Fast-growing trees are taking over the forests of the future, jeopardizing biodiversity and climate resilience

Trees play a central role in life on Earth: they store CO₂, provide habitats for animals, fungi, and insects, stabilize soils, regulate water cycles, and supply resources that humans depend on, from timber and food to recreational spaces and shade on hot days. But the world's forests are entering a new era, characterized by homogenization, biodiversity loss, and weakened ecosystems. This is demonstrated by a large international study recently published in the prestigious journal Nature Plants . Specifically, researchers analyzed more than 31,000 tree species worldwide and offer a global perspective on how forests are likely to change in terms of composition, resilience, and ecological functioning.

According to the study, forests will become increasingly dominated by fast-growing tree species , while slower-growing and more specialized species are at risk of disappearing. Furthermore, the study highlights that the homogenization of forests will have a particularly severe impact on tropical and subtropical regions , where the future increase in risk to species will be concentrated.

“We are talking about highly unique species, especially concentrated in tropical and subtropical regions, where biodiversity is high and ecosystems are closely interconnected. When specialized native species disappear, they leave gaps in ecosystems that invasive species rarely manage to fill, even if they are fast-growing and highly dispersive,” says Professor and Director of the Centre for Ecological Dynamics in a New Biosphere (ECONOVO) of the Danish National Research Foundation, in the Department of Biology at Aarhus University, and one of the lead authors of the study.

The most threatened species are often the slow-growing specialists. These are trees with thick leaves, dense wood, and long lifespans, associated with stable environments, especially in humid tropical and subtropical forests. “They form the backbone of forest ecosystems and contribute to stability, carbon storage, and resilience to change,” Svenning points out.

The most threatened species are often the slow-growing specialists. These are trees with thick leaves, dense wood, and long lifespans, associated with stable environments, especially in humid tropical and subtropical forests. “They form the backbone of forest ecosystems and contribute to stability, carbon storage, and resilience to change,” Svenning points out.

If current trends in climate change and logging continue, forests will become increasingly dominated by nature's "speedsters" : trees with light leaves and low wood density that allow for rapid short-term growth. These include various species of acacia, eucalyptus, poplar, and pine. "Although these species establish themselves and grow well, they are more vulnerable to drought, storms, pests, and climate shocks. This makes forests less stable and less effective at storing carbon in the long term," explains Svenning.

The study also shows that nearly 41% of so-called naturalized tree species—species not native to an area but now growing wild there—possess characteristics such as rapid growth and small leaves. This makes them suitable for disturbed environments, but they rarely perform the same ecological functions as native species.

In the study, researchers modeled how tree species are likely to spread or disappear under future scenarios. The results clearly indicate that already naturalized species will become even more dominant in the coming decades.

Given this situation, it is necessary to limit the uncontrolled spread of invasive alien species and, at the same time, protect slow-growing native trees and those that are threatened . “Furthermore, it is essential to maintain functional diversity among tree species to guarantee the long-term resilience of our ecosystems and to preserve biodiversity in a world of accelerated change,” Peñuelas concludes.

Reference article: Guo, WY., Serra-Diaz, JM, Guo, K. et al. Global functional shifts in trees driven by alien naturalization and native extinction. Nat. Plants (2026). https://doi.org/10.1038/s41477-025-02207-2