Over the last 30 years, great ape numbers have plummeted across Africa, due to increasing rates of commercial hunting, habitat destruction, and disease. A continent-wide, data-based overview of their habitats is now possible, as the results of surveys from over 60 sites have been combined through the IUCN/SSC A.P.E.S. (Ape Populations, Environments and Surveys) database (http://apes.eva.mpg.de). This information is crucial to inform global policy and donor decisions, and to predict and mitigate current and emerging threats. These threats include habitat destruction, large-scale infrastructure developments, resource exploitation projects, intensifying hunting pressure and impacts of climate change.
The research was carried out by 47 researchers and conservationists, who combined over 15,000 field data points on presence localities of chimpanzees, gorillas and bonobos. The result estimated the continent-wide distribution of suitable ape habitat conditions and changes over the past 20 years. Over 200,000 km² of ape habitat have been lost - approximately four soccer fields every day. This, however, varied dramatically among species, where more than 50% of eastern gorilla habitat appears to have become unsuitable over the years, compared with only about 10% or less for chimpanzee habitat. This, the authors say, may be due to differences in ecological requirements, such as dietary preferences, as well as differences in vulnerability to hunting related to the behaviour and social structure of the different species.
The regions that experienced the greatest conversion of suitable ape habitat were the Congo Basin rainforest and the West African coastal forest in Liberia. Importantly, the lack of decline in other areas may reflect the fact that much habitat had already been lost before the 1990s, such as in the East and West African regions. Even more concerning is the finding that suitable habitat loss appears to have been particularly severe in the central African forest block - currently regarded as the remaining stronghold of great apes. Even these vast and once-remote forest tracts have been interlaced with logging and mining roads and subsequent human immigration.
"This study shows how threats to African great apes are increasing over time throughout their range. It highlights the urgent need to intensify conservation measures, including law enforcement and raising awareness. Increased and sustained commitment of all stakeholders - local and international - to conservation efforts throughout the range of African great apes is essential to their survival" says Inaoyom Imong of the Wildlife Conservation Society in Nigeria and PhD student at the Primatology Department of the Max-Planck Institute for Evolutionary Anthropology (MPI-EVA).
"This is the first continent-wide estimate of African great ape distribution and its changes over time", says Jessica Junker, also a PhD student at MPI-EVA and lead author of the study. "This is also the first study to have combined data across 22 African ape range countries in an attempt to bridge the gap between local efforts in the field and global ape distribution patterns. We hope that together with a series of other geo-referenced data on human activities, land-cover, topography, and conservation, our model will aid funding agencies, industry and politicians in making decisions in identifying priority conservation areas, research gaps, potential wildlife corridors and future survey sites."
"Once again, a multi-site analysis has demonstrated the increasingly grave situation in which the African great apes exist" says Fiona Maisels, of the Wildlife Conservation Society. "The threats to these species are rapidly increasing: bushmeat hunting continues to expand and the rate of habitat conversion from forest to oil palm plantations and other monocultures is about to explode. Immediate attention is required to ensure that national and regional land use planning integrates wildlife conservation at the very beginning, and law enforcement is of the essence to maintain and protect great apes and their habitats for the future"
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More information: Jessica Junker, et al., Recent decline in suitable environmental conditions for African great apes. Diversity and Distributions. Published online on September 23, 2012; DOI: 10.1111/ddi.12005