5. Need for SEA: limitations of EIA

Environmental impact assessment of projects was the starting point for SEA, but EIA and SEA have some key differences:

Some Comparisons between EIA and SEA
Source: UNEP (2002) Environmental Impact Assessment Training Resource Manual, 2nd Edition, UNEP, Geneva. Amended from CSIR (1996)
EIA of Projects SEA of Policies, Plans and Programmes
Takes place near the end of decision-making cycle: aims to minimise impacts Takes place at earlier stages of decision-making cycle: aims to prevent impacts
Reactive approach to development proposal Pro-active approach to development proposals
Considers limited number of feasible alternatives Considers broad range of potential alternatives
Limited review of cumulative effects Cumulative effects assessment is key to SEA
Emphasis on mitigating and minimizing impacts Emphasis on meeting environmental objectives, maintaining natural systems
Narrow perspective, high level of detail Broad perspective, lower level of detail to provide a vision and overall framework
Well-defined process, clear beginning and end Multi-stage process, overlapping components, policy level is continuing, iterative
Focuses on standard agenda, treats systems of environmental deterioration Focuses on sustainability agenda, gets at sources of environmental deterioration


These differences account for one of the two main reasons for SEA:

1. SEA addresses limitations of project EIA

Because EIA takes place once many strategic decisions have already been made, it can often address only a limited range of alternatives and mitigation measures: those of a wider nature are generally poorly integrated into project planning.

Consultation in EIA is also limited and the contribution of EIA to the eventual decision regarding the project is unclear.

Although project EIA is widely used and accepted as a useful tool in decision-making, it largely reacts to development proposals rather than proactively anticipating them:

"At this [EIA] stage, the prior questions of whether, where and what type of development should take place are either decided or largely preempted by earlier policy making processes. Often, these decisions will have occurred with little or no environmental analysis. This foreclosure of the range of choice is partially countered by provisions to addressing project justification and alternatives in EIA. In reality, however, prior policy, technological and locational options are not open to serious environmental reexamination; neither is project-by-project EIA an effective way of doing so. Far preferable is the use of SEA or an equivalent approach to incorporate environmental considerations and alternatives directly into policy, plan and programme design." (Sadler and Verheem 1996)

Project EIAs are also generally limited to the project's direct impacts. This approach ignores a wide range of impacts, including:

  • cumulative impacts: the environmental impacts of multiple plans, projects and other actions;
  • global impacts: impacts that go beyond the local, project level, for instance climate change;
  • indirect, secondary or induced impacts: impacts that occur several steps away from the original action, for instance new houses that generate more vehicle movements that increase air pollution that affect the flora in an area;
  • synergistic impacts: where impact A + impact B have a total impact of more than A+B: for instance NOx emissions and ozone emissions which together cause smog, which has impacts over and above those of just the NOx + ozone.

The figure below illustrates how simply carrying out EIAs for individual projects will not address more strategic issues.  It shows long-ago proposals for building a second ring road around London.  The EIAs for the individual road links comprising the ring road would not have dealt with, for instance, long-distance traffic on the ring road, or the additional freight traffic caused by the sudden opening up of better links between the London ports and areas to the west of London.

SEA can deal with many of these difficulties, as it:

  • incorporates environmental issues into project planning and decision making;
  • considers alternatives or mitigation measures beyond project level; and
  • involves consultation on more strategic issues.

June 12, 2006 Uncategorized — brendan @ 4:16 pm


  1. If the limitations of EIAs are so diverse, and we are so sure that SEA address those limitations why not do away with EIAs?

    Comment by Keamogetse Mogae — June 27, 2007 @ 3:24 am

  2. I think the point is that SEA and EIA complement each other. SEA helps decision-makers to make better strategic decisions (like whether to pursue road expansion or whether to increase public transport), while EIA ensures that projects (like a road) are designed in an environmentally benign manner. Both SEA and EIA have their limitations and hopefully, with time and experience, we will get better and better at effectively implementing them.

    Comment by brendan — June 27, 2007 @ 3:47 am

  3. As pointed out brendan, certainly SEA and EIA complement each other. SEA can never replace EIA because it addresses different dimensions of policies, plans and programs and EIA addresses the project level issues. What is most critical is to make sure that SEA is carried out and provides information that will guide the EIA process.

    Comment by Waiswa-Ayazika — August 4, 2007 @ 12:15 am

  4. EIA is not intended to create developments 'with environmentally benign impacts'. It is a decision making tool to ensure that decision makers and third parties, understand the environmental cost-benefit equation of a proposal. The planning system is about deciding whether those costs or benefits have weight.

    Comment by roy — November 21, 2007 @ 1:18 am

  5. Great website. Helped with revision immensely. Thank you

    Comment by will bartholomew — May 20, 2008 @ 12:50 am

  6. Absolutely fantastic website. Well done old boy

    Comment by Bobby Rigby — May 20, 2008 @ 12:51 am

  7. Explains with clarity on fundamental difference between EIA and SEA. Very useful information.

    Comment by Kunj — February 22, 2009 @ 11:51 pm

  8. Really good course. I think the best advantage is that it's so didact, I'm learning SEA step by step. Sorry for insisting, but again I can't see the figure below that ilustrates second part of this section, the one relate of EIA individual projects.

    Comment by Gerardo — March 24, 2009 @ 5:49 pm

  9. Dear All: as i undestood, SEA is Applicable only with new Policy or plan, what about the allready done plans, policy specially in Agricultural field?? How can i use SEA to evaluate Agriculture Planning for the last 30 years with a lot of eniviromental problem resulting from it. i really need your advice. Thanks for this remarkable efforts to explain SEA. Morten

    Comment by Morten Markus — June 3, 2009 @ 1:43 am

  10. SEA like EIA is a methodology that employs various tools in ensuring that the three "legs" of sustainable development, i.e., social, economic and environmental factors are well balanced, i.e., towards meeting what I can called a "sustainability equilibria". It is evident that in both SEA and EIA, a number of processes are involved in testing this equilibrium including CBA, RA and levels of uncertainty. However, due the degree of rigority, SEA takes more qualitative factors as quantifying some of the measures is quite fuzzy at PPPs. EIA gets more quantitative because it focuses on "convincing" factors. It is also evident that while EIA is applied at project level, SEA is applied at PPPs as well as for a cluster of projects that may get out of the EIA scope. Thank you. Lugard

    Comment by Lugard Ogaro — December 13, 2009 @ 8:39 pm

  11. I will like to know how to develop a port focused SEA

    Comment by effiong nyong — January 6, 2010 @ 12:06 am

  12. Hi people, In my masters thesis, my research focused on developing a generic model for carrying out SEA as well as testing if the final product of SEA meets what i termed as, 'sustainability equilibrium'. I can quite comfortably roll out any SEA process by looking at the policy, plan, or program or even a strategic document. I can do this as a volunteer reviewer of your SEA and can surely generate discussions which can help you understand SEA better. I know some people have made SEA look like rocket science, but I assure you, SEA is a mind model that keeps on changing shape as you keep on querrying the process. Cheers, Lugard

    Comment by Lugard Ogaro — October 10, 2011 @ 4:01 am

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