Green areas are an important component of terrestrial carbon cycling as they provide basic ecosystem services and play a crucial role in carbon sequestration. However, dry climate and unsustainable human activities have decreased urban green areas. Land use changes notably lead to degradation and loss of urban green areas worldwide, resulting in one-fourth of the world’s population releasing CO2 annually. Therefore, studying the spatiotemporal changes in carbon storage in urban green spaces is crucial. The data has been acquired using secondary sources. A systematic literature survey has been conducted to understand the impact of wetlands dynamics in urban areas. Google Earth Engine is the main data source of this study. The long-term (1995–2024) Landsat satellite imagery data is the main source for acquiring and interpreting carbon storage and its changes according to land use change under different land use categories and analyzing above- and below-ground carbon storage changes in the Colombo urban and suburbs in Sri Lanka using InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model. Changes could be seen in converting green spaces into built-up areas in the study area, especially urban natural green cover. Along with preserving ecological and agricultural land, the regional carbon balance, the stability of the ecosystem, and the output of food production, these land changes will promote urbanization and steady economic expansion. They also serve as the foundational ideas and guidelines for upcoming planning projects in the study area.