Scientific Assessment to Inform the Identification of Critical Habitat for Woodland Caribou, Boreal Population, in Canada - 2011 Update: Introduction
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 (COSEWIC) as Threatened (COSEWIC 2002), and added to Schedule 1 of the Species at Risk Act (SARA) in 2003. The listing decision was made on the basis of an “observed, estimated, inferred or suspected population size reduction of ≥ 30% over three generations”. Evidence of continued declines exists for many regions of Canada (EC 2008) and has been well-documented in a number of closely-monitored populations since the 2002 COSEWIC assessment (e.g., ASRD & ACA 2010; BC MOE 2010).
Boreal caribou have evolved with and adapted to the natural disturbance regimes of boreal forest ecosystems that govern the spatio-temporal distribution and availability of habitat. However, habitat loss, reduction in habitat patch size and fragmentation due to land conversion and resource development, and increased predation associated with these changes, have been identified as the main cause of the decline of boreal caribou in Canada (COSEWIC 2002).
Critical habitat is defined as “the habitat that is necessary for the survival or recovery of a listed wildlife species” (SARA S.2). In 2007, Environment Canada (EC) launched a scientific initiative that culminated in a report entitled Scientific Review for the Identification of Critical Habitat for Woodland Caribou (Rangifer tarandus caribou), Boreal Population, in Canada (EC 2008; hereinafter referred to as 2008 Scientific Review), which was intended to identify boreal caribou critical habitat in the species’ recovery strategy. In that exercise, "survival and recovery" of boreal caribou was taken to mean the conservation of self-sustaining boreal caribou local populations (i.e., a stable or increasing population that was large enough to persist without human intervention) throughout their current distribution in Canada. Local population ranges were identified by EC as the relevant scale for the identification of conditions that could support self-sustaining populations, and thus for the identification of critical habitat.
A component of the 2008 Scientific Review was the development of a framework, or logic model, for the identification of boreal caribou critical habitat. It was anchored by analysis and synthesis of available data and published scientific information on population and habitat ecology, including boreal caribou population distribution, trends, habitat use, and conditions for self-sustainability. The approach was further grounded in an adaptive management framework, where uncertainties and knowledge gaps could be systematically reported and addressed, and new information considered at each iteration of the planning cycle. The implementation of the framework was bound by a set of guiding principles reflecting the ecological, legal, and scientific underpinnings of the exercise.
The distribution of boreal caribou in Canada (extent of occurrence and the spatial extent of the analysis) was comprised of 57 identified boreal caribou local population ranges or units of analysis. Each range was assessed to determine if the current conditions were sufficient to support a self-sustaining population based on information about current population (size and trend) and habitat (level of anthropogenic and natural disturbance) conditions. The outcome of the assessment was the classification of ranges according to their capacity to maintain self-sustaining populations and consideration of the influence of range-specific conditions relative to critical habitat identification.
The 2008 Scientific Review established a scientific basis for the assessment of critical habitat (i.e., habitat conditions required for recovery of boreal caribou under SARA). To support refinement of these analyses and resultant identification of critical habitat, EC identified key areas that required further exploration:
- implications to critical habitat identification of variation in range delineation approaches across jurisdictions;
- relative impact of different disturbance and habitat types and their configuration on range assessment and critical habitat description;
- identification of disturbance-based management thresholds (hereinafter referred to disturbance thresholds) for self-sustaining local populations; and
- influence of future range conditions on disturbance thresholds given the dynamic nature of disturbance within a given range.
The purpose of this report is to address these information needs using the best available scientific information to inform the identification of critical habitat for boreal caribou. EC has also completed an independent process 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.
In August 2007, EC launched an expert, science-based review of the state of knowledge of boreal caribou critical habitat, with the mandate to develop a consolidated, scientifically defensible identification of critical habitat, and/or a valid Schedule of Studies. The results of these activities led to the publication of the 2008 Scientific Review.
The report was instrumental in establishing a transparent and repeatable science-based process to inform the identification of critical habitat for boreal caribou. In that report, an analytical approach was developed and applied to assessing the probability that current population (size and trend) and habitat conditions (levels of habitat undisturbed by anthropogenic activities and forest fire) within each boreal caribou range in Canada were sufficient to support self-sustaining populations of boreal caribou. The general conclusions included:
- Critical habitat for boreal caribou is most appropriately identified at the scale of boreal caribou ranges, and expressed relative to the probability that the range conditions are sufficient to support a self-sustaining local population.
- Range is a function of the extent and condition of habitat, where habitat includes the suite of resources and environmental conditions that determine the presence, survival and reproduction of a population.
- The assessment assigned one of three outcomes for self-sustaining local populations for each of the 57 recognized local populations or units of analysis for Boreal caribou in Canada: Current Range adequate, Current Range and Improved Conditions necessary, or Current Range and Consider Resilience.
- Critical habitat identification for boreal caribou is a hierarchical process with considerations across multiple spatial and temporal scales. Further elaboration of critical habitat outcomes at spatial scales finer than the range, over specified time frames, may be achieved through spatial population viability analysis linked with dynamic landscape modelling.
- Acknowledging that current knowledge and the dynamic nature of landscapes impart uncertainty, the 2008 Scientific Review findings 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).
Of the 57 local population ranges or unit of analysis, 30 were assessed as "Not Self-Sustaining" (integrated probability of less than 0.5), 17 as "Self-Sustaining" (integrated probability of greater than 0.5), and 10 as either "Self-Sustaining" or "Non-Self-Sustaining" (integrated probability equal to 0.5).
In 2009, EC launched a second science assessment to augment the 2008 Scientific Review, with new information and analyses to inform the identification of critical habitat. EC again engaged experts on caribou ecology and/or related scientific areas who provided advice, guidance, and reviews at key stages during the development of this report.
1 It should be noted that the terminology used to describe the different types of geographical units used in the assessment was modified from the 2008 Scientific Review, as described in Section 2.4.2.
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