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Introducing Cool Communities.

Judging by pop songs ranging from Cole Porter's "Too Darned Hot" to Lovin' Spoonful's "Hot Time (Summer in the City)," among others, it's clear that the high temperatures of our urban areas have caught the attention of more than just meteorologists. But these lyrics have failed to say dearly what the scientists know--that we've made city summers steamier than nature intended.

Cool Communities, a program of American Forests, is hoping to change that. By joining forces with citizens, government officials, business owners, and researchers, Cool Communities plans to put an environmental "icepack" on our urban saunas. Based on the U.S. Environmental Protection Agency's (EPA) guidebook, Cooling Our Communities, this program encourages cities and towns to conserve energy and cool the urban "heat island" with trees and light-colored surfaces.

For most of urban history, people cooled their surroundings naturally--they planted shade trees around homes and buildings and used light-colored surfaces to reflect the sun's heat. Before the 1940s, irrigated and landscaped cities in California were actually "oases," cooler than the surrounding countryside. As Marc Reisner describes Los Angeles in Cadillac Desert,

"Santa Monica Boulevard, once a dry dusty strip, became an elegant corridor of palms; in Hollywood, where the motion picture industry had risen up overnight, outdoor sets resembled New Guinea; and since most Los Angeleans were immigrants from the Middle West, every bungalow had a green lawn." But as urban areas sprawled, and trees and light-colored surfaces were replaced by asphalt and air-conditioned buildings, city temperatures climbed. In just the last 50 years, the temperature of downtown Los Angeles has increased by five degrees Fahrenheit.

Other cities across the nation show similar temperature patterns. San Francisco's Augusts are warming by 0.2 degrees per decade, even though cool ocean breezes still sweep the city. Washington, DC's annual mean temperature-- now increasing at a rate of half a degree per decade-- has jumped four degrees in the last 80 years.

In most cities around the world with human populations of 100,000 or more, there exist noticeable heat islands that are two to eight degrees Fahrenheit warmer than the surrounding countryside. If current trends continue, these cities could be 10 degrees (Fahrenheit) hotter within 50 years.

The main causes of these temperature increases are well known: land clearing, and the construction of heat-absorbing surfaces. By removing trees and other plants during development, cities lose the cooling effects of shade and "evapotranspiration"--the ability of plants to reduce air temperatures by evaporating water from their leaves. Since the pavement and buildings that replace plants don't evapotranspirate, the sun makes the air hotter. And in the evening, these dark-colored buildings and roads also radiate the solar energy absorbed during the day, keeping the area warm when it should be cooling down. Air pollutants exacerbate the problem by acting like a blanket over the city and holding in summer heat. Cars and other machines can also add warmth, but their contribution is significant only in the winter.

We all know how uncomfortable these conditions are -- we've felt the heat radiating from asphalt and sweltered under smoggy brown skies. We've been the person waiting for the bus who complained, "There's no shade. It's so hot." But these summer conditions are more than just unpleasant they're costly. Los Angeles' five-degree increase in temperature since 1940 translates into an added electricity demand of 1,500,000 kilowatts, at a cost of $150,000 per hour. Washington, DC's heat island requires 400,000 kilowatts and costs $40,000 per hour to cool.

Across the nation, each degree rise in summer temperatures means an increase in peak electricity demand of up to 2 percent. Although that's not an especially impressive number, it adds up--an estimated 3 to 8 percent of current national urban electricity demand is used to cool our communities, at a cost of up to $1 million an hour. In addition, the higher temperatures speed up the rate of chemical reactions, increasing the number of days with unacceptable smog levels. And sadly, the carbon dioxide generated by cooling our urban heat islands could be forming a vicious cycle by contributing to global warming.

But cooling these heat islands doesn't have to hurt. As few as three shade trees planted in the right spots around buildings can reduce energy demand for heating and cooling by as much as half, and could reduce summer temperatures by as much as nine degrees Fahrenheit. And trees do all this work at a fraction of the cost of new air conditioners and power plants. Maximizing the albedo, or solar reflectivity, of our cities by surface-color lightening could reduce energy use by 30 to 50 percent and air temperatures by as much as five degrees Fahrenheit. Cities in colder climates also can benefit from implementing these measures, and can save energy without increasing winter heating needs. Cities in the other EPA-defined climate zones--temperate, hot-arid, and hot-humid-- clearly benefit from the cooling of summer heat islands, and could reduce theft year-round energy consumption.

Altogether, energy conserving tree planting and surface-color lightening could save the U.S. up to 50 billion kilowatt-hours of electricity each year, the annual electricity usage of about 500,000 people. Each year these measures could prevent the release of up to 35 million tons of carbon dioxide that would otherwise contribute to global warming. And/or a nation on a budget, it's good to know that planting trees and lightening the color of surfaces in our urban areas is cheaper than other energy-efficiency programs.

Trees and light-colored surfaces affect urban temperatures in two ways: directly and indirectly. Shade provides the direct, or immediate, cooling effect of trees; the direct effect of light-colored surfaces is reflection of warming sun rays. These qualities are well known. Indirect, or area-wide, effects of trees and light-colored surfaces, however, are not as well understood. Trees indirectly affect their environment through mass evapotranspiration. A large tree can evaporate about 100 gallons of water a day, creating in hot and dry climates the equivalent of five air conditioners running for 20 hours.

According to Gary Moll American Forests' vice president for urban forestry, "the amount of water used by a tree depends on its age species, and location. A large tree on a midwestern farm can use hundreds of gallons a day. But trees native to the Southwest are 'water misers,' providing environmental benefits with just a few gallons of water a day."

Increasing the amount of light-colored surface areas could also have an additive cooling effect for a community. With less heat being absorbed by buildings and roads during the day, less heat radiates at night. This means that there is less need,for compensating airconditioning, and thereby lower energy consumption.

Since heat islands are caused by the many small, indirect contributions of treeless city streets, they can be cooled with many small communitywide actions. By planting and painting their town together, communities can capitalize on these energysaving measures.

The Cool Communities program is designed to help communities take on the urban heat-island challenge. Using American Forests' skill in working with people to build a better environment, Cool Communities will help cities and towns plant trees, lighten surfaces, and monitor the results.

Seven model communities--representing a variety of climates, sizes, and needs--have been chosen to initiate the Cool Communities program. These model community studies are expected to last five years. In the first year, sites for energy-conserving tree planting and lighter surface coloring will be identified. The chosen sites, to be announced in July, will be planted, painted, and evaluated over the next three years, and the fifth year will be devoted to final measurements, evaluations, and publications.

Here are a few of the questions that the program will answer:

* How much energy can we actually save with tree planting and surface-color lightening?

* How many trees do we need to have and how much surface area needs to be lightened for optimum energy savings?

* To what extent do trees and light-colored surfaces affect urban temperatures?

* What are the savings and costs of implementing these measures in different parts of the country? Of different types of trees and landscaping services? Of buying and maintaining highly reflective paints, roofing materials, and paving materials? And what are the initial costs versus useful life versus maintenance costs?

* What do people know about trees, light-colored surfaces, and energy conservation? After public education campaigns, how can changes in understanding be recognized?

The answers to these questions as well as the experiences of the initial communities will help guide future programs In other areas. The results of the program in the model cities will be published and widely distributed to interested citizens, civic and business leaders, educators, and organizations. These materials will provide basic, hands-on information on how to plant for energy conservation and care for trees, how to lighten surfaces cost-effectively, how to monitor energy use, and how to get your community involved. As these materials become available and interest grows, the program will expand to include many municipalities.

For the model communities, American Forests is providing overall program coordination, helping communities organize local implementation teams, providing inventory and monitoring systems, gathering funding, and coordinating public relations and program promotion. In addition, an advisory committee has been formed to provide expert input and to help facilitate the efforts of the model communities.

Members of this advisory committee include the U.S. Forest Service, Extension Service, and Department of Energy; the American Association of Nurserymen; the Society of American Foresters; the National Tree Trust; and the National Assodation oi State Foresters. Other important partners Include local and regional utilities, government agencies, businesses, schools, and citizen organizations.

Many of today's greatest environmental challenges-global warming, add rain, air pollution, and toxic waste, to name a few--are directly related to our energy consumption. Urban heat islands are no exception--they've been created by our way of living. But our habits can be changed.

"The Cool Communities program is an easy, effective, and low-cost way to cut back on our energy consumption," Cool Communities Director Guy Betten explains. "Plus, it will help cool the urban heat island and make our local and global environment a healthier place to live."


Although communitywide actions are the focus of the Cool Communities program, individual tree planting and surface-color lightening around the home are important, too. Not only do these actions contribute to the overall cooling of the urban heat island, they can save you money on your electricity bill-- as much as $200 a year.

To take advantage of natural summertime cooling, plant deciduous (leaf-bearing) trees primarily on the west side but also on the east and south sides of your home. These trees will block house-heating sunlight and reduce air temperatures by evaporating water from their leaves. Shading your air conditioner with trees, shrubs, or a vine-covered trellis will improve its energy efficiency.

Plant trees between buildings and paved areas to prevent heat transfer from the pavement to the buildings. Also, plant trees to shade and thereby cool paved areas. Lastly, care for existing trees--the benefits trees provide increase with their age and health.

For extra warmth in the winter, plant evergreens with dense low branches along the northwest side of your home. One or more staggered rows of conifers will help block those cold winter winds. Planting shrubs around your home will create a dead air space that can help insulate it. Ask your local nursery for advice in selecting the right trees. But before planting, check for overhead wires and underground cables.

Light-colored surfacing is easy to incorporate during building, resurfacing, and routine maintenance. Walls can be repainted with light-colored or reflective paints. Dark-colored roofs can be brightened up with light-colored shingles, or they can be painted with light-colored or reflective paints. Light-colored rocks can be added to flat roofs, and light-colored stones or reflective paint can be incorporated into protective roof coatings. For roads and driveways, use light-colored asphalt or concrete, or a light-colored slurry or chip seal when resurfacing.

Because of American

Forests' success with its Global ReLeaf campaign, the U.S. Environmental Protection Agency has agreed to sponsor the model Cool Communities program. The U.S. Department of Energy is another principal sponsor. Other co-sponsors are being recruited from both public and private sectors. For more information on this program, write: Cool Communities, P.O. Box 2000, Washington, DC 20013-2000.

Anne Semrau is the Cool Communities coordinator for American Forests.
COPYRIGHT 1992 American Forests
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:includes related articles; new American Forests program
Author:Semrau, Anne
Publication:American Forests
Date:Jul 1, 1992
Previous Article:Haven in the desert.
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