Science Advisory Report 2007/038

Documenting Habitat Use of Species at Risk and Quantifying Habitat Quality

Summary

For the necessary information to be available to Committee on the Status of Endangered Wildlife in Canada (COSEWIC), terms of reference of the following types should be included in the generic template for the meeting Terms of Reference (ToRs) for pre-COSEWIC Science Advisory Meetings. 

1. Provide functional descriptions of the properties that a species’ aquatic habitat must have to allow successful completion of all life history stages. 
2. Provide information on the spatial extent of the areas that are likely to have the necessary properties.
3. Identify the activities most likely to threaten the properties that give the sites their value, and provide information on the extent and consequences of those activities.
4. Recommend research or analysis activities that are necessary in order for an Recovery Potential Assessment (RPA), if needed for the species, to complete its Terms of Reference on habitat issues for the species.

For the necessary information to be available for consultations, listing recommendations, and commencement of recovery planning, ToRs of the following types should be included in the generic template of ToRs for RPAs.

1. Quantify how the biological function(s) that specific habitat feature(s) provide to the species varies with the state or amount of the habitat, including carrying capacity limits, if any.
2. Quantify the presence and extent of spatial configuration constraints, if any, such as connectivity, barriers to access, etc.
3. Provide advice on how much habitat of various qualities / properties exists at present.
4. Provide advice on the degree to which supply of suitable habitat meets the demands of the species both at present, and when the species reaches biologically based recovery targets for abundance, range, and number of populations.
5. Provide advice on feasibility of restoring habitat to higher values, if supply may not meet demand by the time recovery targets would be reached, in the context of all available options for achieving recovery targets for population size and range.
6. Provide advice on risks associated with habitat “allocation” decisions, if any options would be available at the time when specific areas are designated as Critical Habitat.
7. Provide advice on the extent to which various threats can alter the quality and/or quantity of habitat that is available.

Commentary is provided for addressing each proposed Terms of Reference.

In the process of developing these Guidelines for activities during the pre-COSEWIC and the RPA stages, the need for additional guidelines on other SARA-related tasks were identified.  Key areas include:

• the biological functions that may be related to habitat features,
• what life history stages to consider,
• how to treat and report uncertainty,
• what to consider as a threat to a species and its habitat,
• how to treat habitat features that are not stable in space (and sometimes in time), 
• how to treat habitat features that are not physical or chemical properties of the environment (such as food supply, sound, etc.).

In addition a decision tree is presented for choosing the analytical approach most appropriate for quantifying habitat quality, depending on the quantity and quality of data that are available regarding habitat features and species occurrences.  Key questions in the decision tree are:

1. Are there insufficient data on key habitat features and abundance or distribution of the species of concern, such that it will be necessary to rely on expert opinion for any inferences on what habitats are important for a species?
2. Are the only data available the presence or absence of a species with no information whatsoever on habitat features of the sites where the species is present or absent?
3. Are data available on ecological gradients of habitat use and features of the habitats being used?
4. If only presence or absence data are available for a species’ use of the habitats, are there at least ordinal level data on habitat features where the species was observed?

For each Yes, specific analytical approaches are recommended.  Other relvant questions that influence the selection of analysis methods are:

5. Is the species so severely depleted that it is likely to have zero abundance at many sites where the habitat is capable of supporting substantial abundances of the species (i.e. much suitable habitat is thought to be unutilized).
6. Is the gradient in species’ abundance so strongly determined by some threat other than habitat quality that differences in data on species use of various sites are likely to be uninformative about habitat quality?

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