The National Wind Coordinating Collaborative (NWCC) developed the Probability of Impact workshop to discuss the ability of current methods to accurately assess the probability of impact to wildlife from the development of a proposed wind energy site. The purpose of the meeting was to review methods used to determine impacts and assess the strengths and weaknesses of each.
The accuracy of pre-construction predictions of impact has been debated for years. The Probability of Impact workshop intended to lay common groundwork by identifying mutual terminology and priority issues – allowing participants to begin to determine which impact prediction methods most closely assess actual impacts experienced once wind facilities are operational.
The workshop considered four categories of methods typically used in pre-construction studies to assess probability of impact:
- Potential Impact Index (PII) Score –This protocol was initially proposed in the draft U.S. Fish & Wildlife Service (USFWS) Voluntary Guidelines as a framework for initial investigations of a potential site. Under the PII scoring process, a developer chooses a “reference site,” the site expected to have the highest negative impact in the area where building is anticipated. Additional sites are compared to the reference sites using three checklists – physical attributes, species occurrence and status, and ecological attractiveness to wildlife.
- Reconnaissance Level Site Assessment – After performing background research on existing projects, habitat, and use in the area, a biologist visits the proposed site to evaluate topography, presence of vegetation and wildlife, and identify any special features. A short report is then prepared identifying “red flag issues” and recommending if and what further studies are needed.
- Quantitative Data Collection – This approach involves multiple site visits and provides empirical and statistical data on the population size and diversity of species using the area. Using this data and information on fatalities at wind facilities in similar areas, a biologist will create models of impact and risk.
- Ecological (or “formal”) Risk Assessment – This approach identifies potential “stressors” and devises a strategy for determining the likelihood that negative impacts will occur as a result of wildlife exposure to each stressor. ERA follows a three step process: 1) Problem Formulation, where a conceptual model is developed; 2) Analysis, during which data is collected and inputted into the conceptual model; and 3) Risk Characterization, during which findings and implications are summarized.