With illustrative and detailed examples drawn from throughout the country, Green Infrastructure advances smart land conservation: large scale thinking and integrated action to plan, protect and manage our natural and restored lands. From the individual parcel to the multi-state region, Green Infrastructure helps each of us look at the landscape in relation to the many uses it could serve, for nature and people, and determine which use makes the msense.
In this wide-ranging primer, leading experts in the field provide a detailed how-to for planners, designers, landscape architects, and citizen activists
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About the Author
Mark Benedict is the Senior Associate for Strategic Conservation and the Senior Advisor for the Conservation Leadership Network at the Conservation Fund. He has his Ph.D. in botany/plant ecology from the University of Massachusetts, Amherst.
Ed McMahon is vice presidand director of land use planning for The Conservation Fund and co-author of Balancing Nature and Commerce in Gateway Communities (Island Press 1997).
The Conservation Fund, a national nonprofit organization, acts to protect the nation's legacy of land and water resources in partnership with other organizations, public agencies, foundations, corporations, and individuals. Since its founding in 1985, the Fund has helped its partners safeguard wildlife habitat, working landscapes, community greenspace and historic sites totaling more than 3.4 million acres throughout the nation. Its headquarters are in Arlington, Virginia.
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Linking Landscapes and Communities
By Mark A. Benedict, Edward T. McMahon
ISLAND PRESSCopyright © 2006 The Conservation Fund
All rights reserved.
Why Green Infrastructure?
Green infrastructure is a term that is appearing more and more frequently in land conservation and land development discussions across the United States and the world. The term, however, means different things depending on the context in which it is used: for some it refers to trees that provide ecological benefits in urban areas; for others it refers to engineered structures (such as storm water management or water treatment facilities) that are designed to be environmentally friendly.
Our definition of green infrastructure is loftier and broader. We define it as an interconnected network of natural areas and other open spaces that conserves natural ecosystem values and functions, sustains clean air and water, and provides a wide array of benefits to people and wildlife. Used in this context, green infrastructure is the ecological framework for environmental, social, and economic health—in short, our natural life-support system.
Green infrastructure challenges popular perceptions about green-space planning and protection. To many people, open space is simply land that is not yet developed, and green space refers to isolated parks, recreation sites, or natural areas. Webster's Dictionary defines "infrastructure" as "the substructure or underlying foundation on which the continuance and growth of a community or state depends." Green infrastructure emphasizes the importance of open and green space as parts of interconnected systems that are protected and managed for the ecological benefits they provide. While green space is often viewed as something that is nice to have, green infrastructure implies something that we must have. Protecting and restoring our natural life-support system is a necessity, not an amenity. While green space is often viewed as self-sustaining, green infrastructure implies that green space and natural systems must be actively protected, managed, and in some cases restored.
Green infrastructure differs from conventional approaches to land conservation and natural resources protection because it looks at conservation in concert with land development and man-made infrastructure planning. Other conservation methods typically are undertaken in isolation from—or even in opposition to—development, but green infrastructure provides a framework for conservation and development that acknowledges the need for providing places for people to live, work, shop, and enjoy nature. Green infrastructure helps communities identify and prioritize conservation opportunities and plan development in ways that optimize the use of land to meet the needs of people and nature.
WHAT IS GREEN INFRASTRUCTURE?
Used as a noun, green infrastructure refers to an interconnected green space network (including natural areas and features, public and private conservation lands, working lands with conservation values, and other protected open spaces) that is planned and managed for its natural resource values and for the associated benefits it confers to human populations. Used as an adjective, green infrastructure describes a process that promotes a systematic and strategic approach to land conservation at the national, state, regional, and local scales, encouraging land-use planning and practices that are good for nature and for people.
Taking a green infrastructure approach provides benefits both as a concept and as a process. As a concept, the planning and management of a green infrastructure network can guide the creation of a system of open space hubs and links that support conservation and associated outdoor recreational and other human values, connect existing and future green space resources, and "fill in" gaps. As a process, the approach provides a mechanism for diverse interests to come together to identify priority lands for protection. Green infrastructure provides a framework that can be used to guide future growth and future land development and land conservation decisions to accommodate population growth and protect and preserve community assets and natural resources. Taking a green infrastructure approach facilitates systematic and strategic conservation activities, adds value to project results, and provides predictability and certainty for both conservationists and developers. In areas anticipating growth, a green infrastructure plan can pre-identify key lands for future conservation and restoration efforts and help shape the pattern and location of future growth.
Green infrastructure uses planning, design, and implementation approaches similar to those used for roads, water management systems, and other community support facilities. The approach can be applied at multiple scales (e.g., across landscapes, watersheds, regions, jurisdictions) and can help move communities beyond jurisdictional and political boundaries.
Green infrastructure also provides a strong rationale for funding green space conservation and management. Just as roads, sewer systems, hospitals, and other aspects of the built or gray infrastructure provide for the critical needs of communities, green infrastructure is integral to a community's health and viability. Like gray infrastructure, green infrastructure has evolved to meet specific needs that have resulted from growth (see Table 1.1).
The Need for a New Approach to Conservation and Development
The first European explorers who saw the New World wrote poetically about its vast wilderness. Land was plentiful; the challenge was to tame it, to make way for towns, roads, and farms. Americans today experience a far different landscape from that seen by these explorers. Wilderness and natural areas are no longer plentiful; in fact, they have become scarce. Less than 10 percent of the land in the United States remains in a wild state, and only 4 percent has been set aside in nature reserves.
While previous generations of Americans had the foresight to protect some of America's most beautiful and vital landscapes, our public lands have proven to be inadequate to meet the needs of both people and wildlife. The conditions that existed when the National Park Service and other resource agencies were founded have changed dramatically, but the assumptions that guide our land conservation decisions remain stuck in the past. The rural lands that once surrounded public lands are fast disappearing. National and state parks and wildlife refuges are becoming ecological islands in an increasingly fragmented landscape. Population growth and development in communities that serve as gateways to public lands are creating problems for many pristine and protected lands. Many public lands lack the capacity to handle the increasing number of visitors seeking to connect with nature. Population growth also means more cars, which means more roads, which in turn produces more air pollution, water pollution, and noise. Road construction often means the loss of natural areas, the obstruction of critical wildlife migration routes, and the erosion of historic and natural landscapes.
Growth and Development
In the last fifty years, the amount of urban land in the United States quadrupled. Between 1982 and 2001, about 34 million acres—an area the size of Illinois—were converted to developed uses (see Table 1.2). Between 1997 and 2001, almost 9 million acres were developed, of which 46 percent had been forestland, 20 percent cropland, and 16 percent pasture (see Table 1.3). Much that has been developed for houses, stores, offices, and parking lots was once productive working lands—the farms and forests on the outskirts of America's cities, towns, and suburbs. From 1982 to 1997, an average of 680,000 acres per year of nonfederal forest land, most of which is private, were converted to developed uses, but the rate of conversion "jumped to 1 million acres per year during the last five years of this period" and is expected to continue to increase exponentially in many parts of the country. Because farmland is relatively flat and has rich soils for building—as well as plowing—it is particularly at risk for development. Between 1992 and 2001, the United States witnessed the loss of more than 6 million acres of prime farmland, which accounts for approximately 28 percent of the land developed during this time.
Today, almost 2 million acres of farmland and 500,000 acres of private forestland is lost to development each year. The American Farmland Trust warns that America is losing over seventy-four acres of prime farmland every hour of every day and that 86 percent of America's fruit and vegetables and 63 percent of our dairy products come from farmland that is directly in the path of development. Moreover, the USDA indicates that 44.2 million acres—over 11 percent of our nation's private forestland—may be converted to housing by 2030. Private forests provide over 90 percent of the nation's timber harvests and nearly 30 percent of our freshwater resources; they are critical to water quality and to the survival of many fish and wildlife resources. The conversion of private forestland may be particularly significant in the Southeast, considered the "wood basket" of the United States and an area rich in biodiversity.
Perhaps more alarming than the total number of acres being developed is the escalating rate of land consumption. Between 1992 and 1997, land was converted at a rate of 2.2 million acres per year—a rate that is more than 1.5 times the rate of the previous ten-year period. Today's rates are estimated to be even higher.
The population of the United States is growing. Don't we need houses and commercial areas to support this population growth? Yes. But the rate of open space conversion exceeds population growth. From 1982 to 1997, the nation experienced a 47 percent increase in urbanized land, despite the fact that population grew only 17 percent (see Table 1.4). The situation is often most evident in urban areas. Between 1960 and 1990 populations of metropolitan areas grew by 50 percent, while developed land area increased by 100 percent. From 1970 to 1990, Cook County and the five other counties closest to Chicago experienced a 35 percent increase in developed land, but population increased by only 4 percent. From 1975 to 1995, the population of the New York City metropolitan area increased 8 percent while its urban area increased by 65 percent; and the Cleveland metropolitan area increased 33 percent while it experienced an 11 percent decrease in its population.
Census 2000 figures show the average size of the nation's one hundred most populated cities is about 168 square miles, more than triple the size in 1950. Much of this increase has come as cities have annexed the farms and open space around them to convert to housing developments and strip shopping centers. But rapid development—and the sprawl associated with it—is not only an urban problem. Sixty percent of new homes built from 1994 to 1997 were built in communities of less than forty thousand people. In recent years, rural counties with federally designated wilderness areas grew six times faster than counties without such areas.
In and of itself, such urbanization is not a problem. Many poor communities benefit from the renewal and economic recovery made possible by growth. When land is developed without adequate planning, however, governments find themselves paying for infrastructure improvements needed to support far-flung development and residents suddenly discern the loss of once-cherished natural resources and rural landscapes.
In part, this rapid consumption of land is the result of a growing demand for ever-larger lots. As the footprint of development increases, more land is converted. Almost 90 percent of the land converted for single-family homes from 1993 to 1997 was made into lots of one acre or larger, purchased by just over 33 percent of new homebuyers; since 1994, house lots of ten acres or larger have accounted for 55 percent of the land developed. The nation's largest and fastest growing metropolitan areas risk total eradication of their natural areas—except perhaps those owned by government.
All of these factors contribute to the sprawl that plagues America's suburbs and threatens our rural areas. Without clear plans to check the natural proclivity to situate residential neighborhoods and commercial uses on land that is less expensive—and farther and farther from existing communities—we will continue to threaten plant and animal communities and natural ecological functions and processes.
The Environmental, Social, and Economic Impacts of Sprawl
As natural areas give way to haphazard development, habitat diversity diminishes, resulting in a decline both in the number of species and the number of individuals in those species that survive. The development of wetlands, riparian areas, and other native ecosystems also reduces their capacity to perform their natural functions—control floods, trap sediment, and filter out toxins and excess nutrients. Today, 40 to 50 percent or more of the total land in urban areas is covered by impervious surfaces—roads, parking lots, and buildings. This dramatically increases the rate and volume of storm water runoff and reduces nature's ability to clean our water and cool our air. A significant increase in impervious land cover and the loss of forestland increases the risk of flooding. Worse yet, land clearing and grading add chemicals, sediments, and other substances that degrade water quality. A 2002 study published in Science concludes that the destruction of habitat costs the world the equivalent of about $250 billion each year. The research team further estimates that a network of global nature reserves would provide an annual net benefit of over $4.4 trillion.
In addition, as we convert open land, we fragment it into smaller and more isolated patches. Fragmentation significantly affects landscapes in many critical ways, including resource availability, environmental degradation, and recreational and aesthetic quality. Among the negative effects of fragmentation is the reduction in the amount of habitat of sufficient size to sustain plant and animal species. Moreover, as the distance between undisturbed habitat patches increases, wildlife populations become isolated. This interferes with the ability of animals to move from one habitat to another, decreasing diversity among species and, for some, jeopardizing their survival.
The development and fragmentation of green space puts at risk already endangered plant and animal species. Ninety-five percent of species listed under the federal Endangered Species Act are threatened by habitat loss, fragmentation, or other forms of alteration. Sprawl is the primary cause of habitat loss and fragmentation in California, where 188 of 286 imperiled or endangered species are in areas vulnerable to development. Here, and elsewhere, endangered plants and animals are not confined to remote wilderness areas; their habitat is often intertwined with human settlements. In fact, three-fifths of the nation's rarest and most imperiled species are found within designated metropolitan areas; the thirty-five fastest growing large metropolitan areas are home to nearly one third (29 percent) of these species. A total of 287 imperiled species are found in thirty-seven counties that were expected to lose half or more of their nonfederal open space between 2000 and 2025. The Tampa-St. Petersburg-Clearwater metropolitan area, for example, which is home to twenty-six imperiled species, is expected to lose 40 percent of its remaining natural lands by 2025.
Excerpted from Green Infrastructure by Mark A. Benedict, Edward T. McMahon. Copyright © 2006 The Conservation Fund. Excerpted by permission of ISLAND PRESS.
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Table of Contents
ContentsABOUT ISLAND PRESS,
chapter one - Why Green Infrastructure?,
chapter two - The Green Infrastructure Approach: Principles from Past to Present,
chapter three - The Benefits of a Green Infrastructure Approach,
chapter four - Where Do We Begin?,
chapter five - The Basics of Network Design,
chapter six - The Implementation Quilt: Matching Available Resources to Network Needs,
chapter seven - Management and Stewardship,
chapter eight - Building Support for Green Infrastructure,
chapter nine - Making It Happen,
ISLAND PRESS BOARD OF DIRECTORS,