Cumulative Effects Assessment Practitioners' Guide

5.0 Preparing and Completing a CEA

As there is no one clear approach to conducting a CEA, it is suggested that practitioners should follow the basic guidelines provided in this Guide, learn from the case studies provided, investigate specific techniques to address the issues of concern from other assessments and as described in the literature, and finally select an approach that best suits their assessment needs.

Preparing and Completing a CEA

Preparing to do a CEA

  1. Discuss with the appropriate regulatory authority what its expectations are regarding the assessment of cumulative effects, and determine if it has any specific guidance on the content of the assessment.
  2. Ensure that the Terms of Reference (if the proponent is involved in defining the terms) for the assessment adequately address the concerns of the regulatory authorities and key public stakeholders.
  3. Prepare a complete description of the proposed action.
  4. As early as possible, focus the assessment on only the most important issues and effects. Consult stakeholders. Admit that choices made now may later change as a result of new information.
  5. Review, if available, assessments done for similar types of actions, ideally in a similar geographic area. This may provide valuable baseline data and information on suitable assessment approaches.
  6. Review some of the literature on cumulative effects to familiarize yourself with the latest issues and techniques regarding CEA practice.

Using the Assessment Framework

  1. Complete an assessment of the action's effects as normally done for an EIA (i.e., assess relatively local and direct effects on VECs caused by the action under review). This should generally follow the 5- EIA steps and the associated CEA tasks (Section 3.1).
  2. As you progress through the assessment, expand on the results and conclusions obtained for each step by examining each of the CEA tasks. This may be done during each step as the EIA progresses, or done after much of the EIA has been completed (the more common approach). Use the CEA tasks to form the basis of your CEA approach. Use the "CEA Checklist" (Section 5.3) and "Key Criteria" (Section 5.2) to ensure that you have considered the important attributes of a CEA.
  3. Ensure that conclusions are defensible and the presentation of results can be readily interpreted and are usable by decision-makers.

Provided the assessment meets all legislated requirements, is technically and scientifically sound, addresses the key issues related to the action under review, and meets the minimum requirements expected of any CEA, it is of little importance which type of analysis is used. While doing this, practitioners may wish to consider the following:

  • The ultimate objective of a CEA is to provide information to decision makers to allow them to make more informed decisions.
  • Despite the challenges, assessing cumulative effects is possible and the approaches are improving as more experience is gained by practitioners and regulatory agencies.
  • CEAs cannot do everything for everyone, and are only one step towards providing information on an action's effects and addressing the mitigation of those effects. Expectations as to what CEAs can accomplish must not exceed what can technically be accomplished, what is scientifically known about environmental conditions, and what is possible within the existing regulatory review process and jurisdictional land administration.
  • Cumulative effects methods are currently available for practitioners to conduct CEAs.
  • There is not one comprehensive method by which any CEA may be performed; practitioners must select an appropriate method from a "toolbox" of approaches.
  • Availability of good information may determine not only a practitioner's ability to do a CEA, but also the methods finally used to predict effects.
  • The selected method must incorporate all of the relevant sources that may contribute to the effect being studied.
  • CEAs cannot replace regional land use planning; however, CEAs may provide useful information for a land use planning process. Similarly, existing land use plans can be used to assist in completing project-specific CEAs.
  • Mitigation recommendations in a CEA can be broader than may typically be proposed in a conventional EIA.
  • As more assessments are conducted for various actions within a region, the amount of available data grows and precedent is set regarding best accepted practice.
  • Despite the lack of regional thresholds and the current piece-meal fashion of project-specific assessment in addressing overall nibbling effects, the assessment of cumulative effects under regulatory review process currently represents an opportunity to address concerns of large-scale and long-term changes to the environment.

Where is the CEA Placed in the Submission?

There are at least four options for placing the CEA:

  • within a separate "CEA chapter" after the EIA portion (this is the most common approach);
  • as a stand-alone document, separately bound from the EIA report;
  • integrated within the EIA as a unique sub-section, appearing at the end of each major section assessing effects on major environmental components (e.g., water, air, vegetation); or
  • fully integrated with the EIA as regional issues are raised and examined.

The approach taken will depend on the practitioner's philosophy of cumulative effects (i.e., as inseparable from the EIA or as a unique and different view) and on which approach is most readily accomplished given the division of labour used in assembling the assessment report.

Lessons Learned from the Case Studies

A review of the detailed case studies in this Guide (Appendix B) suggests the following lessons can be learned:

  • Assessment of cumulative effects on some components is relatively straightforward if quantitative tools and thresholds are available (e.g., for regulated constituents of air and water).
  • Qualitative conclusions and ranking systems are useful to communicate results if supported by defensible quantitative analysis.
  • Incremental changes caused by the action under review should be measured relative to an established baseline condition.
  • Assess effects during "snapshot" points in time.
  • Perform an assessment from the point of view of effects on VECs as opposed to interactions between actions.
  • Interactions do not need to be assessed individually; characterize the entire surrounding environment as it "appears" to each VEC.
  • Other past and existing actions often become part of the background environment for a VEC.
  • Lack of information regarding other actions may limit the assessment of their contribution to effects. As many disturbances are temporary, effects often recover within an acceptable period of time.
  • Induced activities (e.g., road proliferation) may be an important cause of effects.

5.1 Effectively Communicating Results to Decision Makers

Environmental assessments are fundamentally the gathering of information, their analysis and presentation of the results. A CEA is one of many tools that may be used to assist decision-makers in their deliberations about project applications, resource management plans and conservation goals. As CEAs may deal with relatively complex issues, the practitioner's challenge is to ensure that the methodological approach and assessment results can be readily interpreted and weighed by decision-makers (e.g., practitioners often use visualization tools such as maps and network diagrams to distill order from apparent chaos and to communicate results to decision-makers).

Decision-makers require sufficient information to allow them to make justifiable and confident decisions as they weigh the environmental effects against social and economic benefits and costs. [Decision-makers, such as Review Boards, often must make decisions on project approval based on issues other than those dealt with in an environmental assessment. One example, with cumulative effects implications, is that the development of a project may foreclose the opportunity for future projects (of the same or different types) to occur in the vicinity of that proposed project (e.g., a pulp mill is approved on condition that it has guaranteed harvesting access to a large forested area surrounding the mill). In deliberating on the approval of such a project, the value of projects prevented from occurring, or occurring at a reduced level, may be considered. As a result, regulatory bodies may push for more stringent mitigation measures or intensive monitoring of project operations. Another example of decision-makers pursuing other matters is when they consider effects and issues beyond those strictly required to meet the conditions of a permit or license application (e.g., triggers from the Law List under the Canadian Environmental Assessment Act).] They also wish to ensure that the legal requirements for the CEA are met. Therefore, assessment practitioners must clearly communicate the results of the assessments to decision-makers so as to best facilitate their deliberation on project approval. Repetitive use of tables of numbers and maps (especially if inadequately explained) are no substitute for a concise and readily defensible conclusions based on the data and analysis applied in the assessment.

One of the most important responsibilities of decision-makers is to determine whether the proposed project ought to be allowed to proceed and, if so, under what conditions. To facilitate this decision, it is essential that the CEA should contain, explicitly, a summary of management options and their consequences. These would include matters such as the mitigation measures to be employed, any compensation programs and follow-up studies (monitoring and management programs) to be conducted. Moreover, it is also important to explain why each of these management features is proposed, by whom it would be carried out and the level of commitment to each task by those responsible.

To effectively communicate the results of the CEA, the practitioner should consider use of the following techniques:

  • Discussion: The discussion should be a description of the analysis and interpretation of the results. Discussion based on professional judgment should be clearly distinguished from that based on a specific form of analysis and data. Assumptions, limitations and degree of confidence (i.e., certainty) placed on the data and analysis should be explained. Full scientific references should be provided for literature and personal communications.
  • Decision Record: A decision record [This is not to be confused with the Decision Report, issued by regulatory agencies, that explains the decision reached regarding a project application.] should be included in the assessment, usually as an Appendix, to provide further clarification and expand on specific points of discussion.
  • Tables: Tables should be used to organize data and summarize the results of calculations.
  • Matrices: A matrix (a table in which the table entries are rankings) can be used to summarize the scale of effects (Section These rankings can take three different forms: 1) qualitative (e.g., low and high), 2) quantitative (i.e., numbers that correspond to an absolute physical quantity), or 3) indices (i.e., non-dimensional numbers that provide a point of relative comparison).
  • Images: Figures should be used as extensively as possible to illustrate the information. Maps, especially those derived from a GIS, are powerful tools for portraying disturbance and environmental conditions over a wide region. Photographs, photomontages and video also help to provide a visual orientation.

5.2 Key Criteria for CEA

The following proposes criteria that establish the expectations of best professional practice in completing a CEA.

Key Criteria for an Acceptable CEA

  1. The study area is large enough to allow the assessment of VECs that may be affected by the action being assessed. This may result in an area that is considerably larger than the action's footprint. Each VEC may have a different study area.
  2. Other actions that have occurred, exist or may yet occur that may also affect those same VECs are identified. Future actions that are approved within the study area must be considered; officially announced and reasonably foreseeable actions should be considered if they may affect those VECs and there is enough information about them to assess their effects. Some of these actions may be outside the study area if their influence extends for considerable distances and length of time.
  3. The incremental additive effects of the proposed action on the VECs are assessed. If the nature of the effects interaction is more complex (e.g., synergistic), then the effect is assessed on that basis, or why that is not reasonable or possible is explained.
  4. The total effect of the proposed action and other actions on the VECs are assessed.
  5. These total effects are compared to thresholds or policies, if available, and the implications to the VECs are assessed.
  6. The analysis of these effects use quantitative techniques, if available, based on best available data. This should be enhanced by qualitative discussion based on best professional judgement.
  7. Mitigation, monitoring and effects management are recommended (e.g., as part of an Environmental Protection Plan). These measures may be required at a regional scale (possibly requiring the involvement of other stakeholders) to address broader concerns regarding effects on VECs.
  8. The significance of residual effects are clearly stated and defended.

5.3 CEA Checklist

Answering the following questions (many during scoping) should ensure that the assessment incorporates important attributes of a CEA.

Local Effects

  • Does the assessment of local effects (i.e., in the EIA) indicate a likelihood of other than negligible residual effects? If so, on which VECs ?
  • Is the proposed action within a relatively undisturbed landscape, or a landscape already disturbed?
  • Do topographic or other constraints spatially limit the effect that the action may have on VECs ?

Other Actions

  • Is there any evidence that the effects of past actions may still be other than negligible?
  • Are the nearest existing actions to the proposed action possibly contributing to effects on the same VECs ?
  • Have any actions been officially announced by other proponents with the intent to begin submission under statutory requirements?

Regional Issues

  • Have any issues or VECs already been identified in the EIA or by local stakeholders that may be of concern beyond the footprint of the proposed action?
  • Are any VEC species locally or regionally rare? Are there any environmentally sensitive areas that may be disturbed?
  • With or without local significant effects, could the action contribute to regional "nibbling" loss of habitat (terrestrial or aquatic) that may affect VECs that reside or pass through the action's local study area?


  • Is the assessment focussed on effects on VECs to which the action under review may contribute?
  • Is there reliable information (both science and traditional-knowledge based) that describes the VECs and the habitat on which some VECs depend?
  • Is there adequate information available about other actions to confidently determine if they are contributing to other than negligible effects on the same VECs ?
  • Are indicators available to assess VECs ?
  • Are there indicators of significance other than thresholds that should be considered?
  • Could the action induce other actions to occur (especially road access)?
  • Can a historical baseline be described against which consecutive changes can be compared?
  • Are any effects traceable back to the action under review? Is the action responsible for incrementally contributing to the effect?
  • Are certain analytical approaches mandatory for assessing effects on some VECs ?


  • Are quantitative thresholds available for any of the VECs ? Are qualitative thresholds available that describe intended land use (e.g., land use plans)?
  • If landscape indicators are proposed, can the derived values be used to determine if the effects on a VEC have exceeded or may exceed the VECs ability to recover?


  • Is the standard or a novel application of mitigation adequate to mitigate significant effects?
  • Can reclamation reduce the duration of land disturbance and hasten the recovery of environmental components to pre-disturbance conditions?
  • Is habitat of equivalent capability available elsewhere to compensate for lost habitat?
  • Is there an opportunity to initiate a regional level mitigation (or compensation) of effects?
  • What is required for monitoring and effects management as follow-up?