Trees use the energy from the sunlight to produce glucose from water and carbon dioxide and in this process, they tend to release oxygen. Suppose a tree is growing by 5 percent every year, it will be producing 100 kg of oxygen each year. A normal healthy human being breathes about 9 and a half tonnes (740 kg) of oxygen in a year which contributes only up to 23% of that air. So roughly, 8 to 9 trees are needed for one person! Currently, India has 28 trees per person and China has 108 trees per person even though their population is slightly higher.
