The effects of human activities related to the use of environmental resources on natural environment is called Environmental Impact. The assessment and evaluation of environmental effects of human activities are collectively called Environmental Impact Assessment (EIA).
Environmental Impact Assessment is, therefore, a method of evaluating environmental consequences such as environmental changes which are likely to be caused by the proposed human activities related to land use changes, construction of dams, reservoirs, roads, rails, bridges, industrial locations, urban expansion, etc. and the possible adverse effects of these environmental changes.
Environmental changes mean environmental degradation and pollution resulting into ecological imbalance and ecosystem disequilibrium. The environmental impact assessment process began with the enactment of the National Environmental Policy Act (NEPA) in the US in 1969.
In view of the colossal damage to the environment, there is a felt need for assessing the environmental impacts of developmental activities. EIA is a tool to anticipate the possible damage to the environment caused by developmental projects and schemes, and propose mitigation measures and strategies.
EIA exerts to declare a national policy to encourage productive and enjoyable harmony between man and environment. It promotes efforts to prevent or eliminate damage to the environment and the biosphere, and stimulate the health and welfare of man.
It seeks to increase the understanding of ecological system and nature resources important to the nation and to provide for appropriate institutional structure to carry out the objectives.
It provides a broad, integrated perspective of a region about to undergo or undergoing developments. EIA ascertains the cumulative impacts from the multiple development in the region. It establishes priorities for environmental protection. It also identifies the positive and negative aspects of any project as well as assesses the policy options and analyzes the impact on the environment therein.