Trees also reduce the greenhouse effect, which is caused when certain gasses accumulate in the upper atmosphere prevent heat from radiating back into space. Carbon dioxide, released by the burning of fossil fuels, is one of the major heat-trapping gases. In one year, a healthy growing tree takes in about 26 pounds of carbon dioxide releases enough oxygen to support four people. Trees help to conserve both land and water resources. Trees growing alongside streams and rivers hold soil in place with their roots.
Leaves slow the erosive force of rain by intercepting and slowing precipitation.
By increasing the infiltration of water into the ground, trees reduce runoff that may often contain pollutants such as sediment, fertilizers and chemicals. Shade cools water, maintaining temperatures suitable for fish and other aquatic wildlife. Leaves dropped by trees each year provide nutrients to both soil and water. If placed strategically around buildings, trees help conserve energy by reducing the need for heating and air conditioning. Deciduous trees, those that lose their leaves each year, provide shade and block heat from the sun during the summer.