Incorporating many real-world examples, Mark Hostetler explains key conservation concepts and techniques, with specific advice for a wide variety of stakeholders that are interested in creating and maintaining green developments. He outlines the key players and principles needed to establish biodiverse communities and illustrates eight key design and management strategies. The Green Leap not only offers essential information for constructing new developments but also helps existing communities retrofit homes, yards, and neighborhoods to better serve both people and nature.
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The Green Leap
A Primer for Conserving Biodiversity in Subdivision Development
By Mark E. Hostetler
UNIVERSITY OF CALIFORNIA PRESSCopyright © 2012 The Regents of the University of California
All rights reserved.
Why Build Biodiverse Communities?
The conservation of our natural resources and their proper use constitute the fundamental problem which underlies almost every other problem of our national life.
Why worry about urban biodiversity? Why not just concentrate on biodiversity conservation outside the boundaries of cities? First, the millions of people who make daily decisions in urban environments can have huge impacts on local and regional natural resources. We have crossed a threshold around the world: more than 50 percent of the world's population resides in urban areas. Over the past century, we have learned that local decisions have global consequences and global decisions have local impacts. Building communities takes a vast amount of natural resources; think about the energy required to make and transport building materials to create homes, roads, and landscapes within a given community. Then think about how we live in these communities: we heat and cool our homes, drive from one place to another, consume food, and maintain our yards. All of this takes energy, in the form of electricity and liquid fuel. Energy has to come from somewhere, and today, most of our energy is derived from fossil fuel sources (coal, natural gas, oil). Mining for coal, and drilling for oil and natural gas, affects our land, air, and water. The construction and maintenance of cities is contingent on the consumption of natural resources gathered from local, regional, and global locations. Calculating the ecological footprint is a popular scientific technique that determines the amount of land and marine area required both to supply the resources a human population consumes and to absorb and dispose of the corresponding waste this consumption generates. In the United States, the biocapacity, or the amount of land available to support the population, is less than the amount of land needed to satisfy current consumption rates (Table 1). So the country is operating at a deficit and will need to find additional land outside its borders to gather the required resources to meet current consumption levels.
How is biodiversity conservation linked to natural resource consumption? Often, the incorporation of biodiversity principles into growth management strategies has the added benefit of reducing natural resource consumption. For instance, the use of native plants and ecologically minded construction techniques to conserve topsoil and existing trees can reduce water and energy consumption and decrease the impacts of residential growth on nearby environments. In landscaping, topsoil conservation and the use of native plants instead of nonnative turf often lead to a reduced need for irrigation, fertilizers, and pesticides. In combination with a reduction of impervious surfaces such as asphalt, and the use of more trees to intercept rainfall, such efforts lead to reduced stormwater runoff and fewer pollutants being carried to nearby wetlands. In neighborhoods, conserved trees help shade homes during the summer, reducing energy needed to cool a home. Conserving urban biodiversity will pay strong dividends to the reduction of natural resource consumption simply because the world's urban population is only going to increase.
In addition, when people have their first or primary experience with nature in their own yards and neighborhoods, an opportunity exists for them to feel a connection with the land, and this can generate a multitude of environmental stewards. Urban neighborhoods and workplaces are where people recreate, interact with friends, spend money, consume resources, and generally spend the majority of their time. Unfortunately, biodiversity in urban areas tends to be minimal, and the species that we see in urban areas are often nonnative and can be seen from one city to the next. Because of this homogenization, urban denizens encounter few of their local plants and animals and become disconnected from their natural heritage. Daily contact with a limited diversity of native species and habitats promotes a sense that biodiversity is not that important to people living in cities. If decision makers, such as elected officials, urban policy makers, and developers, see the current state of urban environments and presume it is as it should be, they will continue to implement design and management strategies that do not incorporate biodiversity principles. Case in point: open space conservation continues to be undervalued and plays second fiddle to other socioeconomic concerns. The experience in a homogenized urban environment can lead to environmental amnesia from one generation to the next. Children who grow up in cities with little biodiversity become accustomed to these environments and, as a result, place little importance on the decline of natural environments that surround their neighborhoods. Ultimately, urban opportunities to experience and understand local natural heritage will promote a conservation ethic.
The ecological integrity of natural areas is directly and indirectly affected by nearby cities. Urban growth fragments the natural environment, and such fragmentation can lead to the disappearance of sensitive animal and plant species. For example, the gopher tortoise (Gopherus polyphemus) is a species of special concern in many states, because its population has declined over the years as urban and agricultural development has destroyed its habitat. Even the design and management of urban landscapes can have significant impacts on surrounding lands that house certain species like the gopher tortoise. With landscaped yards, there is a risk that nonnative plants may spread and become established in surrounding natural habitats. Called invasive exotics, these nonnative plants have frequently originated in urban areas—for example, several invasive exotic plant species have spread from their original locations in urban areas in California. The maintenance of lawns and exotic horticultural plantings often requires the use of an array of pesticides, fertilizers, and herbicides. Fertilizers affect rivers, streams, and lakes by raising the levels of nitrates and phosphates, ultimately contributing to algal blooms, fish kills, coastal dead zones, and the spread of invasive exotic plants.
Recognizing that cities are primary areas through which people interact with and have an effect on nature, a group of scientists from around the world produced a unique document called the Erfurt Declaration (Box 1). This declaration is a good summary of the significance of urban biodiversity conservation. With well-designed and well-managed urban areas, biodiversity within a city's boundaries can be increased and detrimental impacts on surrounding land can be decreased. Such results promote the conservation of healthy, natural environments across a region, and this benefits not only society, public health, and the economy but also entire ecosystems.
Civilization is not, as they often assume, the enslavement of a stable and constant earth. It is a state of mutual and interdependent cooperation between human animals, other animals, plants, and soils.
Urban, rural, and natural areas all interact in dynamic ways; and as stated earlier, what happens within urban areas affects the environment on local, regional, and global scales. Adopting practices that conserve the diversity of urban organisms can pay huge dividends for people. For example, the conservation of natural open space within the urban-rural matrix provides not only a sense of place and of beauty but also a wide variety of critical ecosystem services. Ecosystem services are the resources and processes, such as clean air and water, supplied by natural ecosystems, and these services are useful to humankind. These services, available free of charge, are highly valued economically, and yet they are rarely bought, sold, or factored into the cost of consumer goods and services. Once humans damage the ability of natural areas to provide these services, high costs to society are realized. Scientists around the world have collaborated and produced a nice summary of the consequences of ecosystem change on human well-being. Ecosystem services are essentially the life support system for all species on earth, including humans. In a scientific paper published in the journal Nature, the global economic value of twelve major ecosystem services and five major ecosystem goods was estimated to be approximately $16–54 trillion (U.S. dollars), with an average of $33 trillion (U.S. dollars) annually. The paper additionally estimated the global gross national product to be $18 trillion (U.S. dollars) annually for the services natural ecosystems provide.
The diversity of ecosystems, plants, insects, and animals benefits humans in a variety of ways. For instance, wetlands help purify and remove contaminants from freshwater. Coastal wetlands serve as nurseries for many of the fish and shellfish species that we eat on a daily basis. Most medicines are derived from plant, fungal, and animal sources, and new sources of medicines are sometimes needed to advance our fight against diseases. If a species goes extinct, we lose its genetic material and our ability to derive new medicines from it. Pollination by animals helps in the production of food. A variety of insects and animals pollinate such crops as nuts, fruits, and vegetables, but agriculture currently relies on one or two pollinating insects. Pollination is much more robust if there are many different species providing this service. In the United States, growers rely on European honey bees (Apis mellifera) for pollination of fruits, but the honey bee population is currently being decimated because of a number of factors, including parasitic mites and pesticides. To pollinate citrus groves, farmers have relied on honey bee specialists who ship honey bee hives to each individual citrus grove. Because these managed hives are failing and honey prices have decreased, fewer people are shipping honey bee hives to local farmers. Farmers are scrambling to find adequate pollination services. Because the quantity and diversity of other insect pollinators have been reduced by the applications of pesticides and by habitat destruction, local insect populations are insufficient to take over pollination services. Growers are now attempting to alter their agriculture practices and bring about the return of native pollinators.
Habitat loss, another aspect of biodiversity loss, also can affect ecosystem services. The replacement of coastal ecosystems with development can lead to increased damage caused by tidal surges. When homes are built right on the coast, no buffer in the form of estuaries or dune ecosystems exists to protect human development from tidal surges, and often the beaches have to be rebuilt to save homes, at an enormous economic cost to the public. The Atlantic and Gulf states have spent upward of $2.5 billion to replenish beaches. A highly diverse ecosystem is very good at producing the oxygen we breathe and at sequestering the carbon dioxide we produce in vast quantities through our consumption of fossil fuels.
Many intricate connections exist among the organisms in an ecosystem, and the loss of a few or many species can disrupt this balance and ultimately lead to a disruption in the service an ecosystem provides to us. Even managing pests can sometimes disrupt and alter natural processes, often with unintended consequences. For example, many species of birds serve as checks on insect populations that feed on tree foliage in forests, which we rely on for wood products. Models have predicted that, in the boreal forest, as the use of pesticides increased, forest foliage would become so dense that the populations of pest insects, such as spruce budworm, could not be effectively controlled by birds. Pesticide use would be effective initially, but over time it would become ever more costly and ultimately ineffective because more and more pesticide would be required for the same effect. Eventually, huge insect outbreaks would occur and vast areas of forest would be affected. Thus, bird populations, along with judiciously applied pesticides, play an important role in controlling spruce budworms. If forest bird populations were to significantly decline, spruce budworm containment would become more and more difficult and economically infeasible.
What about loss of biodiversity in terms of species diversity? Could not exotic species that have replaced natives provide the same ecosystem services? Many exotic species can effectively remove CO2, a greenhouse gas, from the atmosphere and sequester it. But homogenizing the species composition around the world may have many unfortunate consequences, such as limiting our genetic resources and ability to create new medicines and biochemicals. And ecosystems that are more biodiverse can sequester more CO2 than can ecosystems with species-poor assemblages, thus they help to decrease the likelihood of climate change. Also, many intricate connections exist between the physical environment and local, native organisms, as in the honey bee example mentioned earlier. Replacing the diverse array of natives with only a few exotics may have many unforeseen consequences, and doing so may be like placing all the eggs in one basket.
SOCIAL AND HEALTH BENEFITS
Whenever the pressure of our complex city life thins my blood and numbs my brain, I seek relief in the trail; and when I hear the coyote wailing to the yellow dawn, my cares fall from me—I am happy.
—Hamlin Garland, American novelist and poet
Natural areas help create a sense of place. Natural areas—forest areas, meadows, coral reefs, natural springs, rivers—contain a unique blend of plants, animals, and other organisms. Each location in the world has its own natural heritage, and people in all parts of the world are connected to the distinctive mix of plants, animals, geography, and climate in their area. Conservation and restoration of biodiversity in and around cities provide urban inhabitants with the opportunity to create a true sense of place. Valuable natural areas can be as small as an individual yard or a neighborhood pocket park. Creatively designed gardens and native landscaping can bring a bit of the natural environment right into urban surroundings, accommodating the needs of humans and wildlife. Natural areas within cities are often used to educate people about their environment and human history. A 2002 study found that when people are exposed to unstructured natural areas as children, they express more positive perceptions of natural environments and outdoor recreation activities later in life. A number of studies have demonstrated that urban residents around the world desire contact with nature in an urban setting and have strong aesthetic preferences for community designs that incorporate natural areas.
Interaction with natural areas promotes better human health. There is a growing body of evidence that our own psychological and physical well-being is rooted in our connection to nature. Conversations about "biophilia" and "deep ecology" discuss the intricate link between nature and humans. Even though many people live in urban environments, and most of their lives are spent in cars, homes, and other buildings, their emotional well-being and health depends on their ability to experience nature. The ways in which urban communities are built and maintained have direct and indirect consequences for natural environments and human health. People recover from stress more quickly when exposed to natural vegetation instead of urban settings. It is especially important that children play outside. A 2003 Environment and Behavior article found that access to natural areas protects children from the impact of life stress. Stress levels were reduced as kids spent more time playing outside, and this protective buffering intensifies with increasing stress levels within children. Furthermore, the amount of time spent in contact with nature affects a variety of human health factors, such as the level of cognitive functioning, the number of physical ailments, and the speed of recovery from illness.
Excerpted from The Green Leap by Mark E. Hostetler. Copyright © 2012 The Regents of the University of California. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
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Table of ContentsList of Boxed Texts
Preface and Acknowledgments
Part One. Key Principles and Players
1. Why Build Biodiverse Communities?
2. Urban Decision Makers
Part Two. The Devil Is in the Details
3. Tree Protection and Natural Area Preservation Strategies
4. Improving Community Engagement and Understanding
5. Landscaping and Individual Lots
6. Trails, Sidewalks, and Common Areas
7. Irrigation and Stormwater Treatment
8. Wildlife-Friendly Transportation Systems
9. Environmental Covenants, Conditions, and Restrictions
10. Certifying Green Communities