Lichen communities in 48 sites were extensively examined from June 19 through August 14, 2001 and collections were deposited with the Rhode Island Nature Conservancy. Relatively high numbers of species were found, with a total count of 92. However, pollution-sensitive species were either poorly represented (e.g. Allocetraria oakesiana, Bryoria furcellata, Peltigera spp., and Tuckermannopsis spp.) or absent entirely (e.g. Cetrelia spp., Collema spp., Dermatocarpon spp., Leptogium spp., Nephroma spp., Pseudevernia consocians, Ramalina spp., and Sticta spp.), thus indicating poor air quality in Rhode Island at the present time.

Both lichen health and lichen community composition appear to indicate that previous levels of air pollution have adversely affected species richness and abundance. Most trees were found to support only the most common pollution-tolerant species, especially Flavoparmelia caperata, Parmelia sulcata, and Punctelia rudecta, while rocks were dominated by Flavoparmelia baltimorensis and crustose species (Porpidia albocaerulescens, for example). Yet, even these species are showing signs of decline due to age (and possibly other unrecognized factors) and many are dying out at the present time.

The good news is that other species are starting to become established where older ones are dying out, as evidenced by new, small-growth specimens of Bryoria furcellata, Candelaria concolor, Evernia mesomorpha, Hypogymnia physodes, Melanelia subaurifera, Phaeophyscia adiastola, Physconia detersa, Rimelia reticulata, Tuckermannopsis americana, and Xanthoparmelia spp.

From the evidence seen, it is presumptive that air pollution from coal-fired, electric power generating plants carried eastward from the Midwestern states of Indiana, Ohio, West Virginia, and Pennsylvania has adversely affected lichen communities in Rhode Island beginning in the middle or late 1970s. Recent air pollution standards enacted in these Midwestern states may have begun to clean up the ambient air of the prevailing westerly winds and Rhode Island's lichen communities are just now beginning to show recovery.

Since it is difficult to evaluate the effects of air pollution on particular lichen distribution patterns from a single survey, it is recommended that re-surveys of selected lichen communities be done at 5- to 10-year intervals to document changes in the lichen flora. The Nature Conservancy Preserves are protected and monitored to prevent significant deterioration of the environment and thus would be ideal study sites for future comparison with the data here presented.