Air pollution vulnerability of 22 midwestern parks

Abstract

It is common knowledge that air pollution increases in United States national parks as sources grow closer. It follows that, as this happens, biota in the parks will be increasingly affected, as has occurred in cities. Given that there are about 360 national park units in this country, can it be determined in advance which parks will be more impacted by these air pollutants than others? Can parks be ranked for vulnerability to air pollutants, and, if so, what variables would be used? Are air pollutant data sufficient for ranking, or are data also needed on sensitive resources? This study of 22 park units in the midwestern United States attempted to answer these questions. Plant lists were compiled for the 22 parks, relative abundances of all species (common, intermediate, rare) estimated, their sensitivities from their life cycle types (annual, perennial-deciduous, perennial-evergreen) determined, and overall vulnerability as the average product of the two was calculated using a 3—2—1 scale for weighting the abundances. Scotts Bluff National Monument in western Nebraska was the most vulnerable park in the region, while Isle Royale National Park in Lake Superior was the least. This difference was due to the higher abundances of annual plant species in Scotts Bluff. Changing the values used for abundances changed the order of park vulnerabilities. Three air pollutants (ozone, sulfur dioxide, and sulfate) were found to increase from west to east in the midwest. Overlaying these patterns on the park vulnerabilities, and a cluster analysis of the data, resulted in a determination of the air pollution risks to groups of parks. The parks most at risk (high vulnerability + high pollution levels) were two in Ohio (Hopewell Culture National Historical Park and Cuyahoga Valley National Recreation Area) and one in Indiana (Lincoln Boyhood National Memorial). Ten parks were grouped at lowest risk and were found in an arc from Lake Superior, northern Minnesota, and Wisconsin through Nebraska and Kansas. Parks were clustered in the same risk groups, regardless of whether or not vulnerability was included. Thus, the determination of risk can be made using air pollutant data only. Slightly different risk groups were found using vulnerability alone, without the air pollutant data. For various reasons, it may still be desirable to calculate park vulnerabilities, but it is a formidable and difficult task using the complete flora for an area. Of three different surrogate methods tested for a relationship with overall vulnerability, only one appeared to be useful. Vulnerability could be directly calculated if a park's vegetative structure was known without assembling the complete flora.