Cumulative Impact Assessment: Is It Just a Fancy Way of Identifying and Managing Risk?

November 30, 2012
Denise Mullen

What is cumulative impact assessment?

What is cumulative impact assessment? This is a good question but also one that is hard to answer – which, perhaps, is part of the problem. On their face, the words mean:

  • Cumulative: increasing or increased in quantity, degree, or force by successive additions.
  • Impact: the action of one object coming forcibly into contact with another.
  • Assessment: the evaluation or estimation of the nature, quality, or ability of someone or something.

The current working definitions of cumulative impact assessment (CIA) include the following:

“any cumulative environmental effects that are likely to result from [a] designated project in combination with other physical activities that have been or will be carried out”[1];

“cumulative effects are the combined effects of past, present and foreseeable human activities, over time, on the environment, economy and society in a particular place”;[2] and,

“a cumulative impact is an impact on the environment [that] results from the incremental impact of the action [under review] when added to other past, present and reasonably foreseeable future actions”[3].

All of these are linear definitions and so if we take a Cartesian view of the world, one that is relatively simple, mathematically oriented, and fairly predictable, it is easy to build a picture of CIA as additive, and then to design a logical stepwise process that enables data gathering and engages stakeholders to varying degrees. This is exactly how we have gone about CIA to date, with generally unsatisfactory results. Most methods described in handbooks and guides around the world, whether for domestic or international audiences, follow a predictable, project-by-project review within a site-specific environmental impact assessment (EIA) process, usually in a way that considers the component parts of each project individually rather than at a systems level. However, “practically speaking there is really no way that EIA, because of its site-specific, single development orientation, can do the job of CIA”.[4] This illustrates why the practice of cumulative impact assessment is still a mystery to most “practitioners”[5].

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[1] Canadian Environmental Assessment Act, S.C. 2012, c. 19

[2] Alberta Environment and Sustainable Resource Development, also adopted by BC in its current working version of their CIA framework

[3] US National Environment Policy Act of 1969

[4] Cumulative Effects: A Binational Perspective, W. James Erckmann , Institute for Environmental Studies , University of Washington, 1986

[5] Impotence of Cumulative Effects in Canada: Ailments and ideas for Redeployment, Peter N. Duinker and Lorne A. Greig, 2006


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