Assessing cumulative effects of multiple activities in New England watersheds

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A cumulative effect analysis (CEA) is a tool that can be utilized for the review of multiple anthropogenic projects or activities for the purposes of planning, regulation, conservation, or the general evaluation of environmental health. Such an assessment is problematic because spatially consistent and temporally repeated data informing the condition of a location are often not available. When such data can be identified, the potential response of that resource to additional impacts may be unpredictable. Despite these limitations, in many cases, it may be critical to identify those locations for further scrutiny which may be vulnerable to collective impacts from development or other environmental challenges. Here, we present an approach which considers the vulnerability of aquatic resources in relation to the anticipated effects of development-related activities that could be used to identify locations where the potential for cumulative effects is the greatest. This application considers CEA in the context of identifying where development-related activities of minimal impact may be viewed as relatively more substantial when viewed cumulatively. We identify HUC 8-level watersheds where the current resource condition and anticipated development-related activities may have greater potential to result in an impact on watershed condition (i.e., water quality, water quantity, and habitat value). The vulnerability of the watershed was estimated from the number, type, and location of a specific suite of reported activities. The existing condition of the watershed was measured as a function of existing assessments of resource conditions. The relationship between the vulnerability and the existing watershed condition was used to project future conditions and to identify watersheds that warrant further scrutiny. This is a unique approach to CEA which allows for transparent, repeatable identification of watersheds which may be adversely impacted by further activities or projects.