Abstract
Land degradation is one of the significant issues the human beings are confronted with, which has become a bottleneck of restricting the sustainable development of the regional society and economy. In order to ascertain the root causes contributed to the land degradation and characteristics of land degradation, Bijiang watershed, the most important Lead-Zinc mine area of Lanping county of Yunnan Province, was selected as the study area. One evaluation index system for land degradation that consists of 5 single factors(water-soil erosion intensity, geological disaster risk, cultivation intensity of arable land, pollution of heavy metals in soil and biodiversity deterioration) was established and 13 indicators were chosen, and the entropy method was adopted to assign weights to each single factor. By using the tools of Geographic Information System (GIS), the land degradation degree was evaluated and one spatial distribution map for land degradation was accomplished. In this study, the land of the whole watershed was divided into 4 types, including extremely-severe degradation area, severely-degraded area, moderately-degraded area and slightly-degraded area, and some solutions for ecological restoration and rehabilitation were also put forward in this study. The study results indicated that: (1) Water-soil erosion intension and pollution of heavy metals in soil have made greater contribution to the comprehensive land degradation in Bijiang watershed; (2) There is an apparent difference regarding land degradation degree in Bijiang watershed. The moderately-degraded area accounts for the most part in the region, which covers 79.66% of the whole watershed. The severely-degraded area accounts for 15.98% and the slightly-degraded regions and extremely severe degradation area accounts for 1.08% and 3.28% respectively; (3) There is an evident regularity of spatial distribution in land degradation in Bijiang watershed. The moderately-degraded areas mainly distribute in the most part of the mid-stream and down-stream, the slightly-degraded areas distribute in the mid-stream, the severely-degraded areas distribute in the upstream and south-west part of down-stream, the extremely severe degradation areas distribute in the east and middle part of the upstream; (4)From the administrative division viewpoint, the slightly-degraded areas primarily distribute in Jiancao township, Baishi town and Nuodeng town. The moderately-degraded areas distribute in Changxin township, Baofeng township, Jiancao township, Baishi town and Nuodeng town. The severely-degraded areas distribute in Jinding town, Baofeng township and Lajing town. The extremely severe degradation areas distribute in Jinding town. By connecting the spatial distribution mode for land degradation with other natural, economical elements, we drew a conclusion that the pollution in heavy metals in soil, serious water erosion and geological disasters are the main causes of the land degradation in Bijiang watershed.
Highlights
The human-land contradiction is becoming more and more serious along with the rapid growth in population, during the last several decades, some inappropriate approaches have been adopted by human beings to exploit and utilize land driven by one-sided emphasis on socio-economic benefits, which has caused a series of land degradation issues, for example water erosion, geological disasters, decreasing productivity of arable land, pollution of heavy metals in soil and the degradation in land biological property, etc [1,2,3]
There is a notable difference in land degradation degree and apparent regularity regarding the spatial distribution of the land degradation in Bijiang watershed
The relevant characteristics and some corresponding countermeasures for land degradation preventing and control are proposed as follows: Slight degradation area The areas with slight degradation takes up the least area, just accounting for 1.08% of the whole watershed, which mainly distribute in the middle stream from a spatial view and in Jiancao township, Baishi town and Nuodeng town from the administrative regionalization point
Summary
The human-land contradiction is becoming more and more serious along with the rapid growth in population, during the last several decades, some inappropriate approaches have been adopted by human beings to exploit and utilize land driven by one-sided emphasis on socio-economic benefits, which has caused a series of land degradation issues, for example water erosion, geological disasters, decreasing productivity of arable land, pollution of heavy metals in soil and the degradation in land biological property, etc [1,2,3]. Jinding Lead-Zinc mine area of Lanping County of Yunan Province is well known with the reputation of “No1 in China and Second in the world” due to its great scale and rich reserves. It is located in the upstream of Bijiang watershed. Are discharged during the process of mineral production, which has caused a serious heavy metal contamination in the water and soil, as well as a great damage to the surrounding arable land and led to frequent occurrence of geological disasters in this watershed. The erosion problem is aggravated by the complicated topography, simplex agricultural productive patterns and intensive cultivation of farmland, etc in the watershed
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