Deciphering biodiversity drivers in Mainland Southeast Asia: Sensitivity and threshold response hotspots

Understanding biodiversity driver responses is crucial to effective conservation. While major drivers are known, their specific response characteristics are poorly understood. This study investigates threatened species — including plants, mammals, birds, reptiles, amphibians — in Mainland Southeast Asia (M-SEA). Random Forests models identified the key environmental drivers of threatened species richness; Accumulated Local Effects (ALE) model then analyzed how richness responds to individual drivers. Subsequently, cubic polynomial regression and marginal utility analysis assessed sensitivity and identified driver thresholds associated with high species richness, enabling the mapping of “threshold response hotspots.” Results indicate: (1) Climate, especially temperature seasonality, primarily determines M-SEA threatened species richness, while the studied human activity indicators showed weaker influence. (2) Species richness responds significantly to key drivers within distinct favorable ranges. For instance, mammalian richness is high when the temperature seasonality index ranges from 33–208, declining rapidly outside this range, particularly near an index of 300. (3) These “threshold response hotspots,” where multiple key drivers are optimal for biodiversity, are mainly located in mountainous regions for mammals, birds, amphibians, and plants; while reptile hotspots favor lowlands. By revealing clear hydro-thermal response thresholds ranges and sensitivities for M-SEA biodiversity, this study provides valuable insights for evidence-based conservation, ecological monitoring, and protected area optimization. • Developing an comprehensive analysis framework for understanding the drivers of biodiversity. • Identifying biodiversity response curve with Random Forests and Accumulated Local Effects models. • Analyzing the sensitivity and threshold response hotspots of biodiversity drivers with cubic polynomial regression and marginal utility analysis. • Providing basis for environmental monitoring system and directional and nodal references for the expansion of protected areas.