成都平原及岷江上游地区生态环境的变化

Variation of ecological environment in the area of Chengdu plain and upper reach of Mingjiang river

以成都市区为中心的成都平原及其毗邻的岷江上游地区, 共同组成了中国西部唯一的一片“森林-水田农业生态区”, 也是中国西部最发达的经济区。近50 年来, 这一地区生态环境发生了明显的变化, 成都平原缺水, 天气变得干而热, 岷江上游森林植被萎缩, 干旱河谷扩大, 水量减少, 水土流失加剧等等。在考察中发现了以下事实: 成都市区近60 年来, 降水量减少25% ; 地下水位由1-3m 下降到10-20m ; 都江堰供水区年缺水量达12亿m 3。而岷江上游地区森林覆盖率则由40年代的39.5% 下降到目前的29.6% ; 干旱河谷扩大到流域面积的1/5,其中有30% 的面积已出现荒漠化; 岷江干流80 年代年迳流量比40 年代减少9.5% , 枯水流量减少27.2% ; 90年代岷江上游水土流失面积比80 年代增加1000km2, 侵蚀总量增加26.3% , 侵蚀模数提高15.1% 。事实表明, 由成都平原和岷江上游组成的“森林-水田农业生态系统”正在遭受破坏。针对这一事实, 提出三条建议: 坚决禁伐天然林,建设岷江上游水源林涵养体系, 重建生态屏障, 尽快把岷江上游森林覆盖率恢复到40% 以上, 水土流失面积控制在20% 以下; 尽快建设具有削洪增枯效益的紫坪铺水库, 解决成都平原缺水问题; 加强成都平原林网建设, 扩大城市绿地面积, 切实改变成都平原的生态环境。

The area of Chengdu plain and the upper reach of Mingjiang river is a unique zone of forest paddy field cultivated ecosystem, which is also the most developed economic area in western China However,there has been a significant change in this ecological environment for the last 50 years,which results in droughts in Chengdu plain, arid climate, shrinking of forest area, expansion of arid valley, serious soil and water loss, etc The author identified that the precipitation has decreased from 25% for the last 60 years, the ground water level goes down from 1 3 meters to 10 20 meters, and the lack of water in Dujiangyan irrigation area is up to 1 2 billion cubic meters Meanwhile, the coverage of forest in the upper reach of Mingjiang river decreased by 39 5% in 1940s to 29 6% now Arid valley expands to 1/5 of the whole reach, among which 30% are deserted The runoff of main Mingjiang decreases by 9 5% and 27 2% in dry season comparing with those in 1980s and 1940s.The area of soil and water loss in the upper reach of Mingjiang river increases by 1000 square kilometers from 1980s to 1990s, the total loss rises by 26 3%,and the amount of erosion goes up 15 1% All these facts show that the forest paddy field cultivated ecosystem in Chengdu plain and the upper reach of Mingjiang river confronts a serious degradation The author gives three suggestions Firstly, logging of natural forest should strictly be forbidden and water conservation forest in the upper reach of Mingjiang river should be built up, and the ecosystem should be recovered to reach 40% of the forest coverage and to control the soil and water loss below 20% Secondly, the reservoir of Zipingpu should be constructed to control water in flooding season and drought season and to supply sufficient water for Chengdu city Finally, the green land in urban area of Chengdu plain should be strengthened and expanded to improve the ecological environment in Chengdu plain