Scientists thought the world's tallest trees would be the first to die in drought; New study reveals astonishing survival secret hidden inside their trunks

For decades, scientists believed that the world's tallest trees were naturally more vulnerable to drought because of the immense challenge of transporting water from their roots to leaves hundreds of feet above the ground. However, a new study has turned that assumption on its head, revealing that some of Southeast Asia's towering rainforest trees have evolved remarkably efficient internal systems to overcome this obstacle.

Published in the journal Science on 2 July, the research found that giant dipterocarp trees in Malaysia possess specialised hydraulic adaptations that allow them to move water more efficiently through their trunks. The discovery suggests that height alone may not make trees more susceptible to drought, potentially reshaping how scientists predict the effects of climate change on forests.

New Science study challenges assumptions about tall trees and drought

The study focused on five species of dipterocarps growing in the Kabili-Sepilok Forest Reserve on the island of Borneo.


These rainforest giants are among the tallest flowering trees on Earth, with some reaching heights of more than 233 feet (around 71 metres).

According to the researchers, previous climate models assumed that taller trees would struggle to transport water efficiently, making them more likely to die during prolonged droughts. The latest findings suggest that this may not always be the case.

Lead author Paulo Bittencourt, a forest ecologist at Cardiff University in Wales, said: "These trees are rare and important, and existing predictions suggest a weaker hydraulic system places them at higher risk of dying due to drought."

He added that those assumptions form part of several climate change models.

"That prediction is included in some models of climate change impacts, and our study suggests this may not be correct. More research is now needed to investigate the hydraulic systems and drought resilience of other tall trees."

Scientists climbed trees taller than 20-storey buildings

To conduct the research, scientists spent three months in 2022 studying 38 dipterocarp trees ranging from approximately 25 feet to 233 feet in height.

Collecting samples was no simple task. The team relied on expert tree climbers to scale trunks comparable in height to 20- to 30-storey buildings before collecting branches, leaves and trunk samples from the forest canopy.

Speaking about the challenges, Bittencourt said: "These are people who, in the middle of the forest, can thread a rope through a tree as tall as a 20- to 30-storey building, climb it and collect branches."

Some collections even had to take place at night, with climbers carefully checking for unstable branches and wasp nests before beginning their ascent.

How do giant trees transport water so efficiently?

After analysing the samples, researchers discovered that taller dipterocarps possess wider xylem vessels near the base of their trunks.

Xylem is the specialised tissue responsible for transporting water and dissolved nutrients from the roots to the leaves. Wider vessels reduce resistance, making it easier for water to travel enormous vertical distances against gravity.

The scientists also found that leaves growing near the tops of the tallest trees were better adapted to tolerate drier conditions without losing function.

Together, these features help maintain a stable water supply throughout the tree despite its extraordinary height.

Study finds taller trees did not suffer more during drought

The researchers also examined how the trees responded during an El Niño-related drought between 2023 and 2024.

By monitoring trunk growth before, during and after the drought, they found that the tallest trees did not experience a greater reduction in growth than their shorter counterparts.

The findings suggest that drought resilience depends on a species' biological adaptations rather than height alone.

Scientists say tree survival is more complex than previously thought

The study adds to growing evidence that tree size is only one factor influencing survival during extreme weather.

Adrian Das, a forest ecologist with the US Geological Survey who was not involved in the research, noted that similar patterns have been observed in California's Sierra Nevada forests.

According to Das, the relationship between tree size and drought-related mortality varies between species, with other threats such as bark beetle infestations often playing a more significant role than height itself.

Meanwhile, Julieta Rosell, a functional ecologist at the National Autonomous University of Mexico, said the research changes the way scientists think about trees.

"They're doing things all the time, making changes in their anatomy all the time."

She added that the findings offer a fresh perspective on organisms that often appear still but are constantly adapting to their environment.

World's tallest trees use different survival strategies

The new findings complement decades of research on other giant tree species around the world.

General Sherman Tree
Located in California's Sequoia National Park, the General Sherman Tree is the world's largest known living single-stem tree by volume.

Standing approximately 83.8 metres tall, it has survived for an estimated 2,200–2,700 years thanks largely to its exceptionally thick, fire-resistant bark, which can exceed 90 centimetres in mature trees.

Hyperion
The tallest known living tree is Hyperion, a coast redwood growing in California's Redwood National and State Parks.

Discovered in 2006, Hyperion stands approximately 115.9 metres tall. Its exact location remains undisclosed to protect it from excessive tourism.

Coast redwoods benefit from cool coastal conditions, where Pacific fog provides additional moisture during dry periods, helping sustain their extraordinary height.

Australia's mountain ash
Australia's mountain ash (Eucalyptus regnans) has also produced trees exceeding 100 metres in the past, although no living specimen currently rivals the tallest coast redwoods.

Like other giant trees, mountain ash has evolved unique adaptations that allow it to thrive in its native environment.

Why the research matters

The world's tallest trees store enormous amounts of carbon and play a crucial role in regulating Earth's climate. Scientists estimate that the tallest one per cent of trees contain more than half of all above-ground forest carbon, making their survival particularly important in the fight against climate change.

The latest study suggests that some of these forest giants may be better equipped to withstand drought than previously believed. While more research is needed across different tree species and ecosystems, the findings challenge long-standing assumptions and could improve future climate models.

As researchers continue to uncover how these remarkable trees adapt to changing environments, their discoveries may prove essential in understanding how forests will respond to a warming world.

Inputs from TOI