Delineating the ecosystems containing protected areas for monitoring and management

Park managers realized more than 130 years ago that protected areas are often subsets of larger ecosystems and are vulnerable to change in the unprotected portions of the ecosystem. We illustrate the need to delineate protected area-centered ecosystems (PACEs) by using comprehensive scientific methods to map and analyze land-use change within PACEs around 13 US national park units. The resulting PACEs were on average 6.7 times larger than the parks in upper watersheds and 44.6 times larger than those in middle watersheds. The sizes of these PACEs clearly emphasized the long-term reliance of park biodiversity on surrounding landscapes. PACEs in the eastern United States were dominated by private lands with high rates of land development, suggesting that they offer the greatest challenge for management. Delineating PACEs more broadly will facilitate monitoring, condition assessment, and conservation of the large number of protected areas worldwide that are being degraded by human activities in the areas that surround them.