Vulnerability to Climate Changes of Tropical Forests Across Africa

Abstract

Aim: Global climate projections identify tropical regions as hotspots of climate change during the 21st century. The few ground data in tropical Africa confirm significant warming and drying over the last decades, but how plant communities will tolerate these new climate conditions remains vastly uncertain. In this study, we assess the climatic vulnerability of tropical moist forests across Africa. Location: Tropical Africa. Methods: We mapped climate change exposure across the tropical moist forest biome, focusing on mean annual temperature (MAT), mean annual precipitation (MAP) and climatological water deficit (CWD) using climate projections for 2085 from five regional models under RCP4.5 and RCP8.5. Using occurrence records for 3,536 tree and shrub species, we estimated species' climatic limits and safety margins, then averaged these margins at the community level. Finally, we combined exposure and safety margins to assess species- and community-level risk by 2085. Results: Under RCP4.5, corresponding to an average warming of 2.4°C by 2085, 92% of species (3,256) could be at risk in at least one community where they occur. This rate increases to 96% (3,405 species) under RCP8.5, with an average warming of 4.3°C. In all scenarios, the most at-risk communities are concentrated in low-elevation regions, where species have few opportunities to migrate if their climatic limits are exceeded. The high risk across the forest biome results from the combination of significant and widespread temperature increases and the relatively narrow safety margins of the species. Specifically, 50% of species have an average safety margin below 1.6°C above baseline temperatures, suggesting they are already near their observed climatic limits. Main Conclusions: Beyond refining our understanding of the vulnerability of tropical moist forests across Africa, our results have far-reaching implications for conservation, allowing us to target species and communities of interest for further monitoring and conservation efforts.