Land cover pattern and habitat suitability on the global largest breeding sites for Black-necked Cranes

Exploring the suitable ecological niche environment for endangered species is essential to maintaining biodiversity and protecting endangered species. The Black-necked Cranes is considered as the environmental indicator and flagship species of the alpine wetland ecosystem, and has been listed as a vulnerable species by the IUCN (International Union for Conservation of Nature) several times. Nearly one-third of the world's Black-necked Cranes breed on the Zoige Plateau. However, no systematic studies have been conducted on the land cover patterns and habitat suitability of their breeding sites. In this study, the fine remote sensing land cover data from 2000 to 2015 and GIS technology were applied to establish habitat suitability index of Black-necked Cranes. Besides, the spatial autocorrelation analysis, geographical detector model and random forest algorithm were used to analyze and discuss the spatial distribution characteristics of habitat suitability and their main climatic drivers on breeding sites. The main results show the following: 1) Marsh wetlands, the dominant land cover types for Black-necked Cranes breeding, which showed a decreasing trend from 2000 to 2005 and an increasing trend from 2005 to 2015, with mainly converting to grassland; the reverse conversion rate of grassland, marsh wetlands, and water body was greater than the positive conversion rate for all three periods; the landscape pattern of most land types increased in fragmentation and decreased in agglomeration and connectivity from 2000 to 2015. 2) Suitable regions (highly-suitable and sub-suitable) accounted for between 11.62 and 13.84% of the total, with a gradual increase in the area of highly suitable regions over the three periods; the Moran's I indices were all greater than 0.80 from 2000 to 2015, indicating high positive spatial autocorrelation of habitat suitability and significant spatial clustering characteristics. 3) Climate influences the breeding habitat of Black-necked Cranes, with the main factors ranked as follows (power of determinant, PD > 0.165): precipitation from May to September > mean temperature from October to November > minimum temperature in November > annual precipitation > annual mean temperature; the interaction effects of climate factors include mutual and non-linear enhancement, with the largest PD value reaching 0.358 for the interaction between precipitation from May to September and November maximum temperature. The research aims to provide scientific evidence for the safe local breeding of Black-necked Cranes and biodiversity conservation in alpine wetland ecosystems.