The significance spectrum and EIA significance determinations

Abstract

The concept of significance is fundamental to environmental impact assessment (EIA). Even though there are many guidelines describing technical characteristics of impacts (such as magnitude, geographic extent, extent and frequency) that should be considered, there has remained a long-standing need for increased clarity on how significance determinations are ultimately reached by significance determiners, those who, on behalf of governments, make a legal determination of significance in EIAs. This involves the application of societal values, in the form of subjective informed judgement, about the acceptability of the predicted impacts. This paper introduces the significance spectrum, a graphic model that illustrates a process for determining significance, using the following steps: (1) determining the threshold of significance for each valued component; (2) weighing the evidence and considering predicted impacts; (3) deciding which side of the threshold the predicted adverse impact falls on; and (4) for unacceptable impacts, deciding if mitigations can make the residual impact acceptable. Concepts such as ecological significance should not be confused with significance in EIAs, which may not only include ecological significance but also considers societal values. We provide specific steps for determining significance that help clarify this fundamental aspect that lies at the core of EIA decision-making.

Making sense of significance in environmental impact assessment

“…It includes the consideration of three broad levels of significance corresponding to impacts that are: (1) significant and not mitigable, (2) significant but mitigable and (3) insignificant (Canter and Canty 1993). Sippe (1999) discussed significance in the context of acceptability of predicted residual impacts, which is realised during the fourth step of the Ehrlich and Ross (2015) framework. It is not our intention to further duplicate the work of Ehrlich and Ross (2015) here.…”

“…Focus EIA attention only on significant issues (Ross et al 2006;Briggs and Hudson 2013;Wood 2003;Sadler and Fuller, 2002 Kennedy and Ross 1992;IAIA & IEA 1999;Sippe 1999;Canter and Canty 1993;Duniker and Beanlands 1986); 3. Ensure that the term significance is specified and applied consistently (Ehrlich and Ross 2015;Ross et al 2006); and 4. Uphold transparency in decision-making so that significance determinations are clear to all EIA stakeholders (Gibson et al 2005;Morrison-Saunders and Bailey 2000;IAIA & IEA 1999).…”

“…Have a clear operational framework for how significance is determined throughout the EIA (Ehrlich and Ross 2015;Wood 2008;Lawrence 2007;Ross et al 2006;Wood 2003;Sippe 1999;Canter and Canty 1993;Kennedy and Ross 1992); 2. Focus EIA attention only on significant issues (Ross et al 2006;Briggs and Hudson 2013;Wood 2003;Sadler and Fuller, 2002 Kennedy and Ross 1992;IAIA & IEA 1999;Sippe 1999;Canter and Canty 1993;Duniker and Beanlands 1986); 3.…”

“…2.1 A clear operational framework for how significance is determined throughout the EIA Ehrlich and Ross (2015) provide an extensive review of impact significance literature leading to their own clear operational framework for determining significance in EIA practice. This is the most advanced and detailed account for significance determination during EIA decision-making in the literature.…”

“…This is the most advanced and detailed account for significance determination during EIA decision-making in the literature. Ehrlich and Ross (2015) refer to the 'significance spectrum' and employ a four-step process to demonstrate how significance determinations should be made:…”