Assessing the impact of urbanization on forest carbon stocks and social costs using a machine learning approach

Urbanization frequently precipitates urban sprawl, resulting in deforestation and alterations in landscape and land alterations. Such transformations profoundly impact the carbon stocks within metropolitan regions. This study examines the ramifications of urbanization on alterations in carbon stocks within urban forests across ten South Korean cities experiencing substantial urbanization over the past 15 years. Leveraging machine learning techniques and high-resolution satellite imagery, we scrutinize changes in land usage and urban forests, utilizing them to gauge the societal costs linked with shifts in urban carbon stocks. Furthermore, we integrate regional-level data sourced from national forests to enhance the precision of carbon stock estimations. Data analysis reveals that over the 15 years, urban areas expanded at an average rate of 4.43 km² annually. In comparison, forested areas decreased by an average of -2.19 km² per year, resulting in an average annual decline of -3171 tC in forest carbon stocks due to urbanization. The fluctuation in carbon stocks across the urban forests of the ten cities ranged from -68 % to 48 % over 15 years, primarily influenced by the extent of preserved forest area, with forest composition playing a secondary role. Concurrently, carbon sequestration efficiency varied between cities, ranging from 8 % to 57 % over 15 years, contingent upon tree type and forest age composition. An approximate loss of 174,380 tCO₂eq of carbon stocks attributable to urbanization is estimated, with the associated social cost of increased emissions estimated at $8,893,396. Effective management of carbon emissions and sinks within urban locales is paramount for climate change mitigation, given the substantial contribution of urban areas to global carbon emissions. This study underscores the significance of urban forest management in carbon governance and furnishes valuable insights into nations undergoing rapid urban expansion.