Environmental Impact Statement

In order to prepare an EIS, federal agencies must fully assess the environmental setting and potential effects of a project. Corporations and individuals must likewise determine whether their businesses and residences meet the environmental standards required by their national, state and local governments. Environmental impact assessment is a process that can be used to identify and estimate the potential environmental consequences of proposed developments and policies. Environmental impact assessment is a highly interdisciplinary process, involving inputs from many fields in the sciences and social sciences. Environmental impact assessments commonly examine ecological, physical/chemical, sociological, economic, and other environmental effects. Many nations require the equivalent of an EIS for projects proposed by their federal agencies, and almost all countries have environmental laws. Environmental assessment is a tool used by developers and civil planners throughout the international community. Governmental agencies, like the EPA in the United States, typically provide guidelines for risk assessment procedures and regulations, but the financial and legal responsibility to conduct a thorough environmental assessment rests with the agency, corporation, or individual proposing the project.

Environmental assessments may be conducted to review the potential effects of: (1) individual projects, such as the construction of a particular power plant, incinerator, airport, or housing development; (2) integrated development schemes, or proposals to develop numerous projects in some area. Examples include an industrial park, or an integrated venture to harvest, manage, and process a natural resource, such as a pulp mill with its associated wood-supply and forest-management plans; or (3) government policies that carry a risk of having substantial environmental effects. Examples include decisions to give national priority to the generation of electricity using nuclear reactors, or to clear large areas of natural forest to develop new lands for agricultural use. Government agencies and businesses proposing large projects usually hire an independent environmental consulting firm to conduct environmental risk assessments, and to preview the possible environmental, legal, health, safety, and civil engineering ramifications of their development plan. Environmental consultants also perform scientific environmental monitoring at existing sites, and, if necessary, recommend methods of cleaning up environmental contamination and damage caused by non-compliant projects.

Any project, scheme, or policy can potentially cause an extraordinary variety of environmental and ecological changes. Consequently, it is rarely practical to consider all a proposal's potential effects in an environmental impact assessment. Usually certain indicators, called "valued ecosystem components" (VECs), are selected for study on the basis of their importance to society. VECs are often identified through consultations with government regulators, scientists, non-governmental organizations, and the public. Commonly examined VECs include: (1) resources that are economically important, such as agricultural or forest productivity, and populations of hunted fish or game; (2) rare or endangered species and natural ecosystems; (3) particular species, communities, or landscapes that are of cultural or aesthetic importance; (4) resources whose quality directly affects human health, including drinking water, urban air, and agricultural soil; and (5) simple indicators of a complex of ecological values. The spotted owl (strix occidentalis), for example, is an indicator of the integrity of certain types of old-growth conifer forests in western North America. Proposed activities, like commercial forestry, that threaten a population of these birds also imperil the larger, old-growth forest ecosystem. Determination of VECs usually requires a site-specific scientific characterization and survey of the proposed development.