Protecting nature in Half of the Earth could affect over one billion people

Humanity is currently experiencing the biggest biodiversity crisis it has ever faced. During this ‘sixth mass extinction’, entirely caused by human activities, species go extinct at a rate 1000 times higher than what would happen naturally. This is problematic because species diversity is the foundation of a healthy planet and, by extension, of a thriving humanity. Scientists are unanimous: we must quickly commit to protect and restore natural environments across the planet and conserve what is left of biodiversity to ensure a better future for people on Earth.

In 2010, 123 countries therefore adopted the Strategic Plan for Biodiversity 2011-2020 of the Convention of Biological Diversity. In doing so, these countries agreed to try and reach the 20 Aichi Biodiversity Targets listed in the Plan, among which they committed to have at least 17% of the world’s land surface and 10% of the seas protected by 2020. Unfortunately, even if we are close to reaching this target, with almost 15% of terrestrial land and 7% of marine areas officially included in protected areas today, it has become clear that it is insufficient as species and natural habitats are being lost faster than ever. More nature will be needed to mitigate the effects of climate change and prevent the collapse of ecosystems worldwide.

Number of assessed species threatened with extinction according to the IUCN Red List of Threatened Species (as of April 2020).

The Half-Earth Proposal

Many conservation scientists, worried about the future of the planet and mankind, are therefore working hard to answer the question: “How much of the planet should we protect to save biodiversity”? A few years ago, the famous biologist E. O. Wilson, in his book entitled ‘Half-Earth, our planet’s fight for life’ proposed to equally share the planet between people and nature. In other words, humanity should aim to conserve the most important natural resources of half of the Earth and allow the other half to be used by people. Because it is straightforward, the proposal has quickly gained a lot of popularity among scientists calling for rapid and drastic actions to be taken.

Although giving 50% of the planet’s surface back to nature may seem like a fair deal, it is actually a very ambitious plan in a world inhabited by almost 8 billion people. Today, few areas in the world are devoid of people or unused for some economic activity. In protected areas, activities that can potentially harm nature and wildlife like cutting trees, grazing cattle, building new infrastructure or hunt are usually restricted or even forbidden. This means that depending on the restrictions imposed on protected land, setting aside half the planet would affect the lives of local people to various degrees. As a result, while scientists all agree that ambitious measures must be taken to ensure the future of life on Earth, they also recognize it is crucial to understand the limitations of proposals like the Half-Earth project and their potential impact on people.

One billion people

In 2018, as I was employed by the Zoological Society of London on a very exciting project about global conservation targets (the results of which should be published soon!), I was lucky to collaborate with a team of brilliant scientists working at Cambridge University. Eager to contribute to finding solutions to this biodiversity crisis that can benefit people as well as nature, we were all intrigued by the Half-Earth proposal, and particularly by its implications on people. What we were wondering was “How many people would be affected if we were to protect half of the planet?” .

To find out, we designed a study in which we created our own version of Half-Earth. We determined which areas could be protected to reach Half-Earth by protecting half of each ecoregion of the world with the lowest human footprint possible. This approach has two benefits. First, by distributing protected areas among ecoregions (i.e regions that contain characteristic, geographically distinct assemblages of natural communities and species ), a diverse array of species and habitats is protected. Second, as areas with lowest human footprint are less densely populated, they are also more likely to have remained in a natural state. The map below shows all areas that require protection to reach Half-Earth as it was included in the Brief Communication we published in Nature Sustainability .

Our conclusion is simple: over one billion people live in areas that would have to be protected to implement the Half Earth proposal. This means that the lives of almost one eighth of the current planet’s human population would be directly affected if we were to restrict activities in half of the Earth’s land surface.

Map depicting the areas to be protected to meet Half Earth 50% protection targets within each ecoregion, on a colour scale of increasing human footprint value. In the frames numbered A to D are shown the additional conserved areas with the highest human footprint in: (A) London, UK; (B) St Lucia; (C) Egypt; (D) Nepal. The map was originally published in Schleicher et al., 2019 in Nature Sustainability.

A future for biodiversity

Of course, this does not mean that we should give up on the idea of protecting biodiversity! It is expected that within a few decades, the loss of biodiversity and ecosystem services associated with intact ecosystems will affect everyone on Earth if we don’t act now. By 2050, this would mean 10 billion people living on Earth. There is therefore no doubt that we must take bold action to conserve nature for future generations.

The upcoming Convention on Biological Diversity COP 15 will be crucial in designing the global conservation actions to be taken for the coming decade. Conservation scientists hope that these actions will be sufficient to protect biodiversity and halt the dramatic loss of natural habitats and species. Nonetheless, our study shows that ambitious plans, like the Half-Earth proposal, could have a strong impact on many people. As we fight to build a better, fairer future for all on Earth, it is crucial to design actions to conserve biodiversity and limit the impacts of climate change which consider and provide solutions to mitigate the social impacts they may have.

Original article published as: Schleicher, J., Zaehringer, J. G., Fastré, C., Vira, B., Visconti, P., & Sandbrook, C. (2019). Protecting half of the planet could directly affect over one billion people. Nature Sustainability2(12), 1094-1096.

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