Anthropogenic stressors such as climate change, fire, and pollution are driving shifts in ecosystem function and resilience. Scientists generally rely on biological indicators of these stressors to signal that ecosystem conditions have been altered beyond an acceptable amount. However, these biological indicators can be non-descript or non-charasmatic species that fail to spur public interest or policy consideration. Therefore, we developed the STEPS (STressor – Ecological Production function – final ecosystem Services) Framework to link changes in a biological indicator of a stressor to an ecosystem component that is directly used, appreciated, or valued by humans; Final Ecosystem Goods and Services (FEGS). The ecological production functions (EPF) provide distinct relationships, based in scientific literature, connecting the initial change to the ecosystem to downstream components. The framework uses a qualitative score (High, Medium, Low) for each link which allows for chains to be ranked based on current knowledge which can identify research gaps and prioritize decision making based on what research has been completed. Each ecological endpoint is linked to discrete beneficiaries, or direct users of the ecological endpoint, who are identified to evaluate who is potentially impacted by the change.
We tested the STEPS Framework by identifying chains for four modes of response to the exceedance of nitrogen and sulfur critical loads: aquatic acidification, aquatic eutrophication, terrestrial acidification, and terrestrial eutrophication. The workshop participants identified 47 biological indicators and linked them to 84 ecological endpoints thorugh 183 unique EPFs. These endpoints were tied to 25 different benefiary groups, averaging 6 groups per endpoint and creating 1103 chains. The SOS scores differentiated the chains so that researchers, managers, and policy makers to understand uncertainty imbedded in responses to critical loads, or select chains with strong scientific foundations for quantitative assessment and subsequent valuation. The chains are also being used to tell compelling stories to translate the impacts of air pollution to a beneficiary-specific audience by using the ecological component that the group values and linking it back to the exceedance of a critical load. The results of the analysis can be transferred to the social science community enabling them to apply valuation measures to multiple or selected chains, providing a more comprehensive analysis of the effects of anthropogenic stressors on measures of human well-being.