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Ecological security can be investigated in both broad sense and narrow sense. Because of the wide area and regional
discrepancy in influencing factors and ecological background, the investigation on regional environment hasn't been
done systematically. Assessment on regional security in fragile region is important content of sustainable development.
The western Jilin Province lines in the semi-arid agro-pastoral interweaving belt (APIB),within which agriculture and
animal husbandry interplay or frequently alternate with each other. Study on the regional ecological security of this
region offer the scientific support for protecting the regional environment and sustainability. This article set up the
Pressure-State-Response model according to the interaction between human and environmental system, and assessed the
ecological safety degree in the western part of Jilin Province in year 2000, using compound model and Grid method
based on GIS and RS. The Ecological Security Index (ESI) was calculated by multilayer synthesis with liner weighting
function method, which divided the area into the following five different conditions: highly damaged, moderately
damaged, early stages of damage, relative safely, and safety, regarding change of environmental key point as the
threshold value that varied under the stress of human activity. The results show that eco-environment in study area is at
medial level. The early stage of damage and relative safely level occupies the largest area proportion accounting for
68.61%. Furthermore, the condition in the eastern part is better than that of the western part and the most serious
degradation is found in the middle part of the study area. When talking about the ten counties in the region, highly
damaged area accounts for a very small percentage. The county that has the widest area of relatively secured area is
Qian'an, and that of the smallest is Da'an. The areas of highly damaged area in Tongyu, Zhenlai and Da'an have
exceeded 10% and they become the region requiring urgent treatment. Regarding average security condition, sequence
of the regions from the best to the worest is as follows: Qian'an, Qianguo, Zhenglai, Songyuan City, Changling,
Baicheng City, Fuyu, Taonan, Da'an and Tongyu. In this study we also analysis the relationship between ESI and
landuse change from 1980 to 2000 in order to find an improving method from landscape. The studying shows that
decreasing of grassland is most import factor influencing the condition of the western Jilin province.
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