Critically endangered Western Chimpanzees affected by roads up to 17.2 km away
Written By Balint Andrasi, Dr. Kimberley Hockings, Dr. Jochen A. G. Jaeger and Dr. Stefanie Heinicke
20th May 2022
Primates in danger
Most primate species are now in decline and many are threatened with extinction. Habitat loss, habitat fragmentation, and hunting are the main reasons behind this global trend. A common cause that underlies these threats is the construction of roads near or within their habitat. However, estimating the area impacted by roads has received limited attention from scientists. In fact, there are only a handful of studies that estimate the size of the road-effect zone (REZs), i.e., areas adjacent to roads, where the abundance of wildlife populations is reduced due to the direct or indirect road impacts. Furthermore, almost all of the existing studies focus on species in temperate regions. Until now there have been no REZ estimations for any primate, which is a major concern given that (1) most primate species have decreasing populations and (2) an unprecedented amount of new transport infrastructure is planned in the tropics, where most primates live. For example, the western chimpanzee is critically endangered in the eight West African countries where the animals still live. Roads affect chimpanzees directly, through vehicle collision and habitat fragmentation and indirectly, through increasing legal and illegal natural resource extraction, such as mining, logging, poaching and bush-meat hunting.
Figure 1. (a) Estimated density (individuals/km2) of western chimpanzees across their present geographic range in West Africa. The brighter colours indicate a density higher than 0.05, while the dark blue colours indicate a density lower than 0.05 individuals/km2; (b) distribution of major and minor roads across West Africa; and (c) examples of road widening projects and western chimpanzees crossing roads in Bossou, Guinea (Photograph credits: author KJH). West African countries are labelled as: BF, Burkina Faso; BJ, Benin; CI, Ivory Coast; CV, Cape Verde; GH, Ghana; GM, Gambia; GW, Guinea Bissau; GN, Guinea; LR, Liberia; MR, Mauritania; ML, Mali; NE, Niger; NG, Nigeria; SL, Sierra Leone; SN, Senegal; TG, Togo.
The area impacted by roads
We used an ecological threshold analysis to estimate the average distance within which the populations of the critically endangered western chimpanzee are reduced. We used the entire current road network of the eight West African countries where this sub-species lives and laid it on top of a map of chimpanzee density across their entire range (Figure 1). We measured how chimpanzee density changed with distance from the edge of most major and minor roads in the region (see Figure 2 for examples). We found that major roads such as highways, reduced chimpanzee density up to 17.2 km (10.7 miles), and up to 5.4 km (3.4 miles) for smaller roads such as footpaths (Figure 3). Overall, less than 5% of the geographic range of the subspecies is outside these road-effect zones and not impacted by roads.
Figure 2. Left, is an example of a major road (trunk road) the Kampala-Entebbe-Highway between Katwe and Zana in Uganda. Right, is an example of a minor road, a foot and cycle path in Luweero, Uganda. The examples above were obtained from OpenStreetMap and were not used in the study.
Limiting road impacts on primates
When lending money for road construction or road widening projects, some lenders such as the International Finance Corporation (IFC) require developers to follow certain environmental standards. For example, if a road is to be built in an area where great apes potentially occur, their presence must be investigated within the “project’s area of influence”. Until now, however, a “project’s area of influence” or REZ has not yet been established for any primate. Our REZ estimations can help the conservation of chimpanzees and other wildlife in three ways:
showing the minimum area that should be investigated for the presence of chimpanzees;
helping to avoid or minimise road impacts if chimpanzee presence has been established. For example, a developer might avoid negative impacts on chimpanzees by relocating a planned major road beyond 17.2 or minor road 5.4 km from all chimpanzee habitat. If this is not possible, minimisation and mitigation measures need to be planned before road construction. For example, road bumps and speed limits to reduce vehicle speed etc., and patrols can be organized to monitor human activities such as hunting and logging;
advising policymakers to maintain or strengthen the legal status of protected areas that fall within the REZs so they are not subjected to de-regulations and/or down-sizing, which would otherwise compromise conservation objectives.
Figure 3. Extent of the road-effect zones (REZs) of (a) major roads (17.2 km), (b) minor roads (5.4 km), and (c) major and minor roads combined across the geographic range of the western chimpanzee. See Figure 1 for country labels.
Urgent need to establish more REZs for other species
Amending the legal framework that exists for the protection of great apes from road impacts, with future REZ estimations for other great apes could yield benefits for the conservation of these charismatic species. Estimations should also be made for other threatened wildlife that live in areas where large-scale road development is planned or already underway.
Author information:
Balint Andrasi - Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall, UK; balint.andrasi@yahoo.com
Dr. Kimberley Hockings - orcid.org/0000-0002-6187-644X; Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall, UK; k.hockings@exeter.ac.uk
Dr. Jochen A. G. Jaeger - Department of Geography, Planning and Environment, Concordia University Montreal, Montréal, Québec, Canada; jochen.jaeger@concordia.ca
Dr. Stefanie Heinicke - orcid.org/0000-0003-0222-5281; Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, Potsdam, Germany; heinicke@pik-potsdam.de
Source:
Andrasi, B., Jaeger, J.A.G., Heinicke, S., Metcalfe, K., Hockings, K., 2021, Quantifying the road-effect zone for a critically endangered primate, Conservation Letters, https://doi.org/10.1111/conl.12839.
Editor:
Lucy Warungi and Rodney van der Ree
Cite this summary:
Andrasi, B., Hockings, K., Jaeger, J.A.G. & Heinicke, S., (2022). Critically endangered Western Chimpanzees affected by roads up to 17.2 km away. Edited by Warungi, L. and van der Ree, R. TransportEcology.info, Accessed at: https://transportecology.info/research/chimpanzee-roadeffectzone [Date accessed].
