Trees provide a multitude of benefits. Unfortunately, much of the general public
is not well informed on this topic. By increasing awareness of the benefits relating to trees, we can all utilize
current scientific evidence to help resolve many challenging issues and improve the livability of our cities. Proper
tree care and sound forest management programs are crucial to the health, longevity, and sustainability of our
urban forests. The care of trees is a wise investment in our future.
A listing of the benefits, in no particular order, would include at least the following:
1. Air Temperature and Energy Consumption
Trees cool air temperature and help to offset the “heat island” effect of hardscapes
by providing shade and by transpiration (the release of water vapor into the air). By properly selecting and planting
trees, yearly energy savings can exceed 40%. Three mature shade trees placed strategically around a house can cut
air conditioning bills by 10% to 50%.
A single large tree can release up to 400 gallons of water into the atmosphere each
day. Water from roots is drawn up to the leaves where it evaporates. The conversion from water to gas
absorbs huge amounts of heat, cooling hot city air.
Dallas area neighborhoods with mature trees can be up to 11 degrees cooler than
neighborhoods without trees. A one-degree rise in temperature equals a 2% increase in peak
electricity consumption.
One simulation found that planting 500,000 trees in the Tucson area would lower
the “heat island” effect by 3 degrees and lower overall cooling costs by up to 25%.
Cities are 5 to 9 degrees warmer than rural areas and 3% to 8% of summer electric
use goes to compensate for this urban “heat island” effect.
The National Arbor Day Foundation calculates that 100 million additional mature
trees in U.S. cities would reduce the “heat island” effect and save $2 billion annually.
2. Air Quality
Trees produce oxygen and store carbon dioxide (just the opposite of humans), which
helps to clean and restore our air. The American Forests organization’s studies foresee the value of the urban
forest to U.S. cities to be $10 billion by storing carbon dioxide, cleaning particulate matter, and generating
oxygen for urban spaces.
One acre of trees produces enough oxygen for 18 people every day.
One acre of trees absorbs the carbon dioxide produced by driving an automobile 26,000
miles.
A fully-grown Sycamore tree can transform 26 pounds of carbon dioxide into life-giving
oxygen every year.
Large trees remove 60 to 70 times more pollutants than small trees. Only a small
portion of the Dallas area tree population exceeds 24 inches in diameter.
For every ton of wood an urban forest grows, it removes 1.47 tons of carbon dioxide
and replaces it with 1.07 tons of oxygen.
A typical tree removes 25 to 45 pounds of carbon from the air each year.
A study of Atlanta’s urban forest showed that intense urban development and subsequent
removal of large urban forest areas increased the “heat island” effect. This raised the levels of
isoprene emissions, increasing the natural formation of harmful ozone.
An EPA study in Chicago showed that the 23.2% of canopy cover in the Lincoln Park neighborhood adjacent to downtown
annually filters 43.9 tons of particulate matter, 14 tons of
carbon dioxide, and 12.4 tons of nitrogen oxides, giving the urban forest an estimated pollution abatement value
of $625,000 per year.
3. Water/Soil
Planting trees along streams, wetlands, and lakes, helps control storm water runoff,
removes soil sediment, reduces flood damage, and increases water quality, by reducing the pollution of the water
runoff by as much as 80%.
Healthy, vegetated stream buffer zones reduce the total suspended solids phosphorus,
nitrogen and heavy metal transfer between urban areas and streams by 55% to 99%.
Numerous studies show that trees along streams increase fish populations.
The urban forest reduces erosion. One square mile of forestland produces 50 tons
of erosion sediment. In contrast, farmland produces 1,000 to 50,000 tons, and land prepared for
construction produces 25,000 to 50,000 tons of sediment per year.
Tree canopy, in one study, reduced surface runoff from a one-inch rain over a 12
hour period by 17%.
In natural watersheds with trees and vegetation, 5% to 15% of stream flow is delivered as surface storm water
runoff. In highly developed areas, over 50% of stream flow is delivered as surface storm water runoff.
4. Animal Habitat
Trees attract wildlife to an area by supporting habitat and creating biodiversity.
Trees provide food and shelter for wildlife.
5. Economics, Health, and Psychological and Social Behavior
Trees offer unlimited climbing challenges and good physical activity opportunities
such as tree swings and tree houses.
Numerous trees and plants have proven useful in phytoremediation or removal of toxic
materials from soils.
Trees can become living witnesses to our history and evidence of our cultures. Without
a cultural history, people are rootless. Preserving historical trees offers lingering evidence to remind people
of what they once were, who they are, what they are, and where they are. Trees feed our sense of history and purpose.
Studies across the nation show that residential home prices increase from 3% to
20% due to the presence of trees, depending on the type of trees, scarcity of treed lots, and the maturity of existing
trees.
One widely reported study showed that viewing trees through a window during surgery
recovery cut the average recovery time by almost one whole day compared to patients with a view of a blank wall.
People turn to the urban forest, preserved by humans as parks, wilderness, or wildlife
refuges, for something they cannot get in a built environment. The quality of human life depends on an ecologically
sustainable and aesthetically pleasing physical environment. The surge of interest in conserving open spaces from
people motivated by ecological and aesthetic concerns is growing.
Trees curtail health care costs by facilitating positive emotional, intellectual,
and social experiences.
Environmental stress may involve psychological emotions such as frustration, anger,
fear and coping responses; plus associated physiological responses that use energy and contribute to fatigue. Many
who live or commute in urban or blighted areas experience environmental stress. Trees in urban setting have a restorative
effect that releases the tensions of modern life. Evidence demonstrating the therapeutic value of natural settings
has emerged in physiological and psychological studies. The cost of environmental stress in terms of work-days
lost and medical care is likely to be substantially greater than the cost of providing and maintaining trees, parks,
and urban forestry programs.
Trees are a source of food for humans, i.e. Pecans, Walnuts, Almonds, etc. On a
large scale, trees require less fertilizer and keep the soil healthier than most crops.
6. Aesthetics
Trees can screen objectionable views, offer privacy, reduce glare and light reflection,
offer a sound barrier (acoustical control), and help guide wind direction and speed.
Trees offer aesthetic functions such as creating a background, framing a view, complementing
architecture, and bringing natural elements into urban surroundings.
