The impact of human activity and climate change on ecosystem services value in the Yanqi Basin, Xinjiang, China

Ecosystem goods and services refer to the dependence of economic wealth and human well-being on natural systems. It is common sense that the structures and functions of ecosystems are changing due to climate change and human activity. There is a heated research on the variations in Ecosystem Services Values (ESV) under intensified global change both in time and space. It is a priority issue to determine, at various spatiotemporal scales, the sensitivity of ecosystems to climate change and anthropogenic pressure in arid areas. To better understand the effect of climate change and human activity on ecosystem services, we evaluated the changes in ecosystem services values from 1973 to 2014 in Yanqi Basin, Xinjiang Uyghur Autonomous Region, China. The evaluation methods used included the Mann-Kendall (MK), Mann-Kendall-Sneyers test, ESV and dynamic land use/cover change (LUCC) degree. The ecosystem services value evaluated included gas regulation, climate regulation, water conservation, soil formation, waste disposal, biodiversity protection, food production, raw materials, recreation and leisure. Landsat images, digital elevation model (DEM) and metrological data were used to evaluate ESV and the related changes. Based on the degree of the effects of climate change and human activity, the research area was divided into two parts — the mountain area (mainly affected by climate change) and the plain oasis area (mainly affected by human activity) at a contour of 1 400 m above sea level. According to the type and effect, land cover was classified as water, wetland, plain desert, cultivated land, glacier, warm shrub grassland, cold meadow steppe and highland vegetation. We analyzed the relationship among the variations in ESV, precipitation and evaporation and then quantitatively differentiated the effect of climate change and human activity on ESV. The results showed that: 1) the MK-Sneyers test detected distinct points of change in precipitation and evaporation in mountain area and plain oasis in Yanqi Basin. Precipitation increased and evaporation decreased in mountain area and plain oasis in the same way. Conversion matrix analysis of LUCC detected expansion of agricultural areas to provide food for the increasing population and socio-economic development in the oasis areas. Thus variations in ESV were caused jointly by climate change and human activity. 2) The declining trend in ESV in mountain area was mainly due to the shrinking of glacier areas. 3) ESV decreased initially and increased afterwards with 2004 as the turning point, following the increasing trend in precipitation and evaporation. The calculated total ESV was 85.86×10⁸ Yuan in 1973, 94.46×10⁸ Yuan in 1977, 84.15×10⁸ Yuan in 1994, 89.40×10⁸ Yuan in 2004 and 96.47×10⁸Yuan in 2014, respectively. The combined effects of climate change and human activity were main causes of ESV variations in the past 40 years in Yanqi Basin. The main reasons for the increasing ESV in the plain oasis included enlargement of artificial oasis due to intensified human activity and supporting favorable climate change such as increasing precipitation and decreasing evaporation.