Effect of conservation efforts and ecological variables on waterbird population sizes in wetlands of the Yangtze River.

Yong Zhang,Lei Cao,Willem Frederik De Boer,Qiang Jia,Herbert H T Prins

doi:10.1038/srep17136

Abstract

Forage quality and availability, climatic factors, and a wetland’s conservation status are expected to affect the densities of wetland birds. However, the conservation effectiveness is often poorly studied. Here, using twelve years’ census data collected from 78 wetlands in the Yangtze River floodplain, we aimed to understand the effect of these variables on five Anatidae species, and evaluate the effectiveness of the conservation measures by comparing population trends of these species among wetlands that differ in conservations status. We showed that the slope angle of a wetland and the variation thereof best explain the differences in densities of four species. We also found that the population abundances of the Anatidae species generally declined in wetlands along the Yangtze River floodplain over time, with a steeper decline in wetlands with a lower protection status, indicating that current conservation policies might deliver benefits for wintering Anatidae species in China, as population sizes of the species were buffered to some extent against decline in numbers in wetlands with a higher level protection status. We recommend several protection measures to stop the decline of these Anatidae species in wetlands along the Yangtze River floodplain, which are of great importance for the East Asian-Australasian Flyway.

Highlights

Analysis of animal population trends is essential for understanding a species’ population status and, if required, for formulating protection strategies
We tested the efficiency of conservation actions, and analysed whether the recent decline of Anatidae species is more severe in areas with a lower protection status compared to areas with a higher one
In this study we demonstrated that various ecological variables affected the densities of Anatidae species and the most important variables were slope and climate variables

Summary

Introduction

Analysis of animal population trends is essential for understanding a species’ population status and, if required, for formulating protection strategies. Eastern China supports around 1.1 million Anatidae birds and 80% of them use inland wetlands along the Yangtze River floodplain[3,13]. These wetlands offer food and raw materials for tens of millions of people. In this paper, using systemic survey data from wetlands along the Yangtze River floodplain in 2004 and twelve years survey data (from 2001 to 2012) in four key wintering sites, we analysed the impact of abiotic and biotic factors on the densities of five Anatidae species to provide insight in the underlying causal factors for spatial and temporal changes in population trends, a prerequisite for effective conservation actions. The tuber-feeding species were expected to be sensitive to rainfall, which changes the availability of the tubers to geese through increasing water levels

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