Using stepping-stone theory to evaluate the maintenance of landscape connectivity under China’s ecological control line policy

Abstract

Developed areas are gradually expanding with the acceleration of urbanization. The degree of fragmentation of urban ecological land is increasing, and the risk of reducing the connectivity between important ecological patches is rising. In this context, the municipal governments in China have delineated ‘ecological control lines’ (ECLs) to protect landscape connectivity—however, its effectiveness has not been evaluated. In the study reported here, circuit theory was used to simulate flow among ecological sources, stepping stones carrying ecological flow were identified, and the effectiveness of the ECL, in terms of maintaining landscape connectivity, was evaluated. In this study, we classified the absence of stepping-stone protection based on stepping-stone area, distribution, and potential loss and identified key stepping-stone categories in urgent need of ECL protection, which will be useful for delineating the ecological red line in the future. The results showed that there were 1488 ecological stepping stones in Shenzhen, with an average area of 0.124 km2 and a total area of 185.2 km2. Under the current ECL protection, five stepping-stone groups were characterized as hotspots lacking protection, and this absence threatened the connectivity between some ecological sources. Through stepping stone classification and analysis, we were also able to show that there were 34 key stepping stones that were not protected effectively by the ECL, and they should be incorporate in the future. Using stepping stone and circuit theory models, our study has provided a reference for policy making that addresses connectivity under landscape fragmentation.