Ecological risk assessment models for simulating impacts of land use and landscape pattern on ecosystem services.

Rapid urbanization involves the expansion of construction land, which changes the land use and landscape pattern in watersheds. Moreover, it degrades ecosystem services and habitat quality, thus creating adverse ecological impacts such as the diffusion of non-point source (NPS) pollution. Therefore, it is urgent to investigate the adverse effects and potential ecological risks caused by variations in land use due to territory development and urbanization. Houxi Basin is a typical Chinese southeastern coastal watershed in the process of urbanization, and the ecological risk from 2011 to 2019 is here assessed. Based on ecosystem vulnerability and the interference with the ecosystem, we evaluated the risk of degradation of habitat services provided by terrestrial ecosystems due to changes in landscape patterns. In addition, the export coefficient model is employed to build an exposure-response relationship between land use and NPS pollution to investigate the risk of degrading water-purification services provided by aquatic ecosystems. The results show that the risks of degrading habitat-provision services increase slightly but for water-purification services increases rapidly. Alternatively, the integrated optimization scenario of key areas for 2030 reduces the risk of pollution diffusion and the landscape risk by 4.27% and 10.25%, respectively, compared with the business-as-usual scenario. In summary, reasonable planning of land-use types and spatial layout is conducive to reducing ecological risks. Other conclusions can be drawn: the combined replacement of forest and grassland more effectively inhibits pollution diffusion than does replacing only forest or only grassland. Optimizing areas with high land-use impact coefficients inhibits pollution diffusion more effectively than does optimizing areas with high export coefficients. Lastly, instead of increasing the area of green land, adjusting its spatial layout proves to be more effective in lowering the ecological risk to water-purification and habitat-provision services.