###### Abstract  
Worldwide, most ecosystem services have declined. However, the theoretical and analytical frameworks for the ecological risk assessment of ecosystem services are still lacking. Here a framework for the risk assessment of ecosystem services was developed based on the formation, changes, risk, and management of ecosystem services. The framework was tested in Ganzi, the upstream area of the Yangtze River Basin, for the regional ecological warning of ecosystem services. Ecosystem services in the form of soil retention and sandstorm prevention and ecological risks including soil and wind erosion were modelled. The results showed that with the increase in area and quality of natural vegetation (forest and grassland), the soil retention service and sandstorm prevention service increased by 66.92% and 8.59% between 2000 and 2015, respectively. Correspondingly, the ecological risk of soil erosion decreased by 8.8%, and wind erosion remained stable. Despite the negative impacts from agricultural development on sandstorm prevention, the increase in vegetation and improvement in ecological quality led to a decrease in the ecological risks of soil erosion and sandstorm erosion by improvement of ecosystem services. This research provides a new perspective for ecological risk assessment, as well as direct management information on ecological risks, by incorporating ecosystem services. ecosystem change; ecosystem quality; ecosystem service approach; regional ecological risk warning; framework for risk assessment; Ganzi; China +
Footnote †: journal:have been developed and are widely used throughout the world, such as the 'three-step method' [6], PETAR (procedure for ecological tiered assessment of risk) [7], and RRM model (relative risk assessment model) [8]. Great progress has been made on the classification, evaluation, and mapping techniques of ecosystem services. However, the theoretical and analytical frameworks for the ecological risk assessment of ecosystem services are still lacking [3]. Furthermore, the linkage between ecological mechanisms and the ecosystem services that create the end products (i.e., final ecosystem services) remains understudied [9; 10; 11]. It is necessary to quantify the ecosystem service provision (i.e., empirical ecosystem service measurements) [11] and the possible adverse effects from human activities [12; 13]. Ecosystem services are the bridge that link nature and society and, as such, are suitable objectives for ecological risk assessment. On the one hand, ecosystems provide diverse products and services to improve human well-being [14]. For instance, marine ecosystems produce secure and adequate fishery products to support our everyday lives, and the service of soil and water retention from terrestrial ecosystems can decrease the risk of drinking water being polluted. Researchers have tried to understand the economic value of nature to global stakeholders through the approach of ecosystem services [15]. By assessing the economic value of ecosystem services, it is beneficial for policymakers to weigh the advantages and disadvantages (i.e., tradeoffs) of economic development and environmental protection. Economic value assessment can provide useful information about the importance of different types of ecosystem services, benefits to multiple stakeholders involved, and program costs of economic development and environmental protection. This is important for determining ways of increasing investment in natural resources protection for enhanced human welfare [14; 16]. On the other hand, the degradation of ecosystem services can cause a series of adverse effects or ecological problems, such as sandstorms [17] and soil erosion [18]. Therefore, the ecosystem services approach may provide important insights to strengthen the utility of ecological risk assessment. In particular ecological models have a great deal of potential to address the problems that are limiting ecological risk assessment [3]. Ecological thresholds are a key issue in developing an ecosystem services approach.