In response to the escalating climate crisis, this study examined the dynamics of carbon absorption in the Seoul metropolitan area, focusing on the effects of urbanization and forest aging. Urban areas face increasing challenges due to climate change, necessitating a deeper understanding of how land-use changes and natural forest aging impact carbon sequestration. We assessed the spatial distribution and carbon absorption capacity of forests by categorizing the regions into urban centers, clusters, and non-urban areas. Using data from the Korea Forest Service and the National Forest Research Institute of Korea, we analyzed carbon absorption in 2013 and 2022, revealing significant shifts driven primarily by land use changes and forest aging. The results showed that urbanization led to a notable reduction in carbon absorption, with new city developments and unplanned expansions converting carbon-rich natural areas into artificial landscapes. Aging forests exhibit a decline in carbon sequestration, highlighting the need for sustainable forest management practices. This study highlighted the importance of tailoring city-specific strategies to enhance carbon absorption. This provides insights for policymakers to balance development with conservation efforts, ultimately contributing to more effective climate change mitigation in urban regions.