The ecosystem change of external forcing

course system

system output of ecosystem in the frame of conception model of the migrants resettled area in Three Gorg es reservoir area is analyzed. In typical watershed

Quxi watershed

the result of external forcing

submerge and migrant

is the resource change of slope cultiva ted lands

economical fo rest

vegetation

water

habitant etc. of the eco system

and the changes of demand for food supplies

energy resource and education. By the action of feedback mechanism

the system outputs are soil and water loss pricking up

biological diversity being destroyed

heavily soil degrading etc. . And then brings forward some countermeasures such as developing watershed management

resuming and rebuilding mountainous region ecosystem

streng thening research on reforestation countermeasure

to easeup the conflict between human and land and achieve the sustainable development.