Research Article: Defining Appropriate Spatial and Temporal Scales for Ecological Impact Analysis

Abstract

Many environmental impact analyses, including those pursuant to the National Environmental Policy Act of 1969, as amended, do not identify the spatial and temporal scales used in the analysis. Without definition of analytical scales, the reader is left to infer scale, which could confound decision making when different readers infer different scales of analysis. For ecological analysis, site-specific spatial and temporal scales based on unique natural features and phenomena are most appropriate, given the inability of ecological resources to restrict themselves according to political boundaries or arbitrary time lines. Definition of scale in the environmental impact document allows the reader or decision maker to consider the impacts in the intended context. Scales of ecological analysis should be based on ecological principles as applied to a specific study area and the ecological resources that may be affected by the proposed action or activity. The multiscalar concept of biological connectivity should be addressed in spatial and temporal analysis, which inherently includes cross-scale considerations such as those for potential effects on metapopulations. Definition of spatial and temporal scales is critical to bound the impact analysis and to inform readers and decision makers, and suggested guidelines are provided as an example of an acceptable method. Although several different scales could be correctly chosen, analysts should identify and define spatial and temporal scales used to promote consistent interpretations of results and to facilitate the decision-making process.