A new study predicts massive range declines of Africa’s great apes — gorillas, chimpanzees and bonobos — due to the impacts of climate change, land-use changes and human population growth.

For their analysis, the authors compiled information on African ape occurrence held in the IUCN SSC A.P.E.S. database, a repository that includes a remarkable amount of information on population status, threats and conservation for several hundred sites, collected over 20 years.

The first-of-its-kind study quantifies the joint effects of climate, land-use, and human population changes across African ape ranges for the year 2050 under best- and worst-case scenarios. «Best case» implies slowly declining carbon emissions and that appropriate mitigation measures will be put in place. «Worst case» assumes that emissions continue to increase unchecked — business as usual.

Under the best-case scenario, the authors predict that great apes will lose 85 percent of their range, of which 50 percent will be outside national parks and other areas protected by legislation. Under the worst-case scenario, they predict a 94 percent loss, of which 61 percent will be in areas that are not protected.

This paper examines whether great apes can or cannot disperse away from where they are currently found, and the best- and worst-case scenarios in each case. For example, mountains are currently less suitable than lowland areas for some great ape species. However, climate change will render some lowlands less suitable — warmer, drier, perhaps less food available — but the nearby mountains will take on the characteristics that those lowlands currently have. If great apes are able to physically move from the lowlands to the mountains, they may be able to survive, and even increase their range (depending on the species, and whether it is the best- or worst-case scenario). However, they may not be able to travel (disperse) away from the lowlands in the time remaining between today and 2050.

Joana Carvalho, postdoctoral researcher in the Faculty of Science, Liverpool John Moores University, lead author of the study says: «By integrating future climate and land-use changes as well as human population scenarios, this study provides strong evidence for synergistic interactions among key global drivers constraining African ape distribution.»

Carvalho adds: «Importantly, massive range loss is widely expected outside protected areas, which reflects the insufficiency of the current network of protected areas in Africa to preserve suitable habitats for great apes and effectively connect great ape populations.»

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