Impact assessment (IA) is a structured a process for considering the implications, for people and their environment, of proposed actions while there is still an opportunity to modify (or even, if appropriate, abandon) the proposals. It is applied at all levels of decision-making, from policies to specific projects.
[Note on terminology: some practitioners of policy analysis use the term impact assessment in a rather different way. Specifically they ask the question: did our policy (or other planned intervention) have the desired impact? Rather than using established evaluation terminology, a number of policy analysis practitioners have started to refer to this as impact assessment. A specific example is the use of “participatory impact assessment” to describe the process of engaging people and communities in assessing the actual impact of policy interventions on livelihoods. Such uses of the term impact assessment are quite distinct from the usage described in this wiki.]
The process involves the identification and characterisation of the most likely impacts of proposed actions (impact prediction/forecasting), and an assessment of the social significance of those impacts (impact evaluation).
IA aims to:
- provide information for decision-making that analyses the biophysical, social, economic and institutional consequences of proposed actions;
- promote transparency and participation of the public in decision-making;
- identify procedures and methods for the follow-up (monitoring and mitigation of adverse consequences) in policy, planning and project cycles; and
- contribute to environmentally sound and sustainable development.
The process of IA benefits proponents, stakeholders and local communities, and decision-makers. Although impact assessment has been criticised since its introduction for being a technocratic tool, based on rational decision-making models, contemporary guidelines and principles for IA practice tend to emphasise a participatory, inclusive approach, which recognises different types of knowledge, and the importance of representing the views of different groups in society, regardless of their economic and political status. Environmental and social justice, and distributional considerations, are important guiding principles of impact assessment.
The concept of “environment” in impact assessment evolved from an initial focus on the biophysical components to a wider definition, including the physical-chemical, biological, visual, cultural, socio-economic and health components of the total environment.
Ideally impact assessment will be an integrated treatment of the likely impacts on any of the facets of the natural and human-modified environment, including people, communities and their wellbeing. To that end, different forms of IA have developed to address specific challenges raised by the need to assess impacts within certain sectors of the environment: hence social IA
, health IA
, cultural IA, ecological IA
, etc. All these forms of IA share the same basic principles, methodology and purpose, but may differ in specific methods and techniques. The need to apply IA to strategic levels of decision-making (e.g., policies, legislation, plans, programs) led to the development of Strategic Environmental Assessment (SEA)
. SEA is generally understood as an impact assessment process that aims to mainstream environmental, social
, and health
issues and ensure the sustainability of strategic decisions. Legal provisions for SEA are emerging, in many cases associated with EIA institutions and legislation. The European Union approved a directive on the environmental assessment of plans and programs in 2001. The SEA is gaining increasing acceptance as a tool that is used early in decision-making to help inform decisions at the sectoral and regional level and to set the parameters for alternatives analysis.
In recent years, IA has become strongly linked to sustainability concepts, and some would argue that sustainability is an integral part of all IA activities. For others, the integration of the environment, social and economic dimensions of assessment justifies the adoption of a distinct term: Sustainability Assessment. On the other hand, it is possible to conduct impact assessments within other policy and value contexts, without direct or indirect reference to sustainability thinking.
The practice of IA relies upon a family of instruments and tools, typically based on the physical and natural sciences and social sciences, in order to predict future expected consequences of possible decisions. Depending on the level of effort and the seriousness with which the process is undertaken, different degrees of success are achieved. The issuing of a report only to fulfil legal compliance for impact assessment is not typically an effective way of practising IA. In some countries, the US for example, the analysis of alternatives is considered the “heart” (the actual word used in the regulations) of the process. Also important to the success of IA is the process of follow-up
which assures that recommendations of the IA are implemented and effective.
Many practitioners and administrators, coming from backgrounds in the sciences, social sciences, planning, architecture, landscape architecture and business, are practising IA professionals. Other professionals who are involved in specific phases or parts of IA processes see IA as a planning and management tool rather than as separate professional discipline. In some countries there are certification and accrediting schemes for IA professionals.
Three key international journals on IA are published, notably Impact Assessment and Project Appraisal
(the journal of IAIA), EIA Review
(Elsevier) and the Journal of Environmental Assessment, Planning and Management
(Imperial College Press).
IA is related to a number of other decision-support processes; historically those links have been with approaches such as technology assessment
and risk assessment
; more recently life cycle analysis has become an important associated method.
Historically, environmental impact statements (EIS) were a late addition to the National Environmental Policy Act (NEPA)
in the US, enacted in 1970. The EIS was an enforcing mechanism, to show how Federal agencies were implementing environmental policy within their major project development activities. This afterthought became the star turn in its own right, and was quickly adopted in several other countries, especially Canada, Australia and New Zealand. The approach was gradually adopted by an increasing number of countries in the following decades, and received a major boost from the UN Conference on Environment and Development 1992
. Principle 17
of the Final Declaration is dedicated to EIA:
“Environmental impact assessment, as a national instrument, shall be undertaken for proposed activities that are likely to have a significant adverse impact on the environment and are subject to a decision of a competent national authority.”
An important consequence of UNCED was that the United Nations agencies concerned in various ways with people and the environment adopted impact assessment as a central tool to support decision-making.
Impact assessment is gradually being recognised in international environmental law, as demonstrated, for example, by
Other global and regional conventions include provisions for EIA and SEA, including
The major funding banks have developed impact assessment requirements and guidelines, as have many national aid agencies. Most multi-lateral development banks have developed EIA systems. The first operational directive on EIA at the World Bank
dates from 1989. Many multi-lateral institutions have built strong internal procedures, and more recently SEA procedures. IA is an important tool used by national development assistance institutions to integrate environmental and social issues into development cooperation, as well as addressing public participation and good governance issues. The OECD
(Organization for Economic Co-operation and Development) has been active in the coordination work on IA and development assistance.
As World Bank funding of major international development projects has shrunk in proportion to private financial support, there has been growing pressure on private sector banks to develop and implement impact assessment requirements, leading to an agreement among the major private sector financial institutions to adopt the Equator Principles
: a set of guiding principles that apply to the social and environmental scrutiny of proposed development projects which involve at least US$10m investment from the private financial institutions. As of June 2009, sixty-six financial institutions, including many commercial banks, with operations in over 100 countries have adopted The Equator Principles, making them the project finance industry standard for addressing environmental and social issues in global project finance. The Principles are based on the environmental and social performance standards of the International Finance Corporation
(IFC) in order to ensure that the major projects they finance are developed in a manner that is socially responsible and reflect sound environmental management practices.
See AlsoBiodiversity, Ecology and Ecosystem Services - IA Considerations/Approaches
Economic and Fiscal Assessment
Health Impact Assessment (HIA)
Social Impact Assessment (SIA)
Strategic Environmental Assessment
Special thanks to Júlio de Jesus and Richard Morgan for providing initial content for this IAIA Wiki topic.