Tropical forests, long thought to be highly vulnerable to drought, may be more resilient than previously believed — at least for now.
Now, a new study published in Science, co-authored by University of Idaho Associate Professor Grant Harley, reveals that tree growth across tropical regions declined only slightly during the driest years of the past century. The research, led by Professor Pieter Zuidema of Wageningen University, analysed 483 tree-ring chronologies from forests in South America, Africa, Asia, Australia, and beyond.
The findings show that stem growth dropped by an average of just 2.5% during the driest 10% of years since 1930. Remarkably, growth often rebounded quickly in subsequent wetter years, suggesting a level of climate resilience that had not been fully appreciated: “These findings are important because they suggest that tropical forests — so vital for carbon storage and climate regulation — have not yet reached a drought tipping point,” Harley said. “But we also see that this resilience is uneven and likely to diminish with continued global warming and atmospheric drying.”
Harley contributed tree-ring data from subtropical sites in the Caribbean, Bangladesh, and southern Florida, helping to illuminate how forests in these regions respond to climate extremes. The study, titled Pantropical Tree Rings Show Small Effects of Drought on Stem Growth, is the first to use a global dataset of tropical tree rings to assess how drought affects carbon sequestration through stem growth. While the overall impact of drought on growth was modest, the researchers caution that resilience varies by location — and may erode as climate change intensifies.
“This isn’t a blanket success story,” Harley added. “Some areas are already showing signs of stress, and the models suggest that this stress will worsen. Tropical forests may not remain as reliable a carbon sink in the future if droughts become more intense or frequent.”
For further information: Pieter A. Zuidema et al. ,Pantropical tree rings show small effects of drought on stem growth.Science389,532-538(2025).DOI:10.1126/science.adq6607.
