Expert opinion survey on the impacts of air pollutants on forests of the USA
A panel of experts was surveyed to obtain subjective estimates of the current impact of five air pollutants (SO2, NOx, O3, H2SO4, and HNO3) on growth, mortality, and leaf area of forests of the continental U . S. for later input to economic analysis. Results from the first two of three questionnaires are discussed. Estimates of impact were highly variable among panelists (CV's near l00% ), but identify forest types at risk. Southern California conifers and high elevation spruce-fir were perceived most damaged with 10 and 12% median growth reductions. Southern pines, southern hardwoods, northern hardwoods and low elevation spruce-fir were equivalent with 5% reductions. Median impact for other western conifers was 0%. Ozone was perceived the most damaging pollutant in each of the seven forest types investigated, with damage by the two acidic pollutants likely limited to the high elevation spruce-fir. The amenity-related leaf area and mortality measures were less familiar and more volatile. Implications of pollutant interactions, temporal stability, and panel selection are also discussed.