Borneo's Giant Trees Challenge Old Theories on Drought Survival

New research from Malaysian Borneo indicates giant Dipterocarp trees pump water efficiently to their highest branches, suggesting they withstand drought better than previously thought.

Giant tropical trees in Malaysian Borneo pump water to their highest branches as easily as to their lower ones, according to a new study. This finding challenges long-held scientific theories that suggested tall trees are more susceptible to drought than shorter trees.

For decades, scientists hypothesized that increasing tree height, combined with gravity and longer water pathways, would impede growth. Researchers in this latest study examined 38 trees of five species from the Dipterocarpaceae family in Malaysia’s Kabili-Sepilok Forest Reserve in northeastern Borneo. The trees, including species like keruing putih and kapur, measured between 7 and 71 meters tall. Dipterocarps are known as the tallest flowering trees globally and are common in Southeast Asian rainforests.

The analysis indicates that these tall trees use two main mechanisms to manage their height. As trees grow taller, they develop wider water-carrying vessels at the base of the trunk compared to shorter trees, which reduces resistance to water flow. Additionally, leaves at the top of the canopy adjust their osmotic potential, or the concentration of dissolved substances in their cells. This allows them to retain more water, even under the low pressure created by gravity at such heights, the researchers say.

Paulo Bittencourt, the study's lead author from Cardiff University in the U.K., told Mongabay that the team expected tall trees to be more vulnerable. He stated they anticipated tall trees would have more difficulty keeping their leaves hydrated as they grew. The study observed the opposite.

These adaptations help the tall trees remain resilient during environmental extremes. By tracking trunk growth during the intense El Niño-linked drought of 2023 and 2024, researchers found that the tallest trees experienced no greater decline in growth than smaller trees. Bittencourt added that existing climate-change forecasting models often assume tall trees are the first to die during droughts due to insufficient water movement. The study's findings suggest tall trees may be more robust than previously understood.

The study also notes that the tallest 1% of trees, despite their small number, store more than half of all aboveground forest carbon. Bittencourt emphasized the need for more field study in tropical forests to understand them properly.

For jungle stay hosts, understanding the deep resilience of these foundational forest components can inform considerations for sustainable construction and site maintenance.