Evaluating comprehensive watershed management sustainability based on the emergy ecological footprint model: A case study of Hainan Island, China

Comprehensive watershed management, which realizes the protection, optimal utilization and ecological restoration of regional soil and water resources is the primary method for controlling soil and water loss in China. However, the deployment of soil erosion control measures requires many resources that increase the environmental load and thus impact ecosystem sustainability. In this study, an emergy ecological footprint model based on emergy theory was developed, and to assess the sustainability of a comprehensive watershed management ecosystem on Hainan Island, China. The results show that: (1) Among the input resources, the emergy ecological footprint (EEF) of machinery was the largest, at 3213.89 hm²; among the construction resources, high-strength materials such as stone, concrete and steel bars were mainly used, and the EEF was greater than 60 %. (2) The primary sources of EEF for comprehensive watershed management were engineering measures project (8554.33 hm²), at >92 %. Gulley erosion control (GEC) was the largest source, followed by slope water works (SWW) and field roads (FR). (3) Renewable resources provide the main ecological carrying capacity (ECC) of the comprehensive watershed management ecosystem; however, the sum of ecological and economic benefit ECCs is 23.92 %. (4) Initially, the ecological profit and loss of the comprehensive watershed management ecosystem (CWME) was −7099.81 hm², and the ecological footprint intensity was 4.28, indicating an ecological deficit, which is not conducive to sustainable development. However, an ecological turning point occurred in 2025: the cumulative ECC exceeded the cumulative EEF, at which point CWME achieved an ecological surplus. Therefore, although the preconstruction period generates considerable ecological pressure, overall, comprehensive watershed management supports sustainable development of the ecological environment. This study provides new trade-off ideas for ecological restoration projects such as comprehensive watershed management.