Urban spatial expansion and its impacts on ecosystem service value of typical oasis cities around Tarim Basin, northwest China

Abstract

Under the background of rapid urbanization, the change of urban land use structure has a great impact on ecological environments, and determination of impacts of urban spatial expansion (USE) on the urban ecosystem service value (ESV) is of particular significance to sustainable development in arid regions. To archive a better understanding of the spatio-temporal characteristics of USE, and to quantitatively describe the impact of USE on ESV, five typical oasis cities around the Tarim Basin are selected as research areas. Based on classifying the land use types from LandsatTM/ETM+/OLI imagery data between 1990 and 2015, the urban spatio-temporal dynamic changes are quantitatively analyzed, ESV changes of each land use types and each ecosystem functions were estimated, and USE impacts on ESV is determined. The results are concluded as follows: (1) Over the researched 25 years, the largest USE area occurred in Korla, followed by 63.65 km2, and the smallest is in Artux, followed by 2.91 km2. (2) Farmland and unused land has a great contribution to the USE, and the reduction of farmland in five cities were 2.68 km2 in Korla, 5.13 km2 in Aksu, 0.54 km2 in Artux, 28.42 km2 in Kashgar, and 14.25 km2 in Hotan during the 1990–2015 years. (3) Both of the expansion speed and expansion intensity are maximal in Hotan (followed by 8.38% and 25.89%) and minimal in Artux. (4) There are the highest compactness, the lowest fractal dimension, and the simplest and most stable shape in Artux. In contrast, Korla has the lowest compactness and highest fractal dimension, and is the most complex, disperse and unstable city. (5) The total ESV of the five cities is reduced at 45.36 million CNY with a decrease rate of −21.54%. Among these cities, only Korla shows an increasing trend of ESV (23.72 million CNY), but the other four cities shows a decreasing trend with 20.98 million CNY in Aksu, 0.15 million CNY in Artux, 35.76 million CNY in Kashgar, and 12.20 million CNY in Hotan. (6) USE has a great effect on the ESV changes, and the increasing runoff, temperature and precipitation are impacting the ESV in some positive ways. (7) Waste treatment, water conservation and soil formation functions are the top three ecosystem functions with high service value, and ecosystem function of the five cities belong to a provision function. In light of these findings, this study conveys important strategies for regional sustainable development and plan in the arid ecologically fragile regions.