Detecting ecological thresholds for biodiversity in tropical forests: Knowledge gaps and future directions

Protecting tropical forests and their biological diversity is a global priority. Understanding if thresholds of forest cover exist beyond which biodiversity displays non-linear declines is key to developing appropriate conservation strategies and policies, but uncertainty remains around the identification and characteristics of these thresholds. We performed a global systematic review of studies using forest cover gradient to identify an ecological threshold across tropical forest ecosystems. Our systematic review finds 68 ecological thresholds reported in 33 peer-reviewed publications. Three main conclusions emerged: first, we show clear geographical gaps in ecological thresholds studies, with 72% of reported thresholds found in South America, over half in Brazil; second, we see ecological threshold studies follow taxonomic biases in line with wider conservation research; and third, there is a lack of homogeneity and comparability in the metrics and sampling designs used to identify a threshold. This global review shows interest in ecological thresholds continues to grow, but further evidence is needed to understand their application in tropical forest management. We identify the main gaps in knowledge and provide guidance to focus research efforts on six key aspects to better understand their potential as a policy-making tool for tropical forest conservation. Abstract in Spanish is available with online material.