Ecological network degradation and conservation prioritization analysis of red-crowned crane habitats: a multi-model...

The loss of coastal wetlands and the degradation of their ecological functions have posed a serious threat to the habitats of global migratory waterbirds, particularly the red-crowned cranes (Grus japonensis). Exploring dynamic changes in the habitat of this flagship species is essential for conserving waterbird diversity and improving wetland ecosystem functions. Therefore, using the Yancheng Biosphere Reserve (YBR)-the largest overwintering site for red-crowned cranes along the East Asian-Australasian Flyway-as a case study, we expanded beyond traditional habitat suitability assessments to include ecological networks, establishing a comprehensive evaluation framework. Specifically, we first enhanced the Habitat Suitability Index (HSI) by incorporating a fuzzy analytic hierarchy process based on the habitat preferences of red-crowned cranes. Ecological corridors were then extracted using the Minimum Cumulative Resistance (MCR) model and their importance was prioritized through a combination of gravity models and landscape connectivity indices. Additionally, circuit theory was employed to identify critical stepping stones and delineate key regions for protection. Our results demonstrated that the current ecological network exhibits poor stability and connectivity, characterized by the fragmentation and loss of ecological sources, degradation and breakup of ecological corridors, and increasing risks to stepping stones. Specifically, during 1991-2022, the total area of ecological sources significantly decreased from 1161.98 km² to 221.81 km², and the ecological sources in the southern YBR entirely loss after 2013. Optional low-importance, weak-connectivity corridors largely disappeared, while a few single high-importance, strong-connectivity corridors gradually emerged in their place, as a result of largely decreasing of key ecological corridors from 43 to 15. The proportion of stepping stones associated with natural wetlands decreased from 55.47 % to 38.37 %, accompanied by a reduction in area of the northern YBR. Based on the above analysis, we proposed three categories of conservation areas, aiming to bolster wetland conservation efforts and enhance waterbird biodiversity.