Science Advisory Report 2021/053

Science advice on revisiting Pathways of Effects (PoE) diagrams in support of FFHPP risk assessment

Summary

• Pathways of Effects are used to link classes of activities in or near water to effects on fish or fish habitat they are likely to cause. This Science Advisory Report (SAR) provides recommendations for changes to draft consolidated Pathways of Effects (PoE) diagrams produced for use in the assessment of projects in or near water.
• These PoE diagrams are intended to focus on the aspects of Works/Undertakings/Activities (WUAs) - pressures - endpoints that DFO manages. They are tools used to communicate potential impacts to proponents, Indigenous Peoples (i.e., First Nation, Metis, and Inuit communities and rights holders), and the general public. While it is recognized that there are likely many more pressures and endpoints that would be included in a fully comprehensive ecosystem effects diagram (e.g., land-use beyond the riparian zone), that is not their intent.
• While PoE diagrams may be useful in wider applications (e.g., restoration projects), the main purpose of these PoE diagrams is to apply to WUAs that may have a negative impact on fish and fish habitat. Therefore, the focus is to identify the most common impacts that could result in negative effects.
• These PoE diagrams are intended to be used nationally in both marine and freshwater systems, to identify the most common pressures that can be managed by applying avoidance and/or mitigation measures. The spatial and temporal scale of the impacts that cannot be mitigated are assessed in a subsequent phase of FFHPP’s decision-making process. Science advice on the broader risk management framework may be requested at a later date once further developed.
• The applicability of pressures and linkages could vary across system types (i.e., stream, river, lakes, marine coastal) and regions, and it is recognized that this context-dependency is to be considered by users of the PoE diagrams.
• For each of the PoE diagrams more changes were discussed than were accepted. All accepted changes are identified in the body of this SAR and highlighted in a corresponding figure as follows:
• Land-based: 35 changes discussed and 26 accepted changes (Figure 4).
• Noise and Energy: 31 changes discussed and 23 accepted changes (Figure 5).
• In-water: 31 changes discussed and 25 accepted changes (Figure 6).
• Flow: 30 changes discussed and 25 accepted changes (Figure 7).
• Recommended changes to all four consolidated PoE diagrams are more fully documented in Brownscombe and Smokorowski (2021).
• As a result of the review and after the recommended changes are taken into account, it was agreed that the resulting PoE diagrams are accurate and valid and are recommended for inclusion in the revised consolidated PoE diagrams.
• It is recognized that there are limitations with the current structure and presentation of these PoE diagrams in that there is necessarily a trade-off between comprehensiveness and tractability. Decisions were made to limit the connections to those that most commonly require consideration, or to ensure that they are considered when relevant.
• It was agreed that the revised diagrams are sufficiently comprehensive and complete, encompassing the core components of WUA impacts on fish and fish habitat with the purpose of being tractable for FFHPP decision-making and communication. Exceptions were noted related to marine or large system coastal processes, aquatic invasive species, and other development-specific PoE diagrams (e.g., shipping) that are not part of the four core diagrams reviewed here.
• The process of using these revised PoE diagrams, if used in a manner that ensures all possible linkages and all applicable PoE diagrams are consulted, will facilitate the application of avoidance and mitigation measures to identify residual impacts.
• There are a number of uncertainties regarding the use of PoE diagrams for regulatory decision making. These include: their generalized nature and variable applicability across system types, regions, and WUAs; variable levels of scientific support for the linkages presented; and the nature of the pathway (i.e., linear vs non-linear) that will influence endpoints in different ways.
• Other considerations should also be kept in mind when using these PoE diagrams to facilitate decisions, including the need to consider cumulative effects and multiple stressors, potential alternatives to the most common direction of a pressure identified in the diagrams, and the need for users to have a relevant science background and training in their standardized use.

This Science Advisory Report is from the February 23-26, 2021, National Advisory Meeting on Science advice on revisiting Pathways of Effects (PoE) diagrams in support of FFHPP risk assessment. Additional publications from this meeting will be posted on the DFO Science Advisory Schedule as they become available.

Science Advisory Report 2021/053 (PDF, 1,887 KB)

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