Dyke demolition led to a sharp decline in waterbird diversity due to habitat quality reduction: a case study of Dongting Lake, China

Dongting Lake, an important wintering habitat for migratory waterbirds in
the East Asian–Australasian Flyway, has suffered serious degradation in
recent decades. To restore habitats for biodiversity conservation and
flood control, 459 dykes were demolished and 14 were preserved in 2017.
However, the direct impact of dyke demolition on wintering waterbirds was
not comprehensively assessed. In this study, based on annual waterbird
census and habitat data (2013/14–2020/21), we compared the differences in
habitat areas and species composition of waterbirds in the dyke-demolished
and preserved areas, and explored whether habitat changes caused by the
dyke demolition were responsible for the changes in the number of species
and percentages of waterbird individuals. The results indicate that the
areas of water (including shallow water) and mudflat habitats
significantly decreased, but the vegetation area significantly increased
in the dyke-demolished areas. The species numbers and percentages of
waterbird individuals at the community and foraging guilds levels, and the
percentages of nine species, were higher in the dyke-preserved areas than
those in the dyke-demolished areas. Changes in the numbers of species and
percentages of individuals of fish eaters, insectivores, and omnivores
positively correlated with drastic changes in the percentages of water
habitats (including shallow water) after dyke demolition. Effective
measures should be carried out to restore hydrological regimes, providing
waterbirds sufficient suitable habitats with different water depths. These
findings improve our understanding of the influence of dyke demolition on
waterbirds and provide insights for wetland management and waterbird
conservation. --