Key findings: Biodiversity in West African PAs is expected to be increasingly impacted by climate change during the 21st century, with a large proportion of amphibian, bird and mammal species expected to be found in areas of lower climate suitability by the end of the century. A high species turnover is also expected in most protected areas, especially in the Guinean Forest region.
With climate change driving changes in species' distributions and abundance patterns, it is crucial to evaluate the effectiveness of the current PA network. PAs are a core component of species conservation, yet their static nature makes their long term effectiveness particularly vulnerable as species' ranges shift in response to changing climatic conditions.
Within the framework of the project, Durham University developed Species Distribution Models (SDMs) that link species' distributions to biologically important climatic variables. The projections of future climatic conditions from the MOHC were used, as well as estimates of species dispersal potential, to assess impacts of changing climatic conditions on faunal (birds, mammals and amphibians) distributions and representation across the region's PA network.
Climate change impacts on West African biodiversity across the region's PA network are projected to increase during the 21st Century (Figure 9). By the 2070-2099 time period, 91% of amphibian, 40% of bird, and 50% of mammal species are projected as 'extremely likely' to have reduced climate suitability across the region's PA network. No amphibian species, and only three bird and one mammal species, are projected as 'extremely likely' to experience improved climate suitability in the region by 2070-2099.
Each PA is likely to both lose and gain species as species' distributions shift, resulting in changes to faunal communities. Species turnover is a measure of loss and gain of species at a site relative to species richness and provides a measure of community change between time periods. Higher species turnover indicates a greater shift in projected community composition and suggests high climate change impacts. Median species turnover for amphibians in PAs is projected to increase from 26.5% in the 2010-2039 time period to 45.7% by 2070-2099. The expected impacts for birds and mammals are lower, yet still represent considerable impacts to communities, with species turnover by 2070-2099 projected at 32.4% and 34.9% for birds and mammals, respectively.
A resampling approach was used to identify PAs that were in the upper quartile of projected species turnover for each taxonomic group for each time period, using three uncertainty tolerance thresholds to indicate those impacts for which there is the most confidence. At the 95% confidence level, 80 out of 1,987 PAs are identified as being highly impacted for two or more taxa by the 2010-2039 time period. However, this falls to only five PAs by 2070-2099. Accepting greater uncertainty, the number of multi-taxa (two or more) 'high impact' sites identified by 2010-2039 increases to 134 at 85% confidence level, and 194 at 75% confidence level. The majority of the multi-taxa 'high impact' PAs identified are located in the Guinean Forest region, with most of the PAs occurring within Ivory Coast.
A regional scale assessment of the impacts of incorporating dynamic climate suitability into projections of climate-driven species range changes for species using a dynamic dispersal model was also undertaken. It was shown that the incorporation of dynamic dispersal across landscapes with changing climates can affect projected range shifts, notably resulting in a marked reduction in the number of species able to colonize an area. However, of the five project countries, only Liberia and Sierra Leone appear to be affected by this additional layer of modelling, with the major impacts expected to occur across Ivory Coast, and to affect, in particular, the species rich Guinea Forest and coastal regions. However, overall the impacts of incorporating dynamically changing climate data are relatively limited across much of West Africa.
To conclude, the projected impacts of climate change represent a significant threat to the region's biodiversity, which is already under considerable pressure from habitat loss and hunting. This study has highlighted areas of greatest potential impact of climate change on PAs. Where species are likely to decline, steps must be taken to locate and properly protect potential refugia and to maximise connectivity between sites to facilitate range shifts.
Projected change in amphibian (top), bird (middle) and mammal (bottom) species in individual PAs for the period 2040-2069. Median projections are derived from multiple SDMs and climate projection scenarios. Negative values denote declining species richness compared to current levels, and positive values denote increasing species richness.