Shrinkage of the Ruoergai Swamp and changes to landscape connectivity, Qinghai-Tibet Plateau

The Ruoergai Swamp (Zoige) at the eastern margin of the Qinghai-Tibet Plateau in western China is the worldʹs largest plateau peat wetland. Rapid shrinkage of the swamp since the 1950s has endangered the local terrestrial and aquatic ecosystems and the water supply of the upper Yellow River. The causes of the swamp shrinkage were evaluated based upon field investigations in 2011–2013 and analyses of remote sensing images and meteorological and hydrological data. Although a slight rise in the temperature was evident, there was no obvious decrease in the precipitation, indicating that climate change was not the primary cause of the recent swamp shrinkage. Remote sensing images indicated that roughly 920 km of artificial ditches excavated from the 1960s to 1990s have affected around 648 km2 of swamp, accounting for 27% of the total shrinkage area (approximately 2400 km2). Bed incision of the upper Yellow River was considered to be the primary cause for the long-term degradation of the Ruoergai Swamp. Ensuing headcut erosion of countless tributaries has induced drainage network extension, draining large areas of the swamp and lowering the groundwater levels. Headcut erosion and construction of the artificial channels have markedly increased the flow and sediment movement in this landscape.