Trees and plants, in general, produce energy for growth using a process known as photosynthesis. Using light, water and carbon dioxide, a plant produces energy in the form of sugar and releases oxygen into the air. Forests cover approximately 30 percent of the land on earth and sustain nearly 80 percent of the world's terrestrial organisms. It is estimated that one acre of trees in urban forests can produce enough oxygen for eight people and remove 188 pounds of carbon dioxide from the air.
Oxygen comprises only about 21 percent of air's chemical component. Yet, it is extremely important to life on earth. Living organisms, from single-celled animals to humans, use oxygen to produce the energy required to sustain them. Since trees are larger plants, their production of oxygen is significant. It is estimated that tropical rainforests, produce 40 percent of the earth's oxygen even though they cover only about 6 percent of the land. Rainforests in the Amazon have declined by 17 percent in the last 50 years as a result of deforestation.
