Forty years of tree monitoring reveal how global change is affecting the diversity of Amazonian and Andean forests

New research published in Nature Ecology and Evolution reveals significant recent changes in tree diversity in Andean and Amazonian tropical forests , driven by global change. The study, led by Dr. Belén Fadrique from the University of Liverpool and with participation from CREAF, uses 40 years of tree species records collected by hundreds of international botanists and ecologists in permanent plots, and provides a comprehensive view of changes in tree diversity in the world's most diverse forests.

At the continental scale, the team found that species richness has remained largely stable, but this hides important regional differences. In some regions, diversity decreased, while in others it increased . Specifically, the analysis revealed that forests located in warmer, drier areas with more pronounced seasonality tended to experience decreases in species richness. Meanwhile, areas with more intact ecosystems and naturally more dynamic forests recorded an increase in species. For example, in the forests of the Central Andes, the Guayanes Massif, and the Central-Eastern Amazon, most forest monitoring plots lost species over time, while most plots in the Northern Andes and Western Amazon showed an increase in the number of tree species.

According to the team, although rising temperatures have a widespread effect on species richness, the research also highlights that precipitation and its seasonal patterns influence and play a fundamental role in shaping these regional trends.

To conduct the study, the research team analyzed data from a huge region spanning the South American tropics, home to more than 20,000 tree species. They worked for more than 40 years in ten countries in South America, in 406 permanent plots measured periodically since the 1970s and 1980s. By examining these unique records, the team was able to track changes in tree richness for the first time and identify the factors driving those changes.

From CREAF, researcher Mariana García-Criado has contributed to designing the methodology to quantify these changes in diversity and assess the effects of climate change. "For the first time, changes in tree diversity in a key area for the planet such as the Andean-Amazonian tropical forests are quantified. This study shows the great value of collaborating on an international scale to understand the effects of global change."

Plant species have limited options for surviving climate change: they can either shift their distribution as environmental conditions change, or they can acclimatize to these new conditions. If species cannot move or acclimatize, their populations will decline, which could lead to extinction.

Dr. Belén Fadrique is a Dorothy Hodgkin Fellow at the Royal Society in the UK and the University of Liverpool. She is the lead author of the study and carried out the research while she was a Marie Curie Fellow at the University of Leeds. “Future studies will focus on complex questions of composition, including the taxonomic and functional identities of species being lost or added, and whether this points to a large-scale homogenisation process within the Andes-Amazon region,” Fadrique says.

The work is the result of an international collaboration involving more than 160 researchers from 20 countries , including Flavia Costa, professor at INPA (National Institute for Amazonian Research) in Brazil, and Professor Oliver Phillips, from the University of Leeds, who leads the Pan-Amazonian network RAINFOR, among other contributions from universities and South American partners. It has also had the support of major research groups, such as RAINFOR, the Andean Forest Network, the Madidi Project and the PPBio network.

Reference article: Fadrique, B., Costa, F., Cuesta, F. et al. Tree diversity is changing across tropical Andean and Amazonian forests in response to global change. Nat Ecol Evol (2026). https://doi.org/10.1038/s41559-025-02956-5