What's the use of big trees?

1. Trees can regulate climate and keep ecological balance. Through photosynthesis, trees inhale carbon dioxide and exhale oxygen, making the air clean and fresh. One acre of forest releases enough oxygen for 65 people to breathe.

2. Trees can prevent wind and fix sand, keep water and soil, and absorb all kinds of dust. An acre of forest can absorb 20-60 tons of dust a year.

3. Woods can reduce noise pollution. A 40-meter-wide forest belt can reduce noise 10- 15 decibels.

The secretions of trees can kill bacteria. There are 34,000 bacteria per cubic meter of air in the open space, while there are only 3,400 bacteria in the forest.