Abstract
Caisang Lake, a human-modified wetland, experienced dramatic habitat alterations from the planting of lotus and culturing of crab. Whether the Caisang Lake still maintains populations of wintering waterbirds is of great concern. Here, we compare the changes in waterbird populations before and after habitat alterations in Caisang Lake and assess the driving factors leading to the dramatic changes in waterbird populations. Results indicate that wintering waterbird populations were significantly impacted by altered forage availability, with species- and guild-specific responses. Dramatic habitat alterations from planting lotus caused significant declines in areas of native vegetation, mudflats, and water that may have caused associated declines in herbivores, insectivores, and fish-eating waterbirds, respectively. In contrast, the increased size of the lotus area appears to have led to an increase in omnivorous waterbirds. A food shortage, potentially caused by a large area of Caisang Lake being used for culturing crab, might be another cause of the observed decline in fish-eating waterbirds. This study demonstrates a powerful approach to systematically evaluate waterbird responses to wetland management policies. These findings are important as efforts are made to protect the wintering waterbirds from the effects of human intervention, particularly at other Ramsar wetlands.
Highlights
Natural wetlands are under heavy pressure and many have been transformed, degraded, or lost with the intensification of human activities and environmental changes[1,2]
Artificial wetlands are performing a crucial role in biodiversity conservation worldwide[13,14,15]; it is still debated whether artificial wetlands are suitable alternatives to natural wetlands for waterbirds
It remains largely unknown whether, after the habitat alterations, the wetlands of Caisang Lake might still be used as foraging or roosting habitats to maintain wintering waterbird populations; uncertainty remains about the crucial driving factors in the habitat that led to dramatic changes in waterbird populations in Caisang Lake
Summary
Natural wetlands are under heavy pressure and many have been transformed, degraded, or lost with the intensification of human activities and environmental changes[1,2]. Caisang Lake suffered dramatic habitat alterations in 2013/2014 with the planting of lotus (Nelumbo nucifera) and culturing of crab (Eriocheir sinensis); this resulted in a sharp decline in the areas of vegetation, mudflats, and water habitats but a significant increase in the areas of lotus (details are discussed further in the Results section) It remains largely unknown whether, after the habitat alterations, the wetlands of Caisang Lake might still be used as foraging or roosting habitats to maintain wintering waterbird populations; uncertainty remains about the crucial driving factors in the habitat that led to dramatic changes in waterbird populations in Caisang Lake. The driving factors that can lead to dramatic changes in waterbird populations may differ among foraging guilds and individual species, due to their distinct feeding requirements
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