The Amazon rainforest is the largest contiguous area of tropical forest in the world and stretches across nine South American countries. It is considered one of the most important “hotspots” of biodiversity, home to millions of animal and plant species. In addition to this unique biodiversity, the Amazon also plays a central role in the global climate system: enormous amounts of carbon are stored there which helps to slow down global warming. “But the ‘Earth’s lungs’ are under pressure. Rising temperatures and erratic rainfall patterns are threatening the rainforest and its diversity,” explains Dr. Liam Langan, the study’s lead author from the Senckenberg Biodiversity and Climate Research Centre Frankfurt (SBiK-F), and he continues, “Droughts – especially prolonged and severe events – threaten the delicate balance of water transport in the trees. If the forest cannot adequately compensate for this, there is a risk of mass tree dieback and disruption of the global carbon cycle.”

Together with his colleagues – Prof. Dr. Simon Scheiter (SBiK-F), Prof. Dr. Thomas Hickler (SBiK-F and Goethe University Frankfurt), and Prof. Dr. Steven Higgins (University of Bayreuth) – Langan has investigated the hydraulic properties of Amazonian trees. These biological characteristics determine how efficiently and reliably trees transport water from the roots to the leaves when water is scarce. “Some species consume water more ‘carefully’ or last longer, while others react more quickly or are more vulnerable,” explains Hickler.

Using an integrative methodology that combines field data, plant trait data, and model simulations, the team shows in their new study how this hydraulic diversity affects the resilience of entire forests to drought stress. Their findings revealed that forests with a broader range of hydraulic strategies among coexisting species showed significantly higher resilience – indicated by more stable water transport and lower mortality rates during droughts. During sudden extreme droughts with 50 percent less rain over four and seven years, simulations showed that biomass losses were reduced by 17 percent and 32 percent, respectively. In the case of long-term decrease in precipitation due to climate change, biomass losses decreased by 34 percent. This protective effect of diversity increased with drought severity, the research team emphasizes.

“The ‘division of labor’ prevents all trees from succumbing to drought at the same time and stabilizes the entire forest,” says Hickler. Scheiter adds, “In addition, hydraulic diversity not only influences the survival of individual trees, but also higher-level ecosystem processes such as carbon storage. Trees that remain functional even in times of drought continue to contribute to carbon sequestration – a crucial factor in the fight against climate change.”

The researchers’ findings are of major importance for reforestation projects and climate models. “Those who plant new forests often rely on a small number of fast-growing species – but this means the forests lack the diversity that provides long-term protection against droughts. For stable, sustainable forests, it is therefore essential to include species with very different hydraulic properties,” recommends Hickler. The study also provides important impulses for climate research and politics. Models that take such differences into account can more accurately predict how forests will react to climate change and how much carbon dioxide they will still be able to store in the future, according to the study.

“Beyond the Amazon, our research results are relevant for tropical forests worldwide, which may be exposed to increasing drought stress in the future. Our message is clear: Diversity is a survival strategy. The more diversely the trees in the Amazon can organize their water supply, the better the entire ecosystem will be able to withstand droughts – and the greater its chance of surviving in a warmer, drier world,” adds Langan in conclusion.

Publication: Langan, L., Scheiter, S., Hickler, T. et al. Amazon forest resistance to drought is increased by diversity in hydraulic traits. Nat Commun 16, 8246 (2025). https://doi.org/10.1038/s41467-025-63600-1