A new study analyzing four decades of tree records across the Amazon and Andes reveals that climate change is altering tropical forest diversity in uneven ways. While overall species richness remains stable, some regions are losing tree species due to hotter and drier conditions, while others are gaining them. Rainfall patterns prove as crucial as rising temperatures in these changes.
Researchers led by Dr. Belen Fadrique from the University of Liverpool examined 40 years of detailed tree records from 406 long-term floristic plots spanning ten South American countries. These plots, monitored since the 1970s and 1980s by hundreds of botanists and ecologists, cover the biologically rich tropics home to more than 20,000 tree species. The findings, published in Nature Ecology and Evolution, indicate that total tree species richness across the region has stayed mostly stable, but this masks significant regional variations.
In areas like the Central Andes, Guyana Shield, and Central Eastern Amazon, most monitoring plots recorded declines in tree diversity. These losses correlate with higher temperatures, drier conditions, and intensified seasonal changes. Conversely, the Northern Andes and Western Amazon saw increases in species numbers in most plots, suggesting these areas may act as refuges for displaced trees as climates shift elsewhere.
The study highlights that while warming temperatures broadly influence diversity, rainfall levels and seasonal patterns play an equally vital role. Forests with naturally dynamic ecosystems appear more resilient, often gaining species over time.
Dr. Fadrique noted, "Our work assessing species responses to climate change points to profound changes in forest composition, and species richness at multiple scales."
Flavia Costa, a professor at Brazil's Instituto Nacional de Pesquisas da Amazônia, emphasized, "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 RAINFOR network, added, "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."
This international effort involved over 160 researchers from 20 countries, supported by networks like RAINFOR and Red de Bosques Andinos. Future work will explore species identities lost or gained, probing potential homogenization in the region.
Plant species respond to warming by shifting ranges or adapting, but failure to do so risks population declines and extinctions. The results call for targeted conservation to safeguard these vital ecosystems amid ongoing global change.