Shading Our Cities is a handbook to help neighborhood groups, local officials, and city planners develop urban forestry projects, not only to beautify their cities, but also to reduce energy demand, improve air quality, protect water supplies, and contribute to healthier living conditions.
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About the Author
Gary Moll was vice-president and director of programs and urban forestry at the American Forestry Association.
Sara Ebenreck, former executive editor of American Land Forum is a Maryland writer, editor, and teacher.
Read an Excerpt
Shading our Cities
A Resource Guide for Urban and Community Forests
By Gary Moll, Sara Ebenreck
ISLAND PRESSCopyright © 1989 American Forestry Association
All rights reserved.
Needed: A New Vision for Our Communities
R. Neil Sampson
PEOPLE ARE BY nature forest dwellers. The evidence is all around us—not in some theoretical book about human origins—but in the way we choose to live. From pioneer families moving into sod huts on the prairie to today's young couples anxiously contemplating the enormity of the mortgage on a first home, the same instincts prevail. As soon as possible, just about everyone plants trees around the dwelling place. Shade trees, fruit trees, windbreaks, ornamentals—all are aimed at marking the site as a home, a place where life is pleasant both inside and outside the four walls and where the dwellers feel secure in their environment.
In the past, those who treasured trees the most seemed to be people who settled in areas where trees were not common. Scandinavians settling in Wilton, North Dakota, planted windbreaks and shelterbelts to soften a cold, windy climate. Germans settling in New Braunfels, Texas, planted trees for shade from a harsh sun.
Today, more than ever before, Americans are city dwellers. Gone are many of the original homesteads of the rural countryside (except, in some cases, for the remaining trees), and gone, too, are many rural families who have migrated to the cities in search of better opportunities. Estimates indicate that the 1990 census will find 75 percent of all Americans living within fifty miles of the nation's coastlines, most of them within the confines or orbits of large urban areas.
At one extreme, this urban environment can be sterile and mechanistic, made up of concrete, stone, iron, and copper—square buildings, each a lot like the ones on either side, connected by a complex system of pipes, wires, tunnels, sidewalks, and streets. Put a dome over the top and introduce artificial heating, cooling, and light, and you have the space city that has long captured the imagination of science fiction writers. But when that same city is softened and buffered by trees, parks, boulevards, flower beds, curved walkways, and shady river banks, it becomes something entirely different. The term habitat comes to mind. This is a place where people—and plants, birds and animals—live. This is home.
The challenge, of course, is not to abandon urban design or workable systems. The challenge is to merge the designed, man-made environment and the managed, natural environment so that neither is destroyed in the process.
FROM HEAT ISLANDS TO TRUE HABITATS
Unfortunately, in most American cities, the downtown area may be from three to ten degrees hotter than the surrounding region on a summer day—a fact that has given rise to the phrase "urban heat islands." City air is almost certain to be polluted, often to the point of being health-threatening. Water, while readily available, is often heavily chlorinated to assure reasonable freedom from bacteria and parasites, at the same time increasing the likelihood that it will contain cancer-causing chloro-organic compounds. City streets are more likely to be known for crime statistics than for safety.
Why are we not more successful in creating a better quality of life in urban areas? It can't be because it doesn't matter; anything that affects the everyday life of the majority of Americans must matter. It can't be that we don't know how; each generation has the knowledge of prior generations at its disposal, and the current generation is the most technologically advanced that ever lived. While we debate the intricacies of Star Wars and space travel, it seems reasonable that keeping our own nest unfouled would be a fairly basic achievement.
It may be that the huge size of many urban areas and the enormity of the problems affecting them paralyze people and overwhelm the institutional capacity of local governments. But that wouldn't explain why a small town that has spent decades enjoying the ambience created by its founders would let that ambience slowly deteriorate.
It may be that American society has become so self-centered and self-indulgent that there are not enough people willing to pay attention to the good of the community and to make the individual effort needed to rebuild community institutions. But there are too many examples of excellent community work to make that a general indictment. So that leaves the possibility that if there were more enlightened leadership—appointed and elected officials willing to take risks—and more public education so that people were more skilled in recognizing the slow and steady deterioration of their community, if the technologies involved in repairing that deterioration were more widely available, and if the job were broken down into small segments that individuals and community-sized groups could successfully tackle—the result would be more livable communities.
One area where this communal effort is doable is in our city forests. The quality of the environment is a major factor in establishing the quality of community life, and it is here that individuals and small groups can make a significant difference.
Trees planted around homes, along streets and parking lots, and in urban lots and parks can break up the heat islands that develop around most communities. The decrease in air-conditioning needed would help lower everyone's energy costs and cut energy usage and its consequent pollutants accordingly. Obviously, trees that shade dark surfaces such as streets, buildings, and parking lots are the most valuable, so older, larger trees are more effective than smaller ones. But every tree is of some value as it affects air currents, cools the air through transpiration, and shades the ground from the summer sun.
Researchers have found that recuperating hospital patients placed in rooms with windows facing trees heal significantly faster and require far less pain-killing drugs than those in rooms without such a view. It seems logical to assume that the same benefits might extend to the concept of "wellness," where people who live within constant view of the natural world enjoy better health, although no research to demonstrate that claim has been conducted.
The best time to make a city fit into the natural environment, of course, is during the planning and development phases. Obviously, that time is long gone in many urban areas, but not everywhere. New developments are a constant factor in many communities. Are those new developments being fitted into the environment skillfully, or are they just being "bulldozed in" as quickly as possible?
Are new homebuyers paying premium prices for "wooded homesites," only to discover in a couple of years that the excavation, construction, and landscaping have compacted soils, damaged root systems, and scarred tree trunks to the point where their valued shade trees are simply high-priced firewood? Are streets, sidewalks, and waterways being designed wide enough to provide room for trees to grow and be healthy?
In established communities, are the trees that our parents planted being cared for properly? Are they trimmed before they become a hazard and removed promptly when they die? Are new trees constantly being planted to replace those that are removed or die or to fill open spaces?
The answer, too often, is no. In many communities, the urban forest is deteriorating—and the quality of life of the community is declining with it. For these areas, a new vision is needed. Instead of being content with letting the natural environment be abused and natural elements such as urban forests die, people can decide to rebuild and renew their community.
Renewing the urban forest won't fix everything that's wrong with a community, but it is an excellent place to begin. The growth in community pride and spirit that results from the work of planting and caring for trees, the very real change in appearance that results in only a few short years, and the unseen but very real benefits—such as cooler temperatures and more healthful surroundings—are soon reflected in a variety of other ways.
Efforts to renew downtown and older urban areas can bring a new infusion of community pride to a city's most neglected residents, its inner city dwellers. Here is where we find the poor, the homeless, the elderly. They are more at the mercy of the elements than their more affluent neighbors, yet too often they live in the most exposed portions of the community. Increasing shade trees, greenways, and parks here is not just a matter of beautification. It can mean air that's fit to breathe on a stifling summer day, tolerable temperatures and places to sit in the shade and cool off, and homes and schools with a far lower level of heat-induced stress and social unrest.
So it is important to all city dwellers—and especially those in charge of city government—to envision new possibilities for our communities. When our communities are shady, tree-covered, pleasant places, we can truly say that they have been designed as home—habitat—for all their residents and visitors.
DISTURBED SOIL TO GYPSY MOTH: THE OBSTACLES WE FACE
The urban environment may be improved by a better urban forest, but getting and maintaining that forest are not easy tasks. In too many cities, the space for trees to grow and thrive no longer exists. Streets, sidewalks, and building foundations take up most of the space, channeling available water into storm sewers and providing almost no open soil to take up air and water needed for healthy tree-root growth. Air pollution concentrations are abnormally high and have exceptionally high levels of ozone, one of the major products created in the air as the result of automobile exhaust and a pollutant that has been scientifically linked to tree damage.
So urban trees are almost always facing bad growing conditions. Drought is rampant because of hotter temperatures in midcity and because most of the available rain is channeled off rather than soaking into the soil. Urban soils are largely construction rubble and have little resemblance to normal soil structure. Fertility may be nonexistent when urban soils are badly disturbed and when there is no undergrowth or animal life to help produce nutrients.
Mechanical damage is common as well. Trees may be destroyed by automobiles, trucks, bicycles, or other sources of bruising, such as lawn mowers. A seemingly innocuous bump may produce an opening to the inner bark, which allows disease or fungus to enter, spelling the beginning of the end for the tree. As a result, according to recent surveys, the average city tree lives only thirty-two years and dies just when it is beginning to reach the most valuable stage of its life.
America's urban forests are in trouble—in the average city, about four trees die or are removed for each new one planted. That number can go as high as eight or ten in some cities. The reasons are many. One is that trees have often been allowed to grow old without maintenance or replacement. Suddenly, the city finds itself awash in dead and dying trees. The budget for urban forestry is fully absorbed with cleaning up these problems, and nothing remains for the necessary planting and tree care needed to rebuild a healthy, productive urban forest.
Another problem in recent years has been insect and disease epidemics that have swept through many portions of the country. Dutch elm disease moved through many cities in the 1970s; where the stately elm was used almost exclusively for its wonderful shade properties, the effect was disastrous. Today, few American elms remain in any city, and the rebuilding process has been both slow and expensive. The gypsy moth, eating its way through hardwoods (primarily oaks), and oak wilt are creating similar problems. When such epidemics hit, shady, pleasant communities can be converted almost overnight into barren urban heat islands.
Urban trees, just like forests everywhere, respond to good management. We can extend the lives of urban and community trees from their current average of thirty-two years to something far longer—and in the process double or triple the benefits each tree confers on the community. Good forest management doesn't cost. It pays.
THE GLOBAL CONTEXT AND THE GREENHOUSE EFFECT
As we look at the opportunities and recognize the difficulties of improving our urban habitats, it is important to look beyond the city's boundaries and think of its relationship to the region, the nation, and the world as a whole. Economically and environmentally, a city's influence extends far beyond its boundaries. Cities that produce significant amounts of waste heat or air pollution affect surrounding and downwind environments for many miles. A serious water pollution problem can affect whole river systems and pollute estuarian and ocean habitats far beyond the river's mouth.
Today, more than ever before, we are aware that many of our actions have global consequences. We're also aware that global systems, even though they appear large and complex beyond all human scale, are being adversely affected by human actions. Thus, we come to an important realization: human actions, whether those of one person, one community, or an entire nation, need to be environmentally constructive. People need to make the earth more healthy, not more sick. If humans continue to wage war upon the planet, there is no guarantee that the planet and its systems will not strike back. The evidence that some of that is already happening is compelling and frightening.
During the 1980s, we endured the six hottest years of the century. According to scientists from the National Aeronautics and Science Administration (NASA), the rate of global warming during the past two decades is the highest since records have been kept (for about 130 years), about three times higher than would be anticipated from normal cycles or fluctuations.
What's happening? Has the greenhouse effect finally begun, some one hundred years after it was first predicted? Scientists can't say for sure, but Dr. James Hansen of NASA told Congress in 1988 that he was "99 percent confident" that the current temperatures represent a real warming trend rather than a chance fluctuation.
Scientists agree that carbon dioxide levels have been rising swiftly and steadily for several decades, causing a 30 percent increase in atmospheric concentration over the past twenty years. Many scientists predict a doubling of the gas within forty to fifty more years. There is significant disagreement, however, on the exact effect this could have on the climate.
Some, like NASA's Hansen, use computer models—called global circulation models—to predict a continuing rise in average global temperatures, particularly in the northern temperate regions. Others, looking at similar models but making different assumptions, predict a new ice age. Still others look at the current temperature trends as simply part of normal weather cycles that will return to cooler years as usual.
But a growing number of scientists agree on the global warming theory. They point to the rise in carbon dioxide as one of the major culprits. This gas acts like the glass in a greenhouse. The sun's rays penetrate the atmosphere, hit the earth, and are reflected as a longer-wave heat. Layers of carbon dioxide bounce the heat waves back toward the earth, trapping heat that would otherwise radiate back into space from earth. Other gases such as chlorofluorocarbons and methane add to this effect, but carbon dioxide is estimated to cause about half the greenhouse effect. If the present rate of carbon dioxide release continues, scientists estimate that atmospheric levels of the gas could double in a few years.
On the basis of global circulation models, these scientists are now convinced that a doubling of carbon dioxide in the atmosphere will be accompanied by a further rise in average temperatures in parts of the United States of anywhere from six to twelve degrees Fahrenheit.
Six to twelve degrees may not seem like much if we consider that on a normal autumn day temperatures may zoom up and down over a thirty-degree span. But overall rises of this magnitude in the average global temperature aren't normal. In fact, they've never occurred in recorded history.
The possible effects are far-reaching. Millions of acres of forests could be lost as heat and drought make trees more susceptible to disease, insects, and fire. Droughts could threaten food crop production. Desert conditions could spread in parts of the South and Midwest, and ocean levels could rise by as much as five feet, polluting groundwater supplies with salt and badly damaging low-lying cities and regions. Personal levels of discomfort felt by heat-sensitive people in summer of 1988 may seem minimal compared with such a future. The thought of such disastrous changes has created intense public pressure to find ways to begin slowing down carbon dioxide buildup and reducing the ultimate effect of the greenhouse phenomenon.
Excerpted from Shading our Cities by Gary Moll, Sara Ebenreck. Copyright © 1989 American Forestry Association. Excerpted by permission of ISLAND PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
PART I. Urban Forests: An Overview
Chapter 1. Needed: A New Vision for Our Communities
Chapter 2. In Search of an Ecological Urban Landscape
Chapter 3. Tough Trees for America's City Forests
Chapter 4. The History of Trees in the City
Chapter 5. City Tree Care Programs: A Status Report
PART II. Urban Forests: The Values
Chapter 6. The Values of Trees
Chapter 7. The Imperative Forest
Chapter 8. Who Owns the Trees?
PART III. What Makes a Tree?
Chapter 9. Journey to the Center of a Tree
Chapter 10. The Forest Underground
PART IV. Planning for Trees
Chapter 11. A Blueprint for Tomorrow: Getting Trees into Urban Design
Chapter 12. The Green Team: Who's Working on Trees?
Chapter 13. Building a Sense of Place
Chapter 14. Critters in the City
Chapter 15. Improving the Health of the Urban Forest
Chapter 16. Planting for Long-term Tree Survival
Chapter 17. Branches and Wires: The Conflict Above
Chapter 18. Developing a Successful Urban Tree Ordinance
Chapter 19. The Urban Forest Balance Sheet
PART V. Rural Places and the City Outer Edge
Chapter 20. When the 'City'? Is a County
Chapter 21. Construction that Fits the Forest
Chapter 22. Timber Cutting and the Law
Chapter 23. Resolving Conflicts in the Urban/Rural Forest Interface
Chapter 24. The Needs of Small Rural Communities
PART VI. Trees for Special Places
Chapter 25. Reforesting the Campus
Chapter 26. Restoring Urban and Historic Parks
Chapter 27. Greenways and the City
Chapter 28. Community Forests: An Investment in the Future
Chapter 29. Shading Your Home
Chapter 30. Creating a Backyard Orchard
Chapter 31. Living Fences
PART VII. Citizen Action and Education
Chapter 32. Citizens with a Vision
Chapter 33. Kids and Trees for a Cleaner Chesapeake
Chapter 34. Profiles of Citizen Action
Chapter 35. Public Awareness and Urban Forestry in Ohio
Chapter 36. Test Your Town's Trees
Chapter 37. A Ten-Step Citizens Action Program
Chapter 38. Cultivating an Appreciation for Trees
Epilogue: What Lies Ahead
Appendix A. Books, Pamphlets, Newsletters, and Periodicals
Appendix B. Audio-visual and Other Educational Aids
Appendix C. Computer Software for Urban Forest Management: A Buyer's Guide
Appendix D. Organizations with Resources
Appendix E. More on Tree Ordinances
Appendix F. Tree Survey Forms
Appendix G. American Forestry Association Resources
Appendix H. State Foresters