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Protect a sixth of the land, save two thirds of species

The scene was typical for an international gathering of governments: bureaucrats, sat behind nameplates and speaking through interpreters. But the less than typical result of the votes cast at this 1992…

Diversity is the key. Agricultural Research Service

The scene was typical for an international gathering of governments: bureaucrats, sat behind nameplates and speaking through interpreters. But the less than typical result of the votes cast at this 1992 Convention in Nairobi was an ambitious international agreement to “halt the loss of biodiversity”.

Exceptional rates of species extinctions, rapid habitat loss, and increasingly variable climate meant the deck were stacked against the newly formed Convention on Biological Diversity achieving its goal to protect the biodiversity of life on Earth. Realising this, the convention established the Global Strategy for Plant Conservation as a taxonomic barometer of progress towards their broader goals.

Plants were a natural choice. They are exceptionally important. Consider, for a moment, the food you eat, clothes you wear, medicine that makes you well, materials used to construct your house, not to mention those that brighten its interior and garden. They are the critical infrastructure that supports the diversity of life on earth.

The first challenge the set was to complete “a widely accessible working list of all known plant species”. By 2010, the major botanic gardens announced they had, through The Plant List, fulfilled the first goal. In what became known as the Aichi Targets, the convention laid down - and governments supported - 20 further aims by 2020.

Among others aims, the body has a target to protect 17% of the earth’s terrestrial surface: a pragmatic, ambitious, but still achievable target, given the proportion of global land already nominally protected stands at around 13%. Another target is to conserve 60% of plant species in national parks and other protected areas. Are these compatible goals, is there a way which they can be achieved together? In our recent paper in the journal Science, we sought to show that, while there are major impediments, it is possible.

To us, the question posed an optimisation problem: how to accumulate the most species into a given amount of area. We started with the extraordinary database assembled by the Royal Botanical Gardens at Kew, England, which holds up-to-date details of 109,000 species of plants, including their distribution across more than 350 separate countries and regions. We applied to this dataset various computational methods, greedy algorithms, which try to create a full set of objects from the smallest number of constituent parts, and genetic algorithms, which mimic evolutionary trends to provide optimal solutions to problems.

All your species are belong to Ecuador, Honduras and the Antilles, apparently. L. Joppa/Science

The result was an unprecedented illustration of how species are concentrated in some of the world’s most biodiverse places. Our algorithm worked by choosing the region with the most species in the least area. Then it continually added regions that, when added to the regions already chosen, brought together the maximum number of species in the least amount of area. We continued until all species were included in our set of regions. This “greedy” approach quickly showed that it was possible to include at least a portion of 86% of all species’ distribution within just 17% of land surface. This makes one inclined to think that the CBD’s ambitions won’t be so hard to realise after all.

But more often conservation biologists are concerned with where endemic species are concentrated. Endemism describes species that live within a region and nowhere else - Madagascar for example, is the only place on the planet where many creatures such as lemurs and loris are found. So we took another measure, and were able to piece together regions of the world that contained the entire distribution of 67% of the world’s plant species within the 17% target.

These regions are the priorities for conservation. Tropical and subtropical islands, moist tropical and subtropical forests (especially those on mountains such as the Ecuadorian Andes), and Mediterranean ecosystems are examples. With the set of regions in hand, we could then ask if our results are representative of other taxonomic groups. An overwhelming majority of distributions of bird species (89%), amphibians (80%), and mammals (74%) overlapped with the regions we identified as important.

Finally, we asked if the regions that we identified as important were being protected preferentially, as doing so would seem to be the most optimal conservation strategy. But in fact the regions we identified were protected just barely (14%) above the global average of 13%.

Our results are just the beginning of determining how to best protect the most important biodiversity hotspots in the world. We think of this work as “strategic” — giving insights into the regions where conservation actions must concentrate. But these are too large - we have to map species on much finer scales to offer recommendations for practical conservation actions. This is something my co-authors Stuart Pimm and Clinton Jenkins are working on through the conservation NGO SavingSpecies.

Our results highlight how national implementation strategies make it difficult to efficiently achieve international conservation goals. Protecting the most species in the least area would place disproportionate pressure on just a few of the world’s countries - as has been seen recently, in the case of the pressure put on Ecuador not to drill for oil in Yasuni National Park. Is this fair? Resolving this issue will likely require many more meetings, and many more bureaucrats. I’m not sure we have the time to wait.

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2 Comments sorted by

  1. Peter Bridgewater

    Visiting Professor at United Nations University

    The science here is interesting and innovative, but the politics and policy linkage are really not believable.
    Firstly, the "an ambitious international agreement to “halt the loss of biodiversity”. in para 1 did not, until 2010 refer to halting the loss, it was all about reducing the rate of loss. Even after nearly 20 years that goal was unachievable by 2010, The post 2010 "halt" is simply a hostage to fortune which will clearly not be achieved, undoubtedly forced by European nations in the early…

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    1. Stewart Lockie

      Head, School of Sociology at Australian National University

      In reply to Peter Bridgewater

      Yes, the science is interesting but it is too immature to draw credible policy inferences.

      The author acknowledges that the scale of analysis is still too coarse. This is more than a little obvious when looking at Australia on any of the maps included in this article or the journal paper it is drawn from, with state/territory level data diluting the imputed importance of biodiversity concentrations in areas like the Wet Tropics World Heritage Area. Whether we look at conservation priorities on…

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