EXPLORING THE TEMPORAL AND SPATIAL VARIATION OF THE NET PRIMARY PRODUCTIVITY IN TROPICAL ISLANDS USING CMIP6 MODEL: A CASE STUDY OF HAINAN ISLAND, CHINA

Vegetation net primary productivity (NPP)is a key ecological indicator for evaluating ecosystem services.Understanding how future climate change will impact NPP in Hainan Island is essential for promoting the sustainable development of ecosystem services on tropical islands.In this study, we employed an improved version of the Carnegie-Ames-Stanford Approach (CASA) model to analyze the spatial and temporal patterns of NPP on Hainan Island from 2000 to 2018 and to identify the main factors influencing these changes.To project future NPP trends in 2050, we integrated the Future Land Use Simulation (FLUS) model with climate projections from the Coupled Model Intercomparison Project Phase6 (CMIP6).The key finding of this study as follows: (1) From 2000 to 2018, the average NPP on Hainan Island exhibited an increasing trend, with a significant positive correlation between NPP and climatic factors such as precipitation, solar radiation, and temperature.(2) During the same period, land use changes led to a decline in NPP; however, this negative effect was offset by favorable climate conditions, resulting in an overall increase in NPP of approximately 12.7%.(3) By 2050, under the combined influence of future climate and land use changes, NPP on Hainan Island is projected to a decline across all three climate scenarios.Among them, the SSP2-4.5 scenario demonstrates a moderate mean NPP level, maintaining the functional stability of NPP while aligning with regional development objectives, thereby positioning it as the optimal pathway to support Hainan Island's future sustainable development.