p>In 2011 the Convention on Biological Diversity released its <a href="https://www.cbd.int/sp/targets/">Aichi Biodiversity Targets</a>. The 20 targets were designed to address and mitigate biodiversity loss across the globe. Target 9 stated that, by 2020, invasive alien species and pathways should be identified and prioritised. Priority species should be controlled or eradicated, and measures taken to block new pathways.</p>
<p>But none of those targets were met. And there has been little or no progress recorded in some African countries. Today, invasive species <a href="https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(20)30174-1/fulltext">are reported</a> to be adversely affecting livelihoods in more than 70% of African countries. </p>
<p>Constrained financial resources and the lack of legal frameworks and related operational systems are largely to blame for the lack of progress. For example, there is a <a href="https://link.springer.com/chapter/10.1007/978-3-030-32394-3_12">huge lack of capacity</a>, mainly at ports of entry – which are the most crucial step in preventing invasions. </p>
<p>Many regions still have to enhance their management plans for effective control of invasive species, starting with identification of common invasive species.</p>
<p><em><strong>4: There are success stories on the continent – lessons should be shared across borders.</strong></em></p>
<p>In South Africa, the management of alien plant invasions has been actively supported by the government’s <a href="https://www.dws.gov.za/wfw/">Working for Water</a> programme since 1995. </p>
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Read more:
<a href="https://theconversation.com/invasive-alien-plants-in-south-africa-pose-huge-risks-but-they-can-be-stopped-94186">Invasive alien plants in South Africa pose huge risks, but they can be stopped</a>
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<p>A study in 2022 <a href="https://www.sciencedirect.com/science/article/abs/pii/S0006320722002944">estimated</a> that an average of R310 million (adjusted to 2020 values) had been spent every year on work that covered 2.7 million hectares across more than 76,000 sites. This doesn’t mean plant invasions are totally under control. But it is clear that, without this kind of programme, the situation would be far worse.</p>
<p>The study recommended that the programme’s future efforts must focus on clearly defined priority sites, improving planning and monitoring, and increasing operational efficiency. These are all valuable lessons for other African countries.</p>
<h2>An African lens</h2>
<p>Its new report did not focus on any one part of the world, but IPBES has previously been clear about the importance of biodiversity to African nations. In a 2018 <a href="https://www.ipbes.net/assessment-reports/africa">regional assessment</a> on Biodiversity and Ecosystem Services For Africa, the organisation wrote that</p>
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<p>biodiversity and nature’s contributions in Africa are economically, socially and culturally important, essential in providing the continent’s food, water, energy, health and secure livelihood, and represent a strategic asset for sustainable development and achievement of the Sustainable Development Goals.</p>
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<p>Most of the data in the newest report comes from the northern hemisphere, as this is where most of the research is conducted, and where the majority of funding comes from. </p>
<p>Different countries and regions will have different needs. That’s where the value of regional coordination and knowledge-sharing becomes clear.</p><img src="https://counter.theconversation.com/content/213778/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Julie Coetzee receives funding from the National Research Foundation SARCHi and the Natural
Resource Management Programme of the South African Department of Forestry, Fisheries, and the Environment. Any opinion, conclusion or recommendation in this material is that of the authors and the NRF does not accept any liability in this regard.</span></em></p>The new report on alien invasive species doesn’t just concentrate on problems. It also offers solutions.Julie Coetzee, Researcher, Rhodes UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2126472023-09-08T00:25:14Z2023-09-08T00:25:14ZExposing Australia’s online trade in pest plants – we’ve found thousands of illegal advertisements<figure><img src="https://images.theconversation.com/files/546310/original/file-20230905-25-ejpcy3.jpg?ixlib=rb-1.1.0&rect=107%2C83%2C7832%2C5214&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/new-plants-delivery-woman-opening-shipping-1836099568">Shutterstock</a></span></figcaption></figure><p>Do you buy plants online? You might be breaking the law without even knowing it.</p>
<p>We found hundreds of different invasive plants and prohibited weeds advertised on a popular online marketplace. </p>
<p>For the first time, <a href="https://neobiota.pensoft.net/article/104472/">our research</a> has exposed the frequent, high volume trade in pest plants across Australia. </p>
<p>State and territory governments are adopting our automated surveillance approach to help regulate the online trade in plants and <a href="https://theconversation.com/buying-bugs-and-beetles-or-shopping-for-scorpions-and-snails-australias-pet-trade-includes-hundreds-of-spineless-species-207932">other wildlife</a>. Biosecurity officers can receive automatic alerts for suspected illegal trade, rather than manually monitoring websites or relying on reports from the public. </p>
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<a href="https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of someone shopping for plants online, showing hands on the laptop keyboard and plants on screen." src="https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547090/original/file-20230907-23-fsbn22.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Australians love online shopping and that passion extends to plants.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hands-searching-plants-buy-online-shop-746765218">Rawpixel.com, Shutterstock</a></span>
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Read more:
<a href="https://theconversation.com/the-true-damage-of-invasive-alien-species-was-just-revealed-in-a-landmark-report-heres-how-we-must-act-211893">The true damage of invasive alien species was just revealed in a landmark report. Here's how we must act</a>
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<h2>What’s the problem and why all the fuss?</h2>
<p>Certain plants are prohibited in Australia because they are harmful to our unique natural environment and agricultural industries. These weeds can threaten native species, <a href="https://www.theguardian.com/australia-news/2023/mar/29/environmental-tragedy-as-fires-burn-through-one-fifth-of-northern-territory-national-park">fuel severe fires</a> and choke rivers. </p>
<p>Weeds are also a <a href="https://theconversation.com/the-buffel-kerfuffle-how-one-species-quietly-destroys-native-wildlife-and-cultural-sites-in-arid-australia-149456">social and cultural threat for First Nations people</a>, because they can compete with traditional food and medicine plants, causing them to decline.</p>
<p>Overall, invasive plants are estimated to have <a href="https://theconversation.com/pest-plants-and-animals-cost-australia-around-25-billion-a-year-and-it-will-get-worse-164969">cost Australia A$200 billion since 1960</a>. </p>
<p>Weeds that are controlled under state and territory laws are referred to as “noxious” or declared plants. Each state and territory has different laws prohibiting the sale and cultivation of these declared plants. </p>
<p>Compliance is generally high within the horticultural industry, save for the occasional <a href="https://www.abc.net.au/news/2016-09-22/bunnings-caught-selling-declared-weed-sagittaria-to-customers/7869226">high profile blunder</a>. The main problem for Australia is the widespread invasive plant trade on public online marketplaces.</p>
<p>Trade of ornamental plants, which are the kinds popularly grown in homes and gardens, is the <a href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2664.12953">major current pathway</a> enabling invasion and spread of weeds into new areas. They’re travelling long distances, to homes in new places. </p>
<p>Invasive cacti and ornamental pond plants are among the most frequently advertised plants, but many are banned from sale and distribution in Australia. </p>
<p>Internet trade has historically been tricky to monitor and regulate, which has led to a variety of invasive species being <a href="https://theconversation.com/new-expose-of-australias-exotic-pet-trade-shows-an-alarming-proliferation-of-alien-threatened-and-illegal-species-203354">widely traded</a>.</p>
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<a href="https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo showing the invasive nature of water hyacinth, with purple flowers in a field of green." src="https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547091/original/file-20230907-23-xlg0k9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Water hyacinth is considered the world’s worst water weed.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/flowers-water-hyacinth-purple-lined-according-583320415">KEEP GOING, Shutterstock</a></span>
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Read more:
<a href="https://theconversation.com/new-expose-of-australias-exotic-pet-trade-shows-an-alarming-proliferation-of-alien-threatened-and-illegal-species-203354">New exposé of Australia's exotic pet trade shows an alarming proliferation of alien, threatened and illegal species</a>
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<h2>Scraping the web</h2>
<p>We used specialised software called “web scrapers” to monitor trade on a public classifieds website. These automated web tools can be used to rapidly harvest information from advertisements. This allowed us to detect thousands of advertisements for weeds over a 12-month period.</p>
<p>We found 155 declared plant species traded on one website, and we suspect there could be more. </p>
<p>Prickly pear cacti were among the most frequently traded declared plants. This is concerning given their history in Australia. In the 1920s, about 25 million hectares of land became unusable due to prickly pear invasion. </p>
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<a href="https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A black and white photo of a farmer standing in a field of prickly pear, it's more than double his height." src="https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=805&fit=crop&dpr=1 600w, https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=805&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=805&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1012&fit=crop&dpr=1 754w, https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1012&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/546312/original/file-20230905-27-quus11.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1012&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The invasion of prickly pear was so dense in areas of Queensland and New South Wales that farming became impossible.</span>
<span class="attribution"><a class="source" href="https://www.archivessearch.qld.gov.au/items/ITM1143347">Queensland Government</a></span>
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<p>Aquatic weeds were another popular group. That includes water hyacinth, which is the world’s most widespread invasive alien species according to a recently published <a href="https://theconversation.com/the-true-damage-of-invasive-alien-species-was-just-revealed-in-a-landmark-report-heres-how-we-must-act-211893">global assessment</a>. </p>
<p>We found some sellers advertised uses for the declared plants they were trading, including for food and medicinal properties. </p>
<p>Aquatic weeds were often stated to have water-filtering properties and provide habitat for fish. Those traits make Amazon frogbit a popular choice for aquariums and ponds, but if the weed enters creeks and rivers it can have <a href="https://www.abc.net.au/news/2021-11-25/amazon-frogbit-statewide-declaration/100648506">devastating consequences</a>.</p>
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Read more:
<a href="https://theconversation.com/buying-bugs-and-beetles-or-shopping-for-scorpions-and-snails-australias-pet-trade-includes-hundreds-of-spineless-species-207932">Buying bugs and beetles, or shopping for scorpions and snails? Australia's pet trade includes hundreds of spineless species</a>
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<h2>Everyone can do their bit</h2>
<p>Better surveillance is not the only solution. Public awareness is key to reducing invasive plant trade. We can all make informed decisions about the plants we buy.</p>
<p>A significant hurdle is a phenomenon called “<a href="https://nph.onlinelibrary.wiley.com/doi/full/10.1002/ppp3.51">plant blindness</a>”. People tend to find plants harder to recognise than animals. We found many weeds sold using generic names such as lily, cactus or pond plant. Some people may not even know the true identity of a plant they are selling, let alone that it is a weed and illegal to trade.</p>
<p>Another complication is the fact that laws differ between states. Plants that might be legal for an interstate trader, might still be illegal for you to buy. This is why caution should be taken when sending or receiving plants by post. Always check your local regulations before buying or selling a plant online. You can find out what is declared on your state or territory’s biosecurity website or on <a href="https://weeds.org.au/">Weeds Australia</a>. </p>
<p>Online marketplaces must also cooperate with local policies. These platforms should be enforced to self-regulate trade and include measures to prevent illegal advertisements from being posted in the first place. Failure to act may result in significant penalties from governments. Last year the <a href="https://www.science.org/doi/10.1126/science.ade0843#:%7E:text=%E2%80%9CFacebook%20fined%20U%242%20million,animals%2Din%2Dbrazil%2F.">Brazilian government fined Meta</a> for failing to remove illegal wildlife trade from Facebook and WhatsApp. </p>
<p>For now, monitoring tools such as the web scrapers we have developed will help to prevent some weeds escaping backyards and into bushland. As plant lovers, it’s important to be mindful of the plants we choose to buy and keep. </p>
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Read more:
<a href="https://theconversation.com/lickable-toads-and-magic-mushrooms-wildlife-traded-on-the-dark-web-is-the-kind-that-gets-you-high-201180">Lickable toads and magic mushrooms: wildlife traded on the dark web is the kind that gets you high</a>
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<img src="https://counter.theconversation.com/content/212647/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jacob Maher receives funding from the Centre for Invasive Species Solutions. </span></em></p><p class="fine-print"><em><span>Phill Cassey receives funding from the Centre for Invasive Species Solutions and the Australian Research Council. </span></em></p>Australians are trading pest plants online, potentially breaking the law without even realising it.Jacob Maher, PhD Candidate, University of AdelaidePhill Cassey, Australian Research Council Industry Laureate Fellow, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2129242023-09-06T12:26:36Z2023-09-06T12:26:36ZInvasive species cause billions of dollars in damage worldwide: 4 essential reads<p>Invasive species – including plants, animals and fish – cause heavy damage to crops, wildlife and human health worldwide. Some prey on native species; other out-compete them for space and food or spread disease. A new United Nations report estimates the losses generated by invasives at <a href="https://zenodo.org/record/8314303">more than US$423 billion yearly</a> and shows that these damages have at least quadrupled in every decade since 1970.</p>
<p>Humans regularly move animals, plants and other living species from their home areas to new locations, either accidentally or on purpose. For example, they may import plants from faraway locations to <a href="https://theconversation.com/invasive-grasses-are-fueling-wildfires-across-the-us-126574">raise as crops</a> or bring in a nonnative animal to <a href="https://theconversation.com/everyone-agreed-cane-toads-would-be-a-winner-for-australia-19881">prey on a local pest</a>. Other invasives <a href="https://theconversation.com/the-invasive-emerald-ash-borer-has-destroyed-millions-of-trees-scientists-aim-to-control-it-with-tiny-parasitic-wasps-158403">hitch rides in cargo</a> or <a href="https://theconversation.com/ballast-water-management-is-reducing-the-flow-of-invasive-species-into-the-great-lakes-190880">ships’ ballast water</a>.</p>
<p>When a species that is not native to a particular area becomes established there, reproducing quickly and causing harm, it has become invasive. These recent articles from The Conversation describe how several invasive species are causing economic and ecological harm across the U.S. They also explain steps that people can take to avoid contributing to this urgent global problem.</p>
<h2>1. The best intentions: Callery pear trees</h2>
<p>Many invasive species were introduced to new locations because people thought they would be useful. One example that’s widely visible across the U.S. Northeast, Midwest and South is the Callery pear (<em>Pyrus calleryana</em>), a flowering tree that botanists brought to the U.S. from Asia more than 100 years ago. </p>
<p>Horticulturists loved the Callery pear for landscaping and wanted to produce trees that all grew and bloomed in the same way. As University of Dayton plant ecologist <a href="https://scholar.google.com/citations?user=uRA-SZ0AAAAJ&hl=en&oi=sra">Ryan W. McEwan</a> explained, they created identical clones from cuttings of trees with the desired characteristics – a process called grafting. Unlike some trees, a Callery pear can’t fertilize its flowers with its own pollen, so plant experts thought it wouldn’t spread.</p>
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<figcaption><span class="caption">Missouri state foresters explain why Callery pear trees became so popular and the problems they cause.</span></figcaption>
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<p>However, “as horticulturalists tinkered with Callery pears to produce new versions, they made the individuals different enough to <a href="https://theconversation.com/once-the-callery-pear-tree-was-landscapers-favorite-now-states-are-banning-this-invasive-species-and-urging-homeowners-to-cut-it-down-198724">escape the fertilization barrier</a>,” McEwan wrote. As wind and birds spread the trees’ seeds, wild populations of the trees became established and started crowding out native species. </p>
<p>Today, Callery pear trees are such scourges that several states have banned them. Others are paying residents to cut them down and replace them with native plants. </p>
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Read more:
<a href="https://theconversation.com/once-the-callery-pear-tree-was-landscapers-favorite-now-states-are-banning-this-invasive-species-and-urging-homeowners-to-cut-it-down-198724">Once the Callery pear tree was landscapers' favorite – now states are banning this invasive species and urging homeowners to cut it down</a>
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<h2>2. Tiny organisms, big impacts: Zebra and quagga mussels</h2>
<p>Invasive species don’t have to be large to cause outsized damage. Zebra and quagga mussels – shellfish the size of a fingernail – invaded the Great Lakes in the 1980s, clogging water intake pipes and out-competing native mollusks for food. Now they’re spreading west via rivers, lakes and bays, threatening waters all the way to the Pacific coast and Alaska.</p>
<p>As Rochester Institute of Technology environmental historian <a href="https://www.researchgate.net/scientific-contributions/Christine-Keiner-2071802254">Christine Keiner</a> wrote, it took several decades for the U.S. and Canada to regulate ships’ management of their ballast water tanks, which was the route by which the mussels were introduced to North America. </p>
<p>“Now, however, other human activities are increasingly contributing to harmful freshwater introductions – and with shipping regulated, the main culprits are <a href="https://theconversation.com/the-westward-spread-of-zebra-and-quagga-mussels-shows-how-tiny-invaders-can-cause-big-problems-185286">thousands of private boaters and anglers</a>,” Keller wrote. Limiting the destructive impacts of invasive species “requires scientific, technological and historical knowledge, political will and skill to persuade the public that everyone is part of the solution.”</p>
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<a href="https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Infographic showing locations on a motorboat to check for invasive mussels." src="https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/546519/original/file-20230905-29-ibkd25.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Many states require boaters to clean and dry their boats after use to avoid spreading zebra and quagga mussels.</span>
<span class="attribution"><a class="source" href="https://neinvasives.com/stop-aquatic-hitchhikers">Nebraska Invasive Species Program</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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Read more:
<a href="https://theconversation.com/the-westward-spread-of-zebra-and-quagga-mussels-shows-how-tiny-invaders-can-cause-big-problems-185286">The westward spread of zebra and quagga mussels shows how tiny invaders can cause big problems</a>
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<h2>3. Threatening entire ecosystems: Lionfish</h2>
<p>When an invasive species is especially successful at spreading and reproducing, it can threaten the health of entire ecosystems. Consider the Pacific red lionfish (<em>Pterois volitans</em>), which has spread throughout the Caribbean and now is <a href="https://theconversation.com/invasive-lionfish-have-spread-south-from-the-caribbean-to-brazil-threatening-ecosystems-and-livelihoods-199229">moving south along Brazil’s coast</a>. </p>
<p>Lionfish thrive in many ocean habitats, from coastal mangrove forests to deepwater reefs, and they prey on numerous smaller fish species. In the Caribbean, they have reduced the number of small juvenile fish on reefs by up to 80% within as little as five weeks. </p>
<p>“Scientists and environmental managers widely agree that the lionfish invasion in Brazil is a potential ecological disaster,” warned Brazilian marine ecologist <a href="https://scholar.google.com.au/citations?user=_ArEYYMAAAAJ&hl=en">Osmar J. Luiz</a> of Charles Darwin University. “Brazil’s northeast coast, with its rich artisanal fishing activity, stands on the front line of this invasive threat.”</p>
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<p>Although the Brazilian government was slow to address the lionfish threat, Luiz asserted that “with strategic, swift action and international collaboration, it can mitigate the impacts of this invasive species and safeguard its marine ecosystems.” That will require many techniques, from recruiting coastal residents to monitor for the invaders to tracking lionfish subpopulations using DNA analysis. </p>
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Read more:
<a href="https://theconversation.com/invasive-lionfish-have-spread-south-from-the-caribbean-to-brazil-threatening-ecosystems-and-livelihoods-199229">Invasive lionfish have spread south from the Caribbean to Brazil, threatening ecosystems and livelihoods</a>
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<h2>4. The value of acting locally</h2>
<p>Public awareness is critical for stemming the spread of many invasive plants and animals. That can involve actions as simple as cleaning your shoes and socks after a hike. </p>
<p>“Certain species of nonnative invasive plants produce seeds <a href="https://theconversation.com/those-seeds-clinging-to-your-hiking-socks-may-be-from-invasive-plants-heres-how-to-avoid-spreading-them-to-new-locations-195697">designed to attach to unsuspecting animals or people</a>. Once affixed, these sticky seeds can be carried long distances before they fall off in new environments,” explains Boise State University ecology Ph.D. candidate <a href="https://scholar.google.com/citations?user=nmAblPEAAAAJ&hl=en&oi=ao">Megan Dolman</a>. </p>
<p>Research shows that recreational trails promote the introduction of invasive plant species into natural and protected areas, including national parks and scenic trails.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CkgNbwptsgc/?utm_source=ig_web_copy_link\u0026igshid=MzRlODBiNWFlZA==","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<p>In her research, Dolman found that few Appalachian Trail hikers were aware of the risk of carrying invasive plant seeds on their shoes or socks, so they typically did not take steps such as cleaning their gear before and after hiking. By knowing about invasive species in their areas and ways to manage them, people can help protect special places and keep invasive species from spreading.</p>
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Read more:
<a href="https://theconversation.com/those-seeds-clinging-to-your-hiking-socks-may-be-from-invasive-plants-heres-how-to-avoid-spreading-them-to-new-locations-195697">Those seeds clinging to your hiking socks may be from invasive plants – here's how to avoid spreading them to new locations</a>
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<p><em>Editor’s note: This story is a roundup of articles from The Conversation’s archives.</em></p><img src="https://counter.theconversation.com/content/212924/count.gif" alt="The Conversation" width="1" height="1" />
According to a new UN report, invasive species do more than US$423 billion in damage worldwide every year. Four articles explore examples, from mollusks to poisonous fish.Jennifer Weeks, Senior Environment + Cities Editor, The ConversationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2118932023-09-04T12:01:47Z2023-09-04T12:01:47ZThe true damage of invasive alien species was just revealed in a landmark report. Here’s how we must act<figure><img src="https://images.theconversation.com/files/546132/original/file-20230904-17-cgmyf9.jpg?ixlib=rb-1.1.0&rect=53%2C53%2C3932%2C2181&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/aerial-top-view-container-cargo-ship-708817909">Avigator Fortuner. Shutterstock</a></span></figcaption></figure><p>Invasive alien species are driving biodiversity loss and extinctions in every country, all over the world. </p>
<p>Responding to the challenge, the United Nations is today releasing the <a href="https://doi.org/10.5281/zenodo.7430692">first global assessment</a> of invasive alien species and their control. </p>
<p>It comes from the <a href="https://www.ipbes.net">Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services</a> (IPBES), which represents almost 140 member states. </p>
<p>Over four years, 86 expert authors from 49 countries gathered the latest scientific evidence and Indigenous and local knowledge on invasive alien species. The report draws on more than 13,000 references, including governmental reports. We were among the authors. Here are some of the key insights for Australia and Aotearoa New Zealand. </p>
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Read more:
<a href="https://theconversation.com/invasive-species-are-australias-number-one-extinction-threat-116809">Invasive species are Australia's number-one extinction threat</a>
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<h2>Hope in the face of increasing threats</h2>
<p>In 2019, IPBES released a <a href="https://www.ipbes.net/global-assessment">global biodiversity assessment</a> that placed invasive alien species in the top five drivers of biodiversity loss - alongside changing land- and sea-use, over-exploitation of natural resources, climate change, and pollution. </p>
<p>This triggered further assessment to determine the current global state of biological invasions, the effectiveness of our existing responses, and recommended management and policy options. </p>
<p>The result, released today, is the most comprehensive overarching policy-relevant report on biological invasions to date. </p>
<p>It promises to help us meet our international obligations under the recently adopted UN <a href="https://www.cbd.int/">Convention on Biological Diversity</a>. In particular, one of the targets in the Kunming-Montreal <a href="https://www.cbd.int/article/cop15-final-text-kunming-montreal-gbf-221222">Global Biodiversity Framework</a> is to “eliminate, minimise, reduce and/or mitigate the impacts of invasive alien species on biodiversity and ecosystem services”.</p>
<p>The world faces increasing biosecurity threats, but effective management can prevent or lessen the extent of subsequent biological invasions. Ambitious progress can be achieved with an integrated approach.</p>
<h2>The experience in Australia and Aotearoa New Zealand</h2>
<p>Australia already has close to <a href="https://www.gbif.org/dataset/15147db1-27c3-49b5-9c69-c78d55a4b8ff">3,000</a> introduced alien species. Aotearoa New Zealand has almost <a href="https://www.gbif.org/dataset/b286f8ee-1e29-4f8a-a041-9106bb1796f3">900</a>.</p>
<p>Globally, we observe around 200 new alien species every year, and many of these species (>10%) have negative impacts, including threats to native species, the health of natural vegetation, or the way ecosystems work. </p>
<p>Australian examples include <a href="https://theconversation.com/1-7-million-foxes-300-million-native-animals-killed-every-year-now-we-know-the-damage-foxes-wreak-177832">foxes</a>, <a href="https://theconversation.com/why-red-fire-ants-and-yellow-crazy-ants-have-given-themselves-a-green-light-to-invade-australia-208479">red imported fire ants</a> and <a href="https://theconversation.com/field-of-nightmares-gamba-grass-in-the-top-end-12178">gamba grass</a>. </p>
<p>Aotearoa New Zealand suffers from invasive Australian <a href="https://www.doc.govt.nz/nature/pests-and-threats/animal-pests/possums/">possums</a>. And the Māori cultural icon the Kauri tree is under siege from a deadly <a href="https://theconversation.com/lord-of-the-forest-new-zealands-most-sacred-tree-is-under-threat-from-disease-but-response-is-slow-100447">dieback disease</a>.</p>
<p>The assessment reveals that invasive alien species have contributed to 60% of global extinctions, and have been the sole driver of 16% of recorded extinctions. </p>
<p><a href="https://theconversation.com/invasive-species-are-australias-number-one-extinction-threat-116809">Australia</a> and <a href="https://www.doc.govt.nz/nature/pests-and-threats/predator-free-2050/">Aotearoa New Zealand</a> have among the highest modern global native species extinction rates. Australia is the worst in the world <a href="https://theconversation.com/gut-wrenching-and-infuriating-why-australia-is-the-world-leader-in-mammal-extinctions-and-what-to-do-about-it-192173">for mammals</a>, while Aotearoa New Zealand has experienced tragic loss in <a href="https://theconversation.com/call-of-the-huia-how-nzs-bird-of-the-century-contest-helps-us-express-ecological-grief-210698">endemic birds</a>, largely due to invasive species. </p>
<p>The economies of both countries rely heavily on agriculture, trade and eco-tourism. These sectors are highly susceptible to threats from invasive alien species. The cost to Australia is <a href="https://theconversation.com/pest-plants-and-animals-cost-australia-around-25-billion-a-year-and-it-will-get-worse-164969">A$24.5 billion a year</a> out of an estimated global cost of $654 billion (<a href="https://doi.org/10.5281/zenodo.7430692">US$423 billion a year</a>). </p>
<p>The cost of biological invasions is quadrupling every decade, but stringent biosecurity policies and practices can protect our environment and economies. They also safeguard our wellbeing and cultural and social livelihoods. </p>
<p>Continued cooperation and investment across our region is paramount to preventing future impacts from increasing threats. These include <a href="https://theconversation.com/to-lock-out-foot-and-mouth-disease-australia-must-help-our-neighbour-countries-bolster-their-biosecurity-188010">foot and mouth disease</a> and <a href="https://theconversation.com/avian-influenza-how-bird-flu-affects-domestic-and-wild-flocks-and-why-a-one-health-approach-matters-182497">avian influenza</a>. </p>
<p>At the same time, already established invasive alien species can supercharge environmental disasters. For example, the wildfire-promoting properties of introduced <a href="https://theconversation.com/feed-or-weed-new-pastures-are-sowing-problems-for-the-future-33733">African pasture grasses</a> exacerbated <a href="https://time.com/6305735/invasive-plants-from-colonists-fueled-maui-wildfires">bushfires in Hawaii</a> this year. </p>
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Read more:
<a href="https://theconversation.com/new-expose-of-australias-exotic-pet-trade-shows-an-alarming-proliferation-of-alien-threatened-and-illegal-species-203354">New exposé of Australia's exotic pet trade shows an alarming proliferation of alien, threatened and illegal species</a>
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<h2>Coordinate, consult and prioritise</h2>
<p>An effective biosecurity system can mitigate the threats from invasive species. But to do so, we’ll need coherent policy across primary production and logistic sectors, better education and greater public awareness.</p>
<p>We need to coordinate and prioritise our efforts, from offshore ports to border control and quarantine, through to eradication or containment of any new pests and weeds.</p>
<p>Government-industry partnerships are leading to trusted “green-lane” trade supply chains. This cuts red tape for businesses that manage import risks and produce pre-costed and co-designed emergency response agreements.</p>
<p>Prevention will not stop arrivals altogether. We will still have to contend with blow-ins on storm winds, <a href="https://theconversation.com/debris-from-the-2011-tsunami-carried-hundreds-of-species-across-the-pacific-ocean-84773">ocean waves</a> and boat hulls. There’s also the $23 billion a year <a href="https://theconversation.com/alien-invaders-the-illegal-reptile-trade-is-a-serious-threat-to-australia-68815">illegal pet trade</a>.</p>
<p>Biosecurity tools work best alongside strong public support, regulation and governance. We share a proud history of effective biological control programs for many <a href="https://theconversation.com/explainer-how-biocontrol-fights-invasive-species-31298">weeds and pests</a>. Australia’s approach to <a href="https://theconversation.com/releasing-a-virus-against-rabbits-is-effective-but-can-make-them-immune-if-let-loose-at-the-wrong-time-176028">rabbit control using a virus</a> was a world-first and it remains in use 70 years later. This has delivered benefits worth more than <a href="https://www.csiro.au/en/research/natural-environment/biodiversity/fighting-plagues-and-predators">$70 billion</a>. </p>
<p>Despite strong biosecurity measures, highly engaged primary industries agricultural industries, excellent research infrastructure and a high level of public awareness, invasive alien species continue to <a href="https://theconversation.com/new-zealand-needs-to-up-its-biosecurity-game-to-protect-the-country-from-the-next-devastating-pest-threat-207104">slip through our borders</a> and multiply. </p>
<p>We tried to defend our countries against recent invasions from the <a href="https://theconversation.com/the-fall-armyworm-invasion-is-fierce-this-year-and-scientists-are-researching-how-to-stop-its-destruction-of-lawns-football-fields-and-crops-167098">fall armyworm</a>, <a href="https://theconversation.com/what-is-myrtle-rust-and-why-has-this-disease-closed-lord-howe-island-to-visitors-202045">myrtle rust</a> and the <a href="https://theconversation.com/australia-is-in-a-unique-position-to-eliminate-the-bee-killing-varroa-mite-heres-what-happens-if-we-dont-205926">varroa mite</a>. But they have still managed to establish. </p>
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<h2>One world, ‘One Biosecurity’</h2>
<p>The rising pressure of trade will likely outpace the resourcing dedicated to biosecurity measures. Frequent interceptions of pests, weeds, and diseases at our border highlight the pressure we are under. We will have to simply become smarter, more effective, and better coordinated across the <a href="https://www.nzherald.co.nz/the-listener/new-zealand/the-new-billion-dollar-biosecurity-threats-at-our-borders/F6AQFEQCE5GUZDMSJM6B5ZSMUI/">human, animal, plant and ecosystem health sectors</a>. </p>
<p>We encourage governments to recognise the threats invasive alien pests pose and mobilise their resources and capability to combat these threats – in regions where a species is first recognised as going rogue, rather than simply monitoring its progressive global spread. This is the <a href="https://www.nzherald.co.nz/the-country/news/covid-19-coronavirus-expert-calls-for-holistic-approach-to-biosecurity/WOWPH22RSVCHIE5D3NDXL6ZZII/">One Biosecurity concept</a>. </p>
<p>Australia and Aotearoa New Zealand can play a much stronger leadership role in <a href="https://www.cookislandsnews.com/internal/national/regional/environment/economy/pacific-islands/pacific-island-countries-meet-in-rarotonga-to-discuss-biosecurity-and-trade/">managing biosecurity risks in the Pacific</a>. After all, lax border protocols in our neighbourhood help pests and diseases end up on our doorstep. </p>
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<strong>
Read more:
<a href="https://theconversation.com/why-red-fire-ants-and-yellow-crazy-ants-have-given-themselves-a-green-light-to-invade-australia-208479">Why red fire ants and yellow crazy ants have given themselves a green light to invade Australia</a>
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<img src="https://counter.theconversation.com/content/211893/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andy Sheppard, as a chief research scientist with CSIRO, receives funding from the Australian federal government. This included funding to participate in the IPBES Assessment process as a coordinating lead author from 2019-2023, where he co-led Chapter 5 and made contributions to three other chapters. He is therefore well connected to the IPBES process, corporate, assessment team and media team. However, as a CSIRO employee he respects all the values of the organisation and does not undertake any commentary that would be seen to criticise Australian government policy or in any way lobby for additional research funding from governments. </span></em></p><p class="fine-print"><em><span>Melodie McGeoch receives funding from the Australian Research Council - ARC SRIEAS Grant SR200100005 Securing Antarctica’s Environmental Future. She is affiliated with La Trobe University and Monash University. She is 1st Vice Chair of the Science Committee of the Global Biodiversity Information Facility, Fellow of the African Academy of Sciences, Member of the Implementation Committee of the Group on Earth Observations Biodiversity Observation Network, Independent Board Member of the National Computation Infrastructure and on the Editorial Board of Global Ecology and Biogeography.</span></em></p><p class="fine-print"><em><span>Philip Hulme receives research funding from the New Zealand government. He is affiliated with Lincoln University, New Zealand. and is a member of the Canterbury-Aoraki Conservation Board and a Director of the QEII Trust. He is a member of the Biosecurity Advisory Groups of both Environment Canterbury and Zespri.</span></em></p><p class="fine-print"><em><span>Phill Cassey receives funding from the Centre for Invasive Species Solutions and the Australian Research Council. </span></em></p>Alien invaders are penetrating the borders of every country in the world. Now the full extent of the problems and potential solutions have been exposed, in a new United Nations report.Andy Sheppard, Research Director CSIRO Health & Biosecurity, CSIROMelodie McGeoch, Professor, La Trobe UniversityPhilip Hulme, Distinguished Professor in Pest Management and Conservation, Lincoln University, New ZealandPhill Cassey, Australian Research Council Industry Laureate Fellow, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2051832023-05-21T20:00:34Z2023-05-21T20:00:34ZA botanical detective story: shedding light on the journey out of Africa for one of Australia’s worst weeds<figure><img src="https://images.theconversation.com/files/526989/original/file-20230518-15-gzmuv8.jpg?ixlib=rb-1.1.0&rect=34%2C97%2C4604%2C2865&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">John K. Scott, CSIRO</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The scrubby harbour-side hills of a South African city recently revealed details of an historical event that transformed Australian coastlines. That event led to the arrival in Australia of a native South African shrub, bitou bush. The invader went on to become one of <a href="https://lists.ala.org.au/speciesListItem/list/dr823">Australia’s worst weeds</a>, smothering coastal dune vegetation.</p>
<p>While bitou bush has been widespread along Australia’s east coast for decades, the weed arrived in Western Australia relatively recently. The species (<em>Chrysanthemoides monilifera</em> subspecies <em>rotundata</em>) was <a href="https://doi.org/10.1614/IPSM-D-13-00052.1">discovered in 2012 at Kwinana</a>, a port and industrial area south of Perth. This new invasion <a href="https://doi.org/10.3897/neobiota.50.35070">required urgent attention</a>.</p>
<figure class="align-right ">
<img alt="A closeup of a bitou bush flower" src="https://images.theconversation.com/files/527179/original/file-20230519-17-k14689.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/527179/original/file-20230519-17-k14689.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527179/original/file-20230519-17-k14689.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527179/original/file-20230519-17-k14689.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527179/original/file-20230519-17-k14689.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527179/original/file-20230519-17-k14689.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527179/original/file-20230519-17-k14689.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bitou bush (<em>Chrysanthemoides monilifera</em> subspecies <em>rotundata</em>) is a weed targeted for eradication in Western Australia. The flowers are bright yellow daisies.</span>
<span class="attribution"><span class="source">Kathryn L. Batchelor, CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Knowing where a weed has come from is fundamental to <a href="https://theconversation.com/attack-of-the-alien-invaders-pest-plants-and-animals-leave-a-frightening-1-7-trillion-bill-158628">managing it well</a>. Understanding how plants are introduced to new regions can enable effective biosecurity measures to be put in place. Establishing a weed’s origin also reveals where to look for its natural enemies, such as insects or fungi, that can be used as classical <a href="https://theconversation.com/explainer-how-biocontrol-fights-invasive-species-31298">biological control</a> agents.</p>
<p>Our research set out to decipher how bitou bush originally entered Australia and then spread from east to west. We reveal how the chance of new bitou bush arrivals in Australia is low and better biological control is possible.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/attack-of-the-alien-invaders-pest-plants-and-animals-leave-a-frightening-1-7-trillion-bill-158628">Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill</a>
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<h2>Establishing relationships between populations</h2>
<p>Earlier <a href="https://doi.org/10.1002/ece3.9179">research</a> on bitou bush established Australian populations went through “genetic bottlenecks”, meaning only a few plants, seeds or parts of plants arrived to begin with. However, the work was unable to identify a population in South Africa that was a genetic match to the bitou bush found in Australia.</p>
<p><a href="https://doi.org/10.1007/s10530-023-03017-3">Our new research</a> took a more comprehensive approach to reveal plants from the South African port of East London were the likely source. Our findings suggested there was a single introduction of bitou bush to eastern Australia, with subsequent movement of material to establish the population in Western Australia more than a century later.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A historical image of the South African port of East London in 1905" src="https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=476&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=476&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524856/original/file-20230508-15-ra6lqy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=476&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The South African port of East London (c. 1905) was the likely source of Australia’s bitou bush.</span>
<span class="attribution"><span class="source">East London Museum</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Travel by ballast</h2>
<p>To build confidence in our results, we scoured historical archives in Australia and South Africa for records that could support or refute these findings. Could we turn a plausible hypothesis into a feasible smoking gun?</p>
<p>In the storage racks of the National Herbarium of New South Wales lies a pressed sheet of dried plant material. Collected in 1908, this sample – later identified as bitou bush – was from the port-side suburb of Stockton in Newcastle. Newspaper reports revealed Stockton’s local government had been complaining for at least ten years about a weed threat from dry ballast, making it likely the introduction of bitou bush to Australia occurred even earlier.</p>
<p>Dry ballast consists of sand, soil, rocks and other matter used to provide stability to wooden sailing ships that had to travel without a heavy cargo load. This material was usually quarried at the port of departure. At the time, an increasingly large area in Stockton was reclaimed land comprised of ship’s ballast.</p>
<p>We found historical shipping records that showed ships were regularly leaving the South African Port of East London after taking on dry ballast, then sailing directly to Newcastle to collect coal. Before taking on coal, these ships discharged their dry ballast onto the ballast field at Stockton. We found documents showing that in 1904, more than half the ballast arriving in Australia was dumped at Stockton. </p>
<figure class="align-center ">
<img alt="Map of harbour and inset photo of docked sailing ships" src="https://images.theconversation.com/files/524840/original/file-20230508-230622-hnfek9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/524840/original/file-20230508-230622-hnfek9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=249&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524840/original/file-20230508-230622-hnfek9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=249&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524840/original/file-20230508-230622-hnfek9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=249&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524840/original/file-20230508-230622-hnfek9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=313&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524840/original/file-20230508-230622-hnfek9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=313&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524840/original/file-20230508-230622-hnfek9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=313&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The location of the first introduction of bitou bush into Australia showing the reclaimed ballast field (red shading, c. 1902) at Stockton, New South Wales and right, barques (sailing ships) waiting to be loaded with coal, having discarded the ballast (c. 1900).</span>
<span class="attribution"><span class="source">Newcastle University and Ralph Snowball</span></span>
</figcaption>
</figure>
<p>Historical maps revealed a ballast quarry on the west side of the Port of East London. This quarry existed in 1902 and exposed remnants can still be seen today. Bitou bush can still be found across the vegetation-covered hillsides near the old quarry. Their seeds are therefore likely to have been contaminants in dry ballast.</p>
<figure class="align-center ">
<img alt="Historical map of the Port of East London, South Africa." src="https://images.theconversation.com/files/524842/original/file-20230508-19-nu8t9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/524842/original/file-20230508-19-nu8t9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=198&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524842/original/file-20230508-19-nu8t9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=198&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524842/original/file-20230508-19-nu8t9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=198&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524842/original/file-20230508-19-nu8t9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=249&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524842/original/file-20230508-19-nu8t9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=249&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524842/original/file-20230508-19-nu8t9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=249&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Likely source location of bitou bush in and around the quarry at the Port of East London (circa 1920).</span>
<span class="attribution"><span class="source">East London Museum</span></span>
</figcaption>
</figure>
<h2>To Newcastle and beyond!</h2>
<p>The arrival of bitou bush at Stockton was the beginning of a wider invasion of the eastern Australian coastline. The plants now cover 1,600 km <a href="https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2908997#overview">from Victoria to Queensland</a>.</p>
<p>This spread included deliberate plantings for dune stabilisation in the 1950s. Our molecular work revealed these dune plantings were enabled by the local collection of seed from a limited number of plants, rather than new material from South Africa or widely sourced seed.</p>
<p>We were not able to conclusively identify the introduction pathway from New South Wales to Western Australia. However, contamination of steel shipments between Newcastle or Port Kembla and Kwinana, or landscape plantings for the companies involved, are considered most likely.</p>
<h2>Why does this matter?</h2>
<p>The discovery of a potential source population and pathway into Australia for bitou bush reveals two avenues for improved invasive species management.</p>
<p>First, it opens the door to improved biological control. Earlier ineffective agents were sourced in South Africa from <a href="https://doi.org/10.2307/2404788">populations distantly related</a> to the material introduced into Australia. Many effective agents, particularly pathogens, are highly host specific. New surveys around East London could discover a more effective biological control agent.</p>
<p>Second, the work has clarified the ongoing risk of new introductions following the same pathway. Thankfully the use of dry ballast ceased with the move to steel-hulled ships carrying wet ballast, although the latter has its own <a href="https://doi.org/10.1098/rsos.150039">biosecurity concerns</a>.</p>
<p>More generally, the case of bitou bush in Australia highlights the problem of inadvertent outcomes from introducing plants, either accidentally or deliberately, without rigorous risk assessment. We must remain vigilant to the risk of introductions facilitated by global trade and maintain <a href="https://theconversation.com/yes-wash-your-shoes-at-the-airport-but-we-can-do-more-to-stop-foot-and-mouth-disease-ravaging-australia-187602">strict border biosecurity</a> protocols.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-wash-your-shoes-at-the-airport-but-we-can-do-more-to-stop-foot-and-mouth-disease-ravaging-australia-187602">Yes, wash your shoes at the airport – but we can do more to stop foot-and-mouth disease ravaging Australia</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/205183/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bruce Webber receives funding from Fremantle Ports Authority and CSIRO Health & Biosecurity. </span></em></p><p class="fine-print"><em><span>John Scott does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Knowing where a weed has come from can improve its management, but this quest can be challenging. CSIRO detective work revealed an unusual pathway for the introduction of South African bitou bush.Bruce Webber, Principal Research Scientist, CSIROJohn Scott, Honorary Fellow, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2024602023-03-30T15:13:04Z2023-03-30T15:13:04ZWhat’s the most sustainable way of dealing with Japanese knotweed? Here’s what we found<figure><img src="https://images.theconversation.com/files/518139/original/file-20230329-26-j3bjij.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4592%2C2577&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">More than £150 million is spent trying to control Japanese knotweed in the UK annually.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/knotweed-japanese-invasive-expansive-species-dangerous-1993556132">Tomas Vynikal/Shutterstock</a></span></figcaption></figure><p>When it was introduced to Europe in the mid-19th century as an ornamental plant, Japanese knotweed, known as <em>Reynoutria japonica var japonica</em>, quickly went rogue. Despite not being native to the British Isles, it was able to rapidly form self-sustaining colonies in the wild. </p>
<p>Today, this invasive plant is found across much of <a href="https://plantatlas2020.org/atlas/2cd4p9h.7mm4kb">Britain and Ireland</a>. It is often spotted growing in areas influenced by people such as waste ground, along riverbanks, roadsides and railway lines.</p>
<p>From an ecological perspective, this plant is very competitive and decreases biodiversity. This means invaded habitats become degraded and we see fewer native plants and animals. </p>
<p>Controlling knotweed is a <a href="https://www.legislation.gov.uk/ukpga/1981/69">legal requirement</a> in the UK and the costs of managing it are estimated to be around <a href="https://www.researchgate.net/publication/298559361_The_Economic_Cost_of_Invasive_Non-Native_Species_on_Great_Britain">£165 million per year</a>. Its management on construction sites can cost <a href="https://www.nonnativespecies.org/non-native-species/information-portal/view/1495">£1,000 per square meter</a> or more. These costs also impact home and landowners and several legal cases associated with knotweed have made <a href="https://www.theguardian.com/environment/2023/feb/14/legal-victory-uk-japanese-knotweed-case-more-claims">headlines</a> recently. </p>
<p>An entire industry has been built around knotweed management. But until fairly recently, the most effective way of controlling knotweed was unknown. Back in 2018, our research group published the results of the <a href="https://link.springer.com/article/10.1007/s10530-018-1684-5">world’s largest Japanese knotweed trial</a>, which is what informs how we currently tackle the plant. </p>
<h2>Sustainability</h2>
<p>Sustainability has never been a more important issue and there’s increasing pressure to find more sustainable management approaches to dealing with knotweed. Growing concerns around the use of herbicides for the environment and human health have led to an increased focus on physical control methods, such as digging and using <a href="https://www.allthescience.org/what-are-geomembranes.htm">geomembranes</a>. These are synthetic liners which stop Japanese knotweed and other unwanted plants from growing by sealing the earth. </p>
<p>However, when we think about sustainable knotweed management, we tend to focus on the immediate impacts, but that is just the tip of the iceberg. What happens before and after we use products to control knotweed is also important. All products and processes have a life cycle and each stage has different impacts. So, the sustainability of alternative approaches to tackling knotweed is often unclear. </p>
<p>To address this, we investigated the <a href="https://www.nature.com/articles/s41598-023-30366-9">impacts of eight Japanese knotweed management methods</a> using life cycle assessment (<a href="https://pre-sustainability.com/articles/life-cycle-assessment-lca-basics/">LCA</a>). That is when you calculate the environmental impact of a product throughout its entire life cycle. </p>
<p>We used our <a href="https://theconversation.com/weve-found-the-best-way-to-control-japanese-knotweed-95320">knotweed trial</a> as a reference system for our investigation.</p>
<figure class="align-center ">
<img alt="A close up of a green leaf with a spray of apple white small flowers in the background." src="https://images.theconversation.com/files/518154/original/file-20230329-18-9wdccw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518154/original/file-20230329-18-9wdccw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518154/original/file-20230329-18-9wdccw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518154/original/file-20230329-18-9wdccw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518154/original/file-20230329-18-9wdccw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518154/original/file-20230329-18-9wdccw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518154/original/file-20230329-18-9wdccw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A Japanese knotweed flower.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/japanese-knotweed-flowers-persicaria-japonica-118949437">Martin Fowler/Shutterstock</a></span>
</figcaption>
</figure>
<p>Of the methods assessed, annual <a href="http://npic.orst.edu/factsheets/glyphogen.html">glyphosate</a> spraying was the most sustainable option in terms of environmental impacts, economic cost and time consumption. This is because it is an approach that uses the fewest amount of materials while being the most effective method at controlling Japanese knotweed.</p>
<p>We found geomembrane covering to be the most damaging. That was due to the production of the plastics needed to manufacture the geomembranes, as well as the ground preparation needed to install them. And we also found that using digging as part of a knotweed management programme was also less sustainable due to the carbon emissions produced from using machinery.</p>
<p>So, the most effective way of controlling knotweed is also the most sustainable. </p>
<p>In light of the current <a href="https://www.ipcc.ch/report/sixth-assessment-report-cycle/">climate crisis</a>, minimising greenhouse gas emissions is vital. As we are aiming to achieve carbon net zero by 2050 in the UK, we need to think carefully about the sustainability of the approaches we use for managing Japanese knotweed and other problematic invasive plants. </p>
<p>Although we recognise the <a href="https://theconversation.com/does-this-cause-cancer-how-scientists-determine-whether-a-chemical-is-carcinogenic-sometimes-with-controversial-results-193431">ongoing discussions</a> regarding the use of glyphosate, its use yields better and more sustainable results than other Japanese knotweed treatments. And understanding the sustainability of different methods also means we can prioritise what we use to control knotweed, which ultimately saves time and money.</p>
<p>One caveat we have is that we evaluated just eight approaches to knotweed management. Assessing environmental impacts relies on comprehensive, long-term data and rigorous record keeping of the time, costs and materials that go into knotweed management. This kind of data can still be hard to come by. But data on the effectiveness and sustainability of different methods will be an essential future consideration for how society selects its weed control treatments.</p>
<p>Our understanding of and ability to quantify the environmental impacts of different products after they have been used is also a growing area of research and something that is not encompassed in our study. This is something we are looking to build upon in the future. It would ensure that different treatments are evaluated in a way that supports the decisions we make as a society over how to control Japanese knotweed.</p><img src="https://counter.theconversation.com/content/202460/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sophie Hocking works for Swansea University. She received funding from Complete Weed Control Ltd as part of her KESS II PhD to support her research. </span></em></p>It’s a plant that is nearly impossible to obliterate, but new research reveals the best way of tackling Japanese knotweed in the most sustainable way.Sophie Hocking, Lecturer in Biosciences, Swansea UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1990492023-03-28T12:15:57Z2023-03-28T12:15:57ZA shortage of native seeds is slowing land restoration across the US, which is crucial for tackling climate change and extinctions<figure><img src="https://images.theconversation.com/files/517710/original/file-20230327-16-yltw9r.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3994%2C2814&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Planting native plant seeds on sand dunes at Westward Beach in Malibu, Calif., to stabilize the dunes.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/sara-cuadra-watershed-program-coordinator-with-the-bay-news-photo/1234406431">Al Seib / Los Angeles Times via Getty Images</a></span></figcaption></figure><p>Spring is planting time for home gardeners, landscapers and public works agencies across the U.S. And there’s rising demand for <a href="https://www.wildflower.org/plants-main">native plants</a> – species that are genetically adapted to the specific regions where they are used. </p>
<p>Native plants have evolved with local climates and soil conditions. As a result, they generally require less maintenance, such as watering and fertilizing, after they become established, and they are hardier than non-native species. </p>
<p>Many federal, state and city agencies <a href="https://law.pace.edu/sites/default/files/Team%20%233%20Brief.pdf">rank native plants as a first choice</a> for restoring areas that have been disturbed by natural disasters or human activities like mining and development. Repairing damaged landscapes is a critical strategy for <a href="https://www.decadeonrestoration.org/">slowing climate change and species loss</a>. </p>
<p>But there’s one big problem: There aren’t enough native seeds. This issue is so serious that it was the <a href="https://doi.org/10.17226/26618">subject of a recent report</a> from the National Academies of Sciences, Engineering and Medicine. The study found an urgent need to build a native seed supply. </p>
<p>As <a href="https://scholar.google.com/citations?user=EAP10S8AAAAJ&hl=en">plant scientists</a> who have worked on <a href="https://www.linkedin.com/in/john-campanelli/">ecological restoration projects</a>, we’re familiar with this challenge. Here’s how we are working to promote the use of native plants for <a href="https://nenativeplants.psla.uconn.edu/wp-content/uploads/sites/3415/2022/08/netcr97_09-2.pdf">roadside restoration in New England</a>, including by building up a seed supply network.</p>
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<figcaption><span class="caption">Landscapers and land managers explain the benefits of planting native plants.</span></figcaption>
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<h2>The need for native plants</h2>
<p>Many stressors can damage and degrade land. They include natural disasters, such as wildfires and flooding, and human actions, such as urbanization, energy production, ranching and development. </p>
<p>Invasive plants <a href="https://doi.org/10.1007/s10530-021-02478-8">often move into disturbed areas</a>, causing further harm. They may <a href="https://doi.org/10.1016/j.gecco.2017.04.008">drift there on the wind</a>, be excreted by <a href="https://doi.org/10.1111/j.1366-9516.2005.00195.x">birds and animals that consume fruit</a>, or be <a href="https://doi.org/10.1641/0006-3568(2001)051%5B0095:HAGPDG%5D2.0.CO;2">introduced by humans</a>, unintentionally or deliberately.</p>
<p>Ecological restoration aims to bring back degraded lands’ native biological diversity and the ecological functions that these areas provided, such as sheltering wildlife and soaking up floodwater. In 2021, the United Nations launched the <a href="https://www.decadeonrestoration.org/">U.N. Decade on Ecosystem Restoration</a> to promote such efforts worldwide.</p>
<p>Native plants have many features that make them an essential part of healthy ecosystems. For example, they provide long-term defense against invasive and noxious weeds; shelter local pollinators and wildlife; and have <a href="https://www.nps.gov/articles/000/reducing-erosion-with-native-plants.htm">roots that stabilize soil</a>, which helps reduce erosion.</p>
<p>Restoration projects require vast quantities of native seeds – but commercial supplies fall far short of what’s needed. Developing a batch of seeds for a specific species takes skill and several years of lead time to either <a href="https://nap.nationalacademies.org/read/26618/chapter/2#2">collect native seeds in the wild or grow plants to produce them</a>. Suppliers say one of their biggest obstacles is unpredictable demand from large-scale customers, such as government and tribal agencies, that don’t plan far enough ahead for producers to have stocks ready.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dozens of small potted seedlings sprouting in large trays." src="https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517737/original/file-20230327-1159-1tiu2v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Wyoming Big Sage seedlings growing in a greenhouse. The U.S. Bureau of Land Management and the Shoshone-Paiute Tribe are working together to produce native seedlings to restore public lands in Idaho that have been damaged by wildfires.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/xkGQ6Q">Bureau of Land Management Idaho/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Restoring roadsides in New England</h2>
<p>Most drivers give little thought to what grows next to highways, but the wrong plants in these areas can cause serious problems. Roadsides that aren’t replanted using ecological restoration methods may erode and be taken over by invasive weeds. Ecological restoration provides effective erosion control and better habitat habitats for wildlife and pollinators. It’s also more attractive. </p>
<p>For decades, state transportation departments across the U.S. used non-native cool-season turfgrasses, such as fescue and ryegrass, to restore roadsides. The main benefits of using these species, which grow well during the <a href="https://extension.psu.edu/the-cool-season-turfgrasses-basic-structures-growth-and-development">cooler months of spring and fall</a>, were that they grew fast and provided a quick cover.</p>
<p>Then in 2013 the <a href="https://www.newenglandtransportationconsortium.org/">New England Transportation Consortium</a> – a research cooperative funded by state transportation agencies – commissioned our research team to help the states transition to native warm-season grasses instead. These grasses <a href="https://extension.psu.edu/warm-season-grasses">grow well in hot, dry weather</a> and need less moisture than cool-season grasses. One of us, John Campanelli, developed the <a href="https://nenativeplants.psla.uconn.edu/wp-content/uploads/sites/3415/2022/08/netcr97_09-2.pdf">framework for selecting plant species</a> based on conservation practices and identified methods for establishing native plant communities for the region.</p>
<p>We recommended using warm-season grasses that are native to the region, such as <a href="https://gobotany.nativeplanttrust.org/species/schizachyrium/scoparium/">little bluestem</a>, <a href="https://gobotany.nativeplanttrust.org/species/eragrostis/spectabilis/">purple lovegrass</a>, <a href="https://plantfinder.nativeplanttrust.org/plant/Panicum-virgatum">switchgrass</a> and <a href="https://gobotany.nativeplanttrust.org/species/tridens/flavus/">purpletop</a>. These species required less long-term maintenance and less-frequent mowing than the cool-season species that agencies had previously used. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dense tall switchgrass plot with some leaves turning red." src="https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517743/original/file-20230327-24-1vtcmc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Switchgrass is native to the U.S. Northeast. It grows very upright, can tolerate dry soil and drought, and produces seeds that are a good winter food source for birds.</span>
<span class="attribution"><a class="source" href="https://extension.unh.edu/blog/2021/02/what-are-some-best-native-ornamental-grasses-landscapes">Peganum via University of New Hampshire Extension</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>To ensure sound conservation practices, we wanted to use seeds produced locally. Seeds sourced from other locations would produce grasses that would interbreed with <a href="https://www.environment.fhwa.dot.gov/env_topics/ecosystems/roadside_use/vegmgmt_rdsduse18.aspx#">local ecotypes</a> – grasses adapted to New England – and disrupt the local grasses’ gene complexes. </p>
<p>At that time, however, there was no reliable seed supply for local ecotypes in New England. Only a few sources offered an incomplete selection of small quantities of local seeds, at prices that were too expensive for large-scale restoration projects. Most organizations carrying out ecological restoration projects purchased their bulk seeds mainly from large wholesale producers in the Midwest, which introduced non-local genetic material to the restoration sites.</p>
<h2>Improving native seed supply chains</h2>
<p>Many agencies are concerned that lack of a local seed supply could limit restoration efforts in New England. To tackle this problem, our team launched a project in 2022 with funding from the New England Transportation Consortium. Our goals are to increase native plantings and pollinator habitats with seeds from local ecotypes, and to make our previous recommendations for roadside restoration with native grasses more feasible.</p>
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<p>As we were analyzing ways to obtain affordable native seeds for these roadside projects, we learned about work by <a href="https://www.linkedin.com/in/eve-allen-b84a38188/">Eve Allen</a>, a master’s degree student in city planning at the Massachusetts Institute of Technology. For her thesis, Allen used supply chain management and social network analysis to identify the best methods to <a href="https://dspace.mit.edu/handle/1721.1/145170">strengthen the native seed supply chain network</a>. </p>
<p>Her research showed that developing native seed supplies would require cooperative partnerships that included federal, state and local government agencies and the private and nonprofit sectors. Allen reached out to many of these organizations’ stakeholders and established a broad network. This led to the launch of the regional Northeast Seed Network, which will be hosted by the Massachusetts-based <a href="https://www.nativeplanttrust.org/documents/1063/221027_Symposium_PR.pdf">Native Plant Trust</a>, a nonprofit that works to conserve New England’s native plants. </p>
<p>We expect this network will promote all aspects of native seed production in the region, from collecting seeds in the wild to cultivating plants for seed production, developing regional seed markets and carrying out related research. In the meantime, we are <a href="https://dailycampus.com/2023/02/10/university-of-connecticut-faculty-members-are-working-to-revive-native-plants-on-the-roadside-of-new-england/">developing a road map</a> for new revegetation practices in New England. </p>
<p>We aim to build greater coordination between these agencies and seed producers to promote expanded selections of affordable native seeds and make demand more predictable. Our ultimate goal is to help native plants, bees and butterflies thrive along roads throughout New England.</p><img src="https://counter.theconversation.com/content/199049/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Native plants help damaged landscapes by stabilizing soil, fighting invasive species and sheltering pollinators. Two horticulture experts explain what they’re doing to help develop new seed sources.Julia Kuzovkina, Professor of Horticulture, University of ConnecticutJohn Campanelli, PhD Student in Plant Science and Landscape Architecture, University of ConnecticutLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1956972023-03-17T12:30:17Z2023-03-17T12:30:17ZThose seeds clinging to your hiking socks may be from invasive plants – here’s how to avoid spreading them to new locations<figure><img src="https://images.theconversation.com/files/514780/original/file-20230311-3629-ak0c82.jpg?ixlib=rb-1.1.0&rect=0%2C3%2C2048%2C1529&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">These stowaways can do a lot of damage.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/8sGFmW">Brett L./ Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>With spring settling in across the U.S. and days lengthening, many people are ready to spend more time outside. But after a walk outdoors, have you ever found seeds clinging to your clothes? Lodged in your socks and shoelaces? Perhaps tangled in your pet’s fur? While most of us don’t give these hitchhikers much thought, seeds and burrs may be the first signs of invasive plant spread. </p>
<p>Certain species of non-native invasive plants produce seeds designed to attach to unsuspecting animals or people. Once affixed, these sticky seeds can be carried long distances before they fall off in new environments. With favorable conditions, they can become established quickly and outcompete native plants.</p>
<p>Outdoor recreation has <a href="https://outdoorindustry.org/resource/2022-outdoor-participation-trends-report/#">expanded at a record pace</a> across the U.S. in recent years. Overcrowding in outdoor spaces <a href="https://thetrek.co/examining-impact-overcrowding-hiking-trails/">has many harmful effects</a>, from <a href="https://doi.org/10.1016/S0169-2046(02)00202-5">degrading trails</a> to accelerating the introduction and spread of invasive plants. </p>
<p>As a <a href="https://scholar.google.com/citations?user=nmAblPEAAAAJ&hl=en&oi=ao">recreation ecologist</a> and an avid hiker, I study how people inadvertently spread invasive plants along trails. There are simple things that everyone can do before, during and after going outdoors to avoid picking up plant hitchhikers and help maintain trail systems for others to enjoy. </p>
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<figcaption><span class="caption">Like many states, Iowa is battling dozens of invasive plants.</span></figcaption>
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<h2>Hardy, numerous and adaptable</h2>
<p>Invasive plants are non-native species that can harm <a href="http://dx.doi.org/10.1016/j.ecolind.2019.106020">the environment, human health and the economy</a> when they are introduced into new areas. However, not all non-native plants are invasive. </p>
<p>Plants with invasive capabilities tend to grow quickly, adapt easily to many different environmental conditions, produce seeds in vast quantities and successfully disperse and germinate them. These characteristics enable the plants to spread efficiently to different areas. Many vectors <a href="https://doi.org/10.3897/natureconservation.24.20607">help invasive plants disperse</a>, including birds, animals, wind, water and humans, via clothing, shoes, pets, gear and vehicles.</p>
<p>Invasive plant seeds tend to be small in size, high in number and hardy. They can persist in soil for many years, remaining viable and ready to germinate when conditions are right.</p>
<p>These seeds will usually germinate earlier in spring than those of native plants and keep their leaves until late fall, crowding out and outcompeting native varieties. Each species produces seeds on a particular schedule – annual, biennial or perennial – and at a specific time. For example, invasive biennial <a href="https://doi.org/10.1890/08-0845.1">garlic mustard</a> releases seeds every two years in late spring. </p>
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<h2>No cheap solutions</h2>
<p>Invasive plants have many harmful ecological impacts. One of the <a href="https://doi.org/10.1080/07352680490505150">most familiar U.S. examples is kudzu</a>, a climbing vine that has smothered trees across the Southeast. </p>
<p>Kudzu grows prolifically, outcompeting native vegetation. It also <a href="https://doi.org/10.1890/ES13-00142.1">alters the nitrogen cycle</a> by increasing soil nitrogen levels and releasing nitric oxide, a gas that reduces air quality and promotes ground-level ozone pollution.</p>
<p>In the western U.S., carpets of <a href="https://theconversation.com/invasive-grasses-are-fueling-wildfires-across-the-us-126574">invasive grasses</a>, such as <a href="https://doi.org/10.1007/s10530-017-1641-8">cheatgrass</a> and <a href="https://www.invasivespeciesinfo.gov/terrestrial/plants/medusahead">medusahead</a>, create highly flammable fine fuels. Their presence makes wildfires more frequent and intense. </p>
<p>Some invasive plants directly threaten human health. <a href="https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/invasive-plants/giant-hogweed/">Giant hogweed</a> is an herb in the carrot family that can grow 15 to 20 feet tall. Its poisonous sap can cause <a href="https://www.fws.gov/story/dont-touch-these-plants">severe skin burns</a>. Others, such as poison hemlock and water hemlock, are highly toxic to humans and animals if consumed.</p>
<p>Managing invasive plants, animals and insects is a growing problem, with costs that <a href="https://doi.org/10.1038/s41586-021-03405-6">run into billions of dollars annually</a>. A 2022 study estimated the annual cost of managing biological invasions in the U.S. at <a href="https://doi.org/10.1016/j.scitotenv.2021.151318">about US$21 billion</a> as of 2020.</p>
<p>Invasives are especially threatening for remote, biodiversity-rich places like <a href="https://doi.org/10.1080/17550874.2022.2144777">Antarctica</a>, where remoteness and geographic isolation <a href="https://www.pnas.org/doi/10.1073/pnas.1804179115">promote endemic species</a> – those only found in a particular geographic region. These endemics evolve in the absence of natural competitors and predators, so introducing invasives can have catastrophic consequences. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hiker's feet, with muddy gaiters zipped over shoes." src="https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=587&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=587&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=587&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fastening gaiters over hiking shoes is an effective way to keep invasive seeds from attaching.</span>
<span class="attribution"><span class="source">Megan Dolman</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Recreational trails act as corridors</h2>
<p>Many invasive plants thrive on disturbed soil. Decades of research has shown that recreational trails promote the introduction of invasive plant species into natural and protected areas, including <a href="https://doi.org/10.1002/eap.2239">national parks</a> and national scenic trails like the <a href="https://www.nps.gov/appa/index.htm">Appalachian Trail</a>.</p>
<p>The Appalachian Trail is the longest hiking-only footpath in the world, extending almost 2,200 miles from Georgia to Maine. <a href="https://appalachiantrail.org/our-work/about-us/media-room/">More than 3 million visitors</a> hike on some portion of it every year. Invasive plants <a href="https://appalachiantrail.org/official-blog/five-common-invasive-species-along-at/">commonly found along the trail</a> include garlic mustard, multiflora rose and purple loosestrife. </p>
<p>In a recent study, I worked with the U.S. Geological Survey to investigate Appalachian Trail hikers’ <a href="https://doi.org/10.1016/j.jort.2022.100581">invasive plant knowledge, perceptions, and behaviors</a>. We found that most hikers were unaware of this issue. As a result, few took precautions to avoid contributing to it.</p>
<p>Here are things that concerned hikers can do to help manage invasive plants:</p>
<p>– <a href="https://www.invasivespeciesinfo.gov/species-type">Identify</a> and <a href="https://www.invasivespeciesinfo.gov/subject/reporting">report</a> sightings of invasive plants. The more land managers know about where these species are present, the more effectively they can monitor and manage their spread. </p>
<p>– <a href="https://www.invasivespeciesinfo.gov/type/smartphone-applications">Smartphone apps</a>, like Early Detection & Distribution Mapping System <a href="https://www.eddmaps.org/">EDDMapS</a>, <a href="https://www.inaturalist.org/">iNaturalist</a> and <a href="https://wildspotter.org/">Wild Spotter</a>, make this task easier. Or you can <a href="https://www.invasive.org/report.cfm">search and report by state</a>. Simply take a picture and identify and report when and where you see invasives. </p>
<p>– Arrive with clean gear. Cleaning shoes, clothing and equipment before and after going outdoors is one of the most effective ways to minimize invasive plant introduction and spread. The <a href="https://naisma.org/">North American Invasive Species Management Association</a>’s <a href="https://playcleango.org/">PlayCleanGo</a> campaign has installed <a href="https://playcleango.org/2021/08/12/boot-brush-stations-are-they-effective/">boot brush stations at trailheads</a> to remove <a href="https://doi.org/10.1080/14486563.2020.1838352">seeds lodged in boot treads</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sign above a metal brush directs hikers to clean their boots." src="https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A boot cleaning station at a Hawaii trailhead.</span>
<span class="attribution"><span class="source">Megan Dolman</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>– Choose clothing and shoes carefully. Certain surfaces, such as uncovered socks, shoelaces, fleece and Velcro, are <a href="https://doi.org/10.1016/j.jenvman.2009.08.002">more seed-friendly</a> than smoother materials such as nylon. Wearing pants that are uncuffed and pocketless to minimize snag points and fastening gaiters over shoes are easy ways to repel plant hitchhikers. Gaiters will also keep pebbles and mud out of your boots.</p>
<p>– Follow the <a href="https://lnt.org/why/7-principles/">Leave No Trace principles</a>, which outline minimum-impact strategies for visiting the outdoors. For example, stick to marked formal trails to avoid dispersing invasive plants off-trail. Camp on designated or well-established campsites, and don’t transport firewood between sites – use certified or local firewood and hay. Clean your pets and vehicles as well as your clothes before and after hitting the trail. </p>
<p>People who want to do more to protect the outdoors can take a <a href="https://lnt.org/courses/online_awareness_take_action_html5/#/">free Leave No Trace online course</a> and take the <a href="https://playcleango.org/take-action/take-pledge/">PlayCleanGo Pledge</a> to make a difference with their actions.</p><img src="https://counter.theconversation.com/content/195697/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Megan Dolman has received travel funding from the School of Geography and the Environment and Brasenose College, University of Oxford. </span></em></p>Invasive species cause billions of dollars in damage across the US every year. Hikers and backpackers can take simple steps to avoid spreading seeds and making the problem worse.Megan Dolman, PhD candidate in Ecology, Evolution and Behavior, Boise State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1987242023-03-08T13:40:36Z2023-03-08T13:40:36ZOnce the Callery pear tree was landscapers’ favorite – now states are banning this invasive species and urging homeowners to cut it down<figure><img src="https://images.theconversation.com/files/513447/original/file-20230303-16-jjphd6.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C1933%2C1283&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Bradford pear trees in bloom along a driveway in Sussex County, Del.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/9xfPoK">Lee Cannon/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>When people think of spring, they often picture flowers and trees blooming. And if you live in the U.S. Northeast, Midwest or South, you have probably seen a medium-sized tree with long branches, covered with small white blooms – the Callery pear (<em>Pyrus calleryana</em>). </p>
<p>For decades, Callery pear – which comes in many varieties, including “Bradford” pear, “Aristocrat” and “Cleveland Select” – was among the most popular trees in the U.S. for ornamental plantings. Today, however, it’s widely recognized as an <a href="https://www.govinfo.gov/content/pkg/FR-1999-02-08/pdf/99-3184.pdf">invasive species</a>. Land managers and plant ecologists <a href="https://scholar.google.com/citations?user=uRA-SZ0AAAAJ&hl=en&oi=sra">like me</a> are working to eradicate it to preserve biodiversity in natural habitats. </p>
<p>As of 2023, it is illegal to <a href="https://ohiodnr.gov/discover-and-learn/plants-trees/invasive-plants/callery-pear">sell, plant or grow Callery pear</a> in Ohio and <a href="https://www.agriculture.pa.gov/Plants_Land_Water/PlantIndustry/NIPPP/Pages/Callery-Pear.aspx">Pennsylvania</a>, and will become illegal in <a href="https://news.clemson.edu/invasive-bradford-pear-3-other-species-to-be-banned-for-sale-in-sc/">South Carolina</a> on October 1, 2024. <a href="https://news.ncsu.edu/2022/03/bounty-offered-on-bradford-pear-trees/">North Carolina</a> and <a href="https://www.lakeexpo.com/community/community_news/cut-down-your-bradford-pear-and-missouri-conservation-will-send-you-a-free-tree/article_df77978a-b51a-11ec-ab85-b39d20e73240.html">Missouri</a> will give residents free native trees if they cut down Callery pear trees on their property. </p>
<p>How did this tree, once in high demand, become designated by the U.S. Forest Service as “<a href="https://www.invasive.org/weedcd/pdfs/wow/callery_pear.pdf">Weed of the Week</a>”? The devil is in the biological details.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/txwrZ1CqzrE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A Kentucky extension specialist explains why Callery pears initially seemed like a solution, but have proved to be a major problem.</span></figcaption>
</figure>
<h2>A quasi-perfect tree</h2>
<p>Botanists brought the Callery pear to the U.S. from Asia <a href="https://arboretum.harvard.edu/stories/the-rise-and-fall-of-the-ornamental-callery-pear-tree/">in the early 1900s</a>. They intentionally bred the horticultural variety to enhance its ornamental qualities. In doing so, they created an arboricultural wunderkind. As The New York Times <a href="https://www.nytimes.com/1964/01/05/archives/bradford-pear-has-many-assets-new-ornamental-fruit-offers-sturdy.html">observed in 1964</a>: </p>
<blockquote>
<p>“Few trees possess every desired attribute, but the Bradford ornamental pear comes unusually to close to the ideal.”</p>
</blockquote>
<p>Modern varieties of Callery pear produce an explosion of white flowers in springtime, followed by deep green summer foliage that turns deep red and maroon in autumn. They also are very tolerant of urban soils, which can be <a href="https://arboretum.harvard.edu/stories/urban-soil-problems-and-promise/">highly compacted</a> and hard for roots to penetrate. The trees grow quickly and have a rounded shape, which made them suitable for planting in rows along driveways and roadsides.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Tree with leaves mostly shaded red." src="https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510742/original/file-20230216-22-hkyqya.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A Callery pear turning red in fall.</span>
<span class="attribution"><span class="source">Ryan McEwan</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>During the post-World War II suburban development boom, Callery pear trees became extremely popular in residential settings. In 2005 the Society of Municipal Arborists named the “Chanticleer” variety the <a href="https://www.concreteconstruction.net/projects/infrastructure/arborists-select-urban-tree-of-the-year_o">urban street tree of the year</a>. But the breeding process that created this and other varieties of Callery pear was producing unexpected results.</p>
<h2>Cloning to produce an American original</h2>
<p>To ensure that each Callery pear tree had bright blooms, red foliage and other desired traits, horticulturists created identical clones through <a href="https://www.britannica.com/topic/graft">a process known as grafting</a>: creating seedlings from cuttings of trees with the desired characteristics. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/LTqG8-OhElY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Grafting is a method for propagating new fruit trees using buds from existing trees and fusing them onto a branch or stem of another tree, which is called the rootstock.</span></figcaption>
</figure>
<p>This approach eliminated the messy complexity of mixing genes during sexual reproduction and ensured that when each tree matured, it would have the characteristics that homeowners desire. Every tree of a specific variety was a genetically identical clone.</p>
<p>Grafting also meant Callery pear trees could not make fruits. Some fruit trees, such as peaches and tart cherries, can <a href="https://extension.umaine.edu/fruit/growing-fruit-trees-in-maine/pollination-requirements/">fertilize their flowers with their own pollen</a>. In contrast, Callery pear is self-incompatible: pollen on an individual tree cannot fertilize flowers on that tree. And since all Callery pears of a specific variety planted in a neighborhood would be identical clones, they would effectively be the same tree. </p>
<p>If a tree can’t produce fruits, it can’t disperse into natural habitats. Gardeners and landscapers thought it was perfectly safe to plant Callery pear near natural habitats, such as prairies, because the species was trapped in place by its reproductive biology. But the tree would break free from its isolation and spread seeds far and wide.</p>
<h2>The great escape</h2>
<p>University of Cincinnati botanist <a href="https://culleylab.com/home-page/members-lab/theresa-culley-pi/">Theresa Culley</a> and colleagues have found that as horticulturalists tinkered with Callery pears to produce new versions, they made the individuals different enough <a href="https://doi.org/10.1007/s10530-008-9386-z">to escape the fertilization barrier</a>. If a neighborhood had only “Bradford” pear trees, then no fruits could be produced – but once someone added an “Aristocrat” pear to their yard, then these two varieties could fertilize each other and produce fruits. </p>
<p>When Callery pear trees in gardens and parks started depositing seeds in nearby areas, wild populations of the trees became established. Those wild trees could pollinate one another, as well as neighborhood trees. </p>
<p>In today’s landscape, Callery pear is astonishingly fertile. The prolific flowering that horticulturists intentionally bred into these varieties now yields tremendous crops of pears each year. Although these little pears are generally not edible by humans, birds feed on the fruit, then fly away and excrete the seeds into natural habitats. Callery pear has become one of the <a href="https://www.fws.gov/program/invasive-species">most problematic invasive species</a> in the eastern United States. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1628379085364957184"}"></div></p>
<h2>A thorny problem</h2>
<p>Like other invasives, Callery pears crowd out native species. Once Callery pear seedlings <a href="https://doi.org/10.1007/s10530-022-02861-z">spread from habitat edges into grasslands</a>, they have advantages that allow them to dominate the site. </p>
<p>In <a href="https://mcewanlab.org/">my research lab</a>, we have found that Callery pear leafs out very early in spring and drops its leaves late in fall. This enables it to <a href="https://doi.org/10.3159/TORREY-D-22-00008.1">soak up more sun than native species</a>. We also have discovered that during invasion, these trees <a href="https://doi.org/10.1016/j.apsoil.2021.103989">alter the soil</a> and release chemicals that suppress the germination of native plants. </p>
<p>Callery pear is highly resistant to natural disturbances. In fact, when <a href="https://www.linkedin.com/in/meg-maloney-51b22b112/">my graduate student Meg Maloney</a> tried to kill the trees by using <a href="https://www.youtube.com/shorts/AeaEsDTnMLw">prescribed fires</a> or applying <a href="https://www.youtube.com/shorts/wtkMey4IItE">liquid nitrogen</a> directly to stumps after cutting the trees down, her efforts failed. Instead, the trees sprouted aggressively and <a href="https://muse.jhu.edu/article/883911#info_wrap">seemingly gained strength</a>.</p>
<p>Once Callery pear has escaped into natural areas, its seedlings produce <a href="https://doi.org/10.21273/HORTTECH04892-21">very sharp, stiff thorns</a> that can puncture shoes or even tires. This makes the trees a menace to people working in the area, as well as to native plants. Another nuisance factor is that when Callery pears bloom, they produce a <a href="https://www.npr.org/2015/04/24/401943000/whats-that-smell-the-beautiful-tree-thats-causing-quite-a-stink">strong odor</a> that many people find unpleasant.</p>
<p>Currently, <a href="https://www.invasive.org/alien/pubs/midatlantic/pyca.htm">directly applying herbicides</a> is the only known control for a Callery pear invasion. But the trees are so successful at spreading that poisoning their seedlings may simply create space for other Callery pear seedlings to establish. It is unclear how habitat managers can escape a confounding ecological cycle of invasion, herbicide application and re-invasion.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An open space studded with Callery pear trees, with dead grasses between the trees." src="https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513473/original/file-20230304-14-ct0blo.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A Callery pear invasion is crowding out native species on this agricultural land, converting it to woodland.</span>
<span class="attribution"><a class="source" href="https://extension.okstate.edu/fact-sheets/the-invasive-callery-pear.html">Oklahoma State University Extension</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Banned but not gone</h2>
<p>In response to work by the <a href="https://www.oipc.info/">Ohio Invasive Plants Council</a> and other experts, Ohio has taken the extraordinary step of <a href="https://codes.ohio.gov/ohio-administrative-code/rule-901:5-30-01">banning Callery pear</a> to thwart its ecological invasion into natural habitats. But the trees are common in residential areas across the state and have established vigorous populations in natural habitats. Ecologists will be working well into the future to maintain openness and biodiversity in areas where Callery pear is invading. </p>
<p>In the meantime, homeowners can help. Horticulturists recommend that people who have a Callery pear on their property should <a href="https://dyckarboretum.org/callery-pear-cut-them-down/">remove it and replace it</a> with something that is not an invasive species. Few trees possess every desired attribute, but many <a href="https://moinvasives.org/2018/03/29/plant-this-not-that-10-native-trees-to-plant-in-place-of-callery-pear/">native trees</a> have visually attractive features and will not threaten ecosystems in your region.</p>
<p><em>This article has been updated to reflect current state bans on Callery pear trees as of March 2024.</em></p><img src="https://counter.theconversation.com/content/198724/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ryan W. McEwan does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>They’re beautiful in bloom, but Callery pear trees crowd out native plants and turn productive open land into woody thickets.Ryan W. McEwan, Professor of Biology, University of DaytonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1824262022-05-04T19:09:46Z2022-05-04T19:09:46ZThe Southwest is on fire, with iconic deserts and towns at risk – 3 reasons the 2022 fire season is so early and intense<figure><img src="https://images.theconversation.com/files/461364/original/file-20220504-23-cykjgs.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2000%2C1332&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Wind quickly spread a blaze that burned homes near Flagstaff, Ariz., in April 2022.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/WesternWildfires/f34e271189d54ce4b1b632e499d4a67c/photo">Coconino National Forest via AP</a></span></figcaption></figure><p><em>New Mexico and Arizona are facing a dangerously early fire season. It has left neighborhoods in ashes and is having such devastating effects that <a href="https://www.whitehouse.gov/briefing-room/statements-releases/2022/05/04/president-joseph-r-biden-jr-approves-new-mexico-disaster-declaration/">President Joe Biden issued a disaster declaration</a> for New Mexico. Over <a href="https://gacc.nifc.gov/swcc/predictive/intelligence/daily/UPLOAD_Files_toSWCC/YTD_10_INFORM_2_STATE.pdf">600 fires</a> had broken out in the two states by early May, and large wildfires had burned through hundreds of homes near Ruidoso and Las Vegas, New Mexico, and Flagstaff, Arizona.</em></p>
<p><em>We asked wildfire scientist <a href="https://www.researchgate.net/profile/Molly-Hunter-4">Molly Hunter</a> at the University of Arizona to explain what’s fueling the extreme fire conditions and why risky seasons like this are becoming more common.</em></p>
<h2>Why is this year’s wildfire season in the Southwest so early and intense?</h2>
<p>Historically, fire season in the Southwest didn’t ramp up until late May or June, because fuels that carry fires – primarily woody debris, leaf litter and dead grasses – didn’t fully dry out until then.</p>
<p>Now, the Southwest is seeing more <a href="https://medialibrary.climatecentral.org/resources/western-fire-weather-days-increasing">fires start much earlier</a> in the year. The earlier fire season is <a href="https://nca2014.globalchange.gov/report/regions/southwest">partly due to the warming climate</a>. As temperatures rise, the snow melts more rapidly, more water evaporates into the atmosphere and the grasses and other fuels dry out earlier in the season.</p>
<p>Unfortunately, the earlier timing coincides with when the region commonly experiences <a href="https://www.weather.gov/abq/features_highwind">strong winds</a> that can drive rapid fire growth. Some of the fires we’re seeing this year, like the <a href="https://www.azcentral.com/story/news/local/arizona-wildfires/2022/04/23/tunnel-fire-destroys-30-homes-displaces-families-near-flagstaff/7417799001/">Tunnel Fire</a> near Flagstaff and the fires in New Mexico, are being driven by these really intense wind events. They’re pretty typical winds for spring, but fuels are now really dry and ready to burn.</p>
<figure class="align-center ">
<img alt="Two fire crew members use axes to chop at burning roots on a charred desert landscape." src="https://images.theconversation.com/files/461369/original/file-20220504-21-3br94n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461369/original/file-20220504-21-3br94n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461369/original/file-20220504-21-3br94n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461369/original/file-20220504-21-3br94n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461369/original/file-20220504-21-3br94n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461369/original/file-20220504-21-3br94n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461369/original/file-20220504-21-3br94n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fire crews dig at burning roots in the wake of a fire near Flagstaff, Ariz., in April 2022.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/WesternWildfires/df543b966a4a4115b5e81d2d8dd9a8d4/photo?">Tom Story/Northern Arizona Type 3 Incident Management Team, via AP</a></span>
</figcaption>
</figure>
<p>This year we also have a lot of fuel to burn. Last summer, in 2021, the Southwest had an <a href="https://www.weather.gov/psr/2021MonsoonReview">exceptional monsoon season</a> that left green hillsides and lots of vegetation. By now the grasses and <a href="https://www.usgs.gov/publications/desert-fires-fueled-native-annual-forbs-effects-fire-communities-plants-and-birds-0">forbs</a> that established during the monsoon have dried out, leaving a lot of biomass that can carry a fire. Often in the Southwest, our biggest fire years come when we have a wet period followed by a dry period, like the <a href="https://www.climate.gov/news-features/blogs/enso/april-2022-la-ni%C3%B1a-update-measuring">La Niña conditions</a> we’re experiencing now.</p>
<h2>What role does climate change play?</h2>
<p>In the Southwest, <a href="https://nca2018.globalchange.gov/chapter/25/">climate change</a> has meant warmer, drier conditions. One immediate effect is the lengthening of the fire season. </p>
<p>We now see fires starting in March and April. And if the Southwest doesn’t get a good summer monsoon – the region’s typical period of heavy rainstorms – fire season won’t really stop until we get significant rainfall or snowfall in fall and winter. That means more stress on firefighting resources, and more stress on communities facing fire, smoke and evacuations.</p>
<p>As fire season lengthens, states are also seeing more fires caused by human activities, such as fireworks, sparks from vehicles or equipment, and power lines. <a href="https://theconversation.com/the-fastest-population-growth-in-the-wests-wildland-urban-interface-is-in-areas-most-vulnerable-to-wildfires-173410">More people are moving</a> out into areas that are fire-prone, creating more opportunities for human-caused ignitions.</p>
<figure class="align-center ">
<img alt="Satellite images shows fires burning near Las Vegas, New Mexico, and Los Alamos." src="https://images.theconversation.com/files/461282/original/file-20220504-12-2aqu7w.jpg?ixlib=rb-1.1.0&rect=284%2C220%2C2074%2C1455&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461282/original/file-20220504-12-2aqu7w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461282/original/file-20220504-12-2aqu7w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461282/original/file-20220504-12-2aqu7w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461282/original/file-20220504-12-2aqu7w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461282/original/file-20220504-12-2aqu7w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461282/original/file-20220504-12-2aqu7w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">By May 4, nearly a quarter-million acres had burned in New Mexico, almost double the state’s 2021 total. Fires shown by satellite and on the map below are near Los Alamos and Las Vegas, N.M.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/149784/wildfires-continue-to-burn-across-new-mexico">NASA</a></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing several large fires around Santa Fe, New Mexico, including in the town of Las Vegas, New Mexico" src="https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=432&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=432&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461286/original/file-20220504-15-8yietu.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=432&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="source" href="https://maps.nwcg.gov/sa/#/%3F/%3F/35.8912/-105.4675/9">National Interagency Fire Center</a></span>
</figcaption>
</figure>
<h2>What effect is the changing fire regime having on the Southwest’s ecosystems?</h2>
<p>When fires burn in areas that didn’t see fire historically, they can transform ecosystems.</p>
<p>People generally don’t think of fire as being a natural part of desert ecosystems, but <a href="https://www.pnas.org/doi/10.1073/pnas.1908253116">grasses are now fueling really big fires</a> in the desert, like Arizona’s <a href="https://www.azcentral.com/picture-gallery/news/local/arizona/2021/06/06/photos-telegraph-fire-burns-tonto-national-forest/7574130002/">Telegraph Fire</a> in 2021. These fires are also spreading farther, and into different ecosystems. The Telegraph Fire started in a desert system, then burned through chaparral and into the mountains, with pine and conifer forest.</p>
<p>Part of the problem is <a href="https://www.pnas.org/doi/10.1073/pnas.1908253116">invasive grasses like buffelgrass and red brome</a> that spread quickly and burn easily. A lot of grass is <a href="https://www.azmirror.com/2019/11/18/arizona-buffelgrass-invasive-grass-a-wildfire-threat-to-sonoran-desert/">now growing in those desert systems</a>, making them more prone to wildfire.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zBi354Q4RuE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Invasive buffelgrass is a threat to desert ecosystems and communities.</span></figcaption>
</figure>
<p>When a fire spreads in the desert, some plant species, like mesquite and other brushy plants, can survive. But the saguaro – the iconic cactuses that are so popular in tourist visions of the Southwest – are <a href="https://www.fs.usda.gov/treesearch/pubs/44459">not well adapted to fire</a>, and they often die when exposed to fire. Paloverde trees are <a href="https://www.fs.fed.us/database/feis/plants/shrub/parmic/all.html">also not well adapted</a> to survive fires.</p>
<p>What does comes back quickly is the grasses, both native and invasive. So in some areas we’re seeing a transition from desert ecosystem to a <a href="https://www.tucsonweekly.com/tucson/summer-invaders-increased-fire-risk-threatens-all-inhabitants-of-the-sonoran-desert/Content?oid=30607881">grassland ecosystem</a> that is very conducive to the spread of fire. </p>
<p>The <a href="http://azfiretracker.azcentral.com/mostsignificant-cavecreekcomplex.html">Cave Creek Fire</a> near Phoenix in 2005 is an example where you can see this transition. It burned over 240,000 acres, and if you drive around that area now, you don’t see lot of saguaros. It doesn’t look like desert. It looks like more like annual grassland. </p>
<p>This is an iconic landscape, so the loss affects tourism. It affects wildlife as well. A lot of <a href="https://www.nps.gov/sagu/learn/nature/saguaros_animals.htm">species rely on saguaro</a> for nesting and feeding. <a href="https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/lesser_long-nosed_bat.shtml">Bats rely on the flowers</a> for nectar.</p>
<h2>What can be done to avoid high fire risk in the future?</h2>
<p>In some respects, people will have to recognize that fire is inevitable.</p>
<p>Fires quickly now surpass our capacity to control them. When winds are strong and the fuels are really dry, there’s only so much firefighters can do to prevent some of these big fires from spreading.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man throws a large log , just cut down, as he and other clear a fire line." src="https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461372/original/file-20220504-12-76ggpg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">People clear trees from around a home as a fire threatens Las Vegas, N.M., on May 2, 2022.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/APTOPIXSpringWildfires/dc1a60758fcf48bfab4f24c1b2c3cc03/photo">AP Photo/Cedar Attanasio</a></span>
</figcaption>
</figure>
<p>Conducting more <a href="https://www.fs.usda.gov/managing-land/prescribed-fire">prescribed fires</a> to clear out potential fuel is one important way to lessen the probability of really big, destructive blazes. </p>
<p>Historically, far more money went into fighting fires than managing the fuels with tactics like thinning and prescribed fire, but the <a href="https://www.doi.gov/wildlandfire/meet-bil-how-bipartisan-infrastructure-law-supports-wildland-fire-management">infrastructure bill</a> signed in 2021 included a huge influx of funding for fuels management. There’s also a push to move some seasonal fire crew jobs to full-time, yearlong positions to conduct thinning and prescribed burns.</p>
<p>Homeowners can also <a href="https://theconversation.com/how-to-build-wildfire-resistant-communities-in-a-warming-world-174582">be better prepared to live with fires</a>. That means maintaining yards and homes by removing debris so they’re less likely to burn. It also means being prepared to evacuate.</p>
<p><em>This article was updated May 5 with Biden issuing the disaster declaration.</em></p><img src="https://counter.theconversation.com/content/182426/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Molly Hunter has received funding from the Bureau of Land Management, National Park Service, U.S. Geological Survey, and U.S. Forest Service. </span></em></p>Fire season is getting longer, and the result is transforming iconic desert ecosystems. The start to 2022 has been so dire, one governor called for a federal disaster declaration.Molly Hunter, Associate Research Professor in Environment and Natural Resources, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1649692021-07-29T19:59:09Z2021-07-29T19:59:09ZPest plants and animals cost Australia around $25 billion a year – and it will get worse<figure><img src="https://images.theconversation.com/files/413674/original/file-20210729-23-1xua4jp.jpg?ixlib=rb-1.1.0&rect=63%2C197%2C4185%2C2624&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">AAP</span></span></figcaption></figure><p>Shamefully, Australia has one of the <a href="https://theconversation.com/australias-threatened-species-plan-has-failed-on-several-counts-without-change-more-extinctions-are-assured-163434">highest extinction rates</a> in the world.
And the <a href="https://theconversation.com/invasive-species-are-australias-number-one-extinction-threat-116809">number one</a> threat to our species is invasive or “alien” plants and animals. </p>
<p>But invasive species don’t just cause extinctions and biodiversity loss – they also create a serious economic burden. Our <a href="http://doi.org/10.3897/neobiota.67.58834">research</a>, published today, reveals invasive species have cost the Australian economy at least A$390 billion in the last 60 years alone. </p>
<p>Our paper – the most detailed assessment of its type ever published in this country – also reveals feral cats are the worst invasive species in terms of total costs, followed by rabbits and fire ants.</p>
<p>Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Feral cats are Australia’s costliest invasive species.</span>
<span class="attribution"><span class="source">Adobe Stock/240188862</span></span>
</figcaption>
</figure>
<h2>Huge economic burden</h2>
<p>Invasive species are those not native to a particular ecosystem. They are introduced either by accident or on purpose and become pests.</p>
<p>Some costs involve direct damage to agriculture, such as insects or fungi destroying fruit. Other examples include measures to control invasive species like feral cats and cane toads, such as paying field staff and buying fuel, ammunition, traps and poisons.</p>
<p>Our previous research put the global cost of invasive species at <a href="https://theconversation.com/attack-of-the-alien-invaders-pest-plants-and-animals-leave-a-frightening-1-7-trillion-bill-158628">A$1.7 trillion</a>. But this is most certainly a gross underestimate because so many data are missing.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/attack-of-the-alien-invaders-pest-plants-and-animals-leave-a-frightening-1-7-trillion-bill-158628">Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill</a>
</strong>
</em>
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<hr>
<p>As a wealthy nation, Australia has accumulated more reliable cost data than most other regions. These costs have increased exponentially over time – up to sixfold each decade since the 1970s.</p>
<p>We found invasive species now cost Australia around A$24.5 billion a year, or an average 1.26% of the nation’s <a href="https://www.abs.gov.au/statistics/economy/key-indicators">gross domestic product</a>. The costs total at least A$390 billion in the past 60 years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Increase in annual costs of invasive species in Australia from 1960 to 2020. The predicted range for 2020 is shown in the upper left quadrant. Note the logarithmic scale of the vertical axis.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<h2>Worst of the worst</h2>
<p>Our analysis found feral cats have been the most economically costly species since 1960. Their A$18.7 billion bill is mainly associated with attempts to control their abundance and access, such as fencing, trapping, baiting and shooting.</p>
<p>Feral cats are a <a href="https://theconversation.com/australia-must-control-its-killer-cat-problem-a-major-new-report-explains-how-but-doesnt-go-far-enough-154931">main driver</a> of extinctions in Australia, and so perhaps investment to limit their damage is worth the price tag.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tasmania’s bane — ragwort (<em>Senecio jacobaea</em>)</span>
<span class="attribution"><span class="source">Adobe Stock/157770032</span></span>
</figcaption>
</figure>
<p>As a group, the management and control of invasive plants proved the worst of all, collectively costing about A$200 billion. Of these, <a href="https://www.agric.wa.gov.au/grains-research-development/annual-ryegrass">annual ryegrass</a>, <a href="https://weeds.dpi.nsw.gov.au/Weeds/PartheniumWeed">parthenium</a> and <a href="https://dpipwe.tas.gov.au/invasive-species/weeds/weeds-index/declared-weeds-index/ragwort">ragwort</a> were the costliest culprits because of the great effort needed to eradicate them from croplands.</p>
<p>Invasive mammals were the next biggest burdens, costing Australia A$63 billion.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The 10 costliest invasive species in Australia.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<h2>Variation across regions</h2>
<p>For costs that can be attributed to particular states or territories, New South Wales had the highest costs, followed by Western Australia then Victoria.</p>
<p><a href="https://www.daf.qld.gov.au/business-priorities/biosecurity/invasive-plants-animals/ants/fire-ants">Red imported fire ants</a> are the costliest species in Queensland, and ragwort is the economic bane of Tasmania. </p>
<p>The <a href="https://weedsofmelbourne.org/common-heliotrope-or-potato-weed-heliotropium-europaeum">common heliotrope</a> is the costliest species in both South Australia and Victoria, and annual ryegrass tops the list in WA. </p>
<p>In the Northern Territory, the <a href="https://dothideomycetes.org">dothideomycete</a> fungus that causes <a href="https://nt.gov.au/industry/agriculture/food-crops-plants-and-quarantine/banana-freckle">banana freckle disease</a> brings the greatest economic burden, whereas cats and <a href="https://www.environment.nsw.gov.au/topics/animals-and-plants/pest-animals-and-weeds/pest-animals/foxes">foxes</a> are the costliest species in the ACT and NSW.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=545&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=545&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=545&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=684&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=684&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=684&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The three costliest species by Australian state/territory.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<h2>Better assessments needed</h2>
<p>Our study is one of 19 region-specific analyses <a href="https://doi.org/10.3897/neobiota.67.69971">released today</a>. Because the message about invasive species must get out to as many people as possible, our article’s abstract was translated into <a href="http://doi.org/10.3897/neobiota.67.58834">24 languages</a>.</p>
<p>This includes <a href="https://omniglot.com/writing/pitjantjatjara.htm">Pitjantjatjara</a>, <a href="https://www.welcometocountry.org/10-most-widely-spoken-aboriginal-languages-in-australia/">a widely spoken Indigenous language</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australias-threatened-species-plan-has-failed-on-several-counts-without-change-more-extinctions-are-assured-163434">Australia’s threatened species plan has failed on several counts. Without change, more extinctions are assured</a>
</strong>
</em>
</p>
<hr>
<p>Even the massive costs we reported are an underestimate. This is because of we haven’t yet surveyed all the places these species occur, and there is a lack of standardised reporting by management authorities and other agencies. </p>
<p>For example, our database lists several fungal plant pathogens. But no cost data exist for some of the worst offenders, such as the widespread <em>Phytophthora cinnamomi</em> pathogen that causes major <a href="https://doi.org/10.1071/BT07159">crop losses and damage to biodiversity</a>.</p>
<p>Developing <a href="https://news.microsoft.com/en-au/features/teaming-up-for-turtles/">better methods</a> to estimate the environmental impacts of invasive species, and the benefit of management actions, will allow us to use limited resources more efficiently.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Phytophthora cinnamomi</em>, a widespread, but largely uncosted, fungal pathogen.</span>
<span class="attribution"><span class="source">Adobe Stock/272252666</span></span>
</figcaption>
</figure>
<h2>A constant threat</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fall armyworm, a major crop pest.</span>
<span class="attribution"><span class="source">Adobe Stock/335450066</span></span>
</figcaption>
</figure>
<p>Many species damaging to <a href="https://www.agriculture.gov.au/pests-diseases-weeds/plant/national-priority-plant-pests-2019">agriculture</a> and the <a href="https://www.agriculture.gov.au/biosecurity/environmental/priority-list">environment</a> are yet to make it to our shores. </p>
<p>The recent arrival in Australia of fall armyworm, <a href="https://www.agriculture.gov.au/pests-diseases-weeds/plant/exotic-armyworm">a major agriculture pest</a>, reminds us how invasive species will <a href="https://doi.org/10.1038/ncomms14435">continue their spread</a> here and elsewhere.</p>
<p>As well as the economic damage, invasive species also bring <a href="https://doi.org/10.1038/ncomms12986">intangible costs</a> we have yet to measure adequately. These include the true extent of ecological damage, human health consequences, erosion of ecosystem services and the loss of cultural values.</p>
<p>Without better data, increased investment, a stronger biosecurity system and interventions such as animal culls, invasive species will continue to wreak havoc across Australia.</p>
<hr>
<p><em>The authors acknowledge the Traditional Owners of the lands on which they did this research.</em></p>
<p><em>Ngadlu tampinthi yalaka ngadlu Kaurna yartangka inparrinthi. Ngadludlu tampinthi, parnaku tuwila yartangka</em>.</p><img src="https://counter.theconversation.com/content/164969/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Corey J. A. Bradshaw receives funding from Australian Research Council. </span></em></p><p class="fine-print"><em><span>Andrew Hoskins receives funding from the Department of Agriculture, Water and the Environment. </span></em></p>Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders UniversityAndrew Hoskins, Research scientist CSIRO Health and Biosecurity, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1586282021-04-18T20:08:08Z2021-04-18T20:08:08ZAttack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill<figure><img src="https://images.theconversation.com/files/395272/original/file-20210415-14-jzhiyk.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C4193%2C2785&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>They’re one of the most <a href="http://ipbes.net">damaging environmental forces</a> on Earth. They’ve colonised pretty much every place humans have set foot on the planet. Yet you might not even know they exist.</p>
<p>We’re talking about alien species. Not little green extraterrestrials, but invasive plants and animals not native to an ecosystem and which become pests. They might be plants from South America, starfish from Africa, insects from Europe or birds from Asia. </p>
<p>These species can threaten the health of plants and animals, including humans. And they cause huge economic harm. <a href="https://www.nature.com/articles/s41586-021-03405-6">Our research</a>, recently published in the journal Nature, puts a figure on that damage. We found that globally, invasive species cost US$1.3 trillion (A$1.7 trillion) in money lost or spent between 1970 and 2017. </p>
<p>The cost is increasing exponentially over time. And troublingly, most of the cost relates to the damage and losses invasive species cause. Meanwhile, far cheaper control and prevention measures are often ignored.</p>
<figure class="align-center ">
<img alt="Yellow crazy ants attacking a gecko" src="https://images.theconversation.com/files/395275/original/file-20210415-15-1pn4p4y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395275/original/file-20210415-15-1pn4p4y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395275/original/file-20210415-15-1pn4p4y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395275/original/file-20210415-15-1pn4p4y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395275/original/file-20210415-15-1pn4p4y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395275/original/file-20210415-15-1pn4p4y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395275/original/file-20210415-15-1pn4p4y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Yellow crazy ants, such as these attacking a gecko, are among thousands of invasive species causing ecological and economic havoc.</span>
<span class="attribution"><span class="source">Dinakarr, CC0, Wikimedia Commons</span></span>
</figcaption>
</figure>
<h2>An expansive toll</h2>
<p>Invasive species have been invading foreign territories for <a href="https://www.nature.com/articles/ncomms14435">centuries</a>. They hail from habitats as diverse as tropical forests, dry savannas, temperate lakes and cold oceans. </p>
<p>They arrived because we brought them — as pets, ornamental plants or as stowaways on our holidays or via <a href="https://theconversation.com/global-trade-increases-exotic-species-incursion-4208">commercial trade</a>. </p>
<p>The problems they cause can be:</p>
<ul>
<li>ecological, such as causing the extinction of native species</li>
<li>human health-related, such as causing allergies and spreading disease</li>
<li>economic, such as reducing crop yields or destroying human-built infrastructure. </li>
</ul>
<p>In Australia, invasive species are one of our <a href="https://www.environment.gov.au/biodiversity/invasive-species/publications/factsheet-invasive-species-australia">most serious</a> environmental problems – and the biggest cause of extinctions.</p>
<p>Feral animals such as rabbits, goats, cattle, pigs and horses can degrade grazing areas and compact soil, damaging farm production. Feral rabbits take over the burrows of native animals, while <a href="https://theconversation.com/one-cat-one-year-110-native-animals-lock-up-your-pet-its-a-killing-machine-138412">feral cats</a> and <a href="https://theconversation.com/is-it-too-late-to-bring-the-red-fox-under-control-11299">foxes</a> hunt and kill native animals.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/invasive-species-are-australias-number-one-extinction-threat-116809">Invasive species are Australia's number-one extinction threat</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394171/original/file-20210409-13-1bznl7v.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Wetlands in the Northern Territory damaged by invasive swamp buffalo (<em>Bubalus bubalis</em>)</span>
<span class="attribution"><span class="source">Warren White</span></span>
</figcaption>
</figure>
<p>Introduced insects, such as <a href="https://theconversation.com/a-tiny-wasp-could-save-christmas-islands-spectacular-red-crabs-from-crazy-ants-69646">yellow crazy ants</a> on Christmas Island, pose a serious threat to a native species. Across Australia, <a href="https://www.environment.gov.au/biodiversity/invasive-species/insects-and-other-invertebrates/invasive-bees">feral honeybees</a> compete with native animals for nectar, pollen and habitat.</p>
<p><a href="https://www.dpi.nsw.gov.au/fishing/aquatic-biosecurity/pests-diseases/freshwater-pests">Invasive fish</a> compete with native species, disturb aquatic vegetation and introduce disease. Some, such as <a href="https://www.environment.nsw.gov.au/topics/animals-and-plants/threatened-species/nsw-threatened-species-scientific-committee/determinations/final-determinations/1996-1999/predation-by-the-plague-minnow-gambusia-holbrooki-key-threatening-process-listing">plague minnows</a>, prey on the eggs and tadpoles of frogs and attack native fish. </p>
<p><a href="http://www.anbg.gov.au/weeds/weeds.html">Environmental weeds</a> and invasive <a href="https://www.environment.gov.au/biodiversity/invasive-species/diseases-fungi-and-parasites">fungi and parasites</a> also cause major damage.</p>
<p>Of course, the problem is global – and examples abound. In Africa’s Lake Victoria, the huge, carnivorous <a href="https://www.invasivespeciesinfo.gov/aquatic/fish-and-other-vertebrates/nile-perch">Nile perch</a> — introduced to boost fisheries – has wiped out <a href="https://link.springer.com/article/10.1007/BF00004782">more than 200</a> of the 300 known species of <a href="https://www.britannica.com/animal/cichlid">cichlid fish</a> — prized by aquarium enthusiasts the world over.</p>
<p>And in the Florida Everglades, thousands of five metre-long <a href="https://doi.org/10.1073/pnas.1115226109">Burmese pythons</a> have gobbled up small, native mammals at alarming rates.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/invasive-predators-are-eating-the-worlds-animals-to-extinction-and-the-worst-is-close-to-home-64741">Invasive predators are eating the world's animals to extinction – and the worst is close to home</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="cichlid fish" src="https://images.theconversation.com/files/395273/original/file-20210415-17-uge3g9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395273/original/file-20210415-17-uge3g9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395273/original/file-20210415-17-uge3g9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395273/original/file-20210415-17-uge3g9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395273/original/file-20210415-17-uge3g9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395273/original/file-20210415-17-uge3g9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395273/original/file-20210415-17-uge3g9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In Africa, numbers of the beautiful cichlid fish have been decimated by Nile perch.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Money talks</h2>
<p>Despite the <a href="https://pubag.nal.usda.gov/catalog/61">serious threat</a> biological invasions pose, the problem receives little political, media or public attention.</p>
<p>Our research sought to reframe the problem of invasive species in terms of economic cost. But this was not an easy task. </p>
<p>The costs are diverse and not easily compared. Our analysis involved thousands of cost estimates, compiled and analysed over several years in our <a href="https://figshare.com/articles/dataset/InvaCost_References_and_description_of_economic_cost_estimates_associated_with_biological_invasions_worldwide_/12668570">still-growing</a> <a href="https://www.nature.com/articles/s41597-020-00586-z"><em>InvaCost</em></a> database. Economists and ecologists helped fine-tune the data.</p>
<p>The results were staggering. We discovered invasive species have cost the world US$1.3 trillion (A$1.7 trillion) lost or spent between 1970 and 2017. The cost largely involves damages and losses; the cost of preventing or controlling the invasions were ten to 100 times lower.</p>
<p>Clearly, getting on top of control and prevention would have helped avoid the massive damage bill. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/global-agriculture-study-finds-developing-countries-most-threatened-by-invasive-pest-species-61280">Global agriculture study finds developing countries most threatened by invasive pest species</a>
</strong>
</em>
</p>
<hr>
<p>Average costs have been increasing exponentially over time — trebling each decade since 1970. For 2017 alone, the estimated cost of invasive species was more than US$163 billion. That’s more than 20 times higher than the combined budgets of the <a href="https://www.who.int">World Health Organisation</a> and the <a href="https://www.un.org">United Nations</a> in the same year.</p>
<p>Perhaps more alarming, this massive cost is a conservative estimate and likely represents only the tip of the iceberg, for several reasons:</p>
<ul>
<li><p>we analysed only the most robust available data; had we included all published data, the cost figure would have been 33 times higher for the estimate in 2017</p></li>
<li><p>some damage caused by invasive species cannot be measured in dollars, such as carbon uptake and the loss of ecosystem services such as pollination</p></li>
<li><p><a href="https://doi.org/10.1016/j.scitotenv.2020.144441">most</a> of the impacts have not been properly estimated</p></li>
<li><p>most countries have little to no relevant data. </p></li>
</ul>
<figure class="align-center ">
<img alt="A bucket by a lake with a sign reading 'Biosecurity station. Please dip your feet and nets'" src="https://images.theconversation.com/files/395276/original/file-20210415-19-10m8e2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395276/original/file-20210415-19-10m8e2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395276/original/file-20210415-19-10m8e2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395276/original/file-20210415-19-10m8e2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395276/original/file-20210415-19-10m8e2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395276/original/file-20210415-19-10m8e2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395276/original/file-20210415-19-10m8e2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=562&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Prevention strategies, such as biosecurity controls, are a relatively cheap way to deal with invasive species.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Prevention is better than cure</h2>
<p>National regulations for dealing with invasive species are patently <a href="https://onlinelibrary.wiley.com/doi/pdf/10.1111/geb.12517">insufficient</a>. And because alien species do not respect borders, the problem also requires a global approach.</p>
<p>International cooperation must include financial assistance for developing countries where invasions are expected to increase substantially in the coming decades, and where regulations and management are <a href="https://www.nature.com/articles/ncomms12485">most lacking</a>. </p>
<p>Proactive measures to prevent invasion must become a priority. As the old saying goes, an ounce of prevention is better than a pound of cure. And this must happen early – if we miss the start of an invasion, control in many cases is <a href="https://www.sciencedirect.com/science/article/abs/pii/S0006320702001611">impossible</a>. </p>
<p>More and better research on the economic costs of biological invasions is essential. Our current knowledge is fragmented, hampering our understanding of patterns and trends, and our capacity to manage the problem efficiently. </p>
<p>We hope quantifying the economic impacts of invasive species will mean political leaders start to take notice. Certainly, confirmation of a A$1.7 trillion bill should be enough to get the ball rolling.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/worried-about-earths-future-well-the-outlook-is-worse-than-even-scientists-can-grasp-153091">Worried about Earth's future? Well, the outlook is worse than even scientists can grasp</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/158628/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Corey J. A. Bradshaw receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Franck Courchamp a reçu des financements de Centre National de la Recherche Scientifique (CNRS) and AXA Research Fund</span></em></p><p class="fine-print"><em><span>Boris Leroy, Camille Bernery, and Christophe Diagne do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Invasive species have been invading foreign territories for centuries. By quantifying the mammoth economic impacts, we hope political leaders will start to take notice.Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders UniversityBoris Leroy, Maître de conférences en écologie et biogéographie, Muséum national d’histoire naturelle (MNHN)Camille Bernery, Doctorante en écologie des invasions, Université Paris-SaclayChristophe Diagne, Chercheur post-doctorant en écologie des invasions, Université Paris-SaclayFranck Courchamp, Directeur de recherche CNRS, Université Paris-SaclayLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1302962020-01-27T18:58:14Z2020-01-27T18:58:14ZPulling out weeds is the best thing you can do to help nature recover from the fires<figure><img src="https://images.theconversation.com/files/311539/original/file-20200123-162232-xs4vf3.jpg?ixlib=rb-1.1.0&rect=23%2C0%2C3867%2C2444&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Australians are keen to help nature recover after a season of devastating bushfires.</span> <span class="attribution"><span class="source">Darren England/AAP</span></span></figcaption></figure><p>Many Australians feel compelled to help our damaged wildlife after this season’s terrible bushfires. Suggested actions have included <a href="https://www.wwf.org.au/get-involved/bushfire-emergency">donating money</a>, <a href="https://theconversation.com/you-can-leave-water-out-for-wildlife-without-attracting-mosquitoes-if-you-take-a-few-precautions-128631">leaving water out</a> for thirsty animals, and learning how to <a href="https://www.marieclaire.com.au/how-to-help-animals-australian-bushfires">help the injured</a>. But there is an equally, if not more, important way to assist: weeding.</p>
<p>An army of volunteers is needed to help land owners with judicious weed removal. This will help burnt habitats recover more quickly, providing expanded, healthy habitat for native fauna. </p>
<p>Other emergency responses, such as culling feral animals and <a href="https://www.smh.com.au/environment/conservation/massive-food-drop-to-help-save-endangered-wallabies-in-fire-affected-areas-20200112-p53qss.html">dropping emergency food from aeroplanes</a>, are obviously jobs for specialists. But volunteer weeding does not require any prior expertise – just a willingness to get your hands dirty and take your lead from those in the know. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/311544/original/file-20200123-162190-4qhus3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311544/original/file-20200123-162190-4qhus3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311544/original/file-20200123-162190-4qhus3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311544/original/file-20200123-162190-4qhus3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311544/original/file-20200123-162190-4qhus3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311544/original/file-20200123-162190-4qhus3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311544/original/file-20200123-162190-4qhus3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Volunteer weeding will help burnt habitats recover more quickly.</span>
<span class="attribution"><span class="source">Silje Polland/Flickr</span></span>
</figcaption>
</figure>
<h2>Why is weeding so critical?</h2>
<p>The recent bushfires burned many areas in national parks and reserves which were infested with weeds. Some weeds are killed in a blaze, but fire also stimulates their seed banks to germinate.</p>
<p>Weed seedlings will spring up en masse and establish dense stands that out-compete native plants by blocking access to sunlight. Native seedlings will die without setting seed, wasting this chance for them to recover and to provide habitat for a diverse range of native species.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/many-of-our-plants-and-animals-have-adapted-to-fires-but-now-the-fires-are-changing-129754">Many of our plants and animals have adapted to fires, but now the fires are changing</a>
</strong>
</em>
</p>
<hr>
<p>This mass weed germination is also an opportunity to improve the outlook for biodiversity. With a coordinated volunteer effort, these weeds can be taken out before they seed – leaving only a residual seed bank with no adult weeds to create more seed and creating space for native plants to flourish.</p>
<p>With follow-up weeding, we can leave our national parks and reserves – and even bushland on farms - in a better state than they were before the fires.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/311542/original/file-20200123-162221-1l3qp1w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311542/original/file-20200123-162221-1l3qp1w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311542/original/file-20200123-162221-1l3qp1w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311542/original/file-20200123-162221-1l3qp1w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311542/original/file-20200123-162221-1l3qp1w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311542/original/file-20200123-162221-1l3qp1w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311542/original/file-20200123-162221-1l3qp1w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bush regeneration groups are well placed to restore forests after fire, but need volunteers.</span>
<span class="attribution"><span class="source">Flickr</span></span>
</figcaption>
</figure>
<h2>Weeding works</h2>
<p>In January 1994, fire burned most of Lane Cove National Park in Sydney. Within a few months of the fire, <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1442-8903.2005.00225.x">volunteer bush regeneration groups were set up to help tackle regenerating weeds</a>.</p>
<p>Their efforts eradicated weeds from areas where the problem previously seemed intractable and prevented further weed expansion. Key to success in this case was the provision of funding for coordination, an engaged community which produced passionate volunteers and enough resources to train them.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/conservation-scientists-are-grieving-after-the-bushfires-but-we-must-not-give-up-130195">Conservation scientists are grieving after the bushfires -- but we must not give up</a>
</strong>
</em>
</p>
<hr>
<p>Following recent fires in the Victorian high country, volunteers will be critical to controlling weeds, <a href="https://bie.ala.org.au/species/http://id.biodiversity.org.au/node/apni/2897651">particularly broom (Scotch broom and related species), which occurs throughout fire-affected areas </a>. </p>
<p>Fire typically kills these woody shrubs but also stimulates seed germination. Without intervention, broom will form dense stands which <a href="https://link.springer.com/content/pdf/10.1007/s11258-005-9046-7.pdf">out-compete native plant species </a>.</p>
<p>However, swift action now can prevent this. Mass germination <a href="https://www.researchgate.net/publication/299041169">reduces the broom’s seedbank to as low as 8% of pre-fire levels, and around half of the remaining seeds die each year</a>. Further, broom usually takes three years to flower and replenish its seedbank. So with no new seeds being produced and the seedbank low and shrinking, this three-year window offers an important opportunity to restore previously infested areas.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/311540/original/file-20200123-162199-1bukveg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311540/original/file-20200123-162199-1bukveg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311540/original/file-20200123-162199-1bukveg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311540/original/file-20200123-162199-1bukveg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311540/original/file-20200123-162199-1bukveg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311540/original/file-20200123-162199-1bukveg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311540/original/file-20200123-162199-1bukveg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Scotch broom, a native shrub of Western Europe, has infested vast swathes of Australia.</span>
<span class="attribution"><span class="source">Gunter Maywald-CSIRO/Wikimedia</span></span>
</figcaption>
</figure>
<p>Parks Victoria took up this opportunity after the 2003 fires in the Alpine National Park. They rallied agencies, natural resource management groups and local landholders to <a href="http://www.aabr.org.au/images/stories/resources/ManagementGuides/WeedGuides/wmg_brooms.pdf">sweep up broom </a>. Herbicide trials at that time revealed that to get the best outcome for their money, it was critical to spray broom seedlings early, within the <a href="https://www.researchgate.net/publication/259323125_Best-practice_chemical_control_of_English_broom_Cytisus_scoparius_evaluated_in_Alpine_National_Park_Victoria_through_an_adaptive_experimental_management_program">first year and a half</a>. </p>
<p>Broom management also needs to use a range of approaches, <a href="https://www.parkconnect.vic.gov.au/Volunteer/public-planned-activity/?id=446c9d83-53b6-e811-a966-000d3ad1c6f2">including using volunteers to spread a biological control agent</a>. </p>
<h2>Plenty of work to do</h2>
<p>Parks Victoria continue to <a href="https://www.parkconnect.vic.gov.au/Volunteer/">engage community groups in park management</a> and will coordinate fire response actions when parks are safe to enter. Similar programs can be found in <a href="https://www.nationalparks.nsw.gov.au/conservation-and-heritage/volunteer-programs">New South Wales</a>, <a href="https://www.dbca.wa.gov.au/parks-and-wildlife-service/volunteering-with-parks-and-wildlife">Western Australia</a>, <a href="https://www.parks.sa.gov.au/volunteer">South Australia</a>, <a href="https://www.qld.gov.au/environment/parks/park-volunteers/start-volunteering">Queensland</a>, <a href="https://parks.tas.gov.au/be-involved/volunteer">Tasmania</a>, <a href="https://nt.gov.au/leisure/parks-reserves/learn-and-be-involved/volunteers-in-parks">the Northern Territory</a>, and the <a href="https://www.environment.act.gov.au/parks-conservation/parks-and-reserves/get-involved/the-ParkCare-initiative">ACT</a>.</p>
<p>A <a href="https://www.researchgate.net/profile/Kevin_Taylor16/publication/331247014_Fire_Weeds_and_the_Native_Vegetation_of_New_South_Wales_A_report_prepared_by_the_Hotspots_Fire_Project/links/5c6e1fa94585156b570d4c51/Fire-Weeds-and-the-Native-Vegetation-of-New-South-Wales-A-report-prepared-by-the-Hotspots-Fire-Project.pdf">wide range of weeds expand after fire</a> and warrant a rapid response. They include <a href="https://www.environment.gov.au/biodiversity/invasive/weeds/publications/guidelines/wons/pubs/l-camara.pdf">lantana</a>, <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0128482">bitou bush</a>, and
<a href="http://caws.org.nz/old-site/awc/2006/awc200612111.pdf">blackberry</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-native-plants-can-flourish-after-bushfire-but-theres-only-so-much-hardship-they-can-take-129748">Yes, native plants can flourish after bushfire. But there’s only so much hardship they can take</a>
</strong>
</em>
</p>
<hr>
<p>Managing weeds after fire is currently a high priority at many sites. At the edges of the World Heritage Gondwana rainforests of southwest Queensland and northern and central NSW, there is a window to more effectively control <a href="https://www.abc.net.au/science/articles/2011/12/12/3387436.htm">lantana</a>. In many forested areas in NSW, Victoria and South Australia, fire has created an opportunity to address important weed problems.</p>
<p>State government agencies have the mapping capacity to locate these places. Hopefully they can make these resources easy for the public to access soon, so community groups can self-organise and connect with park managers. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/311545/original/file-20200123-162240-brb21w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311545/original/file-20200123-162240-brb21w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=386&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311545/original/file-20200123-162240-brb21w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=386&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311545/original/file-20200123-162240-brb21w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=386&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311545/original/file-20200123-162240-brb21w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=486&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311545/original/file-20200123-162240-brb21w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=486&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311545/original/file-20200123-162240-brb21w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=486&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A koala badly injured during the Canberra bushfires before it was returned to the wild.</span>
<span class="attribution"><span class="source">ALAN PORRIT/AAP</span></span>
</figcaption>
</figure>
<h2>All this needs money</h2>
<p>Emergency funding is now essential to enable community-based weed control programs at the scale needed to have a substantial impact. Specifically, funding is needed for group coordinators, trainers and equipment.</p>
<p>While emergency work is needed to control regenerating weeds in the next 6-18 months, <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1442-8903.2005.00225.x">ongoing work is needed after that</a> to consolidate success and prevent reinfestations from the small, but still present, seed bank.</p>
<p><a href="https://vnpa.org.au/wp-content/uploads/2017/02/Assessment-of-the-Weed-Management-program-in-land-managed-by-Parks-Victoria.pdf">Ongoing government funding is needed</a> to enable this work, and prepare for a similar response to the next mega-fires.</p>
<h2>Want to act immediately?</h2>
<p>You can volunteer to do your bit for fire recovery right now. In addition to state-agency volunteer websites, there are many existing park care, bush care and “friends of” groups coordinated by local governments. They’re waiting for you to join so they can start planning the restoration task in fire-affected areas.</p>
<p>Contact them directly or <a href="http://www.aabr.org.au/do/post-fire-wildlife-habitat-recovery-response/">register your interest with the Australian Association of Bush Regenerators</a> who can link you with the appropriate organisations. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/you-can-leave-water-out-for-wildlife-without-attracting-mosquitoes-if-you-take-a-few-precautions-128631">You can leave water out for wildlife without attracting mosquitoes, if you take a few precautions</a>
</strong>
</em>
</p>
<hr>
<p>If we do nothing now, the quality of our national parks will decline as weeds take over and native species are lost. But if you channel your fire-response energy and commitment to help manage weeds, our national parks could come out in front from this climate-change induced calamity.</p>
<p>By all means, rescue an injured koala. But by pulling out weeds, you could also help rescue a whole ecosystem.</p>
<hr>
<p><em>Dr Tein McDonald, president of the Australian Association of Bush Regenerators, contributed to this article.</em></p><img src="https://counter.theconversation.com/content/130296/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Don Driscoll receives funding from the Herman Slade Foundation, OEH NSW Environmental Grants program, DELWP Vic, National Geographic, Rufford Foundation and Bushfire and Natural Hazards CRC. He is Past President of the Ecological Society of Australia, Director of the Centre of Integrative Ecology and Director of the TechnEcology Research Network at Deakin University. Don is a member of the Ecological Society of Australia and Society for Conservation Biology.</span></em></p>By all means, rescue an injured koala. But by pulling out weeds after the fires, you could also help rescue a whole ecosystem.Don Driscoll, Professor in Terrestrial Ecology, Deakin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1265742019-12-03T12:58:58Z2019-12-03T12:58:58ZInvasive grasses are fueling wildfires across the US<figure><img src="https://images.theconversation.com/files/303542/original/file-20191125-74572-19kgvz7.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3840%2C2160&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Burning invasive, nonnative grasses on federal land at Lower Table Rock, Oregon. </span> <span class="attribution"><a class="source" href="https://flic.kr/p/zSrCNK">BLM</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The Santa Ana winds that <a href="https://theconversation.com/how-fierce-fall-and-winter-winds-help-fuel-california-fires-106985">help drive fall and winter wildfires</a> in California have died down, providing welcome relief for residents. But other ecological factors contribute to fires in ways that scientists are still discovering. </p>
<p>I study <a href="https://scholar.google.com/citations?user=XxDxepMAAAAJ&hl=en&authuser=1">how human actions affect fire regimes</a> – the patterns through which fires occur in a particular place over a specific time period. People alter these patterns by adding ignition sources, such as campfires or sparking power lines; suppressing fires when they develop; and introducing nonnative invasive plants.</p>
<p>My research suggests that nonnative invasive grasses may be fueling wildfires across the United States. Some fires are occurring in areas that rarely burn, like the Sonoran Desert and the semiarid shrublands of the <a href="https://en.wikipedia.org/wiki/Great_Basin">Great Basin</a>, which covers most of Nevada and parts of five surrounding states. In the coming months, some of the grasses that help feed these blazes will germinate, producing tinder for future fires.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=671&fit=crop&dpr=1 600w, https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=671&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=671&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=843&fit=crop&dpr=1 754w, https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=843&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/303569/original/file-20191125-74562-1l0i29g.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=843&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Great Basin.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Great_Basin#/media/File:Greatbasinmap.png">KMusser/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In a recent study, I worked with colleagues at the University of Massachusetts and the University of Colorado to investigate how 12 nonnative invasive grass species <a href="https://doi.org/10.1073/pnas.1908253116">may be affecting regional fire regimes</a> across the U.S. We found that eight species could be increasing fire in ecosystems across the country.</p>
<h2>Altering historical fire patterns</h2>
<p>A <a href="https://doi.org/10.1007/s12064-010-0082-z">fire regime</a> is a way to describe fire over space and time or to characterize fire patterns. Understanding fire regimes can help make clear that fire is a <a href="https://theconversation.com/heres-how-forests-rebounded-from-yellowstones-epic-1988-fires-and-why-that-could-be-harder-in-the-future-101495">natural and integral component of many ecosystems</a>. Knowing historical fire patterns also enables scientists to begin to understand when new or different patterns emerge. </p>
<p>The <a href="https://doi.org/10.1146/annurev.es.23.110192.000431">link between invasive grass and fire</a> is well established. Invasive grasses are novel fuels that can act as kindling in an ecosystem where readily flammable material might not otherwise be present. They can catch a spark that might otherwise have been inconsequential. </p>
<p>For example, in August 2019 the <a href="https://inciweb.nwcg.gov/incident/6541/">Mercer Fire</a> burned 25 acres in Arizona, scorching native desert plants, including iconic saguaro cacti. A much larger event, the 435,000-acre <a href="https://inciweb.nwcg.gov/incident/5899/">Martin Fire</a>, destroyed native sagebrush ecosystems in Nevada in July 2018. Invasive grasses helped fuel both fires.</p>
<p>Cheatgrass, which fueled the Martin Fire, is a well-studied invasive grass <a href="https://doi.org/10.1007/s10530-017-1641-8">known to promote fire</a>. But many other invasive grass species have similar potential, and their roles in promoting fire have not been assessed at large scales.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/WqeE4nfrZg0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How land managers are fighting invasive grasses across the Great Basin region of the West.</span></figcaption>
</figure>
<h2>Introducing the suspects</h2>
<p>Researchers describe fire regimes in many ways. Our study focused on fire occurrence (whether or not fire occurred), frequency (how many times fires occurred) and size (the largest fire associated with a place) in 29 ecological regions across the U.S. For each location we tested whether invasive grasses were associated with differences in fire occurrence, frequency or size. </p>
<p>A nonnative invasive species typically comes from another continent, has become established, is spreading and has negative impacts. We used an online <a href="https://www.invasiveplantatlas.org/">Invasive Plant Atlas of the United States</a> as a starting point to determine which invasive grass species to investigate. </p>
<p>Next, we searched the scientific literature and the U.S. Forest Service’s <a href="https://www.feis-crs.org/feis/">Fire Effects Information System</a> to see whether there was reason to believe that any of the invasive grass species promoted fire. This process helped narrow our scope from 176 species to 12 that were suitable for our analysis. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1143611085645328386"}"></div></p>
<p>Who are these “dirty dozen,” and how did they get here? <a href="https://www.usgs.gov/faqs/what-buffelgrass?qt-news_science_products=3#qt-news_science_products">Buffelgrass</a> is native to Africa and was intentionally introduced to Arizona in the 1930s, probably for erosion control and forage. <a href="https://www.invasivespeciesinfo.gov/profile/japanese-stiltgrass">Japanese stiltgrass</a> and <a href="https://www.invasivespeciesinfo.gov/profile/cogongrass">cogongrass</a> are native to much of Asia and were introduced to the southeastern U.S. in the early 1900s, in some instances as packing material. <a href="https://plants.usda.gov/plantguide/pdf/pg_taca8.pdf">Medusahead</a>, which comes from Eurasia, was introduced to the western U.S. in the late 1800s, probably by accident as a contaminant in seed shipments. </p>
<p>The remaining eight species – <a href="https://www.invasivespeciesinfo.gov/profile/giant-reed">giant reed</a>, <a href="https://www.invasivespeciesinfo.gov/profile/common-reed">common reed</a>, silk reed, red brome, <a href="https://www.invasivespeciesinfo.gov/profile/downy-brome">cheatgrass</a>, Chinese silvergrass, Arabian schismus and common Mediterranean grass – have similar stories. People introduced them, sometimes accidentally and at other times intentionally, without an understanding of how they could impact their new settings.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/303533/original/file-20191125-74572-1mdnbf8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cogongrass, which is invasive in the U.S. Southeast, may burn hot enough to kill native fire-adapted tree species.</span>
<span class="attribution"><a class="source" href="https://www.aces.edu/blog/topics/forestry-wildlife/cogongrass-management-faq/">Alabama Cooperative Extension System</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Big data for big questions</h2>
<p>Understanding how multiple species influence fire over many years at a national scale requires using <a href="https://doi.org/10.1890/1540-9295-12.1.3">big data</a>. One person could not collect information on this scale working alone. </p>
<p>We relied on composite data sets that provided thousands of records of invasive grass occurrence and abundance across the country. Combining these records with <a href="https://www.fs.usda.gov/rds/archive/catalog/RDS-2013-0009.4">agency</a> and <a href="https://www.mtbs.gov/">satellite</a> fire records helped us determine whether fire occurrence, frequency or size were different in places with and without grass invasions. </p>
<p>We also used statistical models to assess whether human activities and ecological features could be driving observed differences between invaded and uninvaded areas. For example, it was possible that grass invasions were happening near roads, which are also linked with fire ignitions. By including roads with grass invasion in our statistical models, we can be more confident in the role invasive grasses could play in altering fire regimes.</p>
<p>Our results show that eight of the species we studied are associated with increases in fire occurrence. Six of these species are also linked to increases in fire frequency. Invasions seem to be affecting a variety of ecosystems, ranging from buffelgrass in the Sonoran Desert to Japanese stiltgrass in eastern U.S. forests to cogongrass in southeastern pine systems.</p>
<p>Our statistical models suggest that grass invasion, along with human activities, are likely affecting fire patterns in these ecosystems.</p>
<p>Surprisingly, none of the invasive grass species analyzed appeared to influence fire size. We interpret this result to mean that the areas we studied are seeing more of the same types of fires that already occur there, at least in terms of size.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=303&fit=crop&dpr=1 600w, https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=303&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=303&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=380&fit=crop&dpr=1 754w, https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=380&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/303540/original/file-20191125-74562-ux4ix0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=380&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dispersing seeds over a burned area of the 2015 Soda Fire in southwest Idaho to help stabilize soils and combat invasive weeds such as cheatgrass.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Wildfire-Strategy/c7ed71dd79ea486e97c152e2aba253f1/2/0">BLM via AP</a></span>
</figcaption>
</figure>
<h2>Factoring invasive grasses into fire planning</h2>
<p>People start an estimated <a href="http://dx.doi.org/10.1073/pnas.1617394114">84% of wildfires</a> in the U.S., with the rest ignited by lightning strikes. Studies show that climate change is <a href="https://doi.org/10.1098/rstb.2015.0178">increasing wildfire activity</a>.</p>
<p>With an understanding of interactions between invasive grasses and fire, agencies that handle either fire or invasive species may find opportunities to work together to control invasions that can lead to more frequent burns. Our research can also strengthen predictions of future fire risk by incorporating the presence of invasive grasses into fire risk models. </p>
<p>Although it sometimes may feel as though <a href="https://theconversation.com/california-wildfires-signal-the-arrival-of-a-planetary-fire-age-125972">the world is on fire</a>, this information can provide potential for remediation, and may help communities prepare more effectively for future wildfires.</p>
<p>[ <em>Like what you’ve read? Want more?</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=likethis">Sign up for The Conversation’s daily newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/126574/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emily Fusco receives funding from the National Science Foundation Geography and Spatial Sciences Program</span></em></p>Along with climate change and drought, invasive grasses are promoting wildfires across the US, even in areas that don’t normally burn.Emily Fusco, Postdoctoral Researcher, UMass AmherstLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/897832018-02-01T13:41:33Z2018-02-01T13:41:33ZHow South Africa is keeping its worst invader - famine weed - at bay<figure><img src="https://images.theconversation.com/files/203751/original/file-20180129-100905-d1kkd3.jpg?ixlib=rb-1.1.0&rect=11%2C150%2C1488%2C910&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The leaf-feeding beetle Zygogramma bicolorata is one of the most promising agents used against famine weed in South Africa. </span> <span class="attribution"><span class="source">Blair Cowie</span></span></figcaption></figure><p>The poisonous herb, <em>Parthenium hysterophorus</em>, is one of the world’s most destructive invasive plants. It threatens biodiversity, national food security and human health. Native to parts of Central and South America (Gulf of Mexico) it has spread to more than <a href="https://www.researchgate.net/profile/Kunjithapatham_Dhileepan/publication/29660685_Parthenium_hysterophorus_L_Asteraceae/links/0deec526ba4dc8db3d000000/Parthenium-hysterophorus-L-Asteraceae.pdf">40 countries</a> including Australia, India, Pakistan, Ethiopia, Swaziland and South Africa. In South Africa it’s known as <a href="http://www.invasives.org.za/component/k2/item/295-famine-weed-parthenium-hysterophorus">famine weed</a>.</p>
<p>Much of southern and eastern Africa <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3180.2010.00820.x/full">remains susceptible</a> to famine weed invasion. First recorded in South Africa in <a href="http://www.arc.agric.za/arc-ppri/Fact%20Sheets%20Library/Parthenium%20hysterophorus.pdf">1880</a>, famine weed only became a prominent invader in 1984 after <a href="http://www.weathersa.co.za/learning/weather-questions/48-which-cyclones-have-affected-sa-in-the-last-30-years">cyclone Demoina</a> hit the country. Since then, the plant has rampantly invaded northern and eastern parts of the country prompting major concern. </p>
<p>Famine weed spreads rapidly and is devastatingly destructive. It kills other plants within its vicinity, wipes out entire crop harvests, poisons wildlife as well as livestock, makes food inedible and causes a variety of health problems in humans.</p>
<p>Controlling famine weed is incredibly difficult, but it is possible. <a href="https://link.springer.com/chapter/10.1007/978-1-4020-9202-2_12">A number of approaches</a> have been trialled and include physical and mechanical removal, herbicide sprays, prescribed fires and biocontrol (using the weed’s natural enemies). </p>
<p>So far South Africa is mainly attempting to thwart the spread of famine weed and reduce infestations using biocontrol. Rather than trying to get rid of the weed entirely, biocontrol uses Parthenium’s natural enemies to slow down infestation and spread of the weed. Following biocontrol successes in Australia and India, South Africa become the <a href="http://bugwoodcloud.org/ibiocontrol/proceedings/pdf/Strathie.pdf">first African country</a> to implement biocontrol against Parthenium in 2003.</p>
<p>The use of biocontrol in South Africa has made some progress in slowing the spread of famine weed, but the battle is never ending.</p>
<h2>Devastating effects</h2>
<p>The weed’s rapid growth rate and prolific seed production make it highly troublesome. It’s tiny seeds are easily spread by wind, water, animals, vehicles, or in soil, and can remain viable for up to 10 years. Once germinated, famine weed out-competes and chemically excludes surrounding vegetation in a process known as <a href="http://onlinelibrary.wiley.com/doi/10.1002/ts.21/abstract">allelopathy</a>, decimating an areas biodiversity. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/204203/original/file-20180131-131744-mp6avy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The weed grows rapidly and outcompetes other vegetation.</span>
<span class="attribution"><span class="source">Blair Cowie</span></span>
</figcaption>
</figure>
<p>Famine weed is also toxic to wild game and domestic livestock. It causes ulcers of the mouth, skin lesions and even <a href="http://caws.org.au/awc/1992/awc199211341.pdf">death if consumed in large amounts</a>. Milk and meat from livestock reared on fields or fodder infested with famine weed are <a href="http://www.publish.csiro.au/an/EA9820043">unfit for human consumption</a>. </p>
<p>From an agricultural perspective, the weed lessens the grazing capacity of rangelands (pastures). It also degrades and removes hectares of arable land, costing millions of rand in losses. If uncontrolled, it has the potential to <a href="https://www.cabi.org/isc/abstract/20023090324">reduce crop yields</a> by as much as 97%. Similarly, crop harvests contaminated with famine weed suffer massive reductions in their value. In severe cases, entire harvests become unusable.</p>
<p>The weed and its pollen also pose numerous <a href="https://www.ncbi.nlm.nih.gov/pubmed/7677614">health threats to humans</a>. These include asthma, bronchitis and hay fever but also skin problems like dermatitis, rashes and blisters. </p>
<h2>Controlling famine weed</h2>
<p>Physically removing the weed can work for extremely small infestations but only if the root is removed before the plant sets seed. Mechanical clearing like mowing or slashing is not recommended, as this accidentally spreads seeds and furthers the weed’s invasion. </p>
<p><a href="http://www.bioone.org/doi/abs/10.1614/WT-07-053.1">Herbicides</a> work, but only if proper follow-ups are made to kill new plants. And intensive chemical control may not be suitable for agricultural areas or grazing lands. The high cost of herbicides also makes it unfeasible for areas with low commercial value or in poorer communities.</p>
<p>Prescribed fires may <a href="http://www.bioone.org/doi/abs/10.1614/WT-05-086R1.1?journalCode=wete">hold promise</a> in reducing Parthenium seedbanks, but research into the effects of burning remains preliminary and hotly debated.</p>
<p>Biocontrol is one of the most <a href="http://www.invasives.org.za/legislation/item/1040-biological-control-agents-for-famine-weed-parthenium-hysterophorus">promising and cost-effective solutions</a> to successfully manage infestations. It allows scientists to make use of a weed’s natural enemies to effectively and “naturally” manage the problem species.
Since the initiation of biocontrol efforts in South Africa the country has <a href="https://www.sasta.co.za/wp-content/uploads/Proceedings/2010s/2016_Strathie%20L%20et%20al_Recent%20developments%20in%20the%20management.pdf">released four biocontrol agents</a>: a leaf-rust fungus (<em>Puccinia xanthii</em>), a stem-boring weevil (<em>Listronotus setosipennis</em>), a leaf-feeding beetle (<em>Zygogramma bicolorata</em>) and a seed-feeding weevil (<em>Smicronyx lutulentus</em>). </p>
<p>All of these agents exert different levels of damage to famine weed populations in the field. Researchers hope that the damage inflicted will steadily increase over time and offer greater control, particularly by the <a href="https://www.sciencedirect.com/science/article/pii/S1049964417301858">leaf-feeding beetle</a> and the <a href="http://www.tandfonline.com/doi/abs/10.1080/0958315021000054340">stem-boring weevil</a>. Additional agents are also <a href="http://www.invasives.org.za/events/item/1247-current-and-prospective-insect-agents-for-the-biological-control-of-parthenium-hysterophorus">under investigation</a>. </p>
<h2>Slowing the spread of famine weed</h2>
<p>Prevention is ultimately better than cure. Landowners should <a href="http://www.invasives.org.za/plants/famine-weed#health-risks">familiarise themselves with the weed</a> and remain vigilant. For landowners facing famine weed invasion, every effort should be made to reduce the density and contain spread of the weed. <a href="https://www.environment.gov.au/biodiversity/invasive/weeds/publications/guidelines/wons/pubs/p-hysterophorus.pdf">Good land management practices</a>, particularly maintaining good grass cover, are critical to preventing and reducing famine weed invasion. Sowing bare overgrazed soil patches with native grass seed may aid in restoring grass coverage and limiting infestation.</p>
<p>Biocontrol alone is unlikely to completely control famine weed at present. But in the interim, researchers have come up with a specially catered national strategy to optimise Parthenium <a href="https://abcjournal.org/index.php/ABC/article/view/2053/1980">control</a>. This strategy aims at implementing the best control options throughout different parts of South Africa.</p><img src="https://counter.theconversation.com/content/89783/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Blair Cowie received funding from the University of the Witwatersrand, the Centre of Excellence for Invasion Biology (CIB) & the Agricultural Research Council -Plant Protection Research Institute (ARC-PPRI). </span></em></p>Famine weed spreads rapidly and is devastatingly destructive. Biocontrol is one way of dealing with the problem.Blair Cowie, PhD Candidate Invasive Species Management, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/892812017-12-20T19:05:46Z2017-12-20T19:05:46ZHow invasive weeds can make wildfires hotter and more frequent<figure><img src="https://images.theconversation.com/files/199609/original/file-20171218-17860-8i8ehc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mixed grill: burning combinations of invasive and native plants helps us understand how invasive plants make fires hotter and more likely. </span> <span class="attribution"><span class="source">Sarah Wyse</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Over the past year the global media has been full of reports of catastrophic fires in <a href="https://www.npr.org/sections/thetwo-way/2017/12/13/570391113/californias-thomas-fire-25-percent-contained">California</a>, the <a href="https://theconversation.com/wildfires-are-raging-in-the-mediterranean-what-can-we-learn-81121">Mediterranean</a>, <a href="https://www.nature.com/articles/nclimate3432">Chile</a> and elsewhere. One suggested reason for increases in catastrophic wildfires has been <a href="https://www.nature.com/news/prepare-for-larger-longer-wildfires-1.22821">human-induced climate change</a>. Higher temperatures, drier weather and windier conditions all increase the impact of fires.</p>
<p>While climate change indeed raises the risk of wildfires, our <a href="https://link.springer.com/article/10.1007/s10021-017-0195-z">research</a> shows that another way humans can change patterns of fire activity is by introducing flammable plants to new environments. </p>
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Read more:
<a href="https://theconversation.com/how-will-canada-manage-its-wildfires-in-the-future-86383">How will Canada manage its wildfires in the future?</a>
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<p>Plantations of highly flammable exotic species, such as pines and eucalypts, probably helped to fuel the recent catastrophic fires in <a href="https://theconversation.com/what-links-portugals-deadliest-wildfire-to-grenfell-tower-economics-and-neglect-79815">Portugal</a> and in <a href="https://www.sciencedirect.com/science/article/pii/S1462901117307694">Chile</a>. In arid regions, such as parts of the <a href="http://onlinelibrary.wiley.com/doi/10.1111/gcb.12046/full">US southwest</a>, the introduction of exotic grasses has transformed shrublands, as fires increase in severity. </p>
<h2>Invasive plants and fire</h2>
<p>How do invasive plants change fire patterns? We burned species mixtures (aka “<a href="http://www.radionz.co.nz/national/programmes/ourchangingworld/audio/201768850/firing-up-the-plant-barbecue">mixed grills</a>”) on our <a href="http://www.publish.csiro.au/wf/WF15047">plant barbecue</a> to help find out.</p>
<p>Invasive plants are responsible for <a href="https://academic.oup.com/bioscience/article/54/7/677/223532">changing the patterns of fire activity</a> in many ecosystems around the world. In particular, invasive species can lead to <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1472-4642.2003.00020.x/full">hotter</a> and <a href="https://www.fs.fed.us/rm/pubs/rmrs_gtr042_6/rmrs_gtr042_6_033_046.pdf">more frequent</a> fires. </p>
<p>Invasive plants can also <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2009.02965.x/full">reduce fire frequency and fire intensity</a>, but there are <a href="https://www.fs.fed.us/rm/pubs/rmrs_gtr042_6/rmrs_gtr042_6_033_046.pdf">fewer examples</a> of this occurring worldwide.</p>
<p>One of the main ways flammable invasive plants can have long-lasting impacts on an ecosystem comes from <a href="http://www.annualreviews.org/doi/abs/10.1146/annurev.es.23.110192.000431?journalCode=ecolsys.1&">positive fire-vegetation feedbacks</a>. Such feedbacks can occur when a flammable weed invades a less fire-prone ecosystem. By <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3180.2011.00869.x/abstract">changing the available fuel</a> the invader makes fires more likely and often hotter. </p>
<p>If the invading species has <a href="https://stateoftheworldsplants.com/2017/report/SOTWP_2017_8_global_land_cover_change_wildfires.pdf">characteristics</a> that allow it to outcompete native species after a fire, then it will further dominate the ecosystem. Such traits include thick bark, the ability to resprout following fire, or seeds that survive burning. This invasion will likely lead to more fires, changing the species composition and function of the ecosystem in a “fire begets fire” cycle. Extreme examples of this dynamic are where flammable <a href="http://www.pnas.org/content/111/17/6347.long">grasses</a> or <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1442-9993.1994.tb00493.x/full">shrubs</a> invade forests, leading to loss of the forest ecosystems.</p>
<h2>Mixed grills</h2>
<p>We wanted to understand how invasive plants interact with other species when burned in combination. To explore the mechanisms underpinning such feedbacks, we examined how invasive plants might <a href="https://link.springer.com/article/10.1007/s10021-017-0195-z">change the nature of a fire</a> when burned together with native species. </p>
<p>We collected 70cm shoots of four globally invasive species (of both high and low flammability) and burned them in pairwise combinations with New Zealand native trees and shrubs to determine which characteristics of a fire could be attributed to the invasive plants. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/199600/original/file-20171218-17842-9b7lh0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Samples of <em>Hakea sericea</em> (foreground) and <em>Kunzea robusta</em> (rear) arranged on the grill of our plant barbecue.</span>
<span class="attribution"><span class="source">Sarah Wyse</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We found that overall flammability was largely driven by the most flammable species in the mixture, showing how highly flammable weeds could set in motion fire-vegetation feedbacks. </p>
<p>We established that a greater difference in flammability between the two species led to a larger influence of the more flammable species on overall flammability. This outcome suggests weeds that are much more flammable than the invaded community can have larger impacts on fire patterns. </p>
<p>Importantly, we also showed the influence of the highly flammable species was independent of its biomass, meaning highly flammable weeds may impact community flammability even at low abundances.</p>
<p>When we looked closer at the different components of flammability (combustibility, ignitability, consumability and sustainability) we found some important nuances in our results. </p>
<p>While the maximum temperature reached in our burns (combustibility) and the ignition speed (ignitability) were both most influenced by the more flammable species, consumability (the amount of biomass burned) and sustainability (how long the fire burns) were equally influenced by both the more flammable and less flammable species. </p>
<p>In short, more flammable weeds will cause a fire to ignite more quickly and burn hotter. </p>
<p>However, less flammable species can reduce the duration of a fire compared to when a more flammable species is burnt alone. These results could have important ecological implications, as the <a href="http://www.tandfonline.com/doi/abs/10.1080/02827580701803544">longer a fire burns the more likely it is to kill plants</a>: low-flammability plants could reduce this impact.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/199604/original/file-20171218-17842-1mgqhsa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Measuring how long a fire burns on our plant barbecue.</span>
<span class="attribution"><span class="source">Tom Etherington</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Managing weeds to reduce fire impacts</h2>
<p>Even low abundances of highly flammable invasive weeds could set in motion positive fire-vegetation feedbacks that lead to drastic changes to ecosystems. If this result holds when our shoot-scale experiments are repeated using field trials, then land managers should work quickly to remove even small infestations of highly flammable species, such as gorse (<em>Ulex europaeus</em>) and prickly hakea (<em>Hakea sericea</em>).</p>
<p>Conversely, the role of low flammability plants in extinguishing fires further supports the suggestion that the strategic planting of such species across the landscape as “<a href="https://theconversation.com/low-flammability-plants-could-help-our-homes-survive-bushfires-53870">green firebreaks</a>” could be a useful fire management tool. </p>
<p>In any case, our “mixed grill” study further highlights the role of exotic plants in fuelling hotter wildfires.</p><img src="https://counter.theconversation.com/content/89281/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tim Curran receives funding from the New Zealand National Rural Fire Authority and Lincoln University. </span></em></p><p class="fine-print"><em><span>George Perry receives funding from the NZ National Rural Fire Authority, the NSF and the University of Auckland. </span></em></p><p class="fine-print"><em><span>Sarah Wyse receives funding from the Kate Edger Educational Charitable Trust, the New Zealand National Rural Fire Authority, the Royal Botanic Gardens Kew, and the University of Auckland.</span></em></p>Wildfires are expected to increase in a warming world, but there is another way humans are changing the patterns and intensity of fires: by introducing flammable plants to new environments.Tim Curran, Senior Lecturer in Ecology, Lincoln University, New ZealandGeorge Perry, Professor, School of Environment, University of Auckland, Waipapa Taumata RauSarah Wyse, Early Career Research Fellow, The Royal Botanic Gardens, Kew and Research Fellow, School of Environment, University of Auckland, Waipapa Taumata RauLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/821812017-09-11T19:59:23Z2017-09-11T19:59:23ZInvasive plants have a much bigger impact than we imagine<figure><img src="https://images.theconversation.com/files/185507/original/file-20170911-1336-1ovqssw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Invasive pine trees in the Western Cape have affected lizards causing their numbers to drop significantly.</span> <span class="attribution"><span class="source">Author supplied</span></span></figcaption></figure><p><em>This article is the fifth in a <a href="https://theconversation.com/africa/topics/invasive-species-series-39958">series</a> The Conversation Africa is running on invasive species.</em></p>
<hr>
<p>Most people would agree that <a href="http://www.iucngisd.org/gisd/">invasive plants</a> are unwanted. Invasive plants are plants that are intentionally or accidentally introduced by humans into areas outside of their natural habitat. These species can spread rapidly with negative consequences for native species. </p>
<p>Invasive plant species have an impact on the diversity of local species, they affect water availability and damage the quality of soil nutrients. Once an alien plant has invaded a habitat, it changes the conditions of that environment. It does so by changing the light, solar radiation and temperature levels in the invaded patches. The quality and availability of food, shelter, nest sites, basking sites and perches are changed for a number of animals. </p>
<p>They can also inflict big changes on native vegetation, altering the frequency of fires, nutrient cycling, water availability and soil erosion. For example, pine trees in the Western Cape Province of South Africa <a href="https://link.springer.com/article/10.1007/s00442-016-3726-y">have spread beyond forestry plantations and invaded</a> native fynbos habitat. In these invaded landscapes, the temperatures available to lizards for functioning optimally are generally cooler and the number of lizard species greatly reduced. </p>
<p>In a few cases, some benefits of alien plants have been reported. For example, they can provide fire wood for local communities or add resources for animal species. But these benefits typically do not surpass the negative effects. Invasive plants have an impact on native species through complex interactions and processes. Unless these factors are properly understood, it is difficult to predict what sort of impact invasive plants will have. </p>
<p>How much is known about these processes in South African habitats, where invasive alien plants are a key concern? To find the answer, we read all the studies on the impact of alien plant on animals that we could find from South Africa and presented these findings in <a href="http://www.abcjournal.org/index.php/ABC/article/view/2166">a recent study</a>. We focused on ectothermic animals (reptiles, amphibians and invertebrates), known as “cold blooded”. They <a href="http://www.nhc.ed.ac.uk/index.php?page=24.134.137.139">require heat exchange</a> from the environment to function, grow and reproduce. These animals typically move smaller distances than mammals or birds, which increase their vulnerability to alien plant invasions. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185510/original/file-20170911-1327-wvoh0d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Alien vegetation has shaded Nile crocodile nests which are much cooler than normal sunny nests which female crocodiles prefer.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>A South African perspective</h2>
<p>Habitats that have invasive plants in South Africa have a poorer diversity of animal species than whole native habitats. There are multiple reasons for this poorer animal diversity, like reduced availability of food resources or thermal conditions that are essential for animal survival. These effects can also occur in tandem or accumulate in time and space. This echoes similar findings in other regions <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1461-0248.2011.01628.x/abstract">of the world</a>. There are however many gaps. </p>
<p>Existing studies focus on a few areas of South Africa and look at a small number of alien plants including Acacia, Hakea and Pinus species. Most studies examine the impact of alien plants on invertebrates, especially insects, but we have little data of how they impact reptiles and amphibians. South Africa is unique in its numbers of endemic <a href="http://www.tandfonline.com/doi/abs/10.1080/02541858.1995.11448377">tortoises</a>, lizards, <a href="http://sarca.adu.org.za/index.php">snakes</a> and <a href="http://sarca.adu.org.za/safap/index.php">amphibians</a>. But there are not many <a href="http://link.springer.com/article/10.1007/s00442-016-3726-y">studies</a> that address these species.</p>
<p>A nice example of how alien plants impact native animals comes from a <a href="http://www.sciencedirect.com/science/article/pii/S0006320700001774">study</a> in Lake St. Lucia, on the eastern part of South Africa. Alien vegetation has shaded Nile crocodile nests. Since being invaded, nests are much cooler than normal sunny nests which female crocodiles prefer. Temperature dictates the sex of embryos in reptiles, so this finding implies that development of eggs under these conditions will result in more females. These nest temperature changes could therefore affect the population’s demographics in the long-term and alter higher levels of organisation, like communities and species. So, invasive plant species might affect the environment in more ways than we can imagine.</p>
<p>The Nile crocodile study and <a href="http://www.sciencedirect.com/science/article/pii/S000632071200328X">a few other studies</a> in South Africa are the exception rather than the rule. Most attention to date has gone into comparing numbers of species or individuals between native and invaded areas rather than investigating how these changes take place. Most authors report about the potential impact invasive plants have but very few actually test potential causes of these impacts. </p>
<p>This gap is possibly because of the difficulty to experimentally test the ways these impacts develop or record data in the long-term. For example, monitoring and collecting data on native species in the long run would enable comparing processes before and after an alien plant invasion has taken place. </p>
<h2>Where to now?</h2>
<p>Without understanding what causes the potential impact these aliens plants can have, we cannot project the impact of introduced alien species into new regions or into the future. Management practices need to be shaped by the knowledge of these causes. <a href="http://www.ladybird-survey.org/">Scientists and citizens</a> can keep a fairly good record of newly introduced invasive plant species and the spread of established ones. </p>
<p>It becomes a huge challenge to keep comprehensive records of the ways alien plants affect local plants and animals. This difficulty is mostly because <a href="http://www.sciencedirect.com/science/article/pii/S0169534712001747">these processes</a> are often multiple and can change across time and geographic regions. </p>
<p>So, we face a challenge to capture these processes. But in an era of <a href="http://www.nature.com/nature/journal/v498/n7453/full/498255a.html">big data</a>, <a href="http://www.sciencemag.org/careers/2014/06/give-and-it-will-be-given-you">data sharing</a>, cross-country collaborations and <a href="http://science.sciencemag.org/content/343/6178/1436">public participation</a>, it is a task that can be handled.</p><img src="https://counter.theconversation.com/content/82181/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Susana Clusella-Trullas receives funding from National Research Foundation, South Africa. </span></em></p><p class="fine-print"><em><span>Raquel A Garcia receives funding from the Centre of Excellence for Invasion Biology (CIB). </span></em></p>Invasive plants have an impact on native species and unless these factors are properly understood, it is difficult to predict what sort of impact invasive plants will have.Susana Clusella-Trullas, physiological ecologist at the C·I·B, Stellenbosch UniversityRaquel A Garcia, Postdoctoral fellow at the CIB, Stellnbosch University, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/825182017-08-30T19:00:40Z2017-08-30T19:00:40ZHow we used cameras in the sky to track invasive plant species<figure><img src="https://images.theconversation.com/files/183982/original/file-20170830-29224-2d6hdd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Eugenia uniflora (flowers and young red leaves) a native Brazilian species, now invasive in Hawaii.</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Starr_080610-8163_Eugenia_uniflora.jpg">Forest & Kim Starr/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Pretty pink, orange and white flowers of the shrub <em>Lantana camara</em> or wild sage, are common in ornamental gardens across many parts of the world. Although considered beautiful and hardy by landscape designers, the species is reviled by conservation biologists as “<a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0032407">one of the worst weeds in recorded history</a>”. </p>
<p>The aggressive growth of <em>Lantana camara</em> in habitats outside its native territory (originally the American tropics) has led to its spread over 20 million hectares. In the <a href="http://www.atree.org/resources/ccc/ccc_brt">Biligiri Ranganathaswamy Hills Tiger Reserve</a> in Southern peninsular India, we have studied the spread of the shrub in dense thorny thickets across the park, where it has choked out other plant species, and obstructed the movement of wildlife, creating a major challenge for park managers.</p>
<p>Lantana camara is not unique in its effects. Other <a href="https://www.cbd.int/invasive/WhatareIAS.shtml">invasive alien species</a>, such as the well-known <a href="http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Tamarix_ramosissima.html">salt-cedar which originates in Eurasia</a>, have transformed large landscapes by their rapid spread within a few years.</p>
<p>Conservation planners, such as the managers of the Biligiri Ranganathaswamy reserve, find it a challenge to contain the aggressive expansion of such invasive alien plants, which impact local biodiversity and <a href="http://www.bioone.org/doi/abs/10.1614/IPSM-D-11-00095.1?journalCode=ipsm">ecosystem services</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/182581/original/file-20170818-7944-fntvgy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182581/original/file-20170818-7944-fntvgy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182581/original/file-20170818-7944-fntvgy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182581/original/file-20170818-7944-fntvgy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182581/original/file-20170818-7944-fntvgy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=568&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182581/original/file-20170818-7944-fntvgy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=568&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182581/original/file-20170818-7944-fntvgy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=568&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hedge of Lantana camara at the Berlin cathedral.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/en/berlin-cathedral-lantana-berlin-2111004/">javallma/Pixaba</a></span>
</figcaption>
</figure>
<p>Most aggressive shrub invaders such as <em>Lantana camara</em> <a href="http://www.lyonia.org/articles/volume_23/volume.pdf#page=26%22%22">partially or completely replace</a> the native shrub species in forests. While Lantana was brought in as an ornamental plant and has now spread extensively due to <a href="http://www.tropecol.com/pdf/open/PDF_51_2S/J-04.pdf%22%22">berry-feeding birds</a>, other similar invasive species such as <em>Chromolaena odorata</em> (sunflower family) are wind-dispersed. </p>
<h2>Tracking the invaders</h2>
<p>It is important to find solutions that can provide high quality, frequently updated maps of the distribution of invasive plants, so that they can be effectively located, targeted and removed. Given the large areas over which they spread, managers are increasingly turning to high-tech methods such as remote sensing.</p>
<p>This involves photographing landscapes using special cameras in space (on satellites) or in air (on aircraft), that detect more than what the human eye can see, for example because of their capacity <a href="https://oceanservice.noaa.gov/facts/remotesensing.html%22%22">to record information in the infra-red and thermal visible spectrum of light</a>, and then deriving information from these pictures. </p>
<p>In recent years, very high resolution satellite data has become available. These can detect objects less than a meter in size, and have greater ability to distinguish the identity of plants due to images taken in <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1472-4642.2011.00761.x/abstract">narrow, highly specific wavelengths of the electromagnetic spectrum.</a>. </p>
<p>We <a href="http://www.tandfonline.com/doi/full/10.1080/01431161.2016.1193795?scroll=top&needAccess=true">reviewed</a> recent research in this direction, finding that while the advances in technology help, they need to be combined with ecological knowledge of invasive plant behaviour, for more effective mapping.</p>
<p>Plant functional traits serve as an effective way to capture many important aspects of invasive species that can be used for mapping via satellites. Plant traits are characteristics of plant structure and function <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3627314/">that impact how they spread, survive and respond to environmental and other conditions</a>. Among the numerous traits that plants have, some are well suited to mapping using satellite data. These can be broadly categorised into three types - seasonal (phenological), structural and physiological.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/182583/original/file-20170818-7952-ex3a9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182583/original/file-20170818-7952-ex3a9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182583/original/file-20170818-7952-ex3a9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182583/original/file-20170818-7952-ex3a9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182583/original/file-20170818-7952-ex3a9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182583/original/file-20170818-7952-ex3a9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182583/original/file-20170818-7952-ex3a9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Invasive shrub Lantana camara occupying niches in the understorey tropical forest.</span>
<span class="attribution"><span class="source"> Madhura Niphadkar</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Seasonal traits</h2>
<p>Plants produce leaves, seeds and flowers at specific times of the year, which can be tracked by remote sensing. Differences between invasive species and native species in the onset of senescence (coloured leaves, and leaf fall), leafing (green leaves), or flowering (presence of coloured flowers), show up clearly within specific spectral wavelengths used by satellite sensors at selected times of the year.</p>
<p>This is an especially effective strategy to map shrubs and herbs, which are located below the canopy and hence obscured from the satellite sensors. For instance, the invasive Amur honeysuckle - <em>Lonicera mackii</em> was mapped in the late fall/autumn season, when the deciduous trees were leafless, and the invasive climber was clearly visible through gaps in the leafless branches of the <a href="http://www.tandfonline.com/doi/abs/10.1080/01431160701373721">overstorey trees</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/182586/original/file-20170818-7952-2lk8cs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182586/original/file-20170818-7952-2lk8cs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182586/original/file-20170818-7952-2lk8cs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182586/original/file-20170818-7952-2lk8cs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182586/original/file-20170818-7952-2lk8cs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182586/original/file-20170818-7952-2lk8cs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182586/original/file-20170818-7952-2lk8cs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Amur honeysuckle - the understorey climber.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/w/index.php?curid=745131">Fanghong/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<h2>Structural and physiological traits</h2>
<p>Structural traits – such as clumping into clusters distributed among native plants, or height – can also be used effectively for mapping. <a href="http://journal.frontiersin.org/article/10.3389/fpls.2017.00892/full">In our own research in the Biligiri Ranganathaswamy reserve</a>, we were able to map Lantana camara’s large contiguous clumps spreading patterns. <a href="https://oceanservice.noaa.gov/facts/lidar.html">LIDAR data</a> which use pulsed laser light rays to provide 3 dimensional maps of the earth’s surface, is also handy, for instance to monitor the distribution of <a href="http://www.pnas.org/content/105/11/4519">five invasive trees species in Hawaiian forests</a> .</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/183305/original/file-20170824-18746-1pzrf71.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/183305/original/file-20170824-18746-1pzrf71.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/183305/original/file-20170824-18746-1pzrf71.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/183305/original/file-20170824-18746-1pzrf71.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/183305/original/file-20170824-18746-1pzrf71.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/183305/original/file-20170824-18746-1pzrf71.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/183305/original/file-20170824-18746-1pzrf71.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Lantana species invade almost everything and anything. Here in the Biligirirangana Hills, Karnataka.</span>
<span class="attribution"><span class="source">Madhura Niphadkar</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Invasive alien plants are often able to spread faster because of physiological traits such as faster growth due to higher resource utilisation. For instance, studies have shown that <a href="http://www.mdpi.com/2072-4292/4/9/2510">leaf Nitrogen concentration</a> and <a href="http://www.sciencedirect.com/science/article/pii/S0034425708000199">moisture content</a> of invasive plants is different from native species. </p>
<p><a href="https://www.sciencenewsforstudents.org/article/explainer-what-are-lidar-radar-and-sonar">LIDAR, RADAR (sensors that use radio waves)</a> and imaging spectroscopy can help discriminate invasive species by assessing differences in their photosynthetic efficiency (use of light energy).</p>
<h2>Protecting world biodiversity</h2>
<p>Our review of <a href="http://www.tandfonline.com/doi/full/10.1080/01431161.2016.1193795?scroll=top&needAccess=true">the use of plant traits for invasive species mapping via remote sensing</a> shows that phenological and structural traits have been exploited for mapping, but physiological traits have potential to be better utilised. </p>
<p>This monitoring of invasive plants constitutes one of the <a href="https://www.cbd.int/sp/targets/">20 targets</a> - set under the Convention on Biological Diversity in 2010 at Aichi in Japan - that aim at protecting biodiversity.<br>
Since then, remote sensing has been <a href="http://onlinelibrary.wiley.com/doi/10.1002/rse2.15/pdf">increasingly proposed as a tool to achieve this goal </a> and is currently entering its golden age with <a href="http://www.nature.com/news/drones-in-science-fly-and-bring-me-data-1.13161">drone mapping</a>. </p>
<p>Combining ecological insights with advanced remote sensing technology could better enable society to meet its commitment towards biodiversity protection.</p><img src="https://counter.theconversation.com/content/82518/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Madhura Niphadkar received funding from National Geographic Society for a section of her Doctoral research, which involved this work. This study forms a part of a chapter in her dissertation. </span></em></p><p class="fine-print"><em><span>Harini Nagendra does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>For mapping patterns of plant invasion from the sky, understanding plant behaviour on the ground and using it along with remote sensing cameras, is crucial.Harini Nagendra, Professor of Sustainability, Azim Premji UniversityMadhura Niphadkar, Post Doctoral Fellow, Ashoka Trust for Research Ecology and EnvironmentLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/798682017-07-10T15:24:04Z2017-07-10T15:24:04ZSouth Africa should sort out the bad from the really bad on its invasive species list<figure><img src="https://images.theconversation.com/files/177520/original/file-20170710-29699-vqh4hb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Managing trout is a contentious issue with conflicting views about whether they pose a risk, or are beneficial.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><em>This article is the third in a <a href="https://theconversation.com/topics/invasive-species-africa-40566">series</a> The Conversation Africa is running on invasive species.</em></p>
<p>Alien species have been introduced to Africa for a variety of reasons. They provide food, raw materials for industry, ornamental plants, recreation in the form of sport fishing, hunting and pets. Some that are highly valued have been moved around widely. And in some areas they now form prominent components of societies and ecosystems like the domestic cat for example.</p>
<p>Many alien species bring considerable benefits. But some have become invasive, causing a loss of biodiversity, changes to ecosystems, economic losses and, in some cases, even affecting people’s health.</p>
<p>The shrub <a href="http://www.arc.agric.za/arc-ppri/Pages/Mesquite-Prosopis.aspx"><em>Prosopis</em></a> or mesquite is an example. It was introduced to South Africa to provide fodder, firewood and shade in arid parts of the country. But it’s also a <a href="http://www.arc.agric.za/arc-ppri/Pages/Mesquite-Prosopis.aspx">major water user</a>. And two trout species (<em>S. trutta</em> and <em>O. mykiss</em>) are used for recreational angling and commercial aquaculture. But they’ve also been implicated in having a negative effect on the environment. </p>
<p>Managing invasive species is therefore critical. In South Africa the movement and use of 552 listed invasive species are managed under the <a href="http://www.gov.za/documents/national-environmental-management-biodiversity-act-0">Biodiversity Act</a> and regulations attached to it. But not all the species on the list are equally harmful. Several may in fact be relatively harmless. </p>
<p>All the listed species under these regulations require management. Given that the capacity is limited, regulations should arguably focus on priority species because not all are necessarily harmful to the extent that would justify spending large amounts of time and effort on keeping them under control. </p>
<p>The question then is: are there some species that could be removed from the list? In our recent <a href="https://doi.org/10.4102/abc.v47i2.2160">study</a> we set out to answer this question by classifying species as inconsequential, beneficial, destructive or conflict generating species. This was done by assessing the relative degree of benefit they brought and their negative effects. </p>
<h2>Beneficial and harmful species</h2>
<p>The classification was done by using a simple scoring system. It had two categories for the negatives (ecological and socio-economic) and two for the benefits (economic and intrinsic).</p>
<ol>
<li><p>Inconsequential species: these make up 55% of the species listed under the act and in the regulations. They were associated with relatively low costs and low benefits to society. Species in this group had limited distribution or no known impact and were largely introduced as ornamentals or pets. Some examples include the eastern grey squirrel (<em>Sciurus carolinensis</em>), European perch (<em>Perca fluviatilis</em>), and the Père David’s Deer (<em>Elaphurus davidianus</em>).</p></li>
<li><p>Destructive species: these make up 29% of the list. They don’t bring substantial benefits to society or the environment, but they have a highly negative impact. Many were introduced accidentally and are regarded largely as pests and weeds. Examples include invasive rodents like the black rat (<em>Rattus rattus</em>) which causes damage to infrastructure and <a href="http://dx.doi.org/10.1080/10408410902989837">transmission of zoonotic diseases</a> and pitch canker (<em>Fusarium circinatum</em>) a growing threat to <a href="https://link.springer.com/article/10.1071/AP08036">pine plantations and forests worldwide</a>. </p></li>
</ol>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/177521/original/file-20170710-4369-150l1v6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The jacaranda is an iconic tree species in the city of Pretoria where it’s regarded as part of the identity.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<ol>
<li><p>Beneficial species: they make up 10% of the list and have clear social or environmental benefits. For example the jacaranda (<em>Jacaranda mimosifolia</em>) is an iconic tree species in the city of Pretoria where the species is regarded as part of the identity and <a href="http://www.stratek.co.za/.%5Carchive%5Cronniekasrils.html">“sense of place” of the city</a>. Active management is not necessary or should only be done in particular cases. </p></li>
<li><p>Conflict-generating organisms: these can be either beneficial or destructive, depending on one’s perspective or what value is placed on them. They make up only 6% of the list. There’s huge disagreement about whether these species should be controlled, or how they should be controlled. Examples include woody plants introduced for forestry, erosion control, sand dune stabilisation, agriculture and as ornamentals. Acacias and pines <a href="https://link.springer.com/article/10.1007/s10530-013-0615-8">are examples</a>. Animal examples include species like the Himalayan tahr which was introduced to the Table Mountain National Park. The goat has been the focus of <a href="https://doi.org/10.1016/j.landurbplan.2016.03.010">eradication attempts</a>, despite strong opposition. It also includes species introduced for aquaculture like maroon and brown trout. Managing trout has been highly contentious with conflicting views about whether they pose a risk, or deliver a benefit. This has led to them being listed and delisted. The trout fraternity refuse to acknowledge that trout are invasive species and highlight the lack of scientific evidence of the risks <a href="http://www.farmersweekly.co.za/opinion/by-invitation/is-this-the-end-of-the-line-for-freshwater-fishing/">they pose</a>. </p></li>
</ol>
<h2>Finding common ground</h2>
<p>We need to keep sight of the fact that there is general agreement on 94% of listed species. By identifying the small number that are generating the greatest tension, it’s more likely discussions can be held to reach common ground on regulation.</p>
<p>Most countries in Africa don’t have invasive species regulations. But there’s growing recognition that they’re needed. South Africa offers useful lessons on how this could be done. </p>
<p>The control of species listed under the country’s biodiversity act is compulsory. This means that plans to manage them have to be drawn up and implemented. But this doesn’t seem sensible given that not all are equally harmful and resources are limited. Our study <a href="https://doi.org/10.4102/abc.v47i2.2160">suggests</a> that some of the species currently regulated could be removed from the list. </p>
<p>Countries wanting to set up a system of managing invasive species could start by classifying a prospective list of candidates. Policymakers could then quickly bring out legislation against the most damaging and destructive ones. At the same time, discussions could be had on the ones that generate conflict with the aim of reaching consensus.</p>
<p>This would allow managers and regulators to focus on the most destructive species – as well as those that are at the centre of fierce disagreement.</p><img src="https://counter.theconversation.com/content/79868/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tsungai Zengeya receives funding from National Research Foundation, South Africa.
Affiliation: Centre for Invasion Biology, South African National Biodiversity Institute, Kirstenbosch Research Centre, Claremont, South Africa</span></em></p>Regulating species in South Africa is difficult. But identifying those creating the greatest tension, would shift focus on the most destructive species.Tsungai Zengeya, Researcher at the South African National Biodiversity Institute, South African National Biodiversity InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/786842017-06-14T15:26:34Z2017-06-14T15:26:34ZAlien animals and plants are on the rise in Africa, exacting a growing toll<figure><img src="https://images.theconversation.com/files/173342/original/file-20170612-10193-b97g43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The larger grain borer beetle attacks crops like maize and cassava, threatening food security.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><em>This article is the first in a series The Conversation Africa is running on invasive species.</em></p>
<p>Let’s say you’re travelling from Uganda to South Africa for business. You finally arrive at your hotel after a long day and decide to change before dinner. You unlock and unzip your luggage, but there’s something in your bag that you didn’t pack. As you reach for a clean shirt, a moth flies out. Did that come with you all the way from Uganda? It’ll be fine, right? Surely, something so small won’t cause any harm.</p>
<p>Species are intentionally or accidentally transported by humans between continents to regions where they are not native. With the help of humans or by natural means like flight, these alien species can also spread within continents.</p>
<p>Their spread within continents can be rapid, affecting both the ecology as well as societies and the economy. Unfortunately, it’s really challenging to prevent species from spreading. Given the vast amount of people and goods that are transported between and around continents they can easily be moved across oceans as well as between countries.</p>
<p>The spread of alien species within Africa is increasing. Since 2000 more alien insect pests of eucalyptus trees have spread to other African countries from South Africa, than have been introduced to these African countries <a href="http://www.abcjournal.org/index.php/ABC/article/view/2157">from other continents</a>. To manage the spread of these alien species countries need to <a href="http://www.abcjournal.org/index.php/ABC/article/view/2157">co-operate, communicate and share information and skills.</a>. </p>
<h2>The spread of alien species</h2>
<p>Many alien plants and animals have been introduced to Africa from other regions and then have spread from country to country, often having devastating effects.</p>
<p>Take the larger grain borer beetle, (<em>Prostephanus truncatus</em>) which is thought to have arrived on the continent in imported grain from Mexico and central America. The beetle was introduced to Tanzania before 1984, Togo before 1981 and <a href="http://www.abcjournal.org/index.php/ABC/article/view/2157">Guinea before 1987</a>. It then spread across the continent and within 20 years could be found further south in South Africa. </p>
<p>The beetle attacks crops such as maize and cassava, threatening food security and the <a href="http://www.cabi.org/isc/datasheet/44524">livelihoods of the poor</a>. Infestations often destroy maize that’s been stored by farmers, forcing them to buy maize as well as lose income they could have earned from selling any excess.</p>
<p>But alien species don’t just arrive from abroad. Many that are native to parts of Africa have also spread to countries on the continent where they are not native.</p>
<p>An example is the fish commonly known as the Mozambique tilapia (<em>Oreochromis mossambicus</em>) which is native to rivers on the east coast of southern Africa. Fishermen have transported the Mozambique tilapia to other areas and it is now found in river systems in southern and western South Africa and Namibia. </p>
<p>The Mozambique tilapia is a popular species for fishing but it can pose a threat to native <a href="http://www.iucngisd.org/gisd/speciesname/Oreochromis+mossambicus">fish</a> and has been responsible for the disappearance of native species in some <a href="https://www.fws.gov/fisheries/ans/erss/highrisk/Oreochromis-mossambicus-ERSS-revision-July-2015.pdf">regions</a>.</p>
<p>The spread of alien species within Africa is by no means a new thing. For instance, the bur clover (<em>Medicago polymorpha</em>), a plant from northern Africa, might have been accidentally transported by humans to South Africa <a href="http://www.abcjournal.org/index.php/ABC/article/view/2157">as early as 760 AD.</a></p>
<h2>A high and increasing threat</h2>
<p>Recently a number of alien species have spread extremely rapidly across the continent, posing a particularly high threat to food security and livelihoods.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173341/original/file-20170612-10258-1rjje5i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The fall armyworm, native to the Americas, was first recorded in west and central Africa in early 2016 and then in South Africa in January 2017.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>One is a caterpillar known as the fall armyworm (<em>Spodoptera frugiperda</em>). The species, native to the Americas, was first recorded in west and central Africa in early 2016 and then in <a href="http://www.arc.agric.za/arc-ppri/Fact%20Sheets%20Library/The%20new%20Invasive%20Fall%20Armyworm%20(FAW)%20in%20South%20Africa.pdf">South Africa in January 2017</a>. </p>
<p>The moths of the armyworm are strong fliers and the species may have spread through flight to South Africa from other African countries. Although the species attacks a wide range of crops, it poses a particularly serious threat <a href="https://theconversation.com/armyworms-are-wreaking-havoc-in-southern-africa-why-its-a-big-deal-72822">to grain farmers</a>. It is extremely <a href="https://theconversation.com/why-its-hard-to-control-the-fall-armyworm-in-southern-africa-72890">difficult to manage</a>. </p>
<p>Another example is a wasp known as the bluegum chalcid (<em>Leptocybe invasa</em>), which is native to Australia. In 2000 it was <a href="http://www.fabinet.up.ac.za/publication/pdfs/1952-kelly_et_al_selitrichodes_neseri.pdf">detected in Israel</a> and shortly afterwards it was reported in <a href="http://www.forestry.co.za/uploads/File/home/notices/2011/ICFR%20IS01-2011gallwasp.pdf">Uganda and Kenya</a>. From there it spread rapidly to many African countries including Zimbabwe, Mozambique, and Tanzania and was finally detected in <a href="http://www.forestry.co.za/uploads/File/home/notices/2011/ICFR%20IS01-2011gallwasp.pdf">South Africa in 2007.</a> The insect probably reached Israel on live plant material and spread into Africa the same way, or was carried by people travelling between countries. </p>
<p>The wasp causes swelling or growths on eucalyptus trees, which can lead to <a href="http://www.fao.org/forestry/13569-05912e0e2fe9054c3ed4904ae597e3310.pdf">decreased growth and tree death.</a> As eucalyptus trees are an important source of income and fuel, this species could have an impact on the livelihoods of locals in these countries.</p>
<h2>Preventing the introduction and spread</h2>
<p>Once a species is introduced to one African country it’s highly likely it will spread to others on the continent because borders checks are weak.</p>
<p>The introduction and spread of species could be reduced if countries introduced biosecurity systems. These are used extensively in countries like Australia and New Zealand and involve using technology to check for alien species when people and goods enter a country. In Australia this involves inspecting goods, vehicles and luggage before they enter the country.</p>
<p>But even these systems aren’t a guarantee that species won’t spread. African countries would need to work together and share information and skills. This would also allow countries to prepare for the arrival of species, and to draw up plans to reduce their impact.</p>
<p>This is a tall order. But as a country’s defence against alien species introductions is only as strong as that of its neighbours, such action would benefit all of the countries involved.</p><img src="https://counter.theconversation.com/content/78684/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katelyn Faulkner receives funding from South African National Biodiversity Institute's Invasive Species Programme. </span></em></p><p class="fine-print"><em><span>Mark Robertson receives funding from the DST-NRF Centre for Invasion Biology. </span></em></p><p class="fine-print"><em><span>Brett Hurley does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Many alien plants and animals have been introduced to Africa from other regions and spread from country to country, often having devastating effects.Katelyn Faulkner, Postdoctoral research fellow, University of PretoriaBrett Hurley, Senior Lecturer Zoology and Entomology, University of PretoriaMark Robertson, Associate Professor Zoology & Entomology, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.