Posts Tagged ‘tree benefits’

By  Steve Houser, Dallas Urban Forest Advisory Committee Chair

Trees clean our air, water, and soil. They also add greatly to our health, sense of well being, quality of life, and our economic future in many ways. As a result, the presence of trees and healthy ecosystems provide a strong foundation for a sustainable urban infrastructure in the future. The very essence of nature provides sound guidance for reaching urban sustainability. To quote Mr. Albert Einstein “look deep into nature and you will understand everything better.”

We all breathe the same air plus use the same water and soil to survive; therefore, it is important to understand the interconnectedness of all things as well as the important role that trees and healthy urban ecosystems play in planning for our future. Education is critical in stimulating the public conscience which will ultimately drive environmental causes. We must learn to think globally, plan regionally, and act locally to reach sustainability. We all benefit greatly from a shared regional vision of social, economic, and regional goals for sustainability.

Improved Air Quality

Rising levels of carbon, specifically carbon dioxide (CO2), are accelerating global warming and our urban forest offers the opportunity to mitigate the problem by sequestering (or storing) carbon as well as ozone, nitrogen oxides, and sulfuric oxides plus filtering particulate pollution. Trees are long-term carbon storehouses, or carbon “sinks”, however, they also release the carbon as they die and decompose or when they are burned.

As an urban forest declines in health or significant populations are lost over time, they must constantly be replaced to increase the net carbon storage capacity. Failure to conserve trees or replant what is lost can cause an increase in the release of carbon by an urban forest. Conservation is important because larger healthy trees (over 30 inches) sequester 90 times more carbon than smaller trees (under 4 inches) and store 1,000 times more carbon. Also, poor air quality results in increased health care cost to treat the associated problems.
It is important to note that trees also emit biogenic volatile organic compounds (BVOCs), such as isoprene, benzene, and monoterpenes, which react with nitrogen oxide to form ozone. Research exists on the subject but it is based on trees in other parts of the country. As a result, further study of how local tree species affect air quality in our region is required before we plant a large number of trees that may not be ideal.

Reduced Energy Use

Planting deciduous trees on the west, south, and east exposure of homes and buildings (or strategic shading) can save up to 30 percent on our energy bills. If we can shade our air conditioners, we can save an additional 10 percent on our energy bills. By planting dense evergreen trees on the north side of a building or home to slow the cold winter winds, additional energy savings can be gained. By reducing energy use, we decrease emissions from regional power generation plants and their negative effect on our air quality.

Reduced Urban Temperatures

A 1995 geothermal study of the Dallas area by Dr. Ken Morgan with Texas Christian University, found that various areas could be 10 to 12 degrees hotter than Oak Cliff due to the extensive tree canopy cover and minimal grey infrastructure. The grey infrastructure amounts to large amounts of brick, glass, and concrete that hold heat well into the night which increases urban temperatures—called the urban heat island effect (UHI).
By strategically placing trees in UHI problem areas such as parking lots and vast expanses of grey infrastructure, we reduce urban temperatures as well as evaporative emissions from the fuel tanks and fuel systems of our vehicles. Heated fuel tanks and fuel systems release hydrocarbons and 16 percent of all hydrocarbon emissions are created by evaporative emissions. By reducing urban temperatures, air quality improves because the formation of ozone is dependent on higher temperatures.

Reduced Storm Water Runoff and Flooding

Large amounts of grey infrastructure greatly increase the amount of storm water runoff which can lead to flooding. Trees reduce storm water runoff by allowing the rain to slowly filter through the foliage which decreases the potential for flooding. Strategic shading of grey infrastructure not only reduces flood potential and the UHI effect but it can also extend the life of asphalt by 60 percent. This offers a very large return on our investment in tree planting and care plus reduces the impact that asphalt has on the environment.

Improved Water Quality

Bioremediation or phytoremediation is the use of trees, plants, and biological agents to remove or neutralize contaminants in polluted water or soil. Leaves, twigs, and limbs that lay on the ground stimulate biological activity which also helps to remove pollution. Removing the organic layer on the top of the soil reduces its capacity to grow healthy plants and trees as well as its ability to remove various types of pollution.

Increased Economic Benefit

Trees offer many tangible economic benefits such as increased property values and a better quality of life which will attract corporations and the general public to an area. The result is an increased tax base due to the establishment of a more desirable area to live and conduct business. The more green and sustainable an area becomes in the future, the more successful it will become in economic terms.
Sprawl and “business as usual” will no longer be desirable because sustainable infill developments will attract the public. As far as a return on investment, for every dollar spent on tree planting and care, we receive up to five dollars in benefits according to research. Studies across the nation show that residential home prices can be up to 20 percent higher due to the presence of trees. Also, a home will sell faster with healthy trees as opposed to others with few or no trees.

This article is reprinted with permission from North Central Texas Council of Governments and Steve Houser.

“The more green and sustainable an area becomes in the future, the more successful it will become in economic terms.”

“Reprinted with permission from Texas Nursery & Landscape Association. This article originally appeared in TNLA Green magazine, February 2011 issue.”

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.

Updated 01/19/05