tag:theconversation.com,2011:/us/topics/earthworms-36940/articlesEarthworms – The Conversation2024-03-26T17:01:48Ztag:theconversation.com,2011:article/2266432024-03-26T17:01:48Z2024-03-26T17:01:48ZThe ‘worm moon’ once marked the spring return of earthworms – until global warming kicked in<figure><img src="https://images.theconversation.com/files/584414/original/file-20240326-16-7psmz6.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5982%2C3970&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="source">Darkfoxelixir / shutterstock</span></span></figcaption></figure><p>The worm moon has risen. The final full moon of winter in the northern hemisphere appeared on <a href="https://www.theguardian.com/news/gallery/2024/mar/25/a-volcanic-eruption-and-a-worm-moon-photos-of-the-day">March 25</a> and owes its name to <a href="https://www.nationalgeographic.co.uk/2019/02/full-moon-names-explained">Native Americans</a> who noted winter’s end by the trails of earthworms it illuminated on the newly thawed soil. </p>
<p>Common names of full moons generally come from seasonal animals, colours or crops: wolf moon, pink moon, harvest moon. But the worm moon may be losing its significance, as climate change leads to wetter summers and milder winters in much of the world. I’ve been an earthworm scientist for more than three decades, and, of late, I’m seeing signs of worms at the surface in months when they used to be inactive.</p>
<p>To track how the worm moon might be changing we can look at a particular earthworm species (<em>Lumbricus terrestris</em>, aka the dew worm, nightcrawler or lob worm) which is unusually easy to track. Also sometimes called the common earthworm, if you see a big worm in the garden, it’s likely to be this species. </p>
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<p><em>Do the seasons feel increasingly weird to you? You’re not alone. Climate change is distorting nature’s calendar, causing plants to flower early and animals to emerge at the wrong time.</em></p>
<p><em>This article is part of a series, <a href="https://theconversation.com/uk/topics/wild-seasons-152175?utm_source=InArticleTop&utm_medium=TCUK&utm_campaign=WS">Wild Seasons</a>, on how the seasons are changing – and what they may eventually look like.</em></p>
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<p>Most worms spend most of their lives underground, but the dew worm almost completely leaves its deep burrow, with tail tip left in, as it ventures on to the soil surface every night to feed on dead leaves. These worms also mate on the soil surface. They may be hermaphrodite (both male and female) but still need to exchange sperm with a partner – each fertilising the other.</p>
<p>Such activities usually take place under the cover of darkness to avoid birds and other potential daytime predators. However, the worms are restricted by soil conditions at the top of the burrow. They cannot surface if the soil is baked dry (in summer) or frozen (in winter). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Large worm in soil" src="https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.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"></a>
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<span class="caption"><em>Lumbricus terrestris</em> is a large earthworm found across the world.</span>
<span class="attribution"><span class="source">D. Kucharski K. Kucharska / shutterstock</span></span>
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<p>In theory, the passing of winter would kickstart the surface activity (and therefore the worm moon). Yet if the winter isn’t that cold, we perhaps need to reconsider which moon should be termed the “worm moon”. Maybe a date earlier in the year would be better, or perhaps the term may cease to have any real meaning.</p>
<p>We can get a sense of how these earthworms can adapt to changing circumstances by looking at the northernmost populations, such as those in Finland, which are exposed to 24 hours of daylight in summer. These “white nights”, when the sky never gets dark, put additional stress on these worms as they cannot use darkness to hide from predators but must still feed and mate at the surface while conditions allow.</p>
<h2>Finland v Lancashire v Ohio</h2>
<p>A decade ago, colleagues and I set out to see if Finnish worms behaved any differently during the white night period to worms of the same species taken to Finland from lower latitudes. We <a href="https://www.sciencedirect.com/science/article/pii/S0038071714000248">compared native dew worms</a> from an area in south-west Finland at 60°N, with those from Lancashire in the UK (53°N) and Ohio in the US (40°N, more than 2,000km south of Finland), both of which have dark nights throughout the year.</p>
<p>We put these worms outdoors under ambient (white night) light in soil-filled drainpipes (1m deep) in a large, controlled temperature water bath (an old chest freezer with no lid). We looked at their feeding and mating, and, in parallel, repeated the experiment under darkened conditions at “night”. </p>
<p>In darkness, worms from all three origins were similarly very active in feeding and mating. </p>
<p>Under ambient conditions, the Finnish worms were generally the most active. They emerged earlier in the evening and ceased their activity later in the morning than those from the two more southerly populations. It seems the species had adapted to its conditions, with a normal reluctance to surface during daylight overtaken by a need to feed and mate.</p>
<p>Perhaps with warming soils, earthworms are becoming more active during traditionally colder or drier months. This will increase their effect on the soil – earthworms are ecosystem engineers and generally lead to increased soil fertility – which is generally positive, even if churning up the soil can lead to <a href="https://www.nature.com/articles/nclimate1692">further decomposition and greenhouse gas emissions</a>. </p>
<p>A worm moon and white nights would never normally appear in the same sentence. However, changes in the activities of worms as the global climate becomes less predictable means we may need to rethink at least one of our terms of reference that has marked time for hundreds or thousands of years. Enjoy the traditional worm moon while it lasts.</p><img src="https://counter.theconversation.com/content/226643/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Richard Butt 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>The last full moon of winter can illuminate earthworms in newly-thawed soil.Kevin Richard Butt, Reader in Ecology, University of Central LancashireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2241522024-03-25T12:39:22Z2024-03-25T12:39:22ZWhat is dirt? There’s a whole wriggling world alive in the ground beneath our feet, as a soil scientist explains<figure><img src="https://images.theconversation.com/files/582688/original/file-20240318-24-77z9su.jpg?ixlib=rb-1.1.0&rect=0%2C9%2C3110%2C2057&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dig into soil and you'll find rock dust but also thousands of living species.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/little-childs-hands-digging-in-the-mud-royalty-free-image/619539728">ChristinLola/iStock/Getty Images Plus</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<blockquote>
<p><strong>What is dirt? – Belle and Ryatt, ages 7 and 5, Keystone, South Dakota</strong></p>
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<p>When you think about dirt, you’re probably picturing soil. There’s so much more going on under our feet than the rock dust, or “dirt,” that gets on your pants.</p>
<p>When <a href="https://arts-sciences.und.edu/academics/biology/brian-darby/index.html">I began studying soil</a>, I was amazed at how much of it is actually alive. Soil is teeming with life, and not just the earthworms that you see on rainy days.</p>
<p>Keeping this vibrant world healthy is <a href="https://www.youtube.com/watch?v=Qas9tPQKd8w">crucial for food, forests and flowers to grow</a> and for the animals that live in the ground to thrive. Here’s a closer look at what’s down there and how it all works together.</p>
<figure class="align-center ">
<img alt="Cupped hands holds soil against a dark background with a tendril of plant root dangling through the fingers." src="https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.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">
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<span class="caption">Soil is a vibrant ecosystem.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/bokeh-photography-of-person-carrying-soil-jin4W1HqgL4">Gabriel Jimenez via Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>The rocky part of soils</h2>
<p>If you scoop up a handful of dry soil, the basic dirt that you feel in your hand is actually very small pieces of <a href="https://passel2.unl.edu/view/lesson/c62dc027ae56/1">weathered rock</a>. These tiny bits eroded from larger rocks over millions of years.</p>
<p>The <a href="https://www.soils4teachers.org/physical-properties/">balance of these particles</a> is important for how well soil can hold water and nutrients that plants need to thrive. </p>
<p>For example, <a href="https://www.masterclass.com/articles/sandy-soil-guide">sandy soil</a> has larger rock grains, so it will be loose and can easily wash away. It won’t hold very much water. <a href="https://www.thespruce.com/understanding-and-improving-clay-soil-2539857">Soil with mostly clay</a> is finer and more compact, making it difficult for plants to access its moisture. In between the two in size is <a href="https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/what-is-silt.htm">silt, a mix of rock dust and minerals</a> often found in fertile flood plains.</p>
<p>Some of the most productive soils have a good balance of sand, clay and silt. <a href="https://www.masterclass.com/articles/how-to-create-loam-soil-for-your-garden">That combination</a>, along with the remnants of plants and animals that have died, helps the soil to retain water, allows plants to access that water and minimizes erosion from wind or rain.</p>
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<img alt="Three tipped over pots spill different types of soil – sandy is heavier grain, clay is finer grain and thicker, and loamy is darker." src="https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Loamy soil, ideal for gardens, is a mix of sand, clay and silt.</span>
<span class="attribution"><a class="source" href="https://www.nesdis.noaa.gov/learn-about-soil-types">NOAA</a></span>
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<h2>The wriggling, munching parts of soil</h2>
<p>Among all those rock particles is a <a href="https://doi.org/10.3390/app10113717">whole world of living things</a>, each busy doing its job.</p>
<p>To get a sense of just how many creatures are there, picture this: The zoo in Omaha, Nebraska, boasts <a href="https://www.omahazoo.com/">over 1,000 animal species</a>. But if you scooped up a small spoonful of soil in your backyard, it would likely contain <a href="https://www.ceh.ac.uk/our-science/case-studies/case-study-why-do-soil-microbes-matter">at least 10,000 species</a> and around a billion living microscopic cells.</p>
<p>Most of those species are <a href="https://www.westernsydney.edu.au/newscentre/news_centre/story_archive/2018/first_soil_atlas">still largely a mystery</a>. Scientists don’t know much about them or what they do in soil. In fact, most species in soil don’t even have a formal scientific name. But each plays some kind of role in the vast soil ecosystem, including generating the <a href="https://www.aces.edu/blog/topics/farming/essential-plant-elements/">nutrients that plants need to grow</a>.</p>
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<a href="https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two centipede-like creatures caught on camera immediately after a rock is lifted." src="https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=439&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=439&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=439&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=552&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=552&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=552&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">Lifting a rock reveals a symphylan, or garden centipede, left, and a poduromorph, or plump springtail, munching through the soil.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Symphylan_%26_poduromorph_springtail_(3406419924).jpg">Marshal Hedin via Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Imagine a leaf falling from a tree in late autumn.</p>
<p>Inside that leaf are a lot of nutrients that plants need, such as nitrogen, potassium and phosphorus. There is also a lot of <a href="https://scied.ucar.edu/learning-zone/earth-system/biogeochemical-cycles">carbon in that leaf</a>, which holds energy that can be used by other organisms such as bacteria and fungi.</p>
<p>The leaf itself is too large for a plant to take up through its roots, of course. But that leaf can be broken down into smaller and smaller pieces. This process of breaking down plant and animal tissue is <a href="https://youtu.be/IBvKKMzXYtY?feature=shared">known as decomposition</a>.</p>
<p>When the leaf first falls to the ground, <a href="https://doi.org/10.3390%2Finsects11010054">arthropods</a> – such as insects, mites and <a href="https://www.chaosofdelight.org/collembola-springtails">collembolans</a> – break the leaf down into smaller chunks by shredding the tissue. Then, an <a href="https://youtu.be/n3wsUYg3XV0?feature=shared">earthworm might come along</a> and eat one of the smaller chunks and break it down even more in <a href="https://www.pbs.org/video/how-do-worms-turn-garbage-into-compost-jwj6cm/">its digestive tract</a>.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/2Pa1FwmKZcQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">PBS explores how earthworms help turn dead plants into fertile soil.</span></figcaption>
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<p>Now the broken-up leaf is small enough for microbes to come in. <a href="https://ohioline.osu.edu/factsheet/anr-36">Bacteria</a> and <a href="https://ohioline.osu.edu/factsheet/anr-37">fungi secrete enzymes</a> into the soil that further break down organic material into even smaller pieces. If enough microbes are active, eventually this organic material will be broken down enough that it can dissolve in water and be taken up by plants that need it.</p>
<p>To aid in this process, there are many small animals, such as <a href="https://www.canr.msu.edu/news/are_soil_nematodes_beneficial_or_harmful">nematodes</a> and <a href="https://www.livingsoil.net/protozoa">amoebae</a>, that consume bacteria and fungi. There are also predatory nematodes that feed on other nematodes to make sure they don’t become too abundant, so everything remains in balance as much as possible. </p>
<p>It’s quite a complicated food web of interacting species in a delicate balance.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/IBvKKMzXYtY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A time-lapse video filmed about 4 inches underground shows a leaf decomposing over 21 days in July. At the end, radish roots make their way down into the soil. Video by Josh Williams.</span></figcaption>
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<p>While some fungi and bacteria <a href="https://www.growingagreenerworld.com/bacteria-fungus-and-viruses-an-overview/">can harm plants</a>, there are many species that are considered beneficial. In fact, they <a href="https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soils/soil-health">may be the key</a> to figuring out how to grow enough crops to feed everyone without degrading and overburdening the soil.</p>
<h2>Figuring out your soil type</h2>
<p>Scientists have named <a href="https://www.nrcs.usda.gov/resources/education-and-teaching-materials/soil-facts">over 20,000 different types</a> of unique soils. If you’re curious about the <a href="https://www.nesdis.noaa.gov/learn-about-soil-types">soil and dirt in your area</a>, the University of California, Davis has a <a href="https://casoilresource.lawr.ucdavis.edu/gmap/">website where you can learn</a> more about local soils and their chemical and physical attributes.</p>
<p><a href="https://www.farmers.gov/conservation/soil-health">Caring for soil</a> to promote its living creatures’ benefits and minimize their harm takes work, but it’s essential for keeping the land healthy and growing food for the future.</p>
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<p class="fine-print"><em><span>Brian Darby receives funding from the United States Department of Agriculture. </span></em></p>Rock dust is only part of the story of soil. Living creatures, many of them too tiny to see, keep that soil healthy for growing everything from food to forests.Brian Darby, Associate Professor of Biology, University of North DakotaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2172272023-11-13T16:25:47Z2023-11-13T16:25:47ZEarthworms are our friends – but they will make the climate crisis worse if we’re not careful<figure><img src="https://images.theconversation.com/files/559077/original/file-20231113-22-x1gfqr.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6720%2C4476&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/two-earthworms-on-wet-soil-space-2331008495">New Africa/Shutterstock</a></span></figcaption></figure><p>Earthworms are revered for the way they nourish healthy soils, and scientific evidence validates the affection gardeners feel for these industrious invertebrates. Nevertheless, research has shown that our soil-dwelling friends may be less benevolent as the climate crisis escalates and grants them access to recently defrosted northern soils.</p>
<p>Historically, earthworms were viewed alongside slugs and snails as garden pests and thought to eat flower and vegetable roots from beneath the soil surface. They were killed and removed from gardens until more informed naturalists like Charles Darwin made observations that showed their worth. </p>
<p>Sometimes referred to as “Darwin’s plough”, earthworms naturally till the soil and increase its fertility by pulling leaves underground where they rot and enrich the soil. </p>
<p>Earthworms are considered ecosystem engineers too – species with an outsized influence on their environment. As such, they carry out numerous activities that are beneficial to us, including the formation, drainage and aeration of soils. They are also a protein-rich food source for birds and mammals. </p>
<figure class="align-center ">
<img alt="A bird with earthworms in its beak." src="https://images.theconversation.com/files/559078/original/file-20231113-23-4d70qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559078/original/file-20231113-23-4d70qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=433&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559078/original/file-20231113-23-4d70qz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=433&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559078/original/file-20231113-23-4d70qz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=433&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559078/original/file-20231113-23-4d70qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=544&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559078/original/file-20231113-23-4d70qz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=544&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559078/original/file-20231113-23-4d70qz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=544&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A firm favourite of feathered friends.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/a-bird-with-a-worm-in-its-mouth-standing-in-the-grass-FBWpkk20hoc">Jack Blueberry/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Unfortunately, they now have what may be perceived as a darker side.</p>
<h2>Globetrotters without feet</h2>
<p>European earthworms, such as the well-known lobworm (<em>Lumbricus terrestris</em>), the large and darkly pigmented worm you’ve probably seen writhing in a patch of upturned soil, are now found worldwide. Centuries ago they travelled in the soil of crop and fruit-bearing plants as they were taken by settlers to new lands. On newly ploughed farms this was seen as a bonus and these introduced worms bolstered food production. </p>
<p>More recently, these introduced earthworms have established themselves in more natural habitats, such as the temperate forests of North America. More often than not, their arrival in these forests has been as discarded fishing bait. There, the earthworm’s tendency to bury fallen leaves and till the soil has <a href="https://www.jstor.org/stable/3868431?searchText=&searchUri=&ab_segments=&searchKey=&refreqid=fastly-default%3A184c54dd2618c074f41c077ce668985c&seq=1">caused problems</a>, severely altering the nutrient status of the soil, exposing tree roots and reducing cover for ground nesting birds. </p>
<p>Earthworms are now viewed as invasive alien species in such ecosystems. Further north, in the boreal forests of Arctic and sub-Arctic Canada, an even greater problem is growing</p>
<p>Arctic soils are thought to store <a href="https://bg.copernicus.org/articles/11/6573/2014/bg-11-6573-2014.pdf">around half</a> of all the carbon locked up in soil globally. The greatest risk to the carbon storage of boreal forests was always assumed to be forest fires, which <a href="https://cdnsciencepub.com/doi/10.1139/er-2021-0074">may be increasing</a> as a result of rising global temperatures. </p>
<p>But earthworms may actually pose as great a threat. As land that was once covered with ice or in a semi-permanent frozen state thaws, the carbon-rich nutrients it held for thousands of years become accessible to microorganisms and soil-dwelling animals. </p>
<p>After the last ice age, no earthworms were present in northern soils. Since these creatures spread through the earth at a rate of only <a href="https://link.springer.com/article/10.1007/BF00317626">10 metres per year</a> under normal circumstances, even if they could survive, they wouldn’t be expected to reach such regions for centuries. </p>
<h2>Heading north</h2>
<p>But by building roads and pursuing recreational activities like freshwater angling, people are accidentally transporting ecosystem-engineering earthworms into areas where recently defrosted soil awaits. Again, it is abandoned, living fishing bait that creates a new invasion front.</p>
<p>By exercising their natural behaviour, earthworms are unlocking carbon from this soil and much of it is being released into the atmosphere as carbon dioxide. A study published in 2015 <a href="https://doi.org/10.1016/j.soilbio.2015.05.020">predicted</a> average losses of 10g of carbon per square metre of forest floor per year – a similar figure to that released by wildfires or the removal of trees for timber.</p>
<p>You might think earthworms would struggle to survive Arctic winters, but some, such as the octagonal worm (<em>Dendrobaena octaedra</em>) are relatively freeze-tolerant and their eggs can <a href="https://cdnsciencepub.com/doi/10.1139/er-2021-0074">survive temperatures of -35°C</a>. Others, such as the lobworm, can burrow deep to survive freezing temperatures above. Such species, once established, are not easily eradicated. </p>
<figure class="align-center ">
<img alt="A worm in soil." src="https://images.theconversation.com/files/559120/original/file-20231113-15-e1twa2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559120/original/file-20231113-15-e1twa2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559120/original/file-20231113-15-e1twa2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559120/original/file-20231113-15-e1twa2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559120/original/file-20231113-15-e1twa2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559120/original/file-20231113-15-e1twa2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559120/original/file-20231113-15-e1twa2.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">The lobworm, once confined to western Europe, is now globally distributed.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/common-earthworm-lumbricus-terrestris-nightcrawler-1581313723">Liz Weber/Shutterstock</a></span>
</figcaption>
</figure>
<p>In these newly available soils, earthworms are interacting with a range of microorganisms and enabling them to more easily decompose plant matter which was <a href="https://pub.epsilon.slu.se/31133/1/blume-werry-g-et-al-20230619.pdf">previously locked up in ice</a>, generating large volumes of carbon dioxide, methane and other greenhouse gases in the process.</p>
<p>This creates a positive feedback loop as the further release of greenhouse gases accelerates temperature rise. This is probably an unstoppable process and the best action with respect to earthworms is to prevent their accidental introduction at further sites in the sub-Arctic through education and, potentially, the policing of recreational areas.</p>
<p>Earthworms are vital in most soils, but in extremely northern latitudes, a massive shift has occurred in our view of these exceptional animals. Globally, we – the general public, governments, industry and scientists – must begin to address the issues of the climate crisis that affect us, earthworms, and indeed all living things on Earth.</p>
<hr>
<figure class="align-right ">
<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">
<figcaption>
<span class="caption"></span>
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<p class="fine-print"><em><span>Kevin Richard Butt 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>Thawing permafrost in the far north is an inviting prospect for invertebrate burrowers.Kevin Richard Butt, Reader in Ecology, University of Central LancashireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1475782020-11-11T19:19:33Z2020-11-11T19:19:33ZCurious Kids: Do worms have blood? And if so, what colour is it?<figure><img src="https://images.theconversation.com/files/368765/original/file-20201111-13-x5fk9i.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5742%2C3785&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock </span></span></figcaption></figure><blockquote>
<p><strong>Do worms have blood, and if they do, what colour is it? Momo Bice, aged 9, Carlton</strong></p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Momo. Well, the short answer to your question is: yes. Many worms do have blood, and it is either colourless or pink, or red, or even green! But to answer your question properly, first we need to decide what type of worm we are talking about. </p>
<p>There are lots of different sorts of worms. Generally, a worm is any long, thin animal that does not have a backbone, but scientifically we recognise three types of worms: flatworms, roundworms and segmented worms. Worms live in the sea, in sand and soil. Some live inside plants or animals, and we call them parasites.</p>
<p>So let’s look at what blood you might find inside these different types of worms. </p>
<figure class="align-center ">
<img alt="Segmented worm" src="https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Worms live in sea, sand soil, or – if we’re unlucky – even inside us.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>The three worm types</h2>
<p><strong>Flatworms:</strong> These include tapeworms, which are parasites (meaning they live on a host organism), and planaria, which live in ponds and lakes. These animals are so flat they don’t even need blood. They absorb oxygen through their skin and it spreads directly to every cell in their body. As a result they are pretty much colourless, or whitish.</p>
<p><strong>Roundworms:</strong> Also called nematodes, these worms are mainly found in soil. Roundworms can also live as parasites in humans, causing really <a href="https://theconversation.com/with-fewer-resources-were-finding-clever-ways-to-map-river-blindness-in-africa-32126">nasty</a> <a href="https://www.cdc.gov/parasites/toxocariasis/gen_info/faqs.htm">effects</a> such as blindness and brain defects. One large roundworm that lives in the intestines of humans can grow to more than <a href="https://www.cdc.gov/parasites/ascariasis/biology.html">35 centimetres</a> – that’s longer than a standard ruler!</p>
<p>As the name suggests, roundworms are tube-shaped. Their body cavity contains fluid that delivers oxygen to its organs. But this fluid is not called blood, because it does not circulate around the body.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-are-parasites-and-how-do-they-make-us-sick-121489">What are parasites and how do they make us sick?</a>
</strong>
</em>
</p>
<hr>
<p>Most roundworm species are very small, and so can diffuse oxygen through their skin to all parts of their body. But very large roundworms can’t do this as easily, especially when they live inside animals where there is not much oxygen. These large worms use an oxygen-carrying molecule called haemoglobin – more on that in a minute.</p>
<p><strong>Segmented worms:</strong> These worms include earthworms, leeches and marine worms. Also known as annelids, the bodies of segmented worms are divided by grooves into a series of segments. Most have circulatory systems – that is, blood vessels and a heart that pumps blood around the body. </p>
<figure class="align-center ">
<img alt="A flatworm" src="https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.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">Flatworms have no body cavity.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>So what colour is the blood?</h2>
<p>The <a href="https://biomolecules101.wordpress.com/2020/01/17/oxygen-transport-proteins-the-colors-of-blood/">colour of blood</a> in any animal is determined by the molecule that carries oxygen and other gases in and out of the body. If the molecule uses iron to carry the oxygen, then the blood is usually red. If it uses copper, the blood is usually blue. But these molecules can also be green and pink. </p>
<p>All these colours except blue are found in worms. Haemoglobin is the most common oxygen-carrying molecule, including in worms. Haemoglobin contains iron, which means most worm blood – including that of earthworms and leeches – is red. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-leeches-suck-our-blood-117316">Curious Kids: why do leeches suck our blood?</a>
</strong>
</em>
</p>
<hr>
<p>Some segmented worms use a different oxygen-carrying molecule called <a href="https://doi.org/10.1098/rspb.1926.0008">chlorocruorin</a>. The blood of these worms can be either green or red.</p>
<p>One group of segmented marine worms has pink blood. This is because the molecule that carries the oxygen is a type of blood pigment, known as <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/hemerythrin">hemerythrin</a>, which is described as pink or purple.</p>
<p>A few species of segmented worms don’t have any oxygen-carrying molecules at all, so their blood is colourless.</p>
<p>So, the answer to your question is that all segmented worms have blood, while roundworms and flatworms do not. The blood colour depends on the molecule that carries oxygen in that worm. And most worms have red blood, just like us! </p>
<figure class="align-center ">
<img alt="Child's hands holding worms and soil" src="https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.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">There are three worm types, and not all have blood.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/147578/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Sandeman 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>Pink blood, green blood, or no blood at all – when it comes to what’s inside a worm’s body, the answer is more complicated – and fascinating – than you’d think.Mark Sandeman, Honorary Professor, Federation University AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/778482017-06-15T10:51:49Z2017-06-15T10:51:49ZSilent partners: Are earthworms creating pathways for invasive plants?<figure><img src="https://images.theconversation.com/files/173216/original/file-20170609-4796-1r3i4vk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A National Park Service staffer applies herbicide to invasive honeysuckle along the Natchez Trace Parkway.</span> <span class="attribution"><a class="source" href="https://www.nps.gov/natr/learn/nature/invasivespecies2.htm">NPS</a></span></figcaption></figure><p>Small but mighty, earthworms transform the soil of any ecosystem they inhabit. In farm fields, we appreciate the way they <a href="https://theconversation.com/earthworms-are-more-important-than-pandas-if-you-want-to-save-the-planet-74010">recycle nutrients and aerate soil</a>. But in forests, earthworms’ services can be less welcome. </p>
<p>Glaciers removed native earthworms from northeastern North America and the Great Lakes region 12,000 years ago, so the forests that now stand in these regions developed largely without earthworms. Native earthworms have only slowly returned north. Most earthworms living in these forests today were introduced from Europe and Asia – likely arriving via ships’ ballast and soils of imported plants – and they continue to spread from activities that transport soil or by dumping fishing bait. </p>
<p>Introduced earthworms are considered invasive in forest ecosystems because they have many negative impacts, from <a href="http://dx.doi.org/10.1007/s00442-007-0925-6">eliminating the forest floor layer</a> to <a href="http://conservancy.umn.edu/bitstream/handle/11299/174645/Hale%20et%20al%202006.pdf?sequence=1&isAllowed=y">reducing the diversity of understory plants</a>. In particular, species like nightcrawlers that carry surface leaf litter into deep, vertical burrows have dramatic effects on forest floors. Recently, researchers have <a href="http://teachersites.schoolworld.com/webpages/EKatoa/files/earthworms.pdf">proposed</a> an even more nefarious role for earthworms, which interests me as a plant ecologist: They may be hidden drivers of plant invasions.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/173214/original/file-20170609-307-1w9wx0f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/173214/original/file-20170609-307-1w9wx0f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173214/original/file-20170609-307-1w9wx0f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173214/original/file-20170609-307-1w9wx0f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173214/original/file-20170609-307-1w9wx0f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173214/original/file-20170609-307-1w9wx0f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173214/original/file-20170609-307-1w9wx0f.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">This Minnesota hardwood stand normally would have a thick layer of undecomposed and partly decomposed leaves over the mineral soil, but is totally lacking the duff layer because of the presence of exotic earthworms. The photo, taken in November, shows fresh autumn leaves over bare mineral soil.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/esagor/1993224477/in/photolist-6PAY48-6PAYw4-6PAYa6-6PAYJ2-6PF6Bm-6PF6tU-6PF6k5-6PF6VU-6PAYAX-6PAYrc-438Ncg-527AUE-nkchk1">Eli Sagor/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<h2>Can earthworms pave the way for invasive plants?</h2>
<p>My students and I recently collected earthworms from a local park in northeast Ohio. The technique is delightfully simple: We mix ground yellow mustard with water and pour it on the soil. Earthworms wriggle to the surface, annoyed but lively. </p>
<p>We found hundreds of earthworms in a few square meters, but not a single native one. Here, near the southern boundary of glaciation, we do occasionally find native earthworms, though in much lower numbers than European species. In more northern regions like New England and the northern parts of Minnesota, Wisconsin, Michigan and New York, <a href="https://doi.org/10.1641/0006-3568(2002)052%5B0801:EEIINA%5D2.0.CO;2">all earthworms present belong to introduced species</a>.</p>
<p>Increasingly, ecologists have <a href="http://www.chicagobotanic.org/downloads/staff/steffen/wormpublication.pdf">noticed</a> that invasive plants tend to dominate areas where invasive earthworms are also abundant. In a recent <a href="http://dx.doi.org/10.1111/gcb.13446">synthesis</a> of 645 observations across the United States and Canada, researchers found that the cover of nonnative plant species in forests increased with increasing mass of earthworms in the soil. This evidence supports a positive association between invasive plants and earthworms in eastern North American forests.</p>
<p>But we know less about what may cause this apparent correlation. Invasive plants and earthworms may simply thrive in the same environmental conditions. Both often show up in forests that humans have disturbed or <a href="http://dx.doi.org/10.1007/s10530-008-9418-8">previously used for agriculture</a>, which seems likely to explain at least part of the association. </p>
<p>Could earthworms also create pathways for invasive plants? Or, conversely, could invasive plants lead the way for earthworms? Either pattern would be cause for concern, because synergistic interactions could lead to an “<a href="http://dx.doi.org/10.1111/j.1461-0248.2006.00939.x">invasional meltdown</a>,” in which multiple invasive species together cause greater effects and faster changes than the sum of independent invasions. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/173217/original/file-20170609-18375-kb5qe4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/173217/original/file-20170609-18375-kb5qe4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173217/original/file-20170609-18375-kb5qe4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173217/original/file-20170609-18375-kb5qe4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173217/original/file-20170609-18375-kb5qe4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173217/original/file-20170609-18375-kb5qe4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173217/original/file-20170609-18375-kb5qe4.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">Earthworms collected in a day at Rice Lake National Wildlife Refuge, Minnesota.</span>
<span class="attribution"><a class="source" href="https://www.fws.gov/news/blog/index.cfm/2011/8/18/Whats-Eating-Minnesota">USFWS</a></span>
</figcaption>
</figure>
<p>So far, evidence suggests that earthworms can indeed facilitate plant invasions. In experiments where ecologists created forest-floor habitats with and without earthworms and added seeds of invasive plants, the resulting mass of invasive plants often, but <a href="http://dx.doi.org/10.1007/s10530-008-9315-1">not always</a>, <a href="http://dx.doi.org/%2010.1007/s10530-014-0657-6">increased in the presence of earthworms</a>. For example, in a greenhouse experiment using plant communities native to Minnesota forests, earthworms <a href="http://dx.doi.org/%2010.1007/s00442-014-3175-4">promoted</a> germination and establishment of the invasive shrub <a href="https://plants.usda.gov/core/profile?symbol=RHCA3">buckthorn</a>.</p>
<h2>Eating seeds and changing soil chemistry</h2>
<p>How does this process work? Earthworms affect competition among plants both indirectly, by modifying habitat, and directly, by selectively eating roots, seeds and seedlings. The changes they make in forest habitats could favor invasive plants in several ways. </p>
<p>Physically disturbing the forest floor could allow for aggressive species to establish. Earthworms can <a href="http://dx.doi.org/10.1674/0003-0031-166.1.53">increase soil pH</a> and <a href="https://link.springer.com/article/10.1007/s10021-003-0127-y">mobilize nutrients</a>, potentially favoring invasives, which often capitalize on excess nutrients more effectively than native plants. This effect may also help explain why earthworms tend to promote the growth of <a href="http://www.sciencedirect.com/science/article/pii/S0038071709001874">grass-like plants</a>, which is good news for invasive grasses like <a href="https://plants.usda.gov/core/profile?symbol=MIVI">Japanese stiltgrass</a>.</p>
<p>When earthworms invade forests, they also alter the mix of bacteria, fungi and other <a href="http://dx.doi.org/%2010.1007/s10021-003-0129-9">microbes in the soil</a> and <a href="http://dx.doi.org/10.1890/15-1085">disrupt mycorrhizal relationships</a> between soil fungi and plant roots, which most plants rely on to gather nutrients. For example, <a href="https://plants.usda.gov/core/profile?symbol=ALPE4">garlic mustard</a>, an invasive plant common in eastern North American forests, is unusual in that it does not form mycorrhizal relationships. If earthworms damage the mycorrhizae of surrounding native plants, garlic mustard could gain a relative advantage. This could contribute to the <a href="http://teachersites.schoolworld.com/webpages/EKatoa/files/earthworms.pdf">correlation</a> between earthworm and garlic mustard abundance. </p>
<p>Earthworms’ selective eating and dispersing of seeds has the potential to favor invasives as well. They <a href="http://www.sciencedirect.com/science/article/pii/S0038071710001446">digest most of the seeds</a> they eat, so any species they avoid might benefit. But seeds that pass through the worms’ gut intact could gain from burial in the soil, protecting them from predation and harsh conditions, or end up in nutrient-rich earthworm casts (excrement) or middens (piles of casts around burrow entrances), which are <a href="http://dx.doi.org/10.1111/j.1365-2435.2006.01098.x">good places to germinate</a>. With their diminutive mouths, most earthworms prefer smaller seeds, so they repress the establishment of smaller-seeded plant species and <a href="http://dx.doi.org/10.1111/j.1365-2435.2006.01098.x">promote the establishment of larger seeds</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/7fpoOnH9qx8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A 2013 Smithsonian study found that nonnative earthworms pose a serious threat to North American orchids.</span></figcaption>
</figure>
<h2>Two-way relationships?</h2>
<p>For all the ways in which earthworms may aid invasive plants, the plants may return the favor. For example, many invasives produce the <a href="http://waingerlab.cbl.umces.edu/SupportingLiterature/LiteratureReviewDiagrams_Literature/Forbs/Rodgers_et_al_2008a.pdf">quick-to-decompose</a> leaf litter that earthworms love. When scientists removed invasive shrubs like buckthorn and <a href="https://plants.usda.gov/core/profile?symbol=LOBE">honeysuckle</a> from oak forests in Wisconsin, earthworm abundance <a href="http://dx.doi.org/%2010.1007/s10530-008-9281-7">fell dramatically</a>.</p>
<p>This encouraging outcome shows that we need to understand how earthworms interact with specific invasive plants. Identifying and breaking positive feedback loops could help us counter both invasions.</p><img src="https://counter.theconversation.com/content/77848/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kathryn M. Flinn 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>Most of the earthworms in the US Northeast and upper Midwest are nonnative species. Scientists are finding increasing evidence that invasive worms and invasive plants may help each other.Kathryn M. Flinn, Assistant Professor of Biology, Baldwin Wallace UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/740102017-03-28T13:47:56Z2017-03-28T13:47:56ZEarthworms are more important than pandas (if you want to save the planet)<figure><img src="https://images.theconversation.com/files/161237/original/image-20170316-10898-1x4imnm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">photographyfirm / shutterstock</span></span></figcaption></figure><blockquote>
<p>It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures.</p>
<p>– Charles Darwin, <a href="http://darwin-online.org.uk/EditorialIntroductions/Chancellor_Earthworms.html">The Formation of Vegetable Mould through the Action of Worms</a> (1881)</p>
</blockquote>
<p>Not all wildlife is created equal in our eyes. Take the earthworm, which doesn’t have the widespread appeal of larger, more charismatic animals such as gorillas, tigers or pandas. Worms are never going to get a strong “<a href="http://www.independent.co.uk/life-style/health-and-families/features/why-do-we-find-some-animals-cuter-than-others-a6683076.html">cute response</a>”, and they won’t ever be the face of a conservation campaign.</p>
<p>But what Darwin rightly recognised is that – panda fans avert your eyes – worm conservation is much more important once we factor in their provision of what we now call “ecosystem services”, which are crucial to human survival. Darwin spent 39 years studying these animals for a good reason. In fact, earthworms have even been ranked the <a href="http://voices.nationalgeographic.com/2009/11/04/evolution_most_influential_species/">number one most influential species</a> in the history of the planet – above dinosaurs and humans. </p>
<h2>Why care about the worm?</h2>
<p>Ecologists consider earthworms “keystone species” because of how much they influence the physical, chemical and biological properties of the soil. Here are five reasons why:</p>
<p>1) Earthworms are recyclers. They play a crucial role in breaking down organic matter and fertilising the soil, simply through their constant eating and pooping (about 1.5 times their body weight a day). What comes out the other end – known as a worm cast – is full of nutrients and bacteria that are beneficial for plants. Scientists have measured up to five times the amount of <a href="http://www.msss.com.my/mjss/Full%20Text/Vol%2013/sabrina.pdf">key nutrients in worm casts</a> compared to surrounding soil. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/161340/original/image-20170317-6130-dok7x8.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">Worm cast has up to five times more nutrients than the surrounding soil.</span>
<span class="attribution"><span class="source">photographyfirm / shutterstock</span></span>
</figcaption>
</figure>
<p>A study in Hawaii found that replacing a portion of standard fertiliser with vermicompost (compost from worm casts) <a href="http://www.sciencedirect.com/science/article/pii/S0960852403003043">increased yields</a> of crops such as tomatoes and strawberries by 30%. It’s hard to generate industrial amounts of worm cast, of course, and vermicompost remains more expensive than commercial fertiliser. But it’s an intriguing example of how earthworms can help humans.</p>
<p>2) Earthworms are great “soil engineers”. As they move through the soil, earthworms loosen and mix it up, helping to aerate and drain it. This brings nutrients to the surface, making the soil more fertile, and helps prevent flooding and erosion.</p>
<p>3) Earthworms are barometers of soil health and toxicity. They’re very sensitive to soil pollutants such as pesticide residues or unwanted heavy metals (zinc, lead and so on), and they are badly affected by changes in land use such as deforestation to clear the way for intensive farming. This means the health of local worms is proving to be a useful tool to <a href="http://cdn.intechweb.org/pdfs/25283.pdf">assess the impact of different land usage and pollutants</a>. </p>
<p>4) Juicy earthworms are an important food source. They are protein-rich and feed a number of animals, such as the European badger.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/161336/original/image-20170317-6097-10rbqza.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">Many food chains eventually lead back to an earthworm.</span>
<span class="attribution"><span class="source">nate samui / shutterstock</span></span>
</figcaption>
</figure>
<p>5) Earthworms can help repair damaged soil and may provide solutions to man-made problems. Research suggests that earthworms could help to clean up land contaminated with <a href="http://centaur.reading.ac.uk/20799/1/Sizmur_et_al_Env_Pollut_159_1852-1860.pdf">toxic heavy metals such as lead</a>.</p>
<p>Other studies show how earthworms can speed up the restoration of <a href="http://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers12-08/010043650.pdf">degraded land in the tropics</a>, while research in northern Vietnam found that reduced earthworm diversity due to land use change also had a significant knock on effect on soil fertility, water drainage and soil erosion.</p>
<p>So, earthworms are our underground allies – if we treat them right. Earthworms make it possible for us to live on the planet, simply by eating and pooping, and ploughing up, ventilating and fertilising the soil along the way. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/161337/original/image-20170317-6097-v5y3kc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘I disagree with this article.’</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/hbarrison/5851037702/">Harvey Barrison</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Climate change and human intervention are fast-tracking the world’s loss of biodiversity. The plight of the tiger in India and the <a href="http://www.iucnredlist.org/details/39780/0">orangutan</a> in Indonesia are well known, but scientists are also becoming <a href="http://www.agrsci.jp/ras/article/view/13">concerned about earthworms</a> and other animals that we are less familiar with, but which we can’t afford to lose.</p>
<p>If pandas go extinct, it will be very sad. But, a world without earthworms? Arguably without earthworms in our soils, life could vanish pretty quickly. We would have less food, more pollution, and more flooding.</p>
<p>No matter how cute a panda looks, it is Darwin’s “lowly” earthworms that are doing dirty, but crucial, work in the soil below.</p><img src="https://counter.theconversation.com/content/74010/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Johnson 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>We focus on large, charismatic animals at the expense of these crucial ‘lowly creatures’.Sarah Johnson, PhD Researcher in Environmental Science, King's College LondonLicensed as Creative Commons – attribution, no derivatives.