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For Africa’s great apes, even ‘best-case’ climate change will decimate habitat

  • Africa’s great apes stand to lose up to 94% of their current suitable habitat by 2050 if humanity makes no effort to slow greenhouse gas emissions, a new study warns.
  • Even under the “best-case” scenario, in which global warming can be slowed, gorillas, chimpanzees and bonobos would still lose 85% of their range.
  • The apes’ habitat is under pressure from human encroachment, clearing of wild areas, and climate change impacts that are rendering existing habitats no longer suitable.
  • Researchers say there’s a possibility of “range gain,” where climate change makes currently unsuitable areas habitable for the apes, but warn it could take the slow-adapting animals thousands of years to make the move — much slower than the rate at which their current habitat is being lost.

Gorillas, chimpanzees and bonobos face a bleak future thanks to a perfect storm of human-driven factors, a recent study shows. The triple whammy of the climate crisis, growing human population, and the clearing of wild areas could see Africa’s great apes lose 94% of their suitable living areas by 2050, researchers calculate. This massive range loss, they note, would occur under the “worst-case” scenario, in which humanity does not actively work toward reducing greenhouse gas emissions.

Even the “best-case” scenario, where we slow down the warming of our planet, isn’t much brighter: it would still see the apes lose 85% of their range, the study found.

“African great apes are one of the most vulnerable mammal groups in the world,” said lead author Joana Carvalho, a postdoctoral researcher in the Faculty of Science, Liverpool John Moores University in the U.K. “And I would say this is the first study combining the effects of the main drivers of biodiversity loss for them.”

Today, all species and subspecies of chimpanzees, gorillas and bonobos are classified by the IUCN as endangered or critically endangered. Their homes are being cleared for timber, food, mining and infrastructure projects. Hunting, disease and armed human conflict continue to put immense pressure on their populations. Add to this climate change — which is altering rainfall patterns, intensifying droughts, and making existing habitats of great apes inhabitable by changing the kinds of plants (and food) that grow there — and you have a big crisis at hand.

But, as the study suggests, well-planned conservation actions today might help the apes’ future.

For one, climate change impacts could make some previously unsuitable areas hospitable, at least for some of the great apes. About 50% of this gain is predicted to occur outside protected areas, researchers found. But there’s a catch: the “gain” in range doesn’t mean that the great apes can actually occupy new areas just as their older habitats begin to shrink.

“These two processes occur at different time scales,” Carvalho said. “We can expect hundreds to thousands of years are required for great ape species and subspecies to disperse to new areas, what we call range gain.”

This is because great apes, who tend to reproduce slowly and are poor migrators, may not be able to keep pace and move to new available areas in just 30 years. “So, it is very important not to interpret these results as indicating that range gains will definitely occur,” Carvalho said.

A chimpanzee in Kibale Forest National Park, Uganda. Gorillas, chimpanzees and bonobos face a bleak future thanks to a perfect storm of human-driven factors: climate crisis, growing human population, and the clearing of wild areas. Image by Gregoire Dubois via Flickr (CC BY-NC-SA 2.0).

Even today, there’s suitable great ape habitat outside existing national parks, nature reserves and sanctuaries in Africa. In fact, most great apes live outside protected areas. But the kinds of areas they live in, or prefer, overlap with those that are suitable for agriculture, oil palm plantations and regions that have attracted attention for mining and other infrastructure development. Take the western chimpanzee (Pan troglodytes verus), for example. A 2019 study suggests there may be up to 52,000 of these critically endangered great apes surviving in Africa. Only 17% of them live inside protected areas. Moreover, 10% of these chimpanzees live within 25 kilometers (15 miles) of four multinational “development corridors” currently planned for West Africa, the study found, including the Dakar-Port Harcourt corridor and the Conakry-Buchanan corridor.

So it’s important to urgently first implement conservation actions that slow down range loss, Carvalho said. This, she added, would need to start with existing and proposed protected areas. “We know that the network of protected areas in Africa is not well-protected or enough. Focusing on those actual protected areas will be important.”

Improving conservation efforts within protected areas, for instance, has helped increase numbers of mountain gorillas (Gorilla beringei beringei) within national parks in Rwanda, Uganda and the Democratic Republic of Congo. However, as human communities around these parks have continued to grow, movement of the apes outside the boundaries of protection have become restricted. Consequently, increasing mountain gorilla densities within limited spaces are creating new challenges: the risk of infectious diseases, as well as a rise in violent encounters and infanticides between gorilla groups, recent studies have found.

Given that these gorillas have highly restricted ranges high up in the mountains surrounded by a sea of human communities, they would be particularly susceptible to global warming and extinction, Carvalho and her colleagues write in their paper.

“The future effects of climate change on mountain gorillas is alarming,” said Gladys Kalema Zikusoka, a wildlife veterinarian and founder of Conservation Through Public Health, who’s worked extensively to protect endangered mountain gorillas in Uganda and was not involved in the study. “Reversing this trend is urgently needed by expanding their protected habitat, establishing forest corridors, and reducing human population growth through integrated population, health and environment (PHE) interventions such as promoting voluntary family planning around protected areas and non-protected great ape habitats.”

Mountain gorillas in Rwanda. Mountain gorillas are largely found inside protected areas, whereas great apes like the western lowland gorilla and the central chimpanzee occur mostly outside protected parks. Image by Philip Kromer via Flickr (CC BY-SA 2.0).
Deforestation in Uganda. Great ape habitats across Africa are being cleared for timber, mining and infrastructure projects. In addition, climate change means that farmers regularly seek new fertile areas and water sources higher up in the mountains, leading them to encroach into gorilla habitats. Image by Rod Waddington via Wikimedia Commons (CC BY-SA 2.0).

Other researchers, too, have underscored the need for solutions that include communities living alongside the great apes. For example, climate change is already affecting farmers residing around a critical mountain gorilla habitat, Volcanoes National Park in Rwanda, by worsening droughts and drying up water sources. This, in turn, is pushing farmers to seek new fertile areas and water sources higher up in the mountains, located within gorilla habitats — potentially leading to conflict situations and increasing the risk of disease spread.

“The question is not about whether climate change will affect mountain gorillas directly,” David Greer, coordinator of WWF’s African great apes program, told Mongabay in 2018. “We need to understand how climate change is affecting human behavior, which then affects mountain gorillas.”

Unlike the mountain gorillas that, today, are largely found inside protected areas, great apes like the western lowland gorilla (Gorilla gorilla gorilla) and the central chimpanzee (Pan troglodytes troglodytes), occur mostly outside protected parks. In the best-case scenario of declining greenhouse gas emissions, these primates are predicted to lose much of their current suitable areas, according to Carvalho’s study. However, their extinction can be slowed under this scenario because they are predicted to gain considerable range — that is, if the apes are able to disperse and occupy these new areas.

But for this to happen, both the currently suitable areas, as well as those likely to become valuable for conservation in the future, will need to be kept in mind while planning future land use and infrastructure projects, the researchers write. “It is important to maintain connectivity between the habitats predicted to be suitable in the future, so the range gains will be crucial for the survival of the African great apes,” Carvalho said. “And this means that conservation planners urgently need to integrate land use planning and climate change mitigation and adaptation measures into government policies of great ape countries.”

A troop of bonobos. All species and subspecies of chimpanzees, gorillas and bonobos are classified by the IUCN as endangered or critically endangered. Habitat loss, hunting, disease and armed human conflict continue to put immense pressure on their populations. Image by tsauquet via Pixabay (CC0).

Kalema Zikusoka agreed with the study’s recommendations. “This is a useful study, and if recommendations are implemented to mitigate the impact of climate change as well as other interventions to expand the protected habitats for great apes, the extinction of great apes can be reversed or slowed down.”

For Carvalho, though, the conservation of great apes needs to be more than African governments taking action. It should be our global personal responsibility too, she said. “I think we all need to be aware of our impacts on biodiversity in general, and great apes in particular,” she said. “This is completely linked with the way we live, our lifestyles. You can change your diet, support small farmers and change your routines in terms of consumption of natural resources. So, I think it will be important for us, especially us in the U.K. and the rest of Europe, to do more than what we were doing before.”

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Banner image of a gorilla by Konrads Bilderwerkstatt via Flickr (CC BY 2.0).

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