Climate change and ecological engineering jointly induced vegetation greening in global karst regions from 2001 to 2020

Vegetation dynamics play a dominant role in the global carbon cycle and climate, especially in vulnerable karst ecosystem. Many studies have examined the past several decades changes in vegetation greenness and the associated with climate drivers. Yet, few studies have analyzed the vegetation change in global karst regions particularly in the last decades when climate change and anthropogenic disturbance widely occurred. In this study, we investigated the spatio-temporal variations in vegetation dynamic using the Seasonally Integrated Normalized Difference Vegetation Index (SINDVI) and examined their relationship with climate changes using correlation analysis, the ordinary least squares method investigate the variation trends and the Mann-Kendal test to detect the turning points from 2001 to 2020. As expected, there were greening trends in global karst SINDVI from 2001 to 2020, with significant increasing trends in China (range = 0.836, P < 0.05), Europe (range = 0.456, P < 0.05) and many other regions. According to correlation analyses, SINDVI was water-limited in arid and semi-arid regions, such as Middle East and central Asia, and temperature-limited in northern high-latitude. Our results suggest that anthropogenic activities were mainly responsible for the increasing vegetation greenness in tailoring management measures (e.g., Ecological Engineering, the Grain to Green Project) in China and Europe, and intensive farm in Middle East. Coupling warming temperature and increasing precipitation, southeastern Asia and Russia showed increasing trends in SINDVI. In general, climate factors were the dominant drivers for the variation in vegetation greenness in globally karst regions during research period.