Contribution of karst ecological restoration engineering to vegetation greening in southwest China during recent decade

General greening in vegetation, especially in southwest China, has been observed globally in recent decade. However, temporal-spatial variation patterns and potential causes of vegetation greening are not well understood in southwest China. Here, we used data of the normalized difference vegetation index (NDVI) and climate, land use and land cover, geology, ecological afforestation and karst rocky desertification to analyze the temporal-spatial variation patterns in vegetation coverage and its response to climate change and human-induced factors in southwest China between 2000 and 2016. A general greening trend in vegetation, with significant differences in temporal-spatial variation patterns, was observed in southwest China from 2000 to 2016, and the area of significant vegetation greening from 2006 to 2016 increased by 4.68% relative to the level from 2000 to 2005. The increased proportion of significant vegetation greening was higher in the karst regions (6.95%), especially in the limestone region (8.00%), than in the nonkarst region (3.82%). Of all the vegetation greening trends, 65% was associated with human-induced factors, and 35% was resulted from climate change from 2000 to 2005. After the implementation of karst ecological restoration engineering, the contribution of human-induced factors to vegetation greening increased to 77% from 2006 to 2016, although southwest China experienced a serve drought during that time. These results highlight that karst ecological engineering projects can reduce the risks of desertification and karst ecosystem sensitivity to climate perturbations.