Spatiotemporal variation in carbon sequestration in the forest ecosystem of Hainan Island over a 30-year period and its driving factors

Tropical forest ecosystems are critical for global carbon cycling, yet long-term spatiotemporal dynamics of their carbon sequestration and driving mechanisms remain unclear in island ecosystems—particularly for Hainan Island, China's largest tropical forest stronghold. This knowledge gap limits the formulation of targeted forest carbon management strategies to achieve national“dual carbon”goals. To fill this gap, we analyzed the spatiotemporal variation in forest ecosystem carbon sequestration on Hainan Island from 1990 to 2020 and its driving factors, using 30 m land use data, 1 km resolution NDVI/meteorological/human activity data, and field-measured carbon density data as inputs. Methodologically, we integrated the InVEST model, Local Moran's I, and geographic detector techniques.Model accuracy was validated through multiple approaches: (1) The 30 m land use data showed >90 % overall classification accuracy; (2) Forest area derived from land use data was highly consistent with the 2021 Hainan Forest Resource Survey; (3) Carbon storage results overlapped with regional studies with a relative difference < 5 %.Our results showed that: (1) Land use changed substantially—forested land decreased by 3.62 %, agricultural land expanded by 5.27 %, and urbanized land increased by 4.01 % annually; (2) Forest carbon sequestration exhibited a “double-peak” trend, with five stages of change closely linked to forestry policies; (3) Spatially, carbon sequestration showed significant clustering, with high values in central mountainous regions and low values in coastal areas; (4) NDVI, elevation, and slope were the dominant drivers, and the nonlinear enhancement effect of NDVI and elevation had the strongest synergistic impact.This study not only clarifies the long-term dynamics and driving mechanisms of forest carbon sequestration on Hainan Island but also provides a scientific basis for optimizing tropical island forest carbon management and supporting the achievement of national carbon neutrality goals.