Abstract
Problem statement: The objective of this study is to develop techniques for assessing and analyzing sand desertification in the northern part of Shaanxi Province, China. Approach: In order to reveal the process of land degradation, especially the latest situation of sandy desertification, a method integrating remote sensing, Geographic Information System (GIS) and field survey was employed to build a sandy desertification dataset for analysis. Remote Sensing images included the Landsat Thematic Mapper (TM) images in 1987 and Landsat Enhanced Thematic Mapper Plus (ETM+) images in 1999). Eight land-cover classes, including active sand dunes, fixed sand dunes, semi-fixed sand dunes, grass land, farm land, wet land, built up area and unused land and Normalized Difference Vegetation Index (NDVI), were identified. Results: The results showed that the active sand dunes and semi-fixed sand dunes have increased with a change rate of 128.70 and 55.65 km2 year-1, respectively, in the meantime the fixed sand dunes has decreased with a decreasing rate of 182.14 km2 year-1. During the 1987s, the area of sandy desertified land reached 12,006.11 km2 (57.17% of the total sandy area), of which severely desertified, medium desertified and slightly desertified land areas were 4,442.23, 4,253.45 and 3,310.43 km2, respectively. By the year 1999, the area of desertified land was increased to 13,782.30 km2 (65.63% of the total sandy area), of which severely desertified, medium desertified and slightly desertified land areas were 5,169.89, 4,918.15 and 3,694.26 km2, respectively increasing by 1,776.19 km2. Conclusion: Spatial change detection based on active sand dunes showed that the expansion area was much larger than the reversion in the past two decades and that several active sand belts has been formed, suggesting that sandy desertification of northern part of Shaanxi Province, China, will be a long-term task.
Highlights
Harsh physiographic conditions, irrational land-use practice and population augmentation are regarded as the forces of triggering sandy desertification[3] the sandy desertification assessment and monitoring are always concerned by researchers, the public and the policy-makers
By the year 1999, the area of desertified land was increased to 13,782.30 km2 (65.63% of the total sandy area), of which severely desertified, medium desertified and slightly desertified land areas were 5,169.89, 4,918.15 and 3,694.26 km2, respectively increasing by 1,776.19 km2
By the year 1999, the area of desertified land was increased to 13,782.30 km2 (65.63% of the total sandy area), of which severely desertified, medium desertified and slightly desertified land areas were 5,169.89, 4,918.15and 3,694.26 km2, respectively increasing by 1,776.19 km2
Summary
By the year 1999, the area of desertified land was increased to 13,782.30 km (65.63% of the total sandy area), of which severely desertified, medium desertified and slightly desertified land areas were 5,169.89, 4,918.15 and 3,694.26 km, respectively increasing by 1,776.19 km. “desertification” in the context of assessment is land degradation in arid; semi-arid and sub-humid areas resulting from adverse human impact. According to the United Nations Conference on Environment and Development[13], defines desertification as “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variations and human activities. Sandy desertification is one of the main form of land degradation in China, especially in northern China[9], which has kept expanding since the 1950’s and has exerted severe impacts on regional socioeconomic development and environmental security[11]. Decertified sandy land increased by 25,200 km for the period from 1975-1987 about 40.5% of which was distributed in the semi-arid agro-pastoral regions of northern China[16]
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