| Biodiversity conservation is a primary goal of protected areas. However, over the past half-century in the United States, housing growth at the boundaries of protected areas has boomed, and is predicted to continue throughout the 21st century. It is unclear how this development affects the conservation benefit of these protected areas. We used data from the North American Breeding Bird Survey to explore how the abundance and richness of species of greatest conservation need (SGCN) and synanthropes (species affiliated with human settlement), within protected areas, are associated with housing density on nearby private lands from 1940 to 2100. SGCN were generally strongly negatively associated with housing density whereas the opposite pattern was found for synanthropes. The strength of the association varied geographically. In the densely developed eastern forests, as housing development increased from 1940 to 2010, SGCN steadily declined whereas synanthropes steadily increased. In the sparsely populated west, we found similar trends from 1940 to 2010, though the effect size grew stronger from 2010 to 2100. Our results raise concern that as housing development continues at the boundary of protected areas, the conservation benefit of these lands will likely be diminished. |