Changes in the practice of Environmental Impact Assessment (EIA) and advances in information technology have greatly expanded the range of tools available to the EIA practitioner. Most methods and techniques for identifying, measuring, and assessing impacts rely on expert judgement. In fact, many checklists, matrices, and models used in EIA represent decades of experience accumulated by numerous experts. The experts themselves are heavily involved in all aspects of the assessment they are used to help identify the potential for significant impacts, plan data collection and monitoring programs, provide their judgement on the level of significance for specific impacts, and suggest ways of reducing or preventing impacts.