The rising number of houses built near national parks, forests and wilderness areas may severely limit the conservation values those properties were set aside to protect, a federal study has found.
Examining detailed housing growth data from the last 70 years and projections for the next two decades, researchers found that housing development in the United States may sharply restrict the ability of protected areas to function as a modern Noah's ark and safeguard biodiversity.
Protected areas are crucial because they provide safe havens for species threatened by land-use change and resulting habitat loss, the researchers said. But the areas are only effective when they protect habitat within their boundaries and are connected via corridors to other wild areas.
New homes near protected areas have created a patchwork quilt of land use that has shrunk the impact of public lands, the study shows. Housing development blocks travel corridors for some animals and alters habitat for others.
Researchers compiled spatially detailed housing growth data from 1940 to 2030 and quantified growth for each wilderness area, national park and forest in the continental United States.
Between 1940 and 2000, 28 million housing units were built within 50 kilometers of protected areas, and 940,000 were built within national forests, the researchers found. During the last three decades, the rate of housing growth near the areas has accelerated at the rate of about 20 percent a decade.
Since the 1990s, the growth of housing within a single kilometer of protected areas has far outpaced the national average of new housing units, they said.
If long-term trends continue, another 17 million housing units will be built within 50 kilometers of protected areas by 2030, of which 1 million will be within a kilometer, "greatly diminishing their conservation value," the researchers said.
The study did not look at potential impacts on individual species, but focused on how the housing growth has changed the landscape.
U.S. protected areas are increasingly isolated, and nearby housing development is decreasing their effective size, the researchers found. National forests are threatened by habitat loss even within their administrative boundaries, they added.
"Protected areas in the United States are thus threatened similarly to those in developing countries," the study says. "However, housing growth poses the main threat to protected areas in the United States whereas deforestation is the main threat in developing countries."
Results of the study are being published this week in Proceedings of the National Academy of Sciences.
Funding for the study was provided by the Forest Service. Also participating in the study were researchers from the University of Wisconsin, the Forest Service's Northern Research Station and Rocky Mountain Research Station.
Roger Hammer, an Oregon State University demographer and a co-author of the study, said protected areas have become an amenity that attracts housing development.
"Housing is a convenient gauge because it is something that is easily measured and can be traced back to the 1940s," he said. "In essence, it serves as a proxy for human development impacts that include everything from roads to strip malls."
The growth of telecommuting and seasonal homes has been a factor in the proliferation of housing, Hammer said, and the issue won't go away, given population trends.
"The largest cohort of baby boomers was born in the mid-1950s, and they're just beginning to hit Social Security age," he said. "Retirement has been a key factor in the increase of housing near protected areas -- and that probably won't change."
Click here to read the study.