As a geographically unique biome of East Asia, east Asian evergreen broad-leaved forests (EBLFs) exhibit exceptional biodiversity and high endemism. Although numerous studies have addressed the origin and environmental responses of EBLFs, there is no comprehensive review on a  synthetic framework linking climate change, geological events, and evolution of EBLFs.

In a study published in Journal of Systematics and Evolution, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences highlighted the complex origins and urgent conservation needs of EBLFs. The biodiverse ecosystems, crucial for regional climate regulation and species survival, emerged hand-in-hand with the Asian monsoon system but face unprecedented challenges in the modern era.

The researchers integrated existing studies through literature review to analyze the evolutionary history and current status of EBLFs. They clarified that EBLFs first appeared no earlier than the Eocene epoch. Contrary to being simple relics of ancient "boreotropical" forests, EBLFs represent a unique and dynamic assemblage, including descendants of boreotropical flora, elements from tropical regions, and deciduous broad-leaved forests, evolving despite the presence of an ancient, broad arid belt.

The study underscored the critical need to integrate paleoenvironmental reconstruction, molecular dating, biogeographic analysis, and geological events for a holistic understanding. Improving access to and utilization of fossil data databases alongside molecular evidence is paramount.

The combined pressures of climate change and escalating human activity in subtropical regions pose a severe threat to EBLFs. The researchers suggested that future studies should be extended to non-dominant tree species, such as the understory trees and herbs.

According to the review, east Asian subtropical evergreen broad-leaved forests are not just relics of the past; they are dynamic ecosystems shaped by monsoons and complex interactions.

"Their future resilience hinges on addressing critical research gaps – particularly the integration of diverse data sources, studying connections to neighboring biomes, expanding research beyond dominant trees, and understanding their response to human pressures. Only through this integrated knowledge can we develop effective conservation strategies to protect these vital forests against the dual threats of climate change and human activity," said MENG Honghu of XTBG.

First published: 08 July 2025