Over the past decades, the karst region of southern China has been identified as a hot spot of global tree cover increase. Ecological engineering projects have converted this area that was characterized by a high population pressure, intensive agricultural use and accelerated land degradation into a carbon sink. While the overall increase in vegetation cover is not a new finding of this project, it had not been clear how this massively increasing vegetation cover has impacted the regional and national carbon balance. It was also unclear to which extend the increase in tree cover can be attributed to ecological engineering projects, forest management types, and how population migration impacted on these land transitions. This is however important to understand, as tree plantations and the restoration of degraded landscapes are key to mitigate climate change. Here we have the unique chance to study how large scale human forest management can help to increase the carbon sink and reduce atmospheric CO2. The reason why this topic has not been studied in detail is the fact that traditional satellite data do not go beyond variables describing the greenness of the landscape. This project aimed at developing new methods and applying new data sources to study changes in carbon stocks in southern China. These carbon dynamics are then related to management, like ecological engineering, climate, human migration, and other drivers. The ability of managed forests to act as a carbon sink and mitigate climate change by offsetting CO2 emissions from fossil fuel burning was further studied. We conclude that tree planting from ecological engineering and released pressure on the vegetation via rural depopulation created a large carbon sink in rural southern China. This carbon sink can offset about 1/3 of the CO2 emissions over the past decade, but we also observed saturation in tree growth, making this carbon sink a rather short term and transient solution to mitigate climate change.
