Fig. 2

The trends in snail density from 1997 to 2022: A average snail density downstream from bottomlands of the dam, B trends in snail density at high-, medium-, and low-elevation bottomlands, C trends in snail density in the Dongting Lake area, Poyang Lake area, and Anhui section, D trends in snail density at high-, medium-, and low-elevation bottomlands in the Anhui section