water Article Dynamic of Dalinor Lakes in the Inner Mongolian Plateau and Its Driving Factors during 1976–2015 Haidong Li 1 ID , Yuanyun Gao 1,*, Yingkui Li 2 ID , Shouguang Yan 1 and Yuyue Xu 3 1 Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing 210042, China; [email protected] (H.L.); [email protected] (S.Y.) 2 Department of Geography, University of Tennessee, Knoxville, TN 37996, USA; [email protected] 3 Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, Nanjing University, Nanjing 210046, China; [email protected] * Correspondence: [email protected]; Tel.: +86-25-8528-7645 Received: 15 August 2017; Accepted: 27 September 2017; Published: 30 September 2017 Abstract: Climate change and increasing human activities have induced lake expansion or shrinkage, posing a serious threat to the ecological security on the Inner Mongolian Plateau, China. However, the pattern of lake changes and how it responds to climate change and revegetation have rarely been reported. We investigated the pattern of lake-area changes in the Dalinor National Nature Reserve (DNR) using Landsat imagery during 1976–2015, and examined its relationship with changes in climate and vegetation factors. The total lake-area in the DNR has decreased by 11.6% from 1976 to 2015 with a rate of −0.55 km2 year−1. The largest Dalinor Lake reduced the most (by 32.7 km2) with a rate of −0.79 km2 year−1. The air temperature has increased significantly since 1976, with a rate of 0.03 ◦C year−1 (p < 0.05), while the precipitation slightly decreased during 1976–2015, with a rate of −0.86 mm year−1. The Normalized Difference Vegetation Index (NDVI) increased by 27.7% from 1976 to 2015, especially after 2001 when vegetation has been promoted greatly as a result of the successful ecological protection and restoration in the Dalinor basin. The decrease in lake-areas for the DNR exhibited a negative correlation with NDVI (r = −0.397, p < 0.05) during 1976–2015. It seems that decreasing precipitation drives the reduction in lake-area, while rising temperature and vegetation greenness accelerated this decreasing trend by increasing evapotranspiration. The continuous lake shrinkage increases the ecological risks to the habitat of birds, causing a challenge to the management in the DNR. Keywords: lake-area change; water resources; vegetation greenness; climate change adaptation; ecological protection and restoration; Inner Mongolia 1. Introduction Climate change, especially continuously rising temperature and changes in precipitation, has induced significant environmental changes around the world, including the changes in water resources that are of critical importance to human society and ecosystems [1–3]. Many areas of the world, including China, are currently facing water shortage issues, and will face higher risks of water shortages by the middle of this century due to global warming [4,5]. Water availability in China is already limited, especially in the northern and western part, and demand will continue to rise with population increase and economic growth. Lakes are one of the most direct and sensitive water bodies affected by climate change [6,7]. In general, closed lakes (endorheic lakes), especially, small ones, are more sensitive to changing climate or human interventions than open lakes (exorheic lakes). Under some extremely climatic conditions, small lakes may disappear entirely [4,8]. Studies reported that rising temperature and variations in precipitation have caused dramatic changes in the lakes on the Qinghai-Tibetan and Mongolian Water 2017, 9, 749; doi:10.3390/w9100749 www.mdpi.com/journal/water Water 2017, 9, 749 2 of 13 Water 2017, 9, 749 2 of 13 plateaus and and resulted resulted in in many many ecol ecologicalogical hazards hazards since since the the1970s 1970s [9–11]. [9– For11]. example, For example, in recent in recentyears, theyears, lake the expansion lake expansion on the onQinghai-Tibet the Qinghai-Tibet Plateau Plateau flooded flooded pastures pastures and farmland, and farmland, affecting affecting the safety the ofsafety roads of roadsand infrastructure and infrastructure [11]. [The11]. TheMongolian Mongolian Plateau Plateau is located is located in inthe the hinterland hinterland of of Eurasia, Eurasia, includingincluding Mongolia Mongolia and and the the Inner Inner Mongolia Mongolia Autonomo Autonomousus Region Region of of China. China. In In contrast contrast to to the the trend 2 ofof lake lake expansion expansion on on the the Qinghai-Tibetan Qinghai-Tibetan Platea Plateau,u, the the number number of oflakes lakes with with areas areas of >1.0 of >1.0 km2 km on theon Mongolianthe Mongolian Plateau Plateau dropped dropped from from 785 to 785 577 to and 577 the and to thetal totallake area lake in area Inner in InnerMongolia Mongolia reduced reduced from 2 2 4160from km 41602 to km 2901to 2901km2 kmduringduring 1987–2010. 1987–2010. The The remarkable remarkable lake lake shrinkage shrinkage has has resulted resulted in in water shortagesshortages to to local residents, causing desertificat desertificationion and and grassland degradation [9,10]. [9,10]. In In Mongolia, Mongolia, precipitation was was considered considered as as the the dominant dominant driver driver for for the the lake lake changes, changes, while while in in Inner Inner Mongolia, Mongolia, coalcoal mining mining was was suggested suggested as as the the most most important important factor factor in in the the grassland grassland area, area, and and irrigation irrigation was was the the leadingleading factor factor in in the the cultivated area for lake shrinkage [[10].10]. TheThe Dalinor National Nature Nature Reserve (DNR) is is located within the Hunshandake sandy sandy land land in thethe Inner Inner Mongolia Mongolia Autonomous Autonomous Region. The The Hunshand Hunshandakeake sandy land is one one of of the the 25 25 National National Key Key EcologicalEcological Function Areas in China and one of the the main main sources sources of of sandstorm sandstorm to to Beijing Beijing and and northern northern China.China. It It is is also also one one of of the the key key implementation implementation areas areas of of the the Beijing-Tianjin Wind Wind and Sandstorm SourceSource Control ProjectProject [12[12].]. InIn recent recent years, years, water wate flowingr flowing into into these these lakes lakes decreased decreased significantly, significantly, and andboth both lake-area lake-area and waterand water quality quality have changed have changed greatly. greatly. The lives The of locallives herdsmenof local herdsmen and fishermen and fishermenhave been have affected been (Figure affected1). It(Figure is of critical 1). It is importance of critical importance to understand to understand the ecological the risks ecological of the risks lake ofchanges the lake to changes the biodiversity to the biodiversity and local community. and local community. (a) (b) (c) (d) FigureFigure 1. SignsSigns of: of: lake lake shrinkage shrinkage ( (aa);); and and land land salinization salinization ( (bb)) in in the the DNR DNR in in 2014; and lake-based ecosystemecosystem on on lake lake coastal coastal zone zone (c ();c); and and vegetation vegetation coverage coverage on on sandy sandy land land (d) ( din) inthe the Dalinor Dalinor basin basin in 2016.in 2016. Water 2017, 9, 749 3 of 13 In this paper, we investigate the pattern of lake-area changes in the DNR, and examine how climatic factors affect this pattern. We also examine the potential impact of vegetation change on lake changing pattern using NDVI (normalized difference vegetation index) as an indicator of vegetation greenness. We aim to address three research questions: (1) Does the temporal lake changing trend depend on climate changes? (2) What is the potential role of revegetation of sandy land on the hydrological cycle in the Dalinor basin? (3) What is the best strategy to prevent and adapt climate change risks in this ecologically fragile environment? This study provides useful information for environmental protection and promotes a better understanding of climate change adaptation for this lake-based ecosystem and community. 2. Methods 2.1. Study Area The Dalinor basin is located in the topographic junction of the eastern Mongolian Plateau, the southern end of Greater Khingan Mountains, and Hunshandake sandy land (Figure2). It covers an area of 5550.54 km2, and is a typical inland lake basin, containing three major lakes (Dalinor Lake, Gangnor Lake, and Duolunor Lake with areas of 191 km2, 21.1 km2, and 2.2 km2 in 2015, respectively) and four rivers (Gonggel River, Liangzi River, Shari River, and Haolai River). The total discharge of the four rivers is about 0.61 million m3 year−1. Gonggel River is the largest river, accounting for about 75% of the total discharge. Among the lakes, Dalinor Lake (116◦290–116◦450 E, 43◦130–43◦230 N) is the largest. It belongs to Hexigten County and Chifeng City in Inner Mongolia. It is a brackish-water lake with elevation ranging from 1226 to 1228 m above sea level (a.s.l.). The average depth is 7.5 m, and the maximum depth is 13 m. The other two lakes flow into Dalinor Lake. The DNR lies within the Dalinor Basin (Figure2c), covering an area of 1194.14 km 2. The main protected targets of the DNR are rare birds and their habitats, including lakes, wetlands, grasslands, and forests. The DNR is the largest bird-migration corridor in northern China. It is also one of the gathering places of migratory birds in northeast Asia. Many birds take a short stay when they fly between Siberia and south China, Korea, Japan in spring and autumn. Eight species belong to the national protected birds in the first class (such as Ciconia ciconia, Grus Japonensis, Ciconia nigra, Grus vipio, etc.) and 18 species belong to the second class (such as Cygnus cygnus, Anthropoides virgo, Grus grus, etc.) [13].