Unwelcome (Human) Neighbors

"Bears know their landscape like we know our houses. I have data on one female bear who, I am convinced, has used the same babysitter tree for all the litters of cubs she’s had for the last twelve years. Imagine if she woke up after hibernation with her new cubs to find a road and a sprawling suburban neighborhood in place of that tree. What would she do?" -- Susan Morse, forester, carnivore expert and founder of Keeping Track

Roads and sprawling neighborhoods are replacing pristine wildlife habitats at an alarming pace, putting the survival and reproduction of plants and animals at risk. In just the last few decades, rapidly growing human settlements have consumed large amounts of land in our country, while wildlife habitats have shrunk, fragmented, or disappeared altogether. If the current land use pattern -- expansion of built areas at rates much faster than population growth -- continues, sprawl could become the problem for U.S. wildlife in the 21st century.

Sprawl encroaches on wildlife

First there were tents, then huts, then farmhouses and fields, then towns and cities. Ever since humans set foot on this continent, permanent human settlements have been built and expanded on landscapes that were previously home to wildlife. While loss of habitat to human settlement is not new, the last few decades have seen a dramatic increase in its pace. Nearly one-sixth of the total base of land developed in our country’s long history was claimed for development in just 10 years, from 1982 to 1992. But this expansion was not due to an unprecedented population boom in the 80s. Instead, urban sprawl was rapidly outpacing population growth. From 1960 to 1990, the amount of developed land in all U.S. metropolitan areas more than doubled -- while population grew by less than 50 percent.

Today, this rapid growth continues. Moreover, some of the fastest growth is occurring far beyond our urban areas, in still-rural communities 60 to 70 miles from metropolitan beltways. Such exurbs already account for 60 million people and one-quarter of the recent population growth of the lower 48 states. In the exurbs, developments are often far away from each other, connected only by a system of highways and roads. Such "leapfrog developments" exacerbate the fragmentation of wildlife habitats.

There is wildlife in all these fast-growing areas, metropolitan and rural, and species do not fare well when the natural landscapes are paved over and built on. What kind of wildlife is most at risk? Since sprawl is claiming open lands nationwide across a varied landscape, the species affected by it are also varied.

Species at risk

One victim of sprawl, the Florida panther, is among the most endangered large mammals in the world. It is now reduced to a single population of an estimated 30 to 50 adults. This is especially tragic, considering that the panther -- also known as cougar, mountain lion, puma and catamount -- was once the most widely distributed mammal (other than humans) in North and South America. In the eastern United States, only the Florida subspecies survives. But for how long? Its southern Florida habitat of hardwood hammocks, pine flatwoods and wetlands is still rapidly giving way to residential developments and agricultural fields. Habitat loss has already driven the Florida panther into a small area, where the few remaining animals are highly inbred, causing such genetic flaws as heart defects and sterility.

In the Southwest, where especially rapid growth is taking place, plant and animal species of the fragile desert ecosystem are at risk. For example, the silent victims of Tucson’s rapid expansion into the Sonoran Desert in Arizona include the ancient ironwood, the creosote bush and the graceful saguaro cactus. Growing painfully slowly in the arid lands, these beautiful plants survive for hundreds of years (indeed, some may date back thousands of years). But they take only a few seconds to bulldoze. Disappearing with them are animal species such as the endangered pygmy owl, a beautiful, hand-sized, brown-and-white flecked raptor, and the sonoran pronghorn, a graceful creature that looks like an antelope (see picture) but is, in fact, the sole survivor of a distinct ancient family dating back 20 million years.

In Southern California, another booming area, the coastal sage ecosystem is unraveling. Sprawling development has wiped out over 90 percent of this landscape, identified by the U.S. Fish and Wildlife Service as "one of the most depleted habitat types in the United States." What is left is badly fragmented and, as a result, the region has experienced a dramatic loss of native species of birds and small mammals. A rare bird with an unfortunately unheroic name, the coastal California gnatcatcher is one that has suffered most. The gnatcatcher has lost some three-fourths of its natural habitat, and its remaining population, now dwindled to perhaps 2,500 pairs, is hanging on in shrinking, isolated patches where it is more exposed to predators. It has recently been classified as a threatened species. The coastal sage ecosystem is also home to such endangered species as the kangaroo rat and the quino checkerspot, a large butterfly with a life cycle that makes it especially vulnerable to habitat loss.

Other species in trouble include the redleg frog and the Pacific pond turtle in Sonoma Valley, California; the piping plover, a tiny bird living and nesting on the Atlantic coast; the dusky salamander in New York state’s streams; the hawksbill sea turtle in the Gulf of Mexico; the desert tortoise in the Mojave and Colorado deserts and the nocturnal lynx, with its trademark bobbed tail, in parts of the Northwest and New York state.

Habitat loss, fragmentation and generalization

Before we can talk about change, it is important to understand the many ways that our current patterns of growth hurt wildlife. Habitat loss is one of the most familiar. This concept is perhaps easiest to grasp when a complete transformation of the natural landscape occurs. Almost no on-site wildlife can survive the transition from a meadow to a large new factory, or to an office complex or "big-box" retail outlet surrounded by a vast concrete parking lot. But can wildlife survive when the new use is a residential suburb with some grass and trees? Or an office campus, where buildings are surrounded by green landscaping?

While a few species can adapt to such human-shaped environments, many cannot. And since our suburbs and office campuses are remarkably similar all around the country (and are thus often completely oblivious to their natural surroundings), we are essentially cultivating the few species that do well with irrigated lawns and Norway maples and have learned to eat from our garbage cans and bird feeders. All this is at the expense of the many species that depend on more fragile local habitats.

This trend is called generalization of habitat, and results in the survival of hardy species such as pigeons, squirrels and raccoons. While the overall biomass may not decline -- the generalists take over where more sensitive species are disappearing -- the total number of species plummets. Standing in a suburban backyard, one may still hear birds singing, but the choir is not nearly as diverse as it was before the subdivisions came and the mature trees were chopped down.

Another serious problem is habitat fragmentation. When roads, houses and malls break up ecosystems, large populations that once were genetically diverse are broken up into small groups. With amphibians, for example, even a single road across their habitat may be enough to create genetically divergent groups. A result may be a lack of enough genetic variety within each subgroup, resulting in degenerative inbreeding. This has been a significant factor in the decline of the Florida panther, as fragmentation of wetland and forest habitats has resulted in new generations suffering serious, sometimes fatal, genetic flaws.

Fragmentation of habitat may also separate a species from its feeding or breeding grounds. In some cases, not even the first generation survives. Or, a species may survive only until the first environmental stress, such as a drought, occurs, when it is trapped in a small and isolated area. Prior to habitat fragmentation, the thirsty wildlife could find relief at a nearby river during droughts. After development, that river may now be on the other side of a five-lane highway or a strip mall, impossible to reach. The more fragmented, the more vulnerable to any stress an ecosystem is.

The human toll on wildlife

Habitat loss, generalization and fragmentation are sprawl's three most damaging impacts on wildlife. But sprawl does more: it also pollutes our rivers, lakes and air, further threatening species. It is easy to see why Michael Klemens of the Wildlife Conservation Society described sprawl as an "extremely severe problem for wildlife," and why ecologist Joseph McAuliffe calls sprawl "an environmental abomination."

Twenty-seven ecosystem types have already declined by as much as 98 percent or more since Europeans settled North America. As of mid-1997, the U.S. Fish and Wildlife Service reported that 1,082 species of plants and animals were listed as threatened and endangered, with another 119 proposed for listing. In a comprehensive assessment of some 20,000 species of plants and animals native to the United States The Nature Conservancy reports that fully a third are "of conservation concern," believed to be extinct, imperiled or vulnerable. According to the Conservancy, "current extinction rates are conservatively estimated to be at least 10,000 times greater than background levels."

However, not all is lost -- yet. The United States still has an abundance of natural areas where wildlife thrives. The question is what we can do now to save them from the rising tide of development.

Conservation measures

When feasible, buying land that is threatened by development and setting it aside as a nature preserve is a dramatic and secure way to protect some wildlife. But we cannot save our natural areas by land purchases alone: there is simply not enough money to go around. Developers have just as deep, if not deeper, pockets than conservation groups do, and there is too much land around the country that needs to be protected. Buying conservation easements (paying landowners to restrict development on their property) is a more economical approach, but still insufficient.

If money alone won’t fix the problem, what about national laws that protect wildlife? The most widely influential of these has been the Endangered Species Act, which has succeeded in rehabilitating some endangered species that are now recovering, among them the bald eagle, the gray wolf, the peregrine falcon, the whooping crane and the mountain lion. Indirectly, the law has also benefited additional species in the protected areas. However, by its nature, the law’s scope is limited to the last remaining habitat of the last remaining individuals of a particular species. Surely, we should start protecting our unique ecosystems and dependent species long before the edge of disaster.

Ultimately, purely defensive strategies -- setting aside wildlife reserves, attempting to prevent the diminution of endangered species -- are insufficient. We need to change the way we plan and manage our growth.

Managing growth to protect habitat

Citizens concerned about sprawl should advocate at least three approaches. First, ecological considerations should play a larger role in our local land use planning decisions. Activities such as mapping wildlife habitats and evaluating a proposed project’s impact on those habitats should be routinely incorporated in the planning process. Planners should receive some training in ecology, and interdepartmental cooperation between planners and environmental and wildlife specialists should be encouraged.

Second, ecological thinking does not stop at a local jurisdiction’s border; regional cooperation is essential. Ideally, regions should correspond to biological units, such as watersheds, in order to provide maximum benefit for wildlife. This approach has been coined bioregional planning, and has already yielded some promising results. Some states, for example, have designated "areas of critical state concern" based on these areas’ unique natural resources. Development in these areas is to be carefully managed, so as to minimize environmental damage, by regional bodies or state agencies. Ecosystems as diverse as New Jersey’s pine barrens, Virginia’s tidewater region and Florida’s wetlands are already enjoying some degree of regional protection.

Third, and perhaps most critically, the ultimate answer to reversing the tide of sprawling development should be to grow differently, to accommodate our housing and commercial needs in a more thoughtful way. The alternative to sprawl, smart growth, is not one simple formula, but rather a set of guiding principles. These should be flexible enough to be adapted to diverse and ever-changing local conditions, and to be achieved by a variety of creative policies and market mechanisms.

Among the guiding principles are the following:

• strong central cities and more efficient use of already developed areas;
• compact, walkable developments with several transportation choices;
• a range of housing opportunities and choices;
• mixed land uses;
• growth management and protection of open spaces.

Maybe the most important lesson for those of us who care deeply about the well-being of our nation’s wildlife is that intimate connections exist between the health of our cities (and inner suburbs) and the health of wildlife at the far edges of the metropolitan areas these cities anchor. Protecting open space and wildlife is essential, but not enough, if we want to reverse the damage that urban sprawl inflicts on our wildlife. A more comprehensive approach that aims both to strengthen the urban core and to tame growth at the edge -- smart growth -- is called for.

Notes

1. This paper is drawn from two major sources: the book Once There Were Greenfields: How Urban Sprawl is Undermining America’s Environment, Economy, and Social Fabric, by F. Kaid Benfield, Matthew D. Raimi and Donald D.T. Chen (New York: Natural Resources Defense Council, 1999) and the special section on sprawl and biodiversity in NRDC’s quarterly magazine, The Amicus Journal, Summer 1999, especially the article "The New Suburbanites" by Kathrin Day Lassila. Documentation, references and a more complete discussion of this subject can be found in these resources. Photographs: Environmental Defense (the piping plover, sonoran pronghorn), Defenders of Wildlife (lynx, redleg frog, landscapes), U.S. Fish and Wildlife Service (Florida panther), California Department of Fish and Game (coastal sage ecosystem), and Calthorpe Associates (drawing of transit-oriented neighborhood).