Tall Trees in Borneo Defy Drought Vulnerability Assumptions, Study Finds

Contrary to long-held beliefs, towering trees in Borneo’s rainforests show no greater vulnerability to drought than shorter trees, according to a study published July 2 in Science. Researchers, including plant functional ecologist Arne Scheire, found that trees in the Dipterocarpaceae family—some exceeding 70 meters in height—maintained stable water transport during the 2023–2024 drought, challenging assumptions about gravity’s role in limiting hydration for tall trees.

How Did the Study Challenge Existing Theories?

The research focused on Dipterocarpaceae, a family of trees in Southeast Asia. Scientists climbed 38 trees, including species up to 71 meters tall, to measure water transport traits. They found that taller trees compensated for increased xylem resistance by starting with wider stem diameters at the base. Leaves at higher elevations also adjusted their dehydration thresholds, allowing them to function with less water pressure, according to Scheire, now at the Southeast Asia Rainforest Research Partnership.

“The idea that gravity makes these giants more vulnerable to drought by stymieing hydration of their higher branches and crowns” is the notion the study counters, Scheire said.

What Are the Implications for Conservation?

The study’s results could help inform conservation efforts. Dipterocarpaceae trees store massive amounts of aboveground carbon and support biodiversity. Because this tree family is not at greater susceptibility to drought, it “may be a good long-term spot to sequester carbon,” Scheire said.

Functional ecologist Julieta Rosell of the National Autonomous University of Mexico, who was not involved in the study, noted that the findings align with a competing theory predicting adaptive traits in large trees. “This was never done before,” Rosell said regarding the testing of the uppermost parts of tall trees.

What Methods Did Researchers Use?

The team employed professional climbers to collect samples from 25 water-transport-related traits across 38 trees. Instruments measured the propensity for water to be sucked up into the trees at their most hydrated time of day. Despite the 2023–2024 drought, the team found that there were no height-related declines in growth rate among their sampled trees, indicating consistent drought resilience.

Why Does This Matter for Climate Change?

As climate change intensifies droughts, understanding tree resilience is critical. Dipterocarpaceae trees, which dominate Borneo’s forests, could play a vital role in carbon storage. However, the study cannot confirm that this holds true for all tree families.

“They’re doing things all the time, making changes in their anatomy all the time,” Rosell said. “And that gives a different perspective to trees because they seem so quiet.”