Ecological Security Of The Minjiang River And Its Early Warning

Based on a Pressure-Status-Response model, fifteen selected indexes were formulated to study the status, dynamic changes and their driving factors of ecological security in the Minjiang River Basin on a time span from 1995 to 2020 by an integrated application of Analytic Hierarchy Process, Fuzzy Compositive Assessment, Time Series Forecasting Method and Principal Component Analysis. Moreover, an early-warning model was built for ecological security monitoring within a mid-term period from 2010 to 2020. Main results were summarized as follows:1. In the period of 1995, 2000 and 2005, ecological security in the Minjiang River Basin featured a whole mending process. The area ratio of assessment units (county-level) on a highly threatening level was decreased from 81% in 1995 to 56 % in 2005 whereas that of assessment unit on a moderately threatening level was decreased from 8% in 1995 to 3% in 2005. Contrarily, an area ration of assessment units on a critical threatening level was increased from 0 in 1995 to 11% in 2005 whereas that of assessment units on a safe level was increased from 11% in 1995 to 30% in 2005. As far as a spatial change is analyzed, most counties in the middle reaches of the Minjiang River Basin maintained a safe-level status, and some counties where the ecological security was previously on an unsafe level conducted a gradual progressive increase in the area ratio towards the safe level. Notwithstanding, such counties as Wenchuan, Daofu, Maerkang, Xiaojin, Jiulong, Tianquan, Yucheng, Shimian, Hanyuan, Meigu and Shuangliu, most of which are locating in the upper reaches of the Minjiang River Basin, featured an uneven changes on ecological security status during 1995 and 2005. Basically, the ecological security status in the middle and lower reaches was much better than that in the upper reaches and that in the Daduhe River Basin.2. Driving factors for ecological security changes in the Minjiang River Basin existed in seven classifications, involving in rural economic status attributed by average annual net income per person and highway density, rural non-point pollution condition attributed by chemical fertilizer use and pesticide use per unit area, rural productivity attributed by average grain yield per person and rural labor ratio, landscape pattern attributed by forest coverage and landscape diversity index, rural electricity provision, water and soil loss and agricultural hazards as well. Principal Component Analysis showed that among those factors, rural economic status and rural non-point pollution condition were the major driving factors for ecological security changes in the Minjiang River Basin. 3. Through forecasting by a Time Series Forecasting Method, ecological security status will be significantly changed towards a safer trend in the period of 2010, 2015 and 2020 in the Minjiang River Basin. (1) Complicate changes will occur within different assessment units in the study area. Most of them will generally develop towards a better security level, but some of them will gradually descend their security level. (2) Some assessment units which are presently on the safe level will process little changes in ecological security status, which can be listed as Dujiangyan, Chengdu Downtown, Longquan, Pixian, Wenjiang, and Mianning. Meanwhile, some assessment units presently on a threatening level will also maintain their status. (3)The ecological security status in the middle reaches of the Minjiang River Basin will always be better than that in the lower reaches. Threats will continuously exist in the upper reaches and in the Daduhe River Basin. This result is coincident with reports from other studies, which still deserves more urgent and prompt concerns.4. In terms of a mid-term early-warning, three monitoring regions can be typed into safe region, threatening region and unsafe region, according to comprehensive analysis on ecological security status during 2010 and 2020. The safe region is composed of 49 assessment units, most of which are in the middle reaches, the threatening region contains 15 assessment units of Songpan, Qingsheng, Jingyan, Shawan, Rongxian, Arba, Seda, Rangtang, Jinchuan, Danba, Jiulong, Hanyuan, Jiajiang, Ebian and Ganluo, which are scattered in three sections of the Minjiang River Basin. The unsafe region contains only 2 assessment units, Lixian and Yuexi.5. The main early-warning factors for ecological security during 2010 and 2020 in the study area can be diagnosed by six sensitive components as economic developmental condition, agricultural hazards, land loading capacity, rural population composition, rural electricity and land use changes.6. So as to improve the ecological security in the Minjiang River Basin, some technical and policy-based countermeasures should be applied as: (1) to optimize land use and increased the forest coverage; (2) to develop alternative power source in the rural area;(3)to educate the labor and transfer the overplus;(4)to implement ecological emigration for unloading land pressure; (5)to enforce controlling rural hazards; and (6) to develop alternative livelihood for accelerating rural economic increase.