Extra Climate Benefits From Afforestation Due to Reduced Forest Fragmentation in China.

Afforestation connects isolated forests into larger contiguous forests, reducing forest fragmentation. This process decreases edge areas by transforming edge forests into new interior forests (termed transformed forests). However, the extra climate benefits from edge reductions in transformed forests, beyond those provided by the planted forests themselves, remain unclear. Here, CO2 sequestration from increased biomass (biogeochemical effect) and emissions from decreased albedo (biophysical effect) of transformed forests in China are estimated, using multiple high-resolution remote-sensing datasets. The planted forest area (89.6 M ha) accounted for 35.5% of China's forest area in 2015, transforming 51.8 M ha of edge forests into interior forests. A cumulative increase of 1.4±0.2 Pg CO2e in the transformed forests is found, compared with a biomass increase of 10.3±0.4 Pg CO2e in the planted forests over ~1980-2015. These transformed forests also induce a biophysical warming effect of -0.9 Pg CO2e, partially offsetting the cooling effect from increased biomass. Combining both effects, transformed forests provide a net CO2e gain of 0.5±0.2 Pg CO2e, representing an extra 6.6±2.7% of the direct climate benefits from planted forests. This study reveals previously ignored extra climate benefits from reduced forest fragmentation alongside forest expansion, offering new perspectives on mitigating climate warming through afforestation.