Southeast Asian biodiversity is a fifth lower in deforested versus intact forests

Southeast Asia is highly biodiverse and currently experiences among the highest rates of tropical deforestation globally, but impacts on biodiversity are not well synthesized. We use Bayesian multi-level modeling to meta-analyse 831 pairwise comparisons of biodiversity in sites subject to land-use driven deforestation (for example, plantations or logged forest) versus undisturbed sites (control sites). After controlling for hierarchical dependencies, we show that biodiversity is a fifth lower in sites with these land-use driven deforestation (95% credible interval = 16%-28%, mean = 22%). This reduction was greater when forest losses were of high-intensity (34% reduction in biodiversity) compared to low-intensity (18% reduction), and effects were consistent across biogeographic regions and taxa. Oil-palm plantations led to the greatest reduction in biodiversity (39%, CI 27%-48%), and agroforests the least (24%, CI 10%-37%). We also find that biodiversity was reduced by 26% (CI 4%-42%) in secondary forest sites compared to undisturbed control sites, but biodiversity was the same in intermediate or mature-aged secondary forest compared to control sites (although species composition was potentially altered). Overall, our study provides a new line of evidence of the substantial detrimental impacts of land-use driven deforestation and particular types of land-use on the biodiversity of Southeast Asia.