Global patterns of karst surface exposure and their environmental associations

Karst landscapes cover 15.2% of the global ice-free land surface and supports important ecological functions and human livelihoods, yet their heterogeneous terrain and landcover structure complicate consistent assessments of surface exposure across regions.Despite extensive regional studies of karst desertification, a globally comparable assessment of karst surface exposure remains limited.Here, we develop the Karst Surface Exposure Index (KSEI), a 100-m remote-sensing proxy for exposed, sparsely vegetated, and bare-surface signals in karst regions.KSEI combines PROBA-V reflectance with CGLS-LC100 fractional land-cover information through an externally constrained linear mixture framework, providing a continuous, spectrally weighted measure of surface exposure across heterogeneous karst landscapes.Globally, 31.9% of karst areas show positive KSEI signals, with high values concentrated in West Asia, Central Asia, South Asia, North Africa, and parts of northern Canada.Regional random forest models and SHAP analysis show that long-term precipitation and temperature provide the largest model-attributed contributions to KSEI predictions, while topographic variables and human modification show stronger regional variation.This study offers a global baseline for surface exposure assessment in karst desertification, Downloaded from https://spj.science.orgon October 28, 2026 facilitating tailored restoration and sustainable management of vulnerable karst ecosystems.China (No. 72394401, No.72394404, No.32201435