Rapid loss of lakes on the Mongolian Plateau

Lakes are widely distributed on the Mongolian Plateau and, as critical water sources, have sustained Mongolian pastures for hundreds of years. However, the plateau has experienced significant lake shrinkage and grassland degradation during the past several decades. To quantify the changes in all of the lakes on the plateau and the associated driving factors, we performed a satellite-based survey using multitemporal Landsat images from the 1970s to 2000s, combined with ground-based censuses. Our results document a rapid loss of lakes on the plateau in the past decades: the number of lakes with a water surface area >1 km² decreased from 785 in the late 1980s to 577 in 2010, with a greater rate of decrease (34.0%) in Inner Mongolia of China than in Mongolia (17.6%). This decrease has been particularly pronounced since the late 1990s in Inner Mongolia and the number of lakes >10 km² has declined by 30.0%. The statistical analyses suggested that in Mongolia precipitation was the dominant driver for the lake changes, and in Inner Mongolia coal mining was most important in its grassland area and irrigation was the leading factor in its cultivated area. The deterioration of lakes is expected to continue in the following decades not only because of changing climate but also increasing exploitation of underground mineral and groundwater resources on the plateau. To protect grasslands and the indigenous nomads, effective action is urgently required to save these valuable lakes from further deterioration.The Mongolian Plateau, located in the hinterland of temperate Asia, sustains the eastern part of the Eurasian Steppe (1). The Inner Mongolia Autonomous Region of China (Inner Mongolia hereafter) and the entire territory of Mongolia (formerly the Mongolian People’s Republic) constitute its core region, with an area of about 2.75 million km² and a population of about 28 million (2–4). The plateau is dotted with numerous lakes surrounded by vast grasslands (Fig. 1), which have nourished the Mongolian people and created a unique Mongolian nomadic civilization (5). Many of these lakes on the plateau are internationally important wetlands for threatened species and migratory waterfowls, 13 of which are designated to be protected by the Ramsar Convention (6) (SI Appendix, Text S1).Open in a separate windowFig. 1.Distribution of lakes with water surface area >1 km² on the Mongolian Plateau. Inset shows the study area.However, a number of lakes have shrunk remarkably in recent decades as a result of intensive human activities and climate change. The shrinkage and drying up of lakes have exacerbated the deterioration of regional environment, which has directly threatened the livelihood of local people. Because of the degradation of lakes and grasslands, the plateau has become one of the major sources of sand–dust storms in northern China (7, 8), and dust from this region was even detected in North America in 1998 (9). Although several previous works have examined the changes in some lakes on the plateau (10, 11), a collective study of changes in the lakes across the plateau has not been performed. Using 1,240 available scenes of multitemporal images of Landsat Multispectral Scanner (MSS), Thematic Mapper (TM), and Enhanced Thematic Mapper (ETM+) from the late 1970s to 2010, combined with information on climate, topography, land use, human activity, and high-resolution Google Earth images, we established a database of Mongolian lakes (MONLAKE) for the entire plateau (for details see Materials and Methods and SI Appendix, Text S2 and Table S1). Using this database, we explored the changes in the lakes over the past three decades and investigated their possible driving forces.