Scenic vistas in most U.S. parklands are diminished by haze that reduces contrast, washes out colors, and renders distant landscape features indistinct or invisible. Protecting Visibility in National Parks and Wilderness Areas describes the current understanding of the nature and extent of haze in various regions of the United States. The book addresses the scientific and legal framework of efforts to protect and improve visibility, as well as methods for assessing the relative importance of anthropogenic emission sources that contribute to haze in national parks and for considering various alternative source control measures. The volume provides guidance on how to make progress toward the national goal of correcting and preventing visibility impairment due to human activities affecting large national parks and wilderness areas.
The 1977 Clean Air Act legally mandated the prevention of significant deterioration (PSD) of air quality related values (AQRVs) on wilderness lands. Federal land managers are assigned the task of protecting these wilderness values. This report contains guidelines for determining the potential effects of incremental increases in air pollutants on natural resources in wilderness areas of the National Forests of California. These guidelines are based on current information about the effects of ozone, sulfur, and nitrogen on AQRVs. Knowledge-based methods were used to elicit these guidelines from scientists and resource managers in a workshop setting. Linkages were made between air pollutant deposition and level of deterioration of specific features (sensitive receptors) of AQRVs known to be sensitive to pollutants. Terrestrial AQRVs include a wide number of ecosystem types as well as geological and cultural values. Ozone is already high enough to injure conifers in large areas of California and is a major threat to terrestrial AQRVs. Aquatic AQRVs include lakes and streams, mostly in high elevation locations. Current sulfur and nitrogen deposition is probably too low to warrant immediate concern in most areas (with the exception of nitrogen deposition at some locations in southern California), although the low buffer capacity of many aquatic systems in California makes them sensitive to potential future increases in acidity. Visibility is considered as a discrete AQRV. Guidelines are presented for determining degradation of visibility based on sensitive views in wilderness areas. Estimates of current deposition of ozone, sulfur, and nitrogen are compiled for all California wilderness areas. Recommendations are included for resource monitoring, data collection, and decision criteria with respect to the disposition of permit applications.
A variety of air pollutants are emitted into the atmosphere from human-caused and natural emissions sources throughout the United States and elsewhere. These contaminants impact sensitive natural resources in wilderness, including the national parks. The system of national parks in the United States is among our greatest assets. This book provides a compilation and synthesis of current scientific understanding regarding the causes and effects of these pollutants within national park lands. It describes pollutant emissions, deposition, and exposures; it identifies the critical (tipping point) loads of pollutant deposition at which adverse impacts are manifested.