Loss and fragmentation of marshes in the Sanjiang Plain, northeast China, 1954–2005

Published source details Wang Z., Song K., Ma W., Ren C., Zhang B., Liu D., Chen J.M. & Song C. (2011) Loss and fragmentation of marshes in the Sanjiang Plain, northeast China, 1954–2005. Wetlands, 31, 945-954.
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This study is summarised as evidence for the following.

	Action	Category
	Provide general protection for marshes or swamps Action Link

Provide general protection for marshes or swamps

A before-and-after study in 1954–2005 in northeast China (Wang et al. 2011) reported that following legal protection of wetlands, the area of marshland on the plain decreased but at a slower rate than before protection, and that the same was generally true for landscape structural metrics. Statistical significance was not assessed. Between 1954 and 1986, when wetlands were not protected and government polices instead encouraged conversion of wetlands to farmland, the area of marshland on the plain had decreased by 668 km²/year (from 35,300 km² to 13,900 km²). Between 1986 and 2005, when local and national governments prohibited wetland reclamation and established protected areas, the area of marshland on the plain decreased by 305 km²/year (from 13,900 km² to 8,100 km²). Most landscape structural metrics declined more slowly after protection than before (i.e. largest patch size, variation in patch size, complexity of patch outlines; see original paper for data). In contrast, average patch size declined after protection (from 941 to 781 ha) compared to an increase before (from 735 to 941 ha). Throughout the study, there were increases in cropland area, human population and air temperature, but no significant change in precipitation. Methods: Digital maps of marshland on the Sanjiang Plain were created from paper maps (drawn around the 1954 growing season) and satellite images (taken in growing seasons between 1976 and 2005). The digital maps were verified in the field. “Marshland” was defined as all non-woody vegetated wetlands, so included some open bogs as well as true marshes.

(Summarised by: Nigel Taylor)