The Mightiest Pollution Fighters of All
Let's face it. Most human activities -from breathing to burning fossil fuels- cause air pollution. And, while we may not want Big Brother watching over us, it's a good thing Mother Nature is. It's as if she knew we'd need saving from ourselves and created trees to produce oxygen and reduce the atmospheric levels of carbon dioxide created by everyday living.
The U.S. Department of Agriculture says a single acre of trees puts out four tons of oxygen -enough to meet the annual oxygen needs of 18 people. This same acre of trees can absorb the carbon dioxide produced by driving a car 26,000 miles. This intake of carbon dioxide and output of oxygen happens during photosynthesis...fortunately for us.
Not only do trees give us the oxygen we need to breathe, they also fight air pollution by directly reducing nitrogen oxide and sulfur dioxide, major components of photochemical smog, ozone pollution and acid rain. On a more tangible front, trees act as a giant filter on the world. Their leaves, stems and twigs trap and filter out particulate matter, such as dust, ash, pollen and smoke, from the air.
Trees also help keep our water clean. As paving increases in neighborhoods and business districts, rain from storms flows more quickly across paved areas than it does across treed areas. The faster this storm runoff moves, the more it erodes and washes sediment and chemicals into drainage channels. The runoff carries with it oil and grime from parking lots, soil from construction sites, fertilizers from lawns, and chemicals from industrial discharges.
This storm runoff -with its soil sediment and pollutants- flows into drainage pipes and ditches and then into creeks, rivers and lakes. Increased sediment clouds streams and destroys fish habitat. Chemicals make water undrinkable. So how can we promote clean water?
Trees. Tree leaves help interrupt and slow rainfall, allowing the water to soak into the soil. This reduces runoff and decreases the need for additional erosion control. Tree roots also hold soil in place, further slowing erosion.
Another job to leave to the professionals is pruning tree limbs near electrical and utility wires. Contact utility companies or city maintenance workers to handle this dangerous task.
City workers should also remove other tree branches on city property that overhang homes, garages, parking areas, sidewalks, or obstruct vision at traffic intersections. If you notice a lack of regular pruning in your neighborhood, lobby city officials to get a tree care program in place.
Back on the home front, prune away any branches that obscure your home’s entry to deter potential intruders. If any of your trees appear to be developing two trunks, prune away all but one centrally located trunk. A tree with two or more trunks is not as strong and may be torn apart during ice or windstorms.
One of the most common pruning mistakes is to cut off the top of a tree. “Topping” starves the tree by drastically reducing its food-making ability and leaves stubs that make the tree more susceptible to insects, disease, and decay. It also destroys the plant’s natural shape and promotes the development of weak branch structure. When topped, a tree sends out multiple shoots that grow rapidly. These shoots are weakly attached and are prone to breaking, creating a hazardous condition. Proper pruning removes excessive growth without the problems caused by topping.
Many of us prune our trees to create shapes that we think are more aesthetically pleasing. Pruning should enhance and maintain the natural shape of the plant. Over pruning or trimming into tight geometric forms usually has adverse affects on trees. If the tree is naturally oval-shaped, don't make it cone-shaped. If it is a naturally spreading type, don't attempt to force it to grow upright.
Above all, remember that mature, urban trees are valuable assets to our property and proper pruning will help keep them healthy year round. For more detailed pruning specifications or information about hiring qualified arborists, contact your State Urban Forester or local municipal forester.