Assessment of Water-Related Ecosystem Services and Beneficiaries in the Hainan Tropical Rainforest National Park

Tropical rainforests are of vital importance to the environment, as they contribute to weather patterns, biodiversity and even human wellbeing. Hence, in the face of tropical deforestation, it becomes exigent to quantify and assess the contribution of ecosystem services associated with tropical rainforests to the environment and especially to the people. This study adopted a nuanced approach, different from traditional economic valuations, to estimate the water-related ecosystem services (WRESs) received by the people from 2010 to 2020 in the Hainan Tropical Rainforest National Park (HTRNP). The study focused on water yield, soil conservation, and water purification using InVEST, the SCS-CNGIS model, and spatial analysis. The results show (1) significant land cover changes within the HTRNP, as forest decreased by 4433 ha and water bodies increased by 4047 ha, indicating the active presence of human activities. However, land cover changes were more pronounced within the 5 km buffer area around the HTRNP, suggesting the effectiveness of the tropical rainforest conservation efforts in place. (2) The water yield of the HTRNP in the years studied decreased by 307.03 km3, based on the water yields in 2010 and 2020, which were 5625.7 km3 and 5318.7 km3, respectively. (3) Change detection showed that runoff mitigation in the rainforest has a negative mean (−0.21), indicating a slight overall decrease in soil conservation and runoff mitigation in the rainforest from 2010 to 2020; however, the higher curve number indicates areas susceptible to surface runoff. (4) The ecological effectiveness of water purification to absorb and reduce nitrogen load was better in 2020 (145,529 kg/year), as it was reduced from 506,739 kg/year in 2010, indicating improved water quality. (5) Population growth is more pronounced in areas with high water yields. Overall, the proposed framework has shown that the water yield potential of the HTRNP can meet the water consumption demands of people and industries situated within the buffer area. However, analysis of the study shows that it does not meet the crop water requirements. This study provides insights for decision makers in identifying potential beneficiaries and the essence of effective area-based conservation measures, and the proposed framework can be applied to any area of interest, offering a different approach in ecosystem services assessment.