Characteristics and driving factors of land use change in the Bojiang Lake Basin in Ordos Plateau, China

Land use change can directly affect the variety and intensity of terrestrial ecosystem service functions. The Bojiang Lake Basin (BLB) is located in the Ordos Plateau in China and it belongs to the fragile ecosystem of the arid/semi-arid region.In the last decade, degradation of ecosystem services function in BLB has further jeopardized the endangered Larus relictus birds. Land use structure and pattern in BLB have changed significantly in recent decades. However, few studies have been done on land use change and the related driving factors. This study aimed to investigate the characteristics and the related driving factors of land use change in BLB during 1990-2015 to provide a reference base for the improvement of ecosystem services function and the protection of L. relictus birds. In the study, six periods (1990, 1995, 2000, 2005, 2010 and 2015) of 30 m resolution of land use data were extracted from Landsat remote sensing images. Land use change was investigated using trend and status index methods and then the main driving factors (i.e., climate change and human activity) analyzed. The results showed that grassland, farmland and unused land were the main land use types in 1990-2015, and there was significant change in land use in the BLB study area. Based on spatial variation, there was an increasing trend in farmland in the eastern, western and north-central regions, and then a decreasing trend in unused land in the southern region. The characteristics of the variation in area and dynamic conversion of each land use type were different. There was a dynamic balance in transformation in high, medium and low coverage grasslands, occupying some 70% of the lake basin. Farmland and unused land respectively had an apparent increase and decrease in trend. There was 6.05% increase in farmland area and 7.62% decrease in unused land area in the lake basin. Grassland was the main source of income for farmlands and therefore the main export for unused lands. The water area was decreased by 1.45% of the total area in 1990-2015, with bottomland as the main export. In the period 1995-2000 there was frequently transformation in land use, which in 2005-2010 had the most dynamic imbalance in land use change. Both climatic factors and human activities significantly affected land use change in the BLB study area. Specifically in 1990-2015, the transformation in land use types was due to the combined effects of warming and drying climate (expressed as declining precipitation and rising temperature) and intensifying anthropogenic disturbances (expressed as ecological restoration and water conservancy projects). The increase in farmland, woodland and buildup area and the decrease in unused land were more affected by anthropogenic disturbances. The decrease in water body and high coverage grassland and the increase in medium and low coverage grasslands were due to both climatic factors and human activities. Therefore, a reasonable land use planning such as restricting planting of forest with high water use, reducing the area of farmland in the catchment of the upper reaches of the rivers was critical for the protection for healthy and sustainable development of the study area.