Scientific Assessment to Inform the Identification of Critical Habitat for Woodland Caribou, Boreal Population, in Canada - 2011 Update: Results
The description of boreal caribou critical habitat consists in the delineation and location of the range and the certainty in range delineation (Section 3.1), the integrated range assessment (Section 3.2), information supporting the identification of disturbance-based management thresholds (Section 3.3), and a description of the key bio-physical attributes (Section 3.4). Factsheets regrouping range-specific results and supplemental information for critical habitat identification have also been developed (Appendix 7.10).
Substantial changes to the delineation of boreal caribou ranges have been made since the 2008 Scientific Review, particularly in the Northwest Territories (NT), Alberta, and Ontario (Figure 13). Compared to the 2008 Scientific Review, a total of 57 ranges are still currently recognized by jurisdictions in Canada. However, significant changes occurred, with the number of ranges either decreasing (NT) or increasing (Ontario) in some jurisdictions. Table 10 summarizes the distribution of boreal caribou ranges within the 3 range delineation categories.
Based on the information provided to EC, the main changes to boreal caribou ranges in Canada since the Scientific Review 2008 are:
- Ontario: the province has identified preliminary population ranges as part of the implementation of the Ontario’s Woodland Caribou Conservation Plan (OMNR n.d.). The province reported nine ranges for the update, compared to four in the Scientific Review 2008.
- Northwest Territories: Although the jurisdiction considered that boreal caribou within NT (extending in northern Alberta) consist in a large continuous population, large wildfires have occurred in the central part of the range and a recent study suggests that this discontinuity in habitat has created two, temporary isolated, subpopulations (Nagy et al. 2011). As such, the ranges of the sub-populations were used for the purpose of the current assessment.
- British Columbia: given additional information collected by the province, the Prophet and Parker ranges are no longer considered as "core" habitat, but rather a fair delineation of each local population.
- Alberta: The range known as Deadwood has been merged with the Chinchaga range. Also, various changes to existing range boundaries were made.
Results obtained from applying the methodology for the risk assessment described in Section 2.4.6.1 are presented in Table 10.
Of the 57 currently delineated ranges in Canada, 17 (30%) were assessed in the "self-sustaining" (SS) category, 7 (12%) in the "not self-sustaining/self-sustaining" (NSS/SS) category, and 33 (58%) in the "‘not self-sustaining" (NSS) category. The repartition of likelihood statements for each self-sustaining outcomes was as follow:
- For the 17 self-sustaining ranges: 3 were assigned to the "very likely", and 14 to the "likely" categories;
- For the 33 not self-sustaining ranges: 14 were assigned to the "very unlikely", and 19 to the "unlikely" categories;
- The 7 ranges assessed as NSS/SS were assigned to the "as likely as not" likelihood statement.
Results from the integrated risk assessment were also mapped in Figure 14. The distribution of the assessment outcomes demonstrates an East-West gradient of self-sustainability, with higher proportion of ranges not self-sustaining in the western portion of the caribou distribution. With the exception of Red Wine Mountain, the ranges in the eastern portion assessed as "not self-sustaining" are all in the southern limit of caribou distribution. The underlying causes include small, highly disturbed, isolated populations (Val d’Or, Charlevoix), rapid population decline (Kesagami), and high total disturbance (Sydney, Pipmuacan).
Table 11. Results for the Integrated Risk Assessment and for the supporting indicators assessing boreal caribou ranges based on two criteria of self-sustaining local population: 1) stable or positive population growth over the short term (≤ 20 years) estimated using Pr (λ ≥ stable), and 2) persistence over the long-term (≥ 50 years) estimated using the indicator of quasi-extinction (Pr (N≥Qext)).
Figure 14. Integrated Risk Assessment for boreal caribou ranges in Canada. Self-sustainability outcomes (i.e., self-sustaining, not self-sustaining, or not self-sustaining/self-sustaining) for each range were assigned based on the likelihood statement describing the range’s capacity to maintain a self-sustaining local population of boreal caribou.
The methodology described in Section 2.4.6.2 was implemented for a sample of ranges to demonstrate the potential application and interpretation of a risk-based framework to support recovery planning, including but not limited to the use of management thresholds. As indicated in Section 2.4.6.2 the consideration of management threshold is informed by science but determined by managers in accordance with decisions regarding the acceptable level of risk. To illustrate the approach, the level of acceptable risk necessary for threshold determination was set concordant with the probability interval from the integrated risk assessment associated with a likely outcome, which corresponds to the weight of evidence indicating that a range was likely to support a self-sustaining population, and interpreted as relatively low risk (see Figure 11). sThe interval includes a range of estimated probabilities from greater or equal to 60 to 90%, corresponding to a total range-level disturbance values from 10 to 35%, inclusive of a 500 m buffer on all anthropogenic disturbances. The upper end of the disturbance interval was imposed as the “disturbance threshold” for demonstration purposes (Figure 15).
Figure 15. Intervals of disturbance reflecting relative levels of risk associated with achieving a desired outcome of maintaining range conditions necessary to support a self-sustaining population of boreal caribou. The assignment of “Disturbance Threshold” is for illustrative purposes only.
Three caribou ranges were evaluated using the stepwise approach summarized in Figure 12: West-side Athabasca River, Alberta; Smoothstone-Wapawekka, Saskatchewan, and North Interlake, Manitoba.
West-side Athabasca River: Alberta
At 69% total disturbance (Figure 16a), this range falls in the high risk category and is unlikely to support a self-sustaining population based on habitat condition. This level of disturbance is also well in excess of the “disturbance threshold”. The reported average population trend over five years is rapidly declining (λ = 0.92; last reported value 0.78). While the reported population size of 204-272 indicates high potential for persistence, given a low risk of quasi-extinction under good habitat and population conditions (Pr (N≥Qext) = 0.80-0.83), the projected quasi-extinction risk based on current population and habitat conditions indicates the population is highly unlikely to persist over the next 50 years.
Assessment of potential future scenarios (Figure 16b) indicates some potential for the range condition to improve through passive recovery of presently disturbed areas. However, it could take between 51 and 100 years for the range to recover to a condition consistent with the low risk category (also for illustrative purposes, the disturbance threshold), assuming no new anthropogenic or natural disturbances. Given the very high risk of local extirpation under current conditions, and natural recovery rates that are insufficient to offset short term extinction risk, the management scenario for this population suggests that active recovery efforts are required to reduce risk.
Monitoring of population condition should continue to assess response to recovery actions and associated changes in range condition.
Figure 16. Current disturbance (a) and potential future population and range conditions (b) on the West-side Athabasca River caribou range.
Smoothstone-Wapaweka: Saskatchewan
At 33% total disturbance (Figure 17a), the range falls in the low risk category, which suggests it is likely to support a self-sustaining population based on habitat condition. The “disturbance threshold” has not been surpassed. However, the reported population trend is "declining". In addition, while the reported population size of 700 indicates a very low risk of extinction under good habitat and population conditions (Pr(N≥Qext) = 0.94), the projected quasi-extinction risk inferred from population trend under the observed habitat conditions is estimated at 0.38, indicating that the population faces high risk, and is unlikely to persist above a critical number of 10 individuals if current conditions are maintained. Visual inspection of mapped disturbance on the range (Figure 19a) suggests the highly dispersed nature of the disturbance, in conjunction with significant water bodies (not illustrated here), have contributed to a paucity of large, undisturbed areas within the range.
Assessment of future scenarios (Figure 17b) indicates potential for range condition to be improved within the low risk category through passive recovery of presently disturbed areas, 17% of which (47% of the total) consist of recent burns (≤ 40 years). While the likelihood of persistence is low if current conditions were maintained, natural recovery appears sufficient to offset short term extinction risk, assuming other threats are managed. Although the range is currently below the “disturbance threshold”, the management scenario for this population is for conservation of remaining undisturbed habitat, to avoid increases in risk.
Monitoring should be implemented to confirm expected improvements to population condition in association with recovery of disturbed areas.
Figure 17. Current disturbance (a) and potential future population and range conditions (b) on the Smoothstone-Wapawekka caribou range.
North Interlake: Manitoba
At 17% total disturbance (Figure 18a), the range falls in the low risk category, which suggests it is likely to support a self-sustaining population based on habitat condition. The “disturbance threshold” has not been surpassed. However, the reported population size of 50-75 indicates a moderate risk of local extinction under good habitat and population conditions (Pr (N≥Qext) = 0.52-0.61), due to small population size.
Assessment of future scenarios (Figure 18b) indicates that range condition is likely to remain within the low risk category. The likelihood of persistence will remain uncertain and continue to represent moderate risk unless population size increases. Although the range is currently below the “disturbance threshold”, the risk associated with the small population size suggests a cautious management approach to consideration of additional disturbance to avoid increasing risk. The location of the range on a peninsula, surrounded by water on 3 sides (not illustrated here) suggests isolation that also contributes to risk.
Monitoring should be implemented to confirm population condition and evaluate response to any changes within the range.
Figure 18. Current disturbance (a) and potential future population and range conditions (b) on the North Interlake caribou range.
For purposes of illustrating application of the risk-based framework to thresholds interpretation, it was necessary to assign a isturbance-based management threshold. It is clear from the examples presented that there is considerable utility in the systematic approach to building on the integrated risk assessment to more fully interpret potential outcomes and guide recovery planning, through enhanced understanding of range-specific attributes. This is an objective process that does not require the determination of management thresholds. However, application of disturbance-based management thresholds provides specific direction relative to management objectives and acceptable risk.
In the examples presented, the disturbance threshold was commensurate with the disturbance interval representing a likely outcome with respect to maintaining a self-sustaining population. The selection of higher or lower thresholds would have different interpretations with respect to likelihood of achieving the recovery objective. The results also suggest there may be considerable value in identifying graduated thresholds, to support a variety of conservation and restoration actions given different management scenarios and range-specific circumstances. Indiscriminate application of a single, fixed threshold may not achieve desired outcomes, particularly in the absence of range-specific interpretation.
| Scale of selection | Description |
|---|---|
Broad scale |
Upland tundra dominated by ericaceous shrubs (Ericaceae spp.), lichen, grasses and sedges. |
Calving |
String bogs, treed bogs, small open wetlands (<1 km²) and large muskeg.1, 3 |
Post-calving |
Forested wetlands.1 |
Rutting |
Open wetlands.1 |
Winter |
Forested areas are used in years of low snow accumulation, otherwise winter habitat selection reflects general avoidance of deep snow, including use of tundra habitat at higher elevations in mountainous regions and bogs along lakes or oceans.5, 6 |
Travel |
Connectivity between selected habitat types important given reported patterns of movement among caribou. |
Avoidance |
Avoidance of roads and areas recently burned (< 40 yrs).9 |
1 Brown et al. (1986);
2 Courtois et al. (2004);
3 Brown and Theberge (1985);
4 Schmelzer et al. (2004);
5 Brown and Theberge (1990);
6 Schmelzer et al. (2004);
7 I. Schmelzer (pers. comm.);
8 Schaefer et al. (2000);
9 Appendix 7.3.
| Scale of selection | Description |
|---|---|
Broad scale |
Habitats selected generally to reduce predation risk.1 |
Calving |
Mature conifer stand with and without lichens and wetlands. Preference for higher altitudes compared to habitat use during other periods.1 |
Post-calving |
Fens, bogs and lakes.5 |
Rutting |
Wetlands and conifer stands with lichen. Mature and regenerating conifer stands are also used, albeit to a lesser degree.1 |
Winter |
Dense and mature conifer forests with lichens and wetlands.1, 5 |
Travel |
Movements greatest in fall/winter when caribou transition from calving to winter habitat.8 |
Avoidance |
Avoid herbaceous areas and areas burned within 40 yrs.4 |
1 Courtois (2003);
2 Brown (2005);
3 Magoun et al. (2005);
4 Appendix 7.3;
5 Pearce and Eccles (2004);
6 Brokx (1965);
7 Brown et al. (2007);
8 Brown et al. (2003).
The Boreal Shield ecozone has been divided into 5 sub-regions (Tables 16-20) as per EC 2008 (Appendix 7.3):
| Scale of selection | Description |
|---|---|
Broad scale |
Conifer-feather moss forests on poorly-drained sites and mature conifer uplands with abundant terrestrial lichen.1, 2 |
Calving |
Open wetlands, peninsulas and islands for calving in northeastern Québec.4 |
Post-calving |
Open and forested wetlands and continued use of peninsulas and islands in northeastern Québec.4 |
Rutting |
Open wetlands selected in northeastern Québec.4 |
Winter |
Forested wetlands selected in Labrador and northern Québec.3 Some use of upland-tundra for loafing3 |
Travel |
Caribou move greater distances during the rutting season.4 |
Avoidance |
Avoid deciduous and mixed forests, jack pine forests less than 40 yrs old and heaths without lichens all year round.6, 7, 8 |
1 Arsenault et al. (1997);
2 Courtois (2003);
3 Appendix 7.3;
4 Brown et al. (1986);
5 Bergerud (1972);
6 Crête et al. (2004);
7 Courbin et al. (2009);
8 Courtois et al. (2007).
| Scale of selection | Description |
|---|---|
Broad scale |
Late seral-stage black spruce-dominated lowlands and jack pine-dominated uplands.1 |
Calving |
Open, medium-closed conifer forests.3 |
Post-calving |
Not available. |
Rutting |
Dense and open mature conifer forests of spruce, tamarack, jack pine and young conifer forests between 30 to 50 yrs old.3 |
Winter |
Charlevoix caribou select open stands of balsam fir, balsam fir-black spruce, black spruce, black-spruce-tamarack and jack pine stands older than 70 yrs. Dry bare lands, 30 to 50 yrs old stands of balsam fir or fir-black spruce, as well as 50 yr old jack pine stands, and arboreal and terrestrial lichens are also selected.3, 5 |
Travel |
Not available. |
Avoidance |
1 Duchesne et al. (2000);
2 Appendix 7.3;
3 Lefort et al. (2006);
4 Schaefer and Pruitt (1991);
5 Sebbane et al. (2002).
| Scale of selection | Description |
|---|---|
Broad scale |
Late seral-stage black spruce-dominated lowlands and jack pine dominated uplands.1, 2, 3 |
Calving |
Open canopies of mature black spruce and mesic peatland with ericaceous species for calving are selected for calving in the Claybelt region.3 |
Post-calving |
Not available. |
Rutting |
Not available. |
Winter |
Large areas of contiguous forests dominated by black spruce.8 |
Travel |
Not available. |
Avoidance |
Avoid recently downed woody debris, dense shrubs and larch during the calving season in the Claybelt region.3 |
1 Arseneault et al. (1997);
2 Courtois et al. (2003);
3 Lantin et al. (2003);
4 Bergerud (1985);
5 Vors (2006);
6 Wilson (2000);
7 Appendix 7.3;
8 Brown et al. (2007)
| Scale of selection | Description |
|---|---|
Broad scale |
Mature conifer uplands and conifer/tamarack dominated lowlands.1, 2, 3, 4 |
Calving |
Forested wetlands/treed bog, old burns, sparse conifer and dense spruce selected in areas of northwestern Ontario.9 |
Post-calving |
Peatland with forested islands, islands, and shorelines selected during summer.10, 12 |
Rutting |
Semi-open and open bogs and mature conifer uplands selected during rutting. Terrestrial lichens and arboreal lichens, sedges and bog ericoids (Andromeda glaucophylla, Chamaedaphne calyculata, Kalmia polifolia, Ledum groenlandicum) are important sources of forage.5 |
Winter |
Mature coniferous stands.10, 14 |
Travel |
Caribou in Ontario travel mainly in conifer forests, avoiding open habitats (e.g., lakes, disturbed areas, etc.) when migrating from summer to winter habitat.2 |
Avoidance |
Shrub-rich fens are avoided during calving.9 |
1 Bergerud et al. (1990);
2 Ferguson and Elkie (2004a);
3 Ferguson and Elkie (2004b);
4 Vors (2006);
5 Darby and Pruitt (1984);
6 Schaefer (1988);
7 O’Brien et al. (2006);
8 Appendix 7.3;
9 Hillis et al. (1998);
10 Armstrong et al. (2000);
11 O’Flaherty et al. (2007);
12 Cumming and Beange (1987);
13 Pearce and Eccles (2004);
14 Martinez (1998);
15 Ferguson and Elkie (2005);
16 Antoniak and Cumming (1998);
17 Stardom (1975);
18 Schaefer and Pruitt (1991);
19 Cumming and Hyer (1998);
20 Schindler et al. (2007).
| Scale of selection | Description |
|---|---|
Broad scale |
Conifer/tamarack-dominated peatland complexes and upland moderate to dense mature conifer forests with abundant lichens.1, 2, 3 |
Calving |
Peatlands, stands dominated by black spruce and treed muskeg all used for calving.5, 6 |
Post-calving |
Wooded lakeshores, islands, sparsely treed rock, upland conifer-spruce and treed muskeg are used in summer.8, 7 |
Rutting |
Dense and sparse conifer and mixed forests.3 |
Winter |
Mature upland spruce, pine stands and treed muskeg.8 |
Travel |
Some males move >100 km during the rutting season.10 |
Avoidance |
Avoid shrub-rich habitats and hardwood-dominated stands.1, 2, 8 |
1 Arseneault et al. (1997);
2 O’Brien et al. (2006);
3 Hillis et al. (1998);
4 Appendix 7.3;
5 Rettie (1998);
6 Hirai (1998);
7 Shoesmith and Storey (1977);
8 Metsaranta and Mallory (2007);
9 Lander (2006);
10 V. Chrichton (pers. comm.);
11 Brown et al. (2000).
| Scale of selection | Description |
|---|---|
Broad scale |
Caribou in Boreal Plains of Alberta select late seral-stage (>50 yrs old) conifer forest and treed peatlands with abundant lichens.1, 2, 3, 4, 5 |
Calving |
Bogs and mature forests selected for calving in Alberta.3, 4 |
Post-calving |
Forest stands older than 50 yrs.11 |
Rutting |
Mature forests.3 |
Winter |
Treed peatlands, treed bog and treed fen and open fen complexes with >50% peatland coverage with high abundance of lichens.15, 16, 17 |
Travel |
Not available. |
Avoidance |
Avoid upland and fen habitats, aspen dominated stands, immature stands and large rivers all year round.3, 4, 6, 9 |
1 Stuart-Smith et al. (1997);
2 Smith (2004);
3 Neufeld (2006);
4 James (1999);
5 McLoughlin et al. (2003);
6 Appendix 7.3;
7 Rettie (1998);
8 Arsenault (2003);
9 Hirai (1998);
10 Dyer (1999);
11 Dalerum et al. (2007);
12 Rettie and Messier (2000);
13 Metsaranta and Mallory (2007);
14 Lander (2006);
15 Anderson (1999);
16 Bradshaw et al. (1995);
17 Anderson et al. (2000).
| Scale of selection | Description |
|---|---|
Broad scale |
Little Smoky population spends the entire year in subalpine and upper foothill regions in upland lodge pole pine, mixed conifer lodgepole pine/black spruce and treed muskeg.1 , 4, 5 |
Calving |
Areas closer to cut-blocks with a high proportion of larch are selected during calving.6 |
Post-calving |
Homogeneous areas of conifer dominated stands.6 |
Rutting |
Not available. |
Winter |
Caribou use areas with a high proportion of larch and pine forests during winter.6 |
Travel |
Not available. |
Avoidance |
Avoid areas with a large proportion of cut blocks.6 |
1 Edmonds (1988);
2 Thomas et al. (1996);
3 Szkorupa (2002);
4 Edmonds (1993);
5 Johnson (1980);
6 Neufeld (2006);
7 Saher (2005).
| Selection Scale | Description |
|---|---|
Broad scale |
In NWT caribou prefer open coniferous habitat in all seasons of the year and in the Dehcho prefer using forest stand ages of 100 years or older.1 |
Calving |
Open conifer forests, tussock tundra, low shrub, riparian, and recent burns in northern extreme of the NWT range.4 |
Post-calving |
Open coniferous forests with abundant lichen, low shrub, riparian, tussock tundra, sparsely vegetated habitat, and recent burns in the northern extreme of the NT range.4 |
Rutting |
Open coniferous and mixedwood forests, low shrub, riparian tussock tundra, and recent burns in northern extreme of NWT range.4 |
Winter |
Open coniferous forest with abundant lichen and riparian areas.1, 2, 4 |
Travel |
In NWT some female caribou have little fidelity to calving areas between years, especially in the northern portions of the range, while others show considerable fidelity over successive (2-3) years.5, 6 |
Avoidance |
Avoid edge habita.8 |
1 Nagy and Larter, unpublished data;
2 Culling et al. (2006);
3 McLoughlin et al. (2005);
4 Nagy et al. 2006;
5 Larter and Allaire (2007);
6 Nagy et al., unpublished data;
7 Larter and Allaire (2010);
8 McLoughlin et al. (2005);
9 Dalerum et al. (2007).
| Scale of selection | Description |
|---|---|
| Broad scale | Large patches of spruce peatland and lowland and upland black spruce forests with abundant lichens.1 |
| Calving | Open conifer forests, tussock tundra, low shrub, riparian, recent burns and south and west aspects.2 |
| Post-calving | Open conifer forests with abundant lichens, low shrub, tussock tundra, sparsely vegetated habitat, recent burns and west aspects.2 |
| Rutting | Open coniferous and mixedwood forests, low shrub, riparian, tussock tundra, recent burns and west aspects.2 |
| Winter | Open coniferous forests with abundant lichens and riparian habitats.2 |
| Travel | Not available. |
| Avoidance | Avoid closed mixed forests, and water during calving and parts of the winter.2 Avoid closed spruce forests and conifer forests without lichens in mid-winter.2 Avoid closed deciduous forests year round and avoid mixed forests during post calving and rut. Water is also avoided during the rut.2 |
1 Culling et al. (2006);
2 Nagy et al. (2006)
No information was available for either the Southern Arctic ecozone or Taiga Cordillera ecozone (EC 2008).
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