The evolution of desert grassland around Urumqi City and an evaluation of its ecosystem service value

Desert grasslands around cities have ecological functions such as reducing surface runoff, resisting wind erosion, and sequestration of carbon, and their value is more likely to change due to their own vulnerability and urbanization. Evaluating the value of their ecosystem services is of great significance for the scientific utilization, planning, and protection of such resources. Therefore, this study selected desert grassland within 10 km outside Urumqi city from 1990 to 2020 as the study area, revised the unit price of ecosystem services with biomass, and realized the spatial heterogeneity expression of ecological service value on Landsat image pixels (30 m × 30 m). Based on the understanding of the variation rules of grassland area and biomass, the ecosystem service value of surrounding desert grassland was quantitatively evaluated. The results showed: 1) During Over 31 years, the area of desert grassland around the city decreased by 193.49 km², with a dynamic attitude of −3.27%, mainly turning to construction land. 2) The overall biomass of grassland showed a fluctuating increase; the biomass was 198.06 g∙m⁻² in 2020. 3) The value of grassland ecosystem services generally showed a fluctuating and increasing trend; the highest value was CNY 2.935 billion in 2015, and the total value of ecosystem services was CNY 2.001 billion in 2020. Between 1 and 10 km from the city, the service value of the grassland ecosystem indicated that the closer the distance to the city, the lower the service value. Therefore, in the past 31 years, the area of desert grassland around the city has changed greatly and tended to decrease. Although the biomass was affected by urban expansion, it tended to increase. The ecosystem service value was less affected by the area and biomass of grassland, but mainly affected by social economy.