Dynamic impacts of China’s rural-urban migration on aboveground biomass carbon density in rural counties

Abstract China’s carbon sinks have been greatly affected by the changes in aboveground biomass carbon density in rural areas due to a recent rapid urbanization in the country and ongoing migration from rural to urban. We employ multiple satellite and gridded datasets to estimate aboveground biomass carbon density in rural China at the county level from 2006 to 2018. We further investigate the impacts of rural-urban migration on aboveground biomass carbon density in the rural area, as well as the hidden mechanisms. Our results find a nonlinear relationship between rural-urban migration and rural aboveground biomass carbon density. During 2006–2008, + 1% of rural-urban migration increased + 0.021% of rural aboveground biomass carbon density. However, the increasing impact diminished in later periods due to urban land expansion and excessive human activities in the rural areas. In addition to the abandonment of croplands, our mechanism analysis finds that the increasing effect during 2006–2008 was also achieved through expanding of ecological quality inequality between urban and rural areas, emergence of limited clusters of young trees near urban areas, aggregation of people aged 20–40 years old to urban areas, and feminization of people aged 60–70 years old in rural areas. Based on the mechanism analysis, we quantify the moderating effects of variables on the increasing effect of rural-urban migration. There were + 0.015%, + 0.022% and + 0.019% of moderating effects by 1% changes in transportation convenience at the urban-rural border, urban economic aggregation, and the degree of dislocation between people and forests in rural areas, respectively. Finally, we simulate future aboveground biomass carbon density and potential carbon sinks under scenarios considering the potential changes in moderated variables in the future. We find that an optimized rural-urban migration strategy could achieve up to 33.47 ± 24.58 TgC of aboveground carbon sinks by 2030, which could contribute significantly to China’s climate targets.