Key findings: By using generic species to represent the existing diversity among terrestrial species (using a combination of their habitat preferences and maximum dispersal distances), protected areas and potential links between protected areas of importance for maintaining the connectivity of the network were identified, with a special focus on transboundary protected areas.
In the face of climate change, connectivity conservation is key to prevent the negative effects of habitat fragmentation and isolation, by (i) maintaining existing links and patches of habitats and (ii) restoring or creating links between habitats.
In this study, conducted by UNEP-WCMC, a set of generic focal species were used as surrogates to represent variation amongst terrestrial species. These surrogates were not based on actual species, but were a combination of habitat preferences (forest, grassland and generalist) and maximum dispersal distances (short, 1km; medium, 10km; long, 100km).
This approach was used to model PAs containing habitat as patches and the Euclidean (straight line) distance between PAs as links. Functional links were those within these maximum dispersal distances. PA values in terms of the connectivity they provide were calculated from the overall change in connectivity of the PA network when a PA was removed. The importance of potential links were calculated by measuring the connectivity change of the network, thereby assessing their contribution to connectivity if an intervention (e.g., PA expansion or corridor management) could help bridge such gaps allowing a functional link between PAs. For each combination of generic focal species characteristics, results on the contribution of individual PAs and links were generated, focusing on those near, adjacent to, or crossing country borders.
The results of this study highlighted the importance of using a variety of approaches to improve connectivity for species with different dispersal distances. For short dispersal species, in most instances, habitat management and improvement should be preferentially targeted within PAs, especially since habitat connectivity within PAs is not fully addressed within the framework of this study, most notably for forest or grassland specialists. Medium dispersal species, however, could be appropriate targets for improving links between PAs, especially for forest specialists. For long dispersal species, targeting link improvement may be less cost effective considering that a potentially high number of barriers may be present; therefore, PA habitat management or expansion may be the best use of resources.
The approach used highlighted specific (potential or existing) key transboundary PAs (e.g., Gola Rainforest National Park in Sierra Leone, Niokolo-Koba National Park in Senegal, Grebo National Park in Liberia, Comoé National Park in Cote d'Ivoire, Sahel Partial Faunal Reserve in Burkina Faso, and the WAP complex in Benin, Niger and Burkina Faso) and links between PAs which would greatly improve the overall connectivity of the West African PA network. These results should be taken into consideration when prioritising field studies.
Example: Importance of transboundary PAs for connecting grassland specialist focal species with long range maximum dispersal (100km) abilities.