Rainfall Variability Enhances Resilience of Tropical Forests and Savannahs

With the ongoing global warming, significant changes are projected in both the amount and frequency of precipitation in tropical regions. While previous research has demonstrated that tropical forests and savannahs can thrive within an intermediate mean annual precipitation range, the underlying mechanisms that contribute to the resilience of these ecosystems are not yet fully understood. Specifically, the long-term effects of rainfall variability on ecosystem resilience remain unclear. In this study, we present observational evidence indicating that both tropical forests and savannahs, which have experienced higher rainfall variability, particularly on interannual scales, in their long-term history, exhibit greater overall resilience to climatic disturbances. Using precipitation and tree cover data from the Brazilian Amazon basin, we constructed potential landscapes that allowed for systematic measurements of resilience in different ecosystems. Furthermore, we suggest that transitions from forests to savannahs, as a result of decreasing precipitation in the future, are more likely to occur in regions with lower precursory rainfall variability. Consequently, it is crucial to consider long-term rainfall variability in resilience analyses and projections of vegetation responses to climate change.