Known as “the lungs of earth”, forest is the place where human beings originated and developed. The overall area of forests in the world accounts for 30% of land area. Forests play an important role in climate, living environment, water and soil conservation and the ecological balance. Each hectare of forest can adsorb 50-80 tons of dust and a 40m-width forest belt can decrease noise level by 10-15 decibels. Without forests, most creatures on land will become extinct and most of water will infuse into oceans; oxygen in the atmosphere will be reduced while the amount of carbon dioxide will increase; temperature will rise dramatically and floods and droughts become more frequent, which makes it harder for human to live.