本文通过三峡工程建设前后15年三峡库区耕地的遥感动态监测和耕地变化分析,揭示出耕地变化的影响因子。2007年三峡库区耕地垦殖指数为0.25,三峡工程建设期,耕地资源减少4%,平均每年递减3 977hm²。耕地占补比例为26∶1,占补不平衡,土地承载能力不足;减少耕地中优质耕地占61%,耕地质量总体下降;库区2007年人均耕地为0.069hm²,低于国家18亿亩红线要求人均耕地的0.089hm²,人地关系紧张,而城市化过程减轻了农村人口耕地资源的压力;引起耕地减少的原因包括城市发展、退耕还林/草、果业发展和水库淹没,城市发展是主要原因,三峡工程蓄水淹没的耕地只占减少耕地的16%;目前,三峡库区仍有18%的耕地坡度大于25度,水土流失严重。

The world's largest dam project and Chinese Western Region Development project was implemented in recent decades in the Three Gorge Reservoir Area (TGRA). These human activities lead to and influence widespread cropland change. In this study we used remote sensing data for dynamic monitoring of cropland in TGRA over 15 years before and after the Three Gorges Project and found that cropland plantation index become 0.25 in 2007 in TGRA, cropland of 0.069 hectare per capita in 2007 is lower than 0.089 hectare per capita of critical line based on estimate of the national total cropland control of 18 billion Mu (1.2 billion hectare). Cropland lost 59 655 hectare during the Three Gorges Project construction, that is to say, annual loss of cropland is 3 977 hectare. With the change of cropland, the ratio of the cropland occupied to the cropland reclamation is 26∶1, such an unbalanced situation means a rapid decrease in land capacity. Meanwhile, high-yield cropland accounts for 61% of cropland loss, resulting to a decline in entire cropland quality. It aggravated the deterioration between cropland supply and food requirement. However, the urbanization process decreases rural population and alleviates the pressure of cropland resources per capita. The driving forces of cropland decline included urban development, "Grain for Green" Project, reservoir submergence and orchard plantation, among them urban development is a key factor. The reservoir submergence accounts for 16% of total cropland loss. Up to now, cropland on slopes more than 25 degree accounts for 20% of total cropland area, that means a high risk of serious soil erosion. As for the long run "Grain for Green" Project which aims at improving the ecological environment, there is still many to do in the future.