Quantitative ecology and impact assessment

Abstract

Some of the issues of environmental impact assessment are reviewed from the point of view of quantitative ecology, and on the assumption that evaluations are done on a site by site basis. Two approaches are examined in detail, one being the traditional experimental approach and the other one attempting to predict impacts from data and models. The experimental approach suffers from the fact that there is no true replication. A pseudodesign is proposed, employing pre-operational data on a site and a control area contrasted to post-operational data on both areas, and substituting replication in time for true replicate areas. Even so, the limitations of animal census methods and substantial variability make it doubtful that any but major changes can be detected experimentally. Predictive techniques, employing methods developed primarily for fisheries management, may be preferable to the base line and monitoring concept. However, these methods have not yet been adequately adapted to the present purpose, and some gaps can be foreseen. One is the lack of knowledge about stock-recruitment, when the recruits are at very early life history stages. The population regulation problem is identified as a major issue in impact evaluation. Questions are raised as to the utility of data on productivity and species diversity, as presently used. It is concluded that stock must be taken of what has been done in impact evaluation, and attempt to reach a consensus as to future methodology.