Tropical forests are struggling to keep pace with climate change

A major new study reveals that forests across the Americas are not adapting quickly enough to keep pace with climate change, raising concerns about their resilience.

By combining long-term monitoring of over 250,000 trees with measurements of species traits, the team assessed how tree species are responding to increasing temperatures and changing rainfall.

They found that some forests are changing more than others, but overall, tropical tree communities are changing too slowly to remain in balance with their environment.

The research was led by Dr Jesús Aguirre-Gutiérrez from the University of Oxford’s Environmental Change Institute (ECI), collaborating with over 100 scientists from Mexico to southern Brazil.

Professor Oliver Phillips co-wrote the article. He also coordinates the global ForestPlots network and the Amazon RAINFOR network – long-term international projects that provided most of the data for the study and support tropical partners.

Professor Oliver Phillips said: “To really understand how forests respond to climate change, rather than working with billion-dollar satellites or artificial intelligence, what is most critical is the skilled people power of botanists, foresters and hundreds of other partners. These undervalued colleagues provide a great service to the world.”

Adaptation depends on the traits of trees

The study reveals that forest adaptation is lagging. While climate change is altering temperature and precipitation patterns, tree communities are changing too slowly to remain in equilibrium with their environment.

Investigating specific traits shows that being deciduous and drought tolerant helps trees to survive in a changing climate. Other critical traits are the density of a species' wood, and the thickness of its leaves.

The researchers also found that mountainous forests show more rapid adaptation to changing climate than lowland forests, and that younger trees (recruits) show the most noticeable shifts in traits.

This information can help conservationists and policymakers to best support forests.

By 2100, temperatures in the region could rise by up to 4°C, with rainfall decreasing by as much as 20%.

This could push tropical forests further out of balance, making them more vulnerable to extreme climate events.

Informing conservation and policy

Dr Aguirre-Gutiérrez said: “Tropical forests are among the most diverse ecosystems on Earth, yet their ability to adapt to climate change is limited. Understanding which traits help trees survive can guide conservation efforts and policy decisions.

“Given the changes in climate we have observed over the last 40 to 50 years, you might think there have also been lots of changes in the tree communities in tropical rainforests. But some of these changes are too small and too slow to adapt to the observed changes in climate.

“By looking at individual species from different communities, we found some have suffered due to climate shifts, while others have thrived. By studying the characteristics, also known as 'traits', of those that have survived, as well as new individuals joining the communities and those that have died, we can understand what makes forests react differently to a changing climate.”

“If we know what species of trees are doing better or worse, and what set of traits they have, then we know what they can withstand. It will help inform what conservation actions should be encouraged and where funding should be allocated.”

Professor Beatriz Marimon, a co-author from the State University of Mato Grosso, Brazil, added: “Measuring forests carefully tree-by-tree, species-by-species and year-after-year, teaches us about the health of trees and the risks they face. In some of our Amazon plots the forest is facing a deadly combination of fire, heat and drought. Understanding which tree species can survive these threats is critical to creating a liveable future for all of us.”

The study highlights the urgent need for further research and conservation strategies to support the resilience of these critical ecosystems.