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Trees remove pollutants from the air.
One large tree can absorb up to 10 lbs of air pollutants each year. These include ozone (O3 — the primary component of smog), nitrogen oxides (NOx) and sulfur dioxide (SO2), two major contributors to acid rain, and particulate matter (e.g. dust, soot, and smoke). Each of these pollutants have been shown to have adverse health effects, including asthma, lung cancer, and cardiovascular disease.
Trees are natural air conditioners.
Trees intercept radiant energy from the sun (and block harmful UV rays), providing us with shade and reducing the amount of heat absorbed and reflected by buildings and pavement. Trees also cool the air when the moisture released from their leaves (a process called transpiration) evaporates.
Trees can save us money on our heating and cooling bills.
By planting shade trees in strategic places, homeowners can save an estimated 10-50% on their summer cooling bills. In the winter, trees are estimated to reduce residential heating costs by an additional 10-15% through the formation of a wind barrier. These energy savings also translate into a reduction in the amount of greenhouse gas (CO2) that would have been produced through energy production.
Trees increase curbside appeal and real estate value.
Trees can increase the sale price of a home 5-25% depending on the number and size of trees.
Trees reduce city noise and increase privacy.
Trees protect our soil and water by reducing soil erosion and surface runoff.
By intercepting rainfall and stabilizing soil, trees can reduce soil erosion and surface runoff to our sewers and streams, and thus reduce the amount of our tax money Ottawa must spend on water treatment.
Trees provide habitat and food (fruits and nuts) for wildlife.
The average life span of a downtown urban tree is now estimated to be less than 10 years!
While trees in the outer, more residential areas of the city often live closer to 30 years, the fact remains that trees in the unnatural urban environment are not surviving as well as their rural counterparts, which commonly live for more than 100 years.
Water and nutrient deprivation.
Trees need watering during summer dry spells to prevent drought stress, particularly if they are located in a difficult spot, such as between the sidewalk and road or on a slope. A newly planted tree requires at least 100 liters of water per week!
Physical damage caused by nearby construction, lawnmowers, or string trimmers.
A tree’s bark is like our skin. Striking the trunk of a tree with mowing equipment creates a wound (which can then serve as an entry point for disease) and if repeated often enough can even kill a tree. The best way to prevent wounding by lawn equipment is to create a tree well and/or maintain a thin layer of mulch around the base of the tree, which will prevent grass and weeds from growing around the base of the tree. Mulching will also help the soil retain moisture and improve fertility.
Improper Pruning.
Removing a limb creates a great entry point for rot, insects, and disease. Before pruning a tree, one should know the proper cutting techniques to ensure that the bark will quickly re-seal over the wound, which branches to remove, and the best time of year to prune a particular tree, among other considerations. An arborist is trained to know these things. Tree “topping” is typically considered a poor horticultural practice. Much of the pruning performed by municipal and hydro workers is oriented towards human safety, and can therefore be detrimental to residential tree health.
Girdling.
Items tied around the trunk of tree (e.g. dog chains, clotheslines, tire swings, or forgotten support wires) can become confining if left on too long and will restrict the flow of water and nutrients throughout the tree.
Tree Selection.
Different tree species are adapted to live in different soil, water, and sun conditions, and these should be taken into consideration when planting new trees. Avoid planting many trees of the same species. A monoculture facilitates the spread of pests and increases your chances of losing a large proportion of your trees all at once.
Grade Change.
The majority of the fine, water absorbing roots of a tree are found in the top 6-12 inches of soil. Adding a layer of soil on top of the existing horizon means that air and water must now penetrate further through the soil to reach the roots, and that the tree must expend energy to slowly extend its roots upward, in an unnatural direction, in order to survive. As little as 4 inches of fill can kill certain tree species, including linden, sugar maple, and beech.
Herbicide injury.
If you are spraying a lawn with a herbicide, keep in mind that the roots of a tree extend into the soil beneath the lawn and can be harmed by a herbicide.
Exposure to road salt and pollution.
Soil compaction and forcing a tree to grow in a confined space.
Tree Links:
International Society of Arboriculture
Trees are Good
Tree Canada
Trees Ontario Foundation
