Identifying unique areas in the Congo Basin for conservation

A major challenge in conservation biology is to identify areas to be protected in priority. With the hypotheses in mind that areas presenting unique environmental features when compared to their surroundings are more likely 1) to be vulnerable to changes and 2) hosting relatively more specialized species, we performed a global analysis to identify singular forested areas and further explored the relationship of those areas with forest bird richness and endemism. Using a moving window of 50 x 50 km, we computed, across the earth's surface, on a grid of 5 x 5 km resolution the probabilities for each cell to find similar biophysical features elsewhere in the window. The input variables were, NDVI and NDWI, slope, and the percentages of grassland and tree covers. This systematic screening allowed us to map areas presenting unique features and to further correlate this information with the level of the correlation between bird endemism and species richness. At the global scale, we found the forested biomes of the Congo Basin, namely the Tropical & Subtropical Moist Broadleaf Forests and the Tropical & Subtropical Grasslands, Savannas & Shrublands among the most homogeneous ones for what concern our environmental variables. While it is well-known that the Tropical Moist Forest is the biome holding the biggest diversity in terms of bird-species richness, the relationship between biomes and endemism levels is less documented. If we found that more than half of our variables explained bird endemism for the moist forests, such characterization of the level of endemism was not straightforward for other biomes. More relevant to the identification of potential new areas to focus on for biodiversity conservation, we found that the Tropical and Subtropical Moist Broadleaf Forests shown little ecological heterogeneity and consequently present only a few unique areas. Interestingly, while we found that the relationship between endemism and areas presenting unique environmental features was not obvious for most forested ecosystems, we found a significant relationship between endemism and habitat uniqueness for the Tropical and Subtropical Moist Broadleaf Forest. It is the purpose of this contribution to discuss further our preliminary results and to contrast our findings with the current distribution of protected areas in the Congo Basin. (Texte integral)