Air quality managers need tools for identifying air pollution induced ecological impairment and for documenting improvements due to pollution reductions.  To develop a suite of indicators to guide environmental monitoring and performance assessment, metrics of air pollution exposure and ecological change were investigated through expert workshops and literature review.  Focusing on nitrogen, sulfate, ozone and mercury, twenty-nine experts from public and private institutions evaluated (1) metrics of atmospheric composition, pollutant deposition and ecological condition relevant for monitoring the influence of changing air quality on terrestrial and aquatic ecosystems; (2) analysis needed for strengthening quantitative links between metrics of exposure and ecological response.

Results/Conclusions

Based on review of 30 broad categories of ecological endpoints in 11 major ecosystem types, a refined list of 28 specific indicator metrics, sorted by level of scientific maturity, was produced.  Four metrics of acidification in terrestrial (soil base cations, pH) and freshwater (ANC, sulfate levels) ecosystems were identified; two additional metrics require further research.  Three metrics of nitrogen enrichment in terrestrial systems were identified (C:N ratio in soil organic matter, foliar nitrogen ratios, streamwater nitrogen); ten additional metrics for freshwater and coastal systems require customized analysis or further research.  One metric of ozone-induced plant damage was identified (foliar injury); two additional metrics require customized analysis.  Two metrics of mercury methylation/bioaccumulation in aquatic systems were identified (methyl:total mercury in wetlands, methyl mercury in fish); two additional metrics require further research.

This session will report on key indicator selection and design outcomes as well as cross-cutting indicator development issues including:  (1) Stratified ecosystem reporting to enable tracking of slow and fast responses in affected ecosystems; (2) Parsing confounding factors, such as climate change, disturbance and management, which can obscure or amplify signals of pollution effects; (3) Optimizing geographic scale of reporting to account for spatial variability in air pollutant exposure and ecological response; (4) Optimizing temporal scale of reporting to account for variability  in timing of air pollutant exposure (e.g., seasonal/interannual, contemporary/historical deposition) and ecological response (e.g., acute/chronic, time lag); (5) Linking models of biogeochemical response to pollutant loading and biological response to altered chemical conditions; and (6) Identifying specific ecosystem types likely to be more responsive to changes in air quality.  Findings from customized analyses for indicator development will be described with emphasis on linkages across air pollutant exposure/deposition, primary ecological responses and secondary effects on organisms, species and ecosystems.