Trajectories in land use change around U.S. National Parks and challenges and opportunities for management

Most protected areas are part of a larger ecological system, and interactions with surrounding lands are critical for sustaining the species and ecological processes present within them. Past research has focused on how development rates around protected areas compare to development rates across a wider area as measured within varying sizes of buffer areas or at the county level. We quantified land use change surrounding the 57 largest U. S. National Parks in the contiguous United States for the period 1940 to the present and grouped the parks based on patterns of change. Land use was analyzed within the area considered essential to maintaining natural processes within each park, the protected-area centered ecosystem (PACE). Six variables were measured to determine the current level of development: population density, housing density, percentages of land with impervious surfaces, in agriculture, covered by roads, or in public land. Time series of population density, housing density, and land in agriculture were used to analyze changes over time. Cluster analysis was used to determine if patterns in major land use typologies could be distinguished. Population density within PACEs increased 224% from 1940 to 2000, and housing density increased by 329%, both considerably higher than national rates. On average, private land in PACEs contained a combined 24% exurban and rural housing density, and these increased by 19% from 1940 to 2000. Five distinct land use classes were identified, indicating that groups of parks have experienced differing patterns of development on surrounding lands. The unique management challenges and opportunities faced by each group are identified and can be used by managers to identify other parks to collaborate with on similar challenges. Moreover, the results show park managers how severe land use changes are surrounding their park compared to other parks and the specific locations in the surrounding landscapes that influence ecological function within the parks. This is the first effort to develop a "typology'' of protected areas based on land use change in the surrounding ecosystem. Other networks of protected areas may find this methodology useful for prioritizing monitoring, research, and management among groups with similar vulnerabilities and conservation issues.