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Chapter 1
THE BENEFITS OF TREES
For many of us, trees are a constant force in our lives. They flourish in our backyards, city streets, and neighborhood parks, lending an air of humble nobility to the frenetic pace of our daily routines. In northern climates, the changing characteristics of deciduous trees signal the arrival of new seasons, when blazing foliage of red, orange, and yellow leaves sheds with the approach of winter, and fresh buds and green growth appear during spring, a time of renewed life. In the south, the live oak is a popular and characteristic shade tree, stately and vibrant all year long. Numerous species throughout Canada and the United States, such as the giant Douglas fir of the Pacific Northwest, the flowering magnolia of the Deep South, and the syrup-producing sugar maple of the Northeast are cherished symbols of home, valued for their distinct features, their strength, and their beauty.
The International Society of Arboriculture, the largest and most influential organization of its kind, serves the tree care industry as a scientific and educational organization. The ISA has published a brochure on the benefits of trees, which are outlined in this chapter.
Tree owners know that the impact of trees on a landscape transcends their size and stature. Trees make life pleasant for us, and have social benefits. Time spent amidst a grove of trees is often relaxing. While painters and writers have been inspired by the aesthetic and spiritual appeal of trees, hospital patients have been known to recover from surgery more quickly when their rooms offered views of trees. The strong ties between people and trees are evident in the resistance of community residents to removing trees to widen streets, and in the valiant efforts of individuals to save large or historic trees. Trees benefit our communities by bringing groups together in neighborhood plantings. We often become personally attached to trees.
And why not? Trees are fun — no play equipment will ever replace a good climbing tree. Trees add color, form, and dimension to our gardens. They are our steadfast companions, lasting for lifetimes.
Because of their potential for long life, trees are frequently planted as living memorials, establishing links to our past. Among Earth's longest-lived and largest organisms, many trees can last one to two hundred years, or even longer. The eastern hemlock, for example, can live six hundred to one thousand years. Even smaller trees, considered short-lived, typically survive sixty to eighty years.
In addition to providing social benefits, trees alter the environment in which we live by moderating the climate, improving air quality, conserving water, and providing refuge to wildlife. Radiant energy from the sun is absorbed or deflected by leaves on deciduous trees in the summer and is filtered by their branches during the winter. Trees also combat wind speed — the more compact the foliage on the trees or group of trees, the greater the influence of the windbreak — and have an impressive ability to muffle noise. Leaves and small branches act as baffles, absorbing and deflecting sound. The downward fall of rain is diverted by trees. Trees intercept water and store some of it, thereby reducing storm runoff and the possibility of flooding.
Leaves filter the air we breathe by removing dust and other particles. Leaves absorb carbon dioxide from the air to form carbohydrates that are used in the woody plants' structure and function. In this process, leaves also absorb other air pollutants such as ozone, carbon monoxide, and sulfur dioxide. The combined chemistry of the thousands of leaves on each tree eliminates an enormous volume of pollutants from the air. After processing all the chemicals, trees give off water and oxygen.
A mature maple or oak tree transpires 82 gallons of moisture every twenty-four hours. A great redwood will transpire approximately 500 gallons of moisture a day. This moisture eventually takes the form of dew or rain. Trees draw upon the deep groundwater, thereby lifting water tables and maintaining moisture in the surrounding topsoil.
Even below the ground, trees are doing beneficial things for the landscape. Tree roots anchor the tree in the ground, soak up water and nutrients from the soil, prevent soil from eroding, and support an underground universe of beneficial insects and organisms, which, in turn, keep all the soil around them healthy and teeming with life.
Trees are efficient at cooling the air. The air cools as water vapor from leaves evaporates, which explains why it feels fresh and cool under a tree on a hot day.
Shade trees are tremendous assets for urban communities. When the sun beats down on barren concrete, asphalt, and glass, cities heat up to nine degrees Fahrenheit warmer than their rural counterparts, creating a phenomenon known as the heat island effect. Since such surfaces retain heat, they stay hotter for longer periods of time. After sunset, these hot surfaces continue to radiate stored heat back into the atmosphere well into the evening, making it feel warmer than outside city limits.
Shade trees can cool individual neighborhoods and entire cities by preventing the heat island effect in two ways: in the heat of summer, temperatures are ten degrees Fahrenheit cooler under the shade of a mature tree, and as wind moves air through a shade canopy, it is cooled. A stand of trees, therefore, can create a welcoming oasis effect.
Trees planted effectively will also help you save money and conserve energy. One of the best means of energy conservation is through the planting of windbreaks. Living windbreaks of trees can do much to keep our soil productive and improve our environment, in addition to reducing or eliminating the undesirable effects of excessive wind velocities.
The direct economic benefits provided by trees are usually associated with energy costs. By providing good protection from winds, trees can reduce winter heating costs and summer cooling costs by 25 to 30 percent. Trees also provide indirect economic benefits to communities. For example, customers will receive lower electricity bills when power companies use less water in their cooling towers, build fewer new facilities to meet peak demands, use reduced amounts of fossil fuel in their furnaces, and need to take fewer measures to control air pollution. Communities also save money when fewer facilities are built to control storm water in the region.
Trees have a considerable impact on the value of real estate. Healthy, mature trees can add as much as 20 percent or more to the value of a residential property. Studies show that people are willing to pay 3 to 7 percent more for a house in a well-treed neighborhood. According to the ISA, property values of landscaped homes are 5 to 20 percent higher than those of non-landscaped homes.
Municipal trees often serve several architectural and engineering functions. They provide privacy, emphasize views or screen out unsightly ones, reduce glare and reflection, and direct pedestrian traffic. Their presence complements and enhances buildings and architectural features, much to the delight of city dwellers.
In addition to the material benefits that trees bestow upon urban centers and city inhabitants are the ways in which woody plants enhance the look of residential homes. The use of trees in gardens and landscaped settings provides the opportunity to create, sustain, and enjoy an earthly paradise in our own backyard. Perhaps the greatest benefit offered by trees is the view from a window!
