Humanity's closest cousins are in trouble. The great African apes, which includes gorillas, chimpanzees and bonobos are renowned for their intelligence and fascinate both scientists and laypeople because of their physical and genetic similarities with humans.
Yet as a recent study in the journal PLOS Climate demonstrates that, even though apes and humans are part of the same family tree, humans are the inconsiderate relatives who destroy their hosts' home: Human-caused climate change is going to have a devastating impact on ape species throughout Africa.
Led by by Razak Kiribou at Haramaya University in Ethiopia, the researchers examined 363 sites throughout Africa that are home to various ape species. In addition to studying the temperature and rainfall at those locations from 1981 to 2010, the scientists also developed models to project weather conditions in those same areas both short-term (from 2021 to 2050) and long-term (from 2071 to 2099). While their results sometimes varied significantly from region to region, they consistently found that climate change drastically altered living conditions for African apes — for the worse.
"Climate projections suggest that temperatures will increase across all sites," the authors write, adding that changes in precipitation vary from location to location. "We estimated a future increase in heavy precipitation events for 288 sites, and an increase in the number of consecutive dry days by up to 20 days per year (maximum increase estimated for eastern gorillas)."
Every site will experience increases in wildfires and crop failures, with the latter indirectly impacting apes as local communities compensate by increasing deforestation. More than four out of five sites will be exposed to intensified heatwaves; more than three out of four will be subject to increased river floods. Sites in western and central Africa are also expected to experience tropical cyclones and droughts.
Notably, these figures were developed under the assumption that Earth's temperature does not rise above 1.5 º Celsius from pre-industrial levels (the target established at the 2015 Paris climate accord). If the planet's temperature does exceed that figure, the great apes' future will likely be even more bleak.
"For the first time, we showed that African ape sites have already experienced changes in climatic conditions and are likely to be exposed to extreme events in the future," the authors conclude. "We found that temperatures have increased over the past decades at the majority of ape sites, and in line with a previous study, we found a consistent increase in future temperatures."
This is not the first study to focus on climate change and primates. Scientists from Concordia University wrote a 2020 paper in the journal Climatic Change that analyzed data from the International Union for Conservation of Nature about 426 species and subspecies of non-human primates. The researchers learned that if the global temperatures increases by 2°C due to climate change, it will have a devastating impact on these primate species.
Specifically, they found that when it came to the Pre-industrial Seasonal Maximum Temperatures (PSMT) in these primates' habitats, 26.1% of all the ranges had temperatures exceeding their PSMTs — and for 8% of the species, their entire range exceeded their PSMTs.
"This suggests the potential for considerable loss of or compromised habitat for non-human primates on a global scale, as a result of the emergence of climate conditions that are outside of the scope of historical experience for many species," the authors warn.
Apes are also threatened by the insufficiency of human efforts to protect them. A 2021 study in the journal Diversity and Distributions employed a large international team of scientists who assessed how ape ranges would shift as a result of environmental alterations like climate change. Different models yielded often starkly contrasting results, yet one thing was certain: Climate change is going to make things very difficult for apes, at least when it comes to their habitats. More ominously for these apes, humans' systems of protected areas and other conservation efforts will not rise to the challenge of helping these species.
"Massive range decline is expected by 2050, but range gain is uncertain as African apes will not be able to occupy these new areas immediately due to their limited dispersal capacity, migration lag and ecological constraints," the authors write. "Given that most future range changes are predicted outside PAs [protected areas], Africa's current PA network is likely to be insufficient for preserving suitable habitats and maintaining connected ape populations."
Climate change is not the only human-caused problem that afflicts ape species. The illegal wildlife trade ominously looms over the lives of every ape, each of whom faces the prospect that it will be captured or killed for commercial purposes. Even when they aren't being poached, apes are threatened by habitat loss as human civilization increasingly encroaches on their natural habitats. Assaf Levy, the founder and CEO of the conservation group BioDB, explained in a 2023 Salon editorial why the potential loss of these animals is so significant.
"In the tapestry of life, monkeys play a vital role, adding color and vibrancy to the natural world," Levy wrote. "Their survival is not just their own concern; it is a shared responsibility for all of us."
