The Benefits of Trees

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The Benefits of Trees

Bill Lord

N.C. Cooperative Extension

Recent storms have caused quite a bit of tree damage locally and across the state and nation. When storms bring down trees on houses, cars, and power lines, some people react by cutting down all trees in their yard. While a clear cut will eliminate the possibility of any future tree damage, consider the many benefits of urban trees to daily life when trees are planted, cared for, and kept healthy. On a hot summer’s day, where would you stand, out in the sun or under a shade tree?

One key to avoiding falling trees is to keep them healthy. Avoid driving or parking under trees in the root zone. Compacted soil under a tree’s drip line will slowly kill the tree. Never dig directly underneath a tree and create a no-drive/no-dig zone around trees during construction. Use organic mulch under trees and consider leaving fallen leaves under the tree’s drip line to add organic matter to the soil under the tree. Fallen leaves can be ground up by running a lawn mower over them and leaving them in place. If you choose to use a weed eater near a young tree trunk protect the truck with a flexible plastic guard such as a short piece of plastic drainage pipe sliced down the side to allow the tree to grow out of the trunk guard. Trees benefit from annual fertilization (1 pound of 10-10-10 per inch of diameter per year) and watering during times of drought. Trees should be pruned to keep them healthy but never topped. Weak or damaged limbs should be removed and lower limbs can be removed as the tree grows to allow mowing under the tree. When trees are topped the resulting proliferation of multiple sprouts actually makes the tree weaker and more prone to lose limbs or fall during storms.

Trees help to settle out, trap and hold particle pollutants (dust, ash, pollen and smoke) that can damage human lungs. Trees absorb carbon dioxide and other dangerous gasses and, in turn, replenish the atmosphere with oxygen, and produce enough oxygen on a per acre basis for 18 people every day. Trees absorb enough carbon dioxide on each acre, over a year’s time, to equal the amount you produce when you drive your car 26,000 miles. Trees remove gaseous pollutants by absorbing them through the pores in the leaf surface. Particulates are trapped and filtered by leaves, stems and twigs, and washed to the ground by rainfall.

Trees increase the soil’s permeability and allow more rainfall to soak into the ground rather than run off and cause flooding. The canopy of trees softens falling rain drops (and hail) and disperses the rainfall into smaller droplets. Small rainfall events may be completely absorbed by the canopy of a tree and never reach the ground. Trees create organic matter on the soil surface from their leaf litter and tree roots penetrate the ground creating channels for water to flow into the ground. Tree’s impact from increased soil permeability means reduced surface runoff of water from storms, reduced soil erosion and sedimentation in streams, increased groundwater recharge, and reduced wind erosion of soil.

Strategically placed trees can be as effective as other energy saving home improvements, such as insulation and the installation of weather-tight windows and doors. Trees help reduce your heating and cooling costs. Properly placed shade trees – a minimum of three large trees around your home – can reduce air conditioning costs up to 30 percent. Shade trees offer their best benefits when you plant deciduous trees, which shed their leaves during the winter. These trees provide shade and block heat during hotter months. By dropping their leaves in the fall they admit sunlight in the colder months. Trees perform best for cooling when placed on the south and west sides of buildings and are placed to shade all hard surfaces such as driveways, patios and sidewalks to minimize landscape heat load.

In the winter trees provide a wind break. This result is burning less fossil fuel for heating.

For wind breaks use evergreens, such as pines or eastern red cedars, which retain their leaves or needles all year long. They will serve as windbreaksto save from 10 to 50 percent in energy used for heating. Evergreens offer the best benefits when placed on the north and west side of the home to intercept winter winds.

The scope and condition of a community’s trees and, collectively, its urban forest, is usually the first impression a community projects to its visitors. Studies have shown that trees enhance community economic stability by attracting businesses and tourists. People linger, walk, and shop longer along tree-lined streets. Apartments and offices in wooded areas rent more quickly have higher occupancy rates, and tenants stay longer. Businesses leasing office space in wooded developments find their workers are more productive and absenteeism is reduced.