In comparison with collections from the early 1900's when oxidant air pollution was essentially absent, 50% fewer lichen species were found on conifers during 3 yr (1976—1979) of collecting and sampling in the mountains of Southern California. Among the five mountains ranges studies, the San Bernardino Mountains, the region with the highest oxidant levels, had lower lichen frequency and cover values. Within the San Bernardino Study sites, lichen cover was inversely related to estimated oxidant doses. Furthermore, at sites with high oxidant levels, marked morphological deterioration of the common species Hypogymnia enteromorpha was documented. Transplants of this species from the relatively unpolluted Cuyamaca Rancho State Park into the San Bernardino Mountains exhibited similar deterioration after a year's exposure.

Flavoparmelia caperata (L.) Hale and Umbilicaria mammulata (Ach.) Tuck, were exposed to 262 μg SO2 m−3, 59 μg O3 m−3, and 262 μg SO2 m−3 in combination with 59 μg O3 m−3 for 20 h over a 5-day period. Photosynthesis and ultrastructural observations were made after 12 and 20 h. At these low concentrations of pollutants, ultrastructural changes preceded and accompanied decreases in photosynthesis rates. Ozone was more phytotoxic than SO2. Ultrastructural damage was least with SO2 and greater and very similar with O3 and the combination of O3 and SO2. Photosynthetic data showed that SO2 ameliorates effects of O3. Electron micrographs showed increased accumulation of starch and cavity space around starch grains in the chloroplast and increased lipids in the cytoplasm in F. caperata; there was some increased starch in U. mammulata, but alterations were primarily in increased chloroplast opacity. Photosynthesis of U. mammulata was more sensitive to the pollutants than that of F. caperata. Ultrastructural damage was greater when samples were stored in the light than when they were stored in the dark between fumigations. The study shows that species vary in their responses to pollutants and that combinations of pollutants may give results different from those obtained with single pollutants.

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This article mainly focuses on the use made of strategic environmental assessment in the United States in the preparation of programmatic environmental impact statements (PEISs). In general, these are prepared for groups of actions related geographically or having similarities of project type, timing, media or technological character. The procedural requirements for, and the main types of PEISs which have been prepared, are described and illustrated with examples. Programmatic assessments, though undertaken less fkequently than project-level assessments, are growing in number. So far, NEPA'S provisions have not been applied to broad policies but this is thought likely to occur in the fiture.