Application of Landsat Imagery to Investigate Lake Area Variations and Relict Gull Habitat in Hongjian Lake, Ordos Plateau, China

Abstract

Abstract:Lakes in arid and semi-arid regions have an irreplaceable and important role in the local environment and wildlife habitat protection. Relict Gull (Larus relictus), which is listed as a "vulnerable" bird species in the IUCN Red List, uses only islands in lakes for habitat. The habitat with the largest colonies in Hongjian Lake (HL), which is located in Shaanxi Province in China, has been severely threatened by persistent lake shrinkage, yet the variations in the area of the lake and the islands are poorly understood due to a lack of in situ observations. In this study, using the Modified Normalized Difference Water Index, 336 Landsat remote sensing images from 1988-2015 were used to extract the monthly HL water area and lake island area, and the driving factors were investigated by correlation analysis. The results show that the lake area during 1988-2015 exhibited large fluctuations and an overall downward trend of −0.94 km 2 /year, and that the lake area ranged from 55.02 km 2 in 1997 to 30.90 km 2 in 2015. The cumulative anomaly analysis diagnosed the lake variations as two sub-periods with different characteristics and leading driving factors. The average and change trend were 52.88 and 0.21 km 2 /year during 1988-1998 and 38.85 and −1.04 km 2 /year during 1999 , respectively. During 1988-1998, the relatively high precipitation, low evapotranspiration, and low levels of human activity resulted in a weak increase in the area of HL. However, in 1999-2015, the more severe human activity as well as climate warming resulted in a fast decrease in the area of HL. The variations in lake island area were dependent on the area of HL, which ranged from 0.02 km 2 to 0.22 km 2 . As the lake size declined, the islands successively outcropped in the form of the four island zones, and the two zones located in Northwest and South of HL were the most important habitats for Relict Gull. The formation of these island zones can provide enough space for Relict Gull breeding.

Spatio-Temporal Variations in Precipitation Extremes in the Endorheic Hongjian Lake Basin in the Ordos Plateau, China

“…The Hongjian Lake Basin (HJLB), with a longitude of 109 • 30 38" E-110 • 5 46" E and a latitude of 38 • 51 10" N-39 • 20 20" N, is located in the Ordos Plateau, China [14,42]. The HJLB is also located in the middle regions of the Yellow River Basin, and closest to the Tuwei River, which is one of the main outflow tributaries in the middle reaches of the Yellow River (Figure 1).…”

“…The HJLB is an inflow zone, and its surface water does not flow into the Yellow River system. Seven seasonal rivers flow into the central Hongjian Lake [14]. There are four seasonal rivers in the Inner Mongolia Autonomous Region (i.e., the Maogaitu River, the Zhashake River, the Mudushili River, and the Songdao River) flowing into the lake from the west and northwest, and three seasonal rivers in Shaanxi Province (i.e., the Qibosu River, the Erlintu River, and the Haolai River) flowing into the lake from the south, southeast, and north ( Figure 1).…”

“…The average annual surface water evaporation is generally 964-1124 mm, increasing from southeast to northwest. The average annual temperature is 7.4 • C. The coldest month is January, with an average temperature of −10.0 • C, while the hottest month is July, with an average temperature of 22.4 • C. Grassland, sand land, woodland, cropland, and lake water surface are the main land-use types, and grassland and shrubs are the primary vegetation types in the HJLB [14,39]. The HJLB has an extremely fragile ecological environment.…”

External Groundwater Alleviates the Degradation of Closed Lakes in Semi-Arid Regions of China

“…There are two mainstream views on lake shrinkage. The one is that climate change has mainly led to varying degrees of shrinkage of lakes [39][40][41][42], and the other one is excessive human activities is main reason [43]. As we know from the above, the reasons for the decline of these two lakes are climate and perceived factors.…”

Remote Sensing of Floodpath Lakes and Wetlands: A Challenging Frontier in the Monitoring of Changing Environments

“…Lakes in arid and semi-arid regions have an irreplaceable and important role in the local environment and wildlife habitat protection. Liang and Yan [160] reported a study that used three hundred and thirty-six Landsat images from 1988-2015 and the Modified Normalized Difference Water Index to extract monthly water area and lake island area, in the Hongjian Lake in China. The study site is the only critical habitat option of the Relict Gull (Larus relictus), which is listed as a "vulnerable" bird species in the Red List of the International Union for Conservation of Nature (IUCN).…”