The carbon sink potential of southern China after two decades of afforestation

Abstract

Afforestation and land use changes have turned Southern China into one of the largest carbon sinks globally, which sequesters carbon from the atmosphere thus mitigating climate change. However, forest growth saturation and available land that can be forested limit the longevity of this carbon sink, and while a plethora of studies have quantified vegetation changes over the last decades, the remaining carbon sink potential of this area is currently unknown. Here, we train a model with multiple predictors characterizing the heterogeneous landscapes of Southern China and predict the carbon carrying capacity of the region for 2002-2017. We compare observed and predicted carbon density and find that during two decades of afforestation, 2.34 Pg C have been sequestered between 2002 and 2017, and a total of 5.32 Pg carbon can potentially still be sequestrated. This means that the region has reached 75% of its carbon carrying capacity in 2017, which is 12% more than in 2002, equal to a decrease of 0.83% per year. We identify potential afforestation areas that can still sequester 2.39 Pg C, while old and new forests have reached 87% of their potential with 1.85 Pg C remaining. Our work locates areas where vegetation has not yet reached its full potential but also shows that afforestation is not a long-term solution for climate change mitigation.