Hidden Loss of Wetlands in China.

Weihua Xu,Yuan Zeng,Bingfang Wu,Lu Zhang,Hua Zheng,Xinyue Fan,Stuart L Pimm,Li An,Jungai Ma,Lingqiao Kong,Zhiyun Ouyang,Yi Xiao,Jianguo Liu,Xiaosong Li,Xiaoke Wang

doi:10.1016/j.cub.2019.07.053

Abstract

To counter their widespread loss, global aspirations are for no net loss of remaining wetlands [1]. Weexamine whether this goal alone is sufficient for managing China's wetlands, for they constitute 10%of the world's total. Analyzing wetland changes between 2000 and 2015 using 30-m-resolution satelliteimages, we show that China's wetlands expanded by 27,614km2 but lost 26,066km2-a net increase of 1,548km2 (or 0.4%). This net change hides considerable complexities in the types of wetlands created and destroyed. The area of open water surface increased by 9,110km2, but natural wetlands-henceforth "marshes"-decreased by 7,562km2. Of the expanded wetlands, restoration policies contributed 24.5% and dam construction contributed 20.8%. Climate change accounted for23.6% but is likely to involve a transient increasedue to melting glaciers. Of the lost wetlands,agricultural and urban expansion contributed 47.7% and 13.8%, respectively. The increase in wetlandsfrom conservation efforts (6,765km2) didnot offset human-caused wetland losses (16,032km2). The wetland changes may harm wildlife. The wetland loss in east China threatens bird migration across eastern Asia [2]. Open water fromdam construction flooded the original habitatsof threatened terrestrial species and affected aquatic species by fragmenting wetland habitats[3].Thus, the "no net loss" target measures totalchanges without considering changes in composition and the corresponding ecological functions.It may result in "paper offsets" and shouldbeused carefully as a target for wetland conservation.

Highlights

In the context of several key ecological functions or services and especially biodiversity, we examine the suitability of no net loss as a wetland conservation target using data of wetland changes in China between 2000 and 2015
Climate change, and dam construction are the major factors for wetland expansion
After quantifying the contribution of different factors, we found restoration efforts in wetlands did not offset wetland losses by various human activities

Summary

RESULTS

To counter their widespread loss, global aspirations are for no net loss of remaining wetlands [1]. In the context of several key ecological functions or services and especially biodiversity, we examine the suitability of no net loss as a wetland conservation target using data of wetland changes in China between 2000 and 2015. Driving Forces of Wetland Changes Agricultural Land Expansion and Urbanization Agricultural land and urban expansion are the major factors causing wetland loss They accounted for 47.7% (12,439 km2) and 13.8% (3,593 km2) of the total area of loss, respectively. Climate change, and dam construction are the major factors for wetland expansion. They explain 24.5% (6,765 km2), 23.6% (6,505 km2), and 20.8% (5,731 km2) of the total expansion, respectively. We cannot distinguish the contributions of related driving factors due to the lack of relevant data and so do not take them into account

DISCUSSION

Conclusion

Findings

Background