Environmental Impact Assessment (EIA) is the process of assessing the likely environmental impacts of a proposal and identifying options to minimise environmental damage. The main purpose of EIA is to inform decision makers of the likely impacts of a proposal before a decision is made. EIA provides an opportunity to identify key issues and stakeholders early in the life of a proposal so that potentially adverse impacts can be addressed before final approval decisions are made." (Australian EIA Network)
EIA is not a way of allowing an environmental 'veto' on development proposals. Environmental considerations may be set aside in favour of other considerations including economic and other benefits of going ahead. The Commonwealth and each State and Territory has legislation relating to EIA.
According to a United Nations Environment Program Training Resource Manual:
EIA is a structured approach for obtaining and evaluating environmental information prior to its use in decision-making in the development process. This information consists, basically, of predictions of how the environment is expected to change if certain alternative actions are implemented and advice on how best to manage environmental changes if one alternative is selected and implemented. Until relatively recently, with a few notable exceptions, EIA focused on proposed physical developments such as highways, power stations, water resource projects and large-scale industrial facilities. Slowly, but increasingly, its scope of application is expanding to include policies, plans and other actions which also form part of the development process.
Decision-makers are provided, by EIA, with information (and often recommendations) on the anticipated consequences of their choices. EIA is, therefore, a management tool with technical input, not a technical aid with 'add on' management aspects. This distinction is crucial to an understanding of the objectives of EIA and how it can best be implemented.
EIA has been in existence since 1970 (when it was introduced into the United States of America following the National Environmental Policy Act coming into effect) and has spread rapidly since then to all parts of the world. EIA is still relatively 'young' and the number of countries which use it, as a legal/administrative requirement, is still increasing. At the same time, EIA practice (and the techniques used) is evolving as experience has been gained on its utility in a wide range of development and geographic contexts.
The use of EIA has been formalized by the introduction of national laws and regulations and, in some cases, policies which establish systems of institutionalised procedures to ensure that all proposed physical development, expected to be environmentally damaging, is assessed prior to authorization and possible implementation.