China has experienced unprecedented urbanization and associated rural depopulation during recent decades alongside a massive increase in the total population. By using satellite and demographical datasets, we here test the hypothesis that urbanization and carbon neutrality are not mutually exclusive and that sustainably managed urbanization may even be an integral part of the pathway to reduce atmospheric CO2. We show that, although urban expansion caused an initial aboveground carbon loss of −0.02 PgC during 2002–2010, urban greening compensates these original losses with an overall balance of +0.03 PgC in urban areas during 2002–2019. We further show that a maximum increase in aboveground carbon stocks was observed at intermediate distances to rural settlements (2–4 km), reflecting the decreased pressure on natural resources. Consequently, rural areas experiencing depopulation (−14 million people yr−1) coincided with an extensive aboveground carbon sink of 0.28 ± 0.05 PgC yr−1 during 2002–2019, while at the same time only a slight decline in cropland areas (4%) was observed. However, tree cover growth saturation limits the carbon removal capacity of forests and only a decrease in CO2 emissions from fossil fuel burning will make the aim of carbon neutrality achievable.
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Population density data from WorldPop (2000–2020) can be obtained at https://www.worldpop.org. Demographical data are accessible from the National Bureau of Statistics of the People’s Republic of China. Tree cover from AVHRR (VCF5KYR) can be downloaded from https://search.earthdata.nasa.gov. Tree cover from MODIS (MOD44B) is available from Google Earth Engine. DMSP/OLS Nighttime Lights Time Series Version 4 can be download from https://ngdc.noaa.gov/eog/dmsp/downloadV4composites.html. GlobaLand30 land cover dataset is available at http://www.globallandcover.com/home_en.html. ESA-CCI land cover dataset is available at http://maps.elie.ucl.ac.be/CCI/viewer/. The MODIS carbon density map and mobile phone location-based dataset are available on request.
No custom codes were used. The codes used to analyse the data and create the plot are available on request.
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X.Z. is funded by the National Natural Science Foundation of China (41930652) and China Scholarship Council (CSC, grant no. 201904910835). M.B. received funding from the DFF Sapere Aude (9064-00049B) and the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (TOFDRY, grant agreement no. 947757). X.T. is funded by a Marie Curie fellowship (795970). Y.Y. is funded by the National Natural Science Foundation of China (41930652, U20A2048). X.X. is supported by the US National Science Foundation (1911955). R.F. is supported by the Villum Foundation through the project ‘Deep Learning and Remote Sensing for Unlocking Global Ecosystem Resource Dynamics’ (DeReEco) (project no. 34306).
The authors declare no competing interests.
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Land cover transition in China from GlobeLand30 during 2000–2020.
Topography and vegetation trends. a, Topography; b, significant change (P < 0.05) in tree cover, trends of short vegetation from AVHRR VCF5KYR1, and elevation for 1990-2016.
Extended Data Fig. 4 Trends and temporal profiles separated in groups of population density change for 2000–2020.
Trends and temporal profiles separated in groups of population density change for 2000–2020. a, Spatial distribution of each group of population density change based on WorldPop population density (2000,2020); b, MODIS-based aboveground carbon density; c, MOD44B tree cover; d, AVHRR VCF5KYR tree cover; e, calibrated nighttime light from DMSP/OLS; f, yearly mean Standardized Precipitation-Evapotranspiration Index (SPEI).
Extended Data Fig. 5 Boxplots showing changes in carbon density in relation to distance to settlements in agricultural areas over China (× mean value, - median value).
Boxplots showing changes in carbon density in relation to distance to settlements in agricultural areas over China (× mean value, - median value). a, MODIS-Based aboveground carbon density change for different distance to settlement; b, relative aboveground carbon density change (carbon density change / carbon density in 2002) in relation to distance to settlements.
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Zhang, X., Brandt, M., Tong, X. et al. A large but transient carbon sink from urbanization and rural depopulation in China. Nat Sustain 5, 321–328 (2022). https://doi.org/10.1038/s41893-021-00843-y
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