Wetland restoration in the East Dongting Lake effectively increased waterbird diversity by improving habitat quality

Wetland restoration is an effective way to recover degraded wetlands worldwide. The Dongting Lake wetland, an important wintering habitat for waterbirds, has suffered considerable degradation due to climate change and human disturbance during the last two decades; however, wetland restoration projects have now been implemented to improve waterbird diversity in the Dongting Lake. Based on annual waterbird and habitat survey data (2012/2013–2019/2020), we aimed to compare the differences in habitat variables (e.g., sedge [Carex spp.] meadow area, mudflat area, water area, and the normalized difference vegetation index of the sedge [Carex spp.] meadow) between the restored and unrestored wetlands to confirm whether wetland restorations could improve habitat quality. We also evaluated whether wetland restoration could effectively improve waterbird diversity by comparing the differences in waterbird populations at the community, foraging guild, feeding habitat guild, and species levels in the restored and unrestored wetlands. The results indicated that the restored wetland could provide more diverse and suitable habitats than the unrestored ones, particularly in terms of a sufficient variety of water habitats of different depths for waterbirds. The restored wetland was able to support substantial and diverse waterbird populations during the winter season. Specifically, compared to the unrestored wetlands, the restored wetland generally had higher species richness, individual density, and Shannon–Wiener diversity index at the community level; higher densities or proportions of different foraging guilds (tuber feeders, herbivores, fish eaters, insectivores, and omnivores, except herbivores geese), and of different feeding habitat guilds (G [0–10 cm], G (20–50 cm), G (20–70 cm), and G (>70 cm) guilds); and higher densities or proportions of the target species (except the lesser white-fronted goose and bean goose) at the species level. The larger waterbird populations in the restored wetland might be closely related to suitable crucial habitats, as indicated by positive correlation between their abundance and suitable habitat areas. Creating diverse suitable habitats for waterbirds, according to their habitat requirements, should be the first consideration in future wetland restorations. These findings provide a basis for wetland restoration and protection of wintering waterbird diversity in the Dongting Lake as well as in the middle and lower reaches of the Yangtze River floodplain.