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Housing developments choking wildlife around America’s national parks

Americans are ‘loving [their] protected areas to death’.

Housing developments within 50 kilometers (31 miles) of America’s national parks have nearly quadrupled in sixty years, rising from 9.8 million housing units to 38 million from 1940 to 2000. The explosion of housing developments adjacent to national parks threatens wildlife in a variety of ways, according to a new study in the Proceeding of the National Academy of Sciences (PNAS).

“We are in danger of loving these protected areas to death,” says co-author Anna Pidgeon as assistant professor at the University of Wisconsin-Madison.

Housing developments introduce domestic species like dogs and cats; attract raccoons opossum, and skunks; threaten vital migration routes; give off extensive light pollution; and bring with them increased recreational use to important conservation areas.

Animal footprint in California’s Sierra Nevadas. Photo by: Rhett A. Butler.

The authors provide numerous examples of how the close proximity of houses hurt wildlife. Elk migrate from the mountains in the summer to the valleys in winters, but as Pidgeon points out that “in the Cascades, the valleys are now filled with orchards and houses.”

Ground-nesting birds are threatened by alien predators like domestic cats and dogs. Window in homes also kill over a billion birds a year in the US, while cats kill approximately 400,000 birds a year.

Light pollution can interrupt hunting, travel, and migration for a variety of species including moths and other insects, amphibians and reptiles, bats, birds, and even some plants.

“People don’t always think about this, but a lot of wildlife species base their way-finding on the stars or the moon, and a lot of outside light can be confusing and harmful,” explains Volker Radeloff, lead author and associate professor, also at the University of Wisconsin-Madison.

Housing developments may also stymie natural wildfires, which are key to regenerating ecosystems. If houses are close to a park “the manager of a wilderness area might decide to fight a fire instead of letting this natural process run its course. If the house burns, the manager might be in trouble,” explains Pidgeon.

Top predators like wolves and cougars are also threatened by housing developments surrounding their wilderness.

“People are not building houses intending to kill cougars, but that may be the effect if a cougar starts to threaten children and has to be removed,” says Pidgeon. Recently, as wolves were removed from the Endangered Species Act in Montana and Idaho, a number of well-known and long-studied wolves were killed by hunters just outside of protected areas.

The researchers say that the trend of building adjacent to parks is not slowing down anytime soon: they estimate that by 2030 housing developments will grow by 45 percent from 2000 levels, including another 10 million units.

“I was shocked to think that these protected areas aren’t doing the job we believe they were doing. There are now rings of housing around national parks like Yellowstone and Yosemite. I don’t think it’s occurred to people to think about how that may affect biodiversity. These parks, wilderness areas and forests are intended to protect biodiversity, so we need look at what is going on,” says Pidgeon.

Many countries have established buffer zones around national parks, putting in place regulations to protect species and ecosystems.

Citation: Volker C. Radeloff, Susan I. Stewart, Todd J. Hawbaker, Urs Gimmi, Anna M. Pidgeon, Curtis H. Flather, Roger B. Hammer, and David P. Helmers. Housing growth in and near United States protected areas limits their conservation value. PNAS published online December 22, 2009, doi:10.1073/pnas.0911131107.

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