# Tree diversity is changing across tropical Andean and Amazonian forests in response to global change

## TL;DR

Tropical forests in the Andes and Amazon are experiencing changes in tree diversity due to climate and environmental factors, with some regions gaining species while others lose them.

## Contribution

The study reveals regional variation in species richness trends and identifies climate and environmental drivers across the Amazon-Andes region.

## Key findings

- Species richness increased in Northern Andean and Western Amazon plots but declined in the Central Andes and Central-Eastern Amazon.
- Warmer, drier, and more seasonal forests lost species, while higher elevation and less fragmented areas saw increases.
- Region-specific factors like precipitation seasonality and demographic trends modulate these changes.

## Abstract

Climate and atmospheric changes are impacting forest function and structure worldwide, but their effects on tropical forest diversity are unclear. Nowhere is the scientific challenge greater than in the Andes and the Amazon, which together include the world’s most diverse forests. Here, using 406 permanent plots spanning four decades of intact lowland and montane forest dynamics, we test for long-term change in species richness and assess the influence of climate and other variables. We show that, at a continental scale, species richness appears stable, but this masks substantial regional variation. Species richness increased in Northern Andean and Western Amazon plots, yet declined in the Central Andes, Guyana Shield and Central-Eastern Amazon. Overall, warmer, drier and more seasonal forests lost species, while those at higher elevations, in less fragmented areas and with faster rates of tree turnover experienced increases. Region-specific drivers, particularly precipitation seasonality and demographic factors, modulated these trends. The results highlight the diverse ways in which Amazon–Andes forests are changing and underscore the critical need to preserve large-scale ecosystem integrity to maintain local tree diversity. By doing so, Northern Andean forests in particular could serve as an important refuge for species increasingly displaced by climate change.

This study examines long-term changes in species richness across tropical forests in the Andes and Amazon. Hotter, drier and more seasonal forests in the eastern and southern Amazon are losing species, while Northern Andean forests are accumulating species, acting as a refuge for climate-displaced species.