At the very beginning of our human experience, trees were considered sacred and honorable: Oaks were worshiped by the European druids, redwoods were a part of American Indian ritual, and baobabs were a part of African tribal life. Ancient Greeks, Romans, and scholars during the Middle Ages venerated trees in their literature. Dryads and tree nymphs (tree spirits) were important characters in many ancient Greek myths. In more modern times, naturalist John Muir and President Theodore Roosevelt valued the wilderness, including trees, for its own sake, as they established the modern conservation movement and the National Park System and National Park Service. The modern human community values forests for their calming influence, as evidenced by the Japanese-influenced practice of "forest bathing" or "forest therapy." And people today have other, very practical reasons to admire and honor trees.

01 of 08 Trees Produce Oxygen Human life could not exist if there were no trees. A mature leafy tree produces as much oxygen in a season as 10 people inhale in a year. What many people don't realize is that the forest also acts as a giant filter that cleans the air we breathe. Trees help cleanse the air by intercepting airborne particles, reducing heat, and absorbing such pollutants as carbon monoxide, sulfur dioxide, and nitrogen dioxide. Trees remove this air pollution by lowering air temperature, through respiration, and by retaining particulates.

02 of 08 Trees Clean the Soil The term phytoremediation is the scientific word for the absorption of dangerous chemicals and other pollutants that have entered the soil. Trees can either store harmful pollutants or actually change the pollutant into less harmful forms. Trees filter sewage and farm chemicals, reduce the effects of animal wastes, clean roadside spills, and clean water runoff into streams.

03 of 08 Trees Control Noise Pollution Trees muffle urban noise almost as effectively as stone walls. Trees, planted at strategic points in a neighborhood or around your house, can abate major noises from freeways and airports.

04 of 08 Trees Slow Storm Water Runoff Flash flooding is already reduced by forests and can be dramatically reduced by planting more trees. One Colorado blue spruce, either planted or growing wild, can intercept more than 1,000 gallons of water annually when fully grown. Underground water-holding aquifers are recharged with this slowing down of water runoff. Recharged aquifers counter drought.

05 of 08 Trees Are Carbon Sinks To produce its food, a tree absorbs and locks away carbon dioxide in the wood, roots, and leaves. Carbon dioxide is a "greenhouse gas" that is understood by a consensus of world scientists to be a major cause of global warming and climate change. A forest is a carbon storage area or a "sink" that can lock up as much carbon as it produces. This locking-up process "stores" carbon as wood so it is not available in the atmosphere as a greenhouse gas.

06 of 08 Trees Provide Shade and Cooling Shade resulting in cooling is what a tree is best known for. Shade from trees reduces the need for air conditioning in summer. Studies have shown that parts of cities without cooling shade from trees can become "heat islands" with temperatures as much as 12 degrees higher than surrounding areas.

07 of 08 Trees Act as Windbreaks During windy and cold seasons, trees located on the windward side act as windbreaks. A windbreak can lower home heating bills up to 30 percent and have a significant effect on reducing snow drifts. A reduction in wind can also reduce the drying effect on soil and vegetation behind the windbreak and help keep precious topsoil in place.