Abstract: Coastal areas have undergone substantial land use changes due to rapid economic development and population growth, directly or indirectly affecting the carbon cycle and climate change processes. As one of the primary carbon sinks in coastal areas, mangroves possess substantial and sustainable carbon sequestration potential and play an important role in mitigating climate change. However, mangroves have been notably impacted by the land use conversion, altering not only the composition and area of mangrove species but also the function of the ecosystems, thereby influencing their overall carbon sink capacity. This study focused on Qi’ao Island, known for its rich diversity of mangrove species in China. By integrating field investigations of mangrove species composition with Landsat-5, Landsat-8 and Landsat-9 satellite remote sensing imagery from 2002 to 2023, the study explored the dynamic evolution of land use patterns on Qi’ao Island. Using a carbon emission accounting method, the impact of land use change on aboveground carbon storage and emission was assessed. The results revealed that: (1) From 2003 to 2023, the area of aquaculture ponds on Qi’ao Island decreased from 303.21 hm² in 2003 to 140.31 hm² in 2023, indicating a decreasing trend. Conversely, the mangrove area increased from 196.11 hm² to 645.75 hm², demonstrating the positive effects of effective ecological protection policies and restoration measures, particularly in the preservation and restoration of mangroves. (2) The remote sensing inversion model showed that carbon sequestration in the mangrove area increased from 1,379.59 t to 97,613.53 t, which was attributed not only to the expansion of the mangrove area but also to an increase in aboveground carbon storage per unit area. (3) The carbon dynamics of construction land and non-construction land illustrated the different contributions of various land use types to the carbon balance. As the primary carbon sink on Qi’ao Island, the protection of mangroves is essential for achieving regional and national carbon neutrality goals. This study provides valuable insights into the role of mangrove restoration in enhancing carbon sequestration capacity in coastal areas and offers theoretical support for estimating the carbon sequestration potential of coastal ecosystems.