Land use and cover changes in the critical areas in northwestern China

Abstract

This paper summarizes our research on land use and cover changes in the critical areas named North Ningxia (Yinchuan Region), North Shaanxi (Yulin Prefecture/Mu Us) and Middle Tarim River in northwest China. The objectives of the study were to investigate the present land use situation and changes in the past decades and to understand causes of landuse changes. Multi-temporal Landsat TM and ETM+ images (plus an old Corona image for the Middle Tarim), countylevel socioeconomic data and meteorological data were used for this task. The methods and procedures adopted in this work were image registration, atmospheric correction, tasseled cap transformation, indicator differencing, county-level change mapping, and multivariate regression modeling. The principal conclusions are as follows: (1) Not “advancing desert” was observed; however, signs of serious land degradation, e.g., vegetation degradation and soil salinization, have apparently taken place in the past decades due to cultivation practices, land reclamation and grazing. Some of these changes can be traced back to land use policies. (2) Farmland extension is a remarkable rural environmental change in these sites and is associated with the increase in agricultural output. Taking up a small percentage of the total change, the urban extension is related to about 90% of the GDP growth and driven directly by the urban population and their socioeconomic activities. Some river courses have been narrowing, owing partly to climate variability but mainly to the overuse of water in agriculture.