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

Abstract This study examines long-term carbon sequestration in the forest ecosystems of Hainan Island from 1990 to 2020 using the InVEST model and a geographic detector technique. We analysed changes in land use and forest cover, observing an 85.78%, 87.55%, and 256.96% decrease in undeveloped, shrub-covered, and burned urbanised land, respectively. Urbanised land increased by 4.01% annually. Forested land decreased by 3.62%, agricultural land expanded by 5.27%, and aquatic bodies decreased by 2.05%. The forest ecosystems sequestered 335.09–372.80 TgC of carbon, showing an upward trend from 1991 to 1997, a decline from 1997 to 2004, an increase from 2004 to 2010, a decrease from 2010 to 2015, and overall stability from 2015 to 2020. Spatial clustering analysis revealed substantial clustering of carbon sequestration, with central mountainous regions exhibiting elevated levels, coastal areas having diminished levels, the east experiencing higher levels than the west, and the south showing escalated levels compared to the north. Geographical detector analysis identified NDVI, elevation, and slope as primary drivers of spatial variance in carbon sequestration. Forested area changes and government forestry policies played a pivotal role in enhancing carbon sequestration. The combined effect of NDVI and elevation normalisation on vegetation coverage had the most potent synergistic impact.