New research published in Nature Ecology and Evolution reveals significant recent shifts in tree diversity among the tropical forests of the Andes and Amazon, driven by global change.
The study, led by Dr Belen Fadrique from the University of Liverpool, uses 40 years of records on tree species collected by hundreds of international botanists and ecologists in long-term plots to offer comprehensive insights into tree diversity change in the world's most diverse forests.
Key Findings
At the continental level, the team found that species richness has remained largely stable, but this masks significant regional differences. In some extensive regions diversity was declining, while in others it increased.
The analysis revealed that forests in hotter, drier, and more seasonal areas tended to experience declines in species richness. Meanwhile, some areas with more intact ecosystems and with naturally more dynamic forests actually gained species.
In the Central Andes, Guyana Shield and Central-Eastern Amazon forests the majority of forest monitoring plots lost species through time, while most in the Northern Andes and Western Amazon showed an increase in tree species number.
While temperature increase has an overall pervasive effect on richness, the research highlights that rainfall and its seasonal patterns play a major role in shaping these regional trends.
Notably, the Northern Andes is identified as a potentially critical "refuge" that could shelter species displaced by climate change.
The research team analysed data from a huge region spanning the South American tropics which is home to more than 20,000 tree species.
They worked over 40 years across ten South American countries in 406 long-term floristic 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 driving factors behind those shifts.
Impact of climate change on plant species
Plant species have limited options to survive climate change: they can alter their distributions as environmental conditions change, or they can acclimate to these new conditions. If species cannot move or acclimate, their populations will decline, potentially leading to extinction.
Dr Belen Fadrique is a Dorothy Hodgkin Royal Society and University of Liverpool Research Fellow with the Department of Geography & Planning. She is the lead author of the study and conducted the research when she was a Marie Curie Fellow at the University of Leeds.
Dr Fadrique said: "Our work assessing species responses to climate change points to profound changes in forest composition, and species richness at multiple scales."
Flavia Costa, Professor at INPA (Instituto Nacional de Pesquisas da Amazônia) in Brazil, added "This study underscores the uneven impacts of climate change on tree diversity across different tropical forests, highlighting the need for specific monitoring and conservation efforts in each region."
Professor Oliver Phillips from the University of Leeds, who leads the pan-Amazon RAINFOR network, emphasised the significant threat posed by deforestation: "Our findings stress the vital links between preserving forests, protecting biodiversity, and fighting climate change. It is especially critical to protect remaining forests where the Amazon meets the Andes. Only if they stay standing can they offer a long-term home to species in adjacent lowlands."
The research team plans to continue their work to better understand the impacts of climate change on tropical tree diversity.
Dr Fadrique added: "Future studies will focus on complex compositional questions, including the taxonomic and functional identities of species being lost or recruited, and whether this points to a large-scale process of homogenisation within the Andes-Amazon region"
The work was an international collaboration involving more than 160 researchers from 20 countries with many contributions coming from South American universities and partners. It benefited from the support of large research collectives, including RAINFOR, Red de Bosques Andinos, the Madidi Project, and the PPBio network.
The paper, titled "Tree Diversity is Changing Across Tropical Andean and Amazonian Forests in Response to Global Change", is available in Nature Ecology and Evolution: https://www.nature.com/articles/s41559-025-02956-5
