Drought Impacts on Tropical Forest Ecosystems

Tropical forests are among the most diverse and carbon-dense ecosystems on Earth, yet they are acutely sensitive to variations in water availability. Prolonged or extreme droughts can disrupt physiological processes in trees, leading to reduced growth rates, increased mortality and shifts in species composition. Soil moisture deficits impair water transport and photosynthesis, while elevated vapour-pressure deficits exacerbate hydraulic stress. At the community level, drought can favour species with conservative water-use strategies over those adapted to moist environments, reducing functional and phylogenetic diversity. These changes undermine the role of tropical forests as carbon sinks and weaken evapotranspirative cooling, with potential consequences for regional climate feedbacks. As drought frequency and intensity are projected to rise under climate change, understanding the mechanisms that govern forest resilience and vulnerability has become critical for forecasting carbon-cycle dynamics, guiding conservation strategies and informing sustainable land-management policies.

Research from Nature Portfolio

Recent studies have quantified the sensitivity of intact South American tropical forests to an extreme El Niño-driven drought. Ground-based measurements across numerous forest plots revealed that the regional carbon sink collapsed during the event, with net biomass accumulation falling to near zero, though long-term vulnerability did not exceed that observed in previous moderate droughts.

In a lowland aseasonal Malaysian forest, experimental analysis of tree dynamics demonstrated that excessive rainfall events can be more detrimental than periods of water deficit. Species exhibited significantly lower growth and survival rates during phases of high soil moisture, suggesting that shifts in rainfall regimes may impose novel stresses on tropical ecosystems alongside drought.

Drought Impacts on Tropical Forest Ecosystems publication trend

The graph below shows the total number of articles in drought impacts on tropical forest ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Biomass carbon sink: The net uptake of carbon by living vegetation, typically measured as the difference between primary production and respiratory and mortality losses.

Functional traits: Morphological or physiological characteristics of organisms (e.g., leaf area, wood density) that influence their performance and ecosystem processes.

Hydraulic conductivity: A measure of the ease with which water moves through plant vascular tissues, critical to understanding drought susceptibility.

Evapotranspiration: The combined process of water evaporation from soil and transpiration from plants, central to the water cycle and regional climate regulation.

Vapour-pressure deficit: The difference between the amount of moisture in the air and the maximum it can hold when saturated; higher values increase plant water stress.

Throughfall exclusion: An experimental approach to simulate drought by diverting rainfall away from the forest floor to study ecosystem responses to reduced soil moisture.

References

1. Sensitivity of South American tropical forests to an extreme climate anomaly. Nature Climate Change (2023).
2. Tree growth and survival are more sensitive to high rainfall than drought in an aseasonal forest in Malaysia. Communications Earth & Environment (2024).
3. Warming, drought, and disturbances lead to shifts in functional composition: A millennial‐scale analysis for Amazonian and Andean sites. Global Change Biology (2023).
4. Long‐term ecological responses of a lowland dipterocarp forest to climate changes and nutrient availability. New Phytologist (2023).