Satellite evidence for China's leading role in restoring vegetation productivity over global karst ecosystems

Karst ecosystems occupy approximately 20% of the Earth's land surface with the unique and vulnerable geomorphological and hydrogeological characteristics. To date, it remains a challenge to accurately monitor ecosystem productivity from space, as well as their responses to the environmental conditions due to climate change and anthropogenic pressure, which is pivotal to the sustainable development strategies in global karst areas. Here we use a reconstructed long-term solar-induced chlorophyll fluorescence dataset (SIF) and two satellite-based gross primary productivity (GPP) products to examine the patterns and trends of vegetation productivity within global karst ecosystems, and to assess the relative contributions of different countries to the restoration of these fragile ecosystems over the period 2001-2016. As an effective proxy for terrestrial GPP, SIF reveals a greening trend across most of the world's karst areas. China and the European Union (EU) lead the world in vegetation greening within their karst areas by 78.02% and 42.44%, respectively. The total net increase in SIF shows that China alone accounted for 43.66% with just 7.0% of global karst area. Brazil is the only country with a negative greening trend. Recent land cover changes caused by the grain-for-green programme in China and deforestation in Brazil account for 36.93% and 64.71% of the increases and decreases, respectively. Our results have significant implications for restoring ecosystem productivity in global karst areas.