Optimization of ecological security pattern in Gansu section of the Yellow River Basin using OWA and circuit model

Ecological Security Pattern (ESP) is considered to be one of the important spatial approaches to alleviate the contradiction between ecological protection and economic development, thereby ensuring regional security and maintaining socially sustainable access to ecosystem services. Multiple ecosystem services have widely been coupled to explore the ESP in recent years. Generally speaking, most previous studies reported that there was no trade-off relationship between ecosystem services, where different ecological processes were independent of each other. In the process of ecological node identification, it is often ignored to identify the ecological obstacle points that hinder the movement or communication between organisms, or the ecological pinch points that are more likely or very frequent in the process of biological migration. The Yellow River Basin is the main birthplace of Chinese civilization, serving as an important ecological barrier in China. It is necessary to identify the patches and corridors on regional ecological security and optimize the ecological space, thereby improving the ecosystem service function for the high-quality development of the basin. In this study, five typical ecosystem services were selected: the food supply, carbon sequestration, oxygen release, water production, and soil conservation in the Gansu section of the Yellow River Basin in 2019. A multi-scenario Ordered Weighted Averaging (OWA) model was used to evaluate the priority protection areas of ecosystem service in the study area in 2019 as the ecological source areas. The minimum cumulative resistance model was used to construct the basic resistance surface. The circuit theory model was selected to extract the ecological corridor and identify the ecological pinch points. The ESP was constructed for the Gansu section of the Yellow River basin with the ecological source as the core, the ecological protection priority areas with different gradients as the benchmark framework, and the ecological corridor pinch points as the axis. An optimal ecological space was achieved during the optimization. The results showed that there were 169 ecological source patches in the study area, with an area of 27 460.56 km2, accounting for 19.2% of the total study area. Five ecosystem services showed a collaborative relationship from an overall perspective. Three natural regions of Gannan Plateau, Longzhong Plateau, and Longdong Loess Plateau were significantly affected by topographic climate, vegetation cover, and human activities. There were some differences in ecosystem services in different regions. In the combination of rank weight, seven schemes were given for the ecosystem service protection, where the extracted priority reserve was the core and comprehensiveness of ecological sources, to achieve the goal of high efficiency and balanced allocation of ecosystem service protection. Considering the trade-off degree (0.935), the priority conservation areas under scenario 4 were selected as the ecological source of the study areas. The minimum cumulative resistance model was used to identify the ecological corridor, whereas, the circuit model was introduced to identify the spatial scope of the ecological corridor. A total of 441 ecological corridors with a length of 6 774.9 km were identified in the study area. 49 ecological pinch points were identified by the current density of the ecological corridor. An optimal system was proposed for the space layout of ecological safety in the Gansu section of the Yellow River Basin with "four axes, six regions, and multiple centers", in order to form an ecological space structure with the functional, networked and regional layout. The findings can provide decision-making support for sustainable and ecosystem management in the upstream ecosystem of the Yellow River Basin.