Development near national parks impacts park ecology

Though many Western national parks are buffered by other public lands, housing development on their outskirts has been on the rise. Between the 1940s and 2000, the number of homes within 30 miles of national parks grew from 1.5 million to 6.6 million, according to a study which appeared in the Proceedings of the National Academy of Sciences in 2010. Even when it's sparse, such development can have ripple effects, including introduction of invasive species, fragmented habitat, increased human-wildlife conflicts and blocked migration routes.

Fifty miles outside Yellowstone National Park, for example, migratory birds like the yellow warbler have long thrived in low-elevation riparian areas, boosting populations within the park where higher elevations provide less favorable habitat. When Montana State University ecologists Andrew Hansen and Jay Rotella compared recent residential land use in that area to presettlement conditions in 2002, their models showed housing development overtaking those riparian areas, decreasing bird populations inside the park and out.