In the rainforests of Borneo, the towering dipterocarps—some reaching heights of 70 meters—do not suffer more during droughts than their shorter neighbors, defying common expectations. A study published in the journal Science on July 2, 2026, overturns the long-held assumption that gravity and the sheer length of water-conducting vessels leave these forest giants uniquely vulnerable during dry spells.
Researchers from the University of Exeter and their Malaysian partners teamed up with professional climbers to scale the canopies of five dipterocarp species within the Kabili-Sepilok Forest Reserve. They collected leaf, branch, and trunk samples at various heights from 38 different trees, ranging from seven to 71 meters tall. The team meticulously measured 25 separate parameters related to internal water transport.
The study revealed that the tallest trees possess wider xylem at the base of their trunks, a feature that compensates for the increased resistance water faces on its long ascent. Furthermore, the leaves at the very top of the canopy have evolved to withstand lower water levels without losing their turgidity. During the severe drought of 2023–2024, growth rates remained consistent across trees of all heights, suggesting that their physiological response is independent of size.
These specialized adaptations ensure the giants maintain water access even as the soil parches. Large trees serve as massive above-ground carbon sinks and provide essential habitats, food, and shelter for a vast array of tropical organisms. If the dipterocarp family is truly resilient to drought, it could serve as a vital and stable carbon reservoir for Southeast Asia for decades to come.
This research demonstrates that trees are not merely passive organisms but active agents that modify their own anatomy to suit environmental conditions. Such insights allow for more accurate assessments of which forests will remain resilient under a changing climate and help prioritize areas for conservation.
Understanding these survival mechanisms offers a practical roadmap for reforestation; by prioritizing species with similar adaptations, scientists can improve the chances of entire ecosystems weathering future droughts.
