Extreme drought alters waterfowl distribution patterns and spatial niches in floodplain wetlands

Abstract

The Yangtze River Basin was among the areas most severely affected by the widespread extreme drought in the Northern Hemisphere in 2022. Drought conditions in this basin extended into the wintering season, significantly influencing waterfowl habitat availability. Exploring how waterfowl distributions and ecological niches respond to these changes in wetland environmental conditions and the underlying ecological mechanisms are important for biodiversity conservation and understanding wetland ecological processes. By integrating field observations, remote sensing, and ecological niche modelling, we analysed habitat changes over the past decade and investigated how extreme drought affected the distribution patterns and spatial niches of two waterfowl guilds, ducks and geese, in the Dongting Lake Region, a key wetland ecosystem in the Yangtze River Basin. The extreme drought led to a drastic reduction in the waterbody area of natural habitats and caused vegetation to enter the wilting stage prematurely. In response, a substantial proportion of waterfowl shifted to adjacent managed wetlands with stable water levels, especially the ducks, whose distribution pattern was fundamentally altered. The proportion of both waterfowl guilds in the managed wetland showed a significant correlation with the proportion of the waterbody area. Further, we compared the spatial niche of waterfowl in 2022 with that in the former year, which represented a typical year with normal hydrology. The spatial niche of ducks underwent a substantial contraction, while that of geese remained large in both years but shifted inward in 2022 towards areas with lower elevation, and foraging resource use was altered. Therefore, for both waterfowl guilds, the extent of habitat overlap between the two years was small. This study has important implications for understanding the impact of extreme climatic and hydrological events on wetland ecosystems. Furthermore, our results emphasise the importance of water level-managed wetlands for biodiversity conservation.