西北地区历史时期生态环境变迁及其基本特征

我国西北地区按自然地理区域划分 ,除包括今之陕西、甘肃、宁夏、青海、新疆等 5省、自治区外 ,还当划入内蒙古自治区西半部与山西省。其下又可分为 8个二级自然区。这一地区在历史时期以迄现代 ,生态环境发生了多方面的明显变化 ,主要是 :1 .天然植被大多消失殆尽 ;2 .水土流失不断加剧 ;3.土地沙漠化扩大 ;4.高山冰川雪线后退 ,冰雪储量减少 ;5.河流湖泊变化显著。一些河流河道流程减少、发生断流 ,有的湖泊湖面缩小、甚至消失 ;6.绿洲萎缩。总结其变化特征主要为 :生态环境变化主要反映在干旱化、沙漠化与水土流失不断加剧 ;生态环境发生变化的原因既有气候干旱化的影响 ,也与人为活动关系密切 ;生态环境变化在历史时期以秦汉、唐、明清时期最为显著 ,中华人民共和国建立后更趋剧烈 ;生态环境变化影响广泛深远 ,不仅制约着本地区社会经济的发展 ,还威胁着其周边地区 ,尤其是其东部华北平原与京津地区之生态安全。

The Changes and Basic Characteristics of Ecological Environment during Historical Period in Northwest region

In term of natural geograghical districts , Northwest region not only includes Shaanxi, Ningxia, Gansu, Qinghai, Xingjiang ,but also includes western part of Inner Mongolia autonomous region and Shanxi, which can be divided 8 secordary natural districts. From historical period to today, many changes of ecological environment had happened in this region as follows:1. All the natural vegetation nearly disppeared; 2. Water and soil erosion became more serious; 3. Soil desertification became larger; 4. Snow line of glacier shrink a lot; 5. Rivers and lakes changed seriously; 6. Oasis became smaller and smaller. Generally speaking, its changing characteristics mainly included: Dry is main characteristics of ecological environmental change; The reason of ecological environmental change is weather as well as human-being behavior; The change of ecological environment is obvious during Qinhan,Tang and Mingqing period, it is more obvious after the building of people's republic of China; The change of ecological environment not only affected development of social and economic of this region,but also affected ecological safety of northren plain and Beijing-Tianjing region.