Trees serve many functions. People normally think only of their ability to beautify an area, but there are other benefits as well.
Trees, like brick and mortar, can be used to make walls and ceilings, screen unwanted light, intercept glare, divert sound, and reduce erosion.
Direct light and glare from natural and manufactured reflective surfaces can be reduced when trees of correct mature size, shape and density are planted in the proper places. Dense foliage and branching reduce light intensity, while open, loose foliage allows moderate filtration. The tree should be placed between the sun and viewer. When reflecting surfaces are involved, the tree should be placed either between the sun and the reflecting surface, or between the reflecting surface and the viewer.
Noises from nearby highways, industries and playgrounds can be reduced through proper placement of trees, particularly when used in conjunction with land forms or other solid barriers. The degree of sound control depends on the density of planting. A well-designed planting will include evergreens as well as deciduous trees (those trees that drop their leaves in autumn) for effective year-round sound control.
Failure to protect soil from wind and water results in erosion. Tree characteristics such as coarse leaf textures, horizontal branching habits, fibrous root systems and rough bark can help slow water movement and reduce wind speed, thus reducing soil erosion from rain and wind.
Plants can modify the environment on a small scale. One of the best known effects of plants in this area is the ability of deciduous trees to allow light to pass through the leafless canopy during the winter months and warm up a structure beneath. The leaves then shade that same structure during the summer months and keep the building cooler. Trees that keep the building cooler in summer and allow passive solar heating in the winter can help reduce heating and cooling costs, as shown below.
Trees are capable of guiding, deflecting and filtering winds. A structure in a wooded area will experience lower wind speeds, which will result in lower heat loss.
Areas beneath trees are somewhat protected from the effects of precipitation. Only about 80 percent of the rain that hits the top of the tree canopy will reach the ground. Perhaps an even more dramatic example of precipitation control is the use of evergreens as living snow fences. A windbreak of evergreens will filter wind and allow snow to be deposited about 11/2 times the height of the screen downwind of the planting.
Trees add beauty and interest to urban and suburban areas. Urban areas are often harsh and are greatly softened by the presence of trees. Trees can enhance architectural designs, provide privacy and frame views. Varying textures and colors of foliage, flowers, bark and fruit create multiple seasons of interest. Trees also provide habitat and food for wildlife, attracting birds and animals into urban and suburban areas where they can be enjoyed by the residents.
Trees are known to affect property appraisals. Real estate appraisers classically value an attractively planted home higher than they would an unplanted home. Trees are primary contributors to this property value increase.