Linking landscape characteristics to shorebird habitat quality changes in a key stopover site along the East Asian–Australasian Flyway migratory route

The area and quality of shorebird stopover habitat along the key East Asian–Australasian Flyway migratory route has decreased. The cause is not fully understood. We apply an InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model to examine shorebird habitat quality between 1975 and 2020 in the Yellow River Delta (YRD), and link landscape characteristics to habitat quality. Mean habitat quality declined from 0.42 to 0.20, areas of high habitat quality declined by 31.75%, and those of low and medium quality increased by 18.67% and 12.98%, respectively. Increased percentages of landscape (PLAND) and largest patch index (LPI) for city, industrial mining, reservoir/pond, and mariculture land-usage categories, and decreased PLAND and LPI for coastal wetlands significantly contribute to decreased mean habitat quality. Increased mean patch area (AREA_MN) and area-weighted mean patch fractal dimension (FRAC_AM) for city and reservoir/pond also greatly contribute to habitat quality decrease. For Spartina alterniflora, increased PLAND, LPI, number of patches (NP), AREA_MN, FRAC_AM and aggregation index (AI) contribute to reduced mean habitat quality. In the Shandong YRD National Nature Reserve, the impact of increased S. alterniflora invasion on shorebird habitat quality is greater than that of other forms of land use. In contrast, in Non-Reserve, the increased area of degraded land poses a greater threat to habitat quality than other factors. Managing S. alterniflora in Reserve, and reducing human activity in Non-Reserve, is required to curtail further decreases in habitat quality.