Urban effects, distance, and protected areas in an urbanizing world

With rapid global urban growth, the proximity between urban and protected areas will increase. We identify four categories of nations, based on the proportion of people in urban areas, the amount of protected area, and the 1995 and estimated 2030 distance between cities and protected areas: urbanized nations (>60% urban) with a high population density (>40 people/km2) and close proximity between urban and protected areas (e.g., Europe); urbanized nations with a relatively low population density and moderate proximity between urban and protected areas (e.g., United States); rural nations with a lots of parks (>5% of land area), where proximity will dramatically increase (e.g., China); and rural nations with limited protected area systems (e.g., West Africa). A literature review of 163 studies identified 22 important urban effects on protected areas. Effects range from global to local, with two-thirds of the effects essentially limited to within 50 km of an urban area. We also examined conservation projects of The Nature Conservancy to determine if threats reported by conservation practitioners varied with proximity to urban area. Although many types of threats occurred at all proximities, threat types overall correlated significantly with proximity to an urban area, including more frequent problems with habitat loss due to residential development and wastewater/sewage. Thus, with the median distance from a park to an urban area already less than 50 km in many regions, we conclude that thousands of protected areas are already impacted by urban areas and many more will be impacted in the future.