Scientific Assessment to Inform the Identification of Critical Habitat for Woodland Caribou, Boreal Population, in Canada - 2011 Update: Executive Summary
Boreal Caribou and the Species at Risk Act
The Woodland Caribou (Rangifer tarandus caribou), Boreal Population (hereinafter referred to as boreal caribou), was last assessed by the Committee on the Status of Endangered Wildlife in Canada as Threatened (COSEWIC 2002), and listed under the Species at Risk Act (SARA) in 2003. Under the Act, the Minister of the Environment is responsible for the development of a National Recovery Strategy, including the identification of critical habitat.
2008 Scientific Review
In 2007, Environment Canada (EC) launched a science-based review with the mandate to identify boreal caribou critical habitat to the extent possible, using the best available information, and/or prepare a Schedule of Studies to complete this task. The results were summarized in a report entitled Scientific Review for the Identification of Critical Habitat for Woodland Caribou (Rangifer tarandus caribou), Boreal Population, in Canada (hereinafter referred to as the 2008 Scientific Review).
Identifying critical habitat for boreal caribou was framed as an exercise in decision analysis and adaptive management. Establishment of a systematic, transparent and repeatable process was central to the approach. The resultant Critical Habitat Framework was anchored by synthesis and analysis of available quantitative data and published scientific information on boreal caribou population and habitat ecology.
The 2008 Scientific Review established caribou ranges as the appropriate scale at which to identify critical habitat, and applied a probabilistic approach to assessing the adequacy of the current range conditions to support a self-sustaining population based on three lines of evidence: percent total disturbance, population growth and population size. The results were used to classify critical habitat for each local population into one of three states: maintain current conditions, improve current conditions, or assess resilience to further disturbance.
The 2008 Scientific Review recognized that current knowledge and the dynamic nature of landscapes impart uncertainty and that critical habitat identification should be monitored and assessed for the purposes of refinement and adjustment over time, as new knowledge becomes available (i.e., as part of adaptive management).
Additional Scientific Activities
The 2008 Scientific Review established a foundation for the assessment of critical habitat (i.e., habitat conditions required for recovery of boreal caribou under SARA). To support refinement of the resultant description of critical habitat, EC identified key areas for further exploration:
- implications to critical habitat identification of variation in approaches applied by jurisdictions to delineate ranges;
- relative impacts of different disturbances and habitat types, and their configurations, on the ability of ranges to support self-sustaining populations, and resultant critical habitat identification;
- identification of disturbance-based management thresholds (hereinafter referred to disturbance thresholds) for self-sustaining local populations;
- influence of future range conditions on disturbance thresholds given the dynamic nature of disturbance within a given range.
The purpose of addressing these knowledge gaps was to further inform the identification of critical habitat for boreal caribou, using the best available information. To this end, EC undertook the work presented in this report, and once again engaged experts to provide scientific advice and reviews during the development of this work and completion of this report. An independent process was undertaken to consider Aboriginal Traditional Knowledge (ATK) in the development of the National Recovery Strategy. Information flowing from the two bodies of knowledge will inform strategies to support the survival and recovery of boreal caribou in Canada.
2011 Scientific Assessment: Concepts and Methodology
Similar to the 2008 Scientific Review, the present assessment was designed to provide a probabilistic evaluation of critical habitat relative to the set of conditions (demographic and environmental) within each range. The framework and components developed in the 2008 Scientific Review were expanded and enhanced through the following scientific activities.
- Enhanced Disturbance Mapping: new anthropogenic disturbance maps using an enhanced methodology were created to provide a better temporal match with available caribou data and investigate the relative impact of different disturbance types and their configuration on the assessment of boreal caribou ranges. The maps were supplemented with updated fire data available from jurisdictions.
- Habitat Selection Analysis: evaluation of habitat selection at different spatial scales (national and regional) was conducted using available caribou location data to identify additional bio-physical attributes influencing habitat condition for caribou, beyond the percentage of total disturbance.
- Buffer Analysis: the effects of buffering on 1) the configuration of disturbance and 2) effects of landscape configuration and connectivity on caribou demography were examined.
- Meta-Analysis of Boreal Caribou Population and Habitat Condition: the 2008 meta-analysis of caribou demography in relation to range-level disturbances (i.e., anthropogenic and fire) was extended to incorporate the enhanced disturbance mapping, and results from the habitat selection and buffer analyses.
- Assessment of Current Conditions: the probability that current conditions could support self-sustaining caribou populations was assessed using indicators of two ecological components of sustainability - stable or positive population growth and long term persistence. The indicators were quantified using a non-spatial population model and probabilistic decision-analysis tool, and integrated through a set of decision rules. Certainty in the result for each range was evaluated based on the quality and consistency of information available.
- Representation of Future Conditions: a simple habitat dynamics model was developed to better understand how future changes in habitat conditions within a range could affect the sustainability of boreal caribou populations. The model included natural disturbance and natural recovery but did not attempt to model future anthropogenic disturbance.
- Determination of Range-Specific Disturbance Thresholds: a methodology for establishing risk-based, range-specific disturbance thresholds based on best available information was developed.
Description of Critical Habitat
The description of boreal caribou critical habitat provided in this report for each range consists of the following four components:
- The delineation and location of the range, and certainty in range delineation.
- An integrated risk assessment based on multiple lines of evidence from three indicators, and application of hierarchical decision rules to evaluate the probability that current conditions on a range will support a self-sustaining population. The result is expressed as a likelihood statement relative to achieving the recovery objective.
- Information to support the identification of disturbance-based management thresholds. Specifically, a consistent methodology for deriving such thresholds is provided, along with examples of their potential application, and discussion of their interpretation relative to the criteria and indicators evaluated.
- A description of the bio-physical attributes, defined as the habitat characteristics required by caribou to carry out life processes necessary for survival and reproduction. The results from the habitat selection analyses (this report) and published reports were used to summarize key bio-physical attributes by ecozone.
The related goals of assessing the ability of ranges to support self-sustaining populations, and establishment of management thresholds for disturbance, must acknowledge uncertainties arising from the availability and reliability of information about current population condition, as well as how populations might respond to additional and often interacting stressors. The probabilistic approach applied in this assessment explicitly incorporated the effects of uncertainties and data quality in the assessment process. This approach is consistent with the concept of adaptive management, which expresses probable outcomes as hypotheses. Monitoring and evaluation of realized outcomes informs adaptations of management strategies over time.
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