Science Advisory Report 2006/041
Identification of Ecologically Significant Species and Community Properties
- Identifying Ecologically Significant Species and Community Properties is not a general strategy for protecting all populations and marine communities that have some ecological role. Rather, it is a tool for calling attention to a species or community property that has particularly high ecological significance, to facilitate provision of a greater-than-usual degree of risk aversion in management of human activities that may affect such species or community properties.
- The “criteria” referred to in this report are actually the ecosystem properties that are ecologically significant. These “criteria” do not identify a species or community property as ecologically significant if the consequences when perturbed are primarily for humans. The process for identifying Social and Economic Objectives, including culturally important species, needs to progress within the larger framework of objectives-based Integrated Management.
- We have limited knowledge of the ecological processes that affect all aquatic species, including those potentially affected by human activities we are trying to manage in a sustainable manner. Hence many species and community properties may NOT be identified as exceptionally ecologically significant based on the best information available but with further study they may be found to be as important as parts of the ecosystem that are given very high priority on these criteria.
- Ecological scale is a key factor in the ecological role of a species or community property. The ecological significance of a species or community property must always be interpreted relative to both spatial and temporal scales.
- Criteria are given for assessing four types of Ecologically Significant Species and Community Properties;
- The most direct and tractable cases will be species-based assessments of ecological significance; that is, identifying species with potentially controlling influence on ecosystem structure and function. This may occur either because a species has a crucial trophodynamic role (type 1);
- Or because it provides three-dimensional structure important to biodiversity and productivity (type 2).
- Above the species level, there are aggregate ecosystem properties that are themselves essential to maintaining ecosystem structure and function (type 3).
- Species or species groups which, if abundant, could pose a particular threat to ecosystem structure and function may be candidates for enhanced management for their ecological significance; to control their abundance and/or distribution rather than protect and promote it (type 4).
- The best approach for identifying Ecologically Significant Species on the basis of their trophic roles is to assess the interaction strengths of all the species in the food web. However, for almost all aquatic food webs at present we lack the information needed to quantify how interaction strengths are distributed among species. Where we cannot directly identify the species with large interaction strengths, the best science practice for trophic relationships is to focus on key trophic roles. These include
- Forage species;
- Highly influential predators;
- Nutrient importing (and exporting) species;
- Primary production and decomposition are also essential to ecosystem structure and function. However, they may be less useful as criteria for assessing the ecological significance of species, because they are often difficult to associate with individual species. However, they are often tied to places that meet EBSA criteria, so they often receive enhanced protection through spatial management approaches.
- Assessment of structure-providing species requires assessing quantity of the species present, quality of the structural habitat being provided, and the significance of the structural habitat to the overall ecosystem structure and function.
- Management advice is feasible for community properties above the species level as well, although with current knowledge few criteria can be made operational for assessing community properties above the species level as ecologically significant at this time. However, research on community properties of ecosystems is expected to increase the specificity of community-scale science advice that can be provided. Those proposed for use now include:
- Size based properties;
- Frequency distribution of abundance and/or biomass across species.
- Whether or not Conservation Objectives are set and management actions taken to address species considered to be threats to ecosystem structure and function will depend on many things including the nature of the threat posed, societal values, and tractability of management responses. What this criterion does is to flag the need for focused discussion of these topics. Specific types of species for consideration include:
- Invasive species;
- Harmful or toxic species.
- Two additional factors, rarity and sensitivity/recoverability, affect the application of the preceding criteria and may move a species or community property somewhat higher in priority ranking.
- DFO needs to make it a priority to reduce the knowledge gaps in this report. Science should be vigilant to monitor changes in additional properties and management should be responsive to major changes in them, even if the ecological significance of each change is not fully understood.
- Overall, using this set of criteria for assessing the ecological significance of species and linking the assessment to the degree of risk aversion expected in management represents a fundamental change in the conceptual basis for management.
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