ABSTRACT
The use of spatial overlays in Environmental Impact Assessment (EIA) was first suggested by landscape architects at the University of Pennsylvania. Using this technique, analysts would visualize the spatial implications of alternative transportation routes by overlaying a series of shaded or coloured transparencies depicting important environmental factors with transparencies depicting development characteristics. Weighted-checklist methods for EIA include the Environmental Evaluation System, developed by Battelle Laboratories for the US Bureau of Land Reclamation. The compartmentalization of environmental entities into discrete and unrelated categories was seen to discourage interdisciplinary collaboration among specialists, further contributing to the production of fragmented and descriptive EIAs. It was concluded that the resulting impact scores are based largely on implicit expert opinion, rather than observable properties of the biophysical environment, and therefore do not represent valid or testable measures of environmental impact. A second generation of scientific guidance materials — some North American and some European — provided further insight into the application of science in EIA.
