Vulnerability to climate changes of tropical forests across Africa

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 remain
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 2080, 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 tolerance 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 to target species and communities of interest for further
monitoring and conservation efforts.