Alternatives in environmental impact assessment: a taxonomy

The consideration of alternatives is central to environmental impact assessment (EIA), as decisions cannot be made without options to choose from. Despite its significance, the treatment of alternatives in EIA practice has inadequacies, driven by factors such as a lack of interest, predefined options, and a limited understanding of the possibilities. An essential requirement for alternatives is that they must be reasonable. We identify three types of unreasonable alternatives-false, contrived, and subtle-which may distort the EIA process. To address ambiguities in existing literature, we propose a taxonomy classifying alternatives into seven groups: implementation, spatial, timing, functional, design, constructive, and operational, answering the questions why, where, when, what, and how. The aim of this taxonomy is to enhance the consideration of alternatives in EIA practice by improving knowledge of the existing possibilities. Early integration of alternatives, particularly during the scoping phase, and a proactive approach are essential to strengthening EIA; otherwise, the process risks becoming a mere environmental authorization rather than a robust decision-making tool.