The existent main disasters on the Yangtze valley are flood

loss of water

erosion of soil and deposit of silt. Among them

the loss of water and erosion of soil lead up to a decrease of productivity of land

a reduction of yield

a shortening of channel and a loss of reservoir efficiency. To construct total protection forest system on the whole valley is the fundamental to control or eliminate these disasters. It includes: 1)the system of forest for conserv'ation of water supply on high mountainous gorge district in upper reaches; 2)the system of soil and water conservation forest in middle reaches; and 3)the system of protective belts of agricultural land and bund protective forest in plain of middle and lower reaches. After completion of these systems

the ratio of forest cover in the Yangtze valley may reach 20-30% and the virtuous cycle in the ecological system will be realized.