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Caribou Strategy Report
TABLE OF CONTENTS EXECUTIVE SUMMARY SECTION I: INTRODUCTION
SECTION II: IMPACTS OF FOREST HARVEST PATTERNS, ACCESS AND PREDATION ON CARIBOU
SECTION III: INTERIM STRATEGY FOR EASTERN CARIBOU
SECTION IV: INTERIM STRATEGY FOR ITCHA-ILGACHUZ CARIBOU
SECTION V: INTEGRATION ISSUES RELATED TO CARIBOU
SECTION VI: CONCLUSIONS REFERENCES
Introduction
Impacts of Forest Harvest Patterns, Access and Predation on Caribou
1) maintaining suitable habitat 2) controlling access 3) managing predation (if necessary)
Interim Strategy For Eastern Caribou
Interim Strategy For Itcha-Ilgachuz Caribou
CCLUP Integration Issues Related to Caribou The Caribou Strategy Committee met five times with the Short Term Timber Availability (STTAA) Committee to address integration of the two strategies.
Outstanding, unresolved issues with the STTAA include the following:
Conclusions
Mountain caribou in the eastern portion of the Cariboo Region are of provincial significance and are a species at risk. Of thirteen mountain caribou subpopulations identified in southern British Columbia, the three subpopulations in the eastern part of the Cariboo are ranked amongst the highest provincially in terms of biological criteria (including viability and being a part of the central, core mountain caribou range). The 300 caribou in this area represent 12% of the provincial mountain caribou population.
The Itcha-Ilgachuz caribou population, located in the western portion of the Cariboo region, is a provincially significant caribou population as it has the highest density of any caribou population in southern British Columbia. The 1500 caribou in this area represent 8% of the total woodland caribou population in B.C.
This report presents the interim strategies for the Eastern and Itcha-Ilgachuz caribou populations developed by the Caribou Strategy Committee (see Appendix A for Terms of Reference), key issues specific to strategy development, caribou research and inventory requirements and issues related to caribou and integration with other CCLUP strategies.
Cariboo-Chilcotin Land-Use Plan Guidance
The Cariboo-Chilcotin Land Use Plan provides the following guidance in regard to caribou:
The Cariboo-Chilcotin Land Use Plan requires the development of Eastern and Itcha-Ilgachuz (Western) caribou strategies. The major requirements are the development of a research and inventory program that will lead to the development of an integrated management approach. An area has been identified for both caribou populations that is deferred in the short term (until after 1999), therefore no harvest is necessary in the first 5 years. In the future, 35% of each area will be available for timber harvest under the modified harvest category using more sensitive harvesting practices that maintain caribou habitat values.
Interim strategies, identifying no harvest and modified harvest areas within each existing deferral area, have been developed. The interim strategies also identify the most suitable timber management practices to maintain some caribou habitat values, based on present knowledge. There will need to be an assessment of the interim strategies within four years, once further research and inventory is completed, to assure that the strategies are realistic in meeting the CCLUP objective of maintaining habitat values for caribou.
Implications Of CCLUP For Caribou It is imperative that everyone has a clear understanding of decisions and future expectations in relation to maintenance of caribou habitat and populations. The following points within the CCLUP Implementation Report must be appreciated in order to put caribou management in perspective.
The implications of CCLUP to caribou populations in the Cariboo-Chilcotin is that these populations will be at increased risk of decline or complete loss in some areas. Critical winter ranges of both the eastern and Itcha-Ilgachuz populations are primarily located outside of protected areas and will be impacted by logging development. Sensitive calving habitats will be threatened through increased access development. Figure 1 illustrates the relative risk to Itcha-Ilgachuz Caribou of CCLUP decisions and options in relation to the compromise Moderate Risk Option determined by the Western Caribou Working Group. The risk to caribou will be increased in a cumulative manner with each land use decision that deviates negatively from the moderate risk option. A similar risk analysis and illustration is shown for eastern caribou in Figure 2.
It is important to recognize that the Caribou Strategy Committee is working on developing caribou strategies that will follow the CCLUP targets but, in so doing, these strategies will not be ideal for caribou. There will be much uncertainty about the maintenance of caribou habitat, however through research and inventory the caribou strategies will attempt to identify the options with the highest probability of maintaining caribou values, given the constraints of the CCLUP.
Figure 1. Risk analysis for Itcha-Ilgachuz caribou in relation to land use planning issues.
Figure 2. Risk analysis for Eastern caribou in relation to land use planning issues.
SECTION II: IMPACTS OF FOREST HARVEST PATTERNS, ACCESS AND PREDATION ON CARIBOU
Each of these issues will be discussed in the following sections.
Forest Harvest Patterns and Caribou Habitat The initial observation in the 1940’s and 1950’s that caribou were "wilderness" animals, dependent on large intact blocks of mature forest (Edwards 1954) has been validated with recent scientific studies. The early investigators thought that the loss of arboreal and terrestrial lichens was the primary cause of decline or that human disturbance without major habitat changes could precipitate the loss of caribou populations (Klein 1982). More direct mortality factors have been identified as the cause in virtually all recent studies (Bergerud et al. 1984, Seip 1992a).
These factors in order of importance have primarily been 1) predation due to wolves or grizzly bears, 2) poaching or sport hunting or 3) accidental death, mainly in avalanches. Starvation, which would be expected if loss of forage was the primary cause, is virtually unknown from studies on radio-collared caribou. To minimize loss to these mortality factors requires special habitat management at the landscape level. Although winter habitats for caribou must provide adequate forage, it is also important how the habitat is distributed on the landscape.
An anti-predator strategy of caribou is to space out over very large areas so that it is harder for predators to find them. Caribou populations therefore exist at low densities. If the amount of mature forest that caribou can occupy is decreased, then the density of caribou in the remaining stands will be increased, probably resulting in greater predator efficiency. Predator efficiency may also be increased during winter if roads and snowmobile tracks provide easier travel routes for wolves.
As well, logging, like fire, converts mature forest into early successional stages, creating habitat favored by moose. An increase in numbers of moose can support a larger predator population and can result in increased predation pressure on caribou. In southeastern British Columbia, predation pressure on caribou was lower in Wells Gray Park, where caribou were spatially separated from moose (the alternative prey), than in the Quesnel Highland where less spatial separation existed (Seip 1992a). In Ontario, the southern limit of woodland caribou has receded during the last 100 years, coincident with the northern range expansion of white-tailed deer and moose. Wolf predation has been implicated as the major limiting factor of woodland caribou populations in Alaska, the Yukon, western Alberta, and southeastern British Columbia (Gasaway et al. 1983; Farnell and McDonald 1987; Edmonds 1988; Seip 1992a).
These modified habitat requirements have been incorporated into caribou guidelines in Ontario, Manitoba and Alberta. The forests in these provinces are similar to those of the Itcha-Ilgachuz caribou herd which primarily feeds on terrestrial lichens in dry pine and spruce. Habitat conditions of the eastern caribou do not occur in other provinces, but the spatial patterning implications are similar.
As an example, Ontario has adopted the principle of large cutblocks (of up to 10,000 ha) as the primary caribou habitat management technique. These blocks are designed to achieve 3 effects: 1) Minimize fragmentation of unharvested or residual habitat; 2) Create large areas of habitat for the second rotation; 3) Minimize the quality of moose habitat (OMNR 1994). Large blocks of older forest retain lichen, minimize access and do not create new moose forage that would increase wolf populations.
Modified harvest dispersed across the caribou range is a poor caribou habitat management strategy as it will leave few areas undisturbed and will result in maximum access development. Aggregating the modified harvest into specific areas is a far better caribou habitat management strategy because this will keep large blocks of caribou habitat intact (undisturbed), thereby minimizing the overall impact on caribou and caribou habitat. Furthermore, this approach allows for a better scientific evaluation of the modified harvest areas to determine whether suitable habitat for caribou can be maintained. For these reasons, the Caribou Strategy Committee has chosen the latter approach for locating modified harvest areas within caribou range.
The risk of illegal hunting and human disturbance of caribou is increased with the development of vehicle access. Development of access over broad areas can further increase the risk of high disturbance levels, displacement of caribou due to snowmobiling activity, poaching and greater wolf predation (wolves have increased mobility, and therefore greater efficiency, on road networks, particularly if roads are plowed and packed). Another potential impact of improved access in the winter range, is corresponding improved access to the summer calving range and increased risk of disturbance by humans during calving. Calving areas are the most sensitive of all habitats for caribou, and in some cases have been included in protected areas. Activity in the surrounding area can still have negative impacts and must be carefully managed.
The interim caribou strategy partially addresses access management concerns by locating modified harvest in large, aggregated areas. If followed, this strategy will minimize access development across the entire caribou winter range, thereby reducing the overall impact of access development on the caribou populations. In addition to this broad-scale, landscape approach to address access concerns, the Caribou Strategy Committee recommends the following access measures where timber harvesting proceeds within caribou range:
Another access issue specific to the Itcha-Ilgachuz herd is the need to ensure human activity is minimized on the caribou calving grounds during spring and summer. During calving, caribou require undisturbed mountainous terrain where they can distance themselves away from other prey and predators. As caribou cows with new born calves are concentrated in the alpine within the confines of the Itcha-Ilgachuz Provincial Park, management of human activity adjacent and within this area during this crucial time period will be essential if increases in calf mortality are to be minimized. The Itcha-Ilgachuz caribou population is a provincially significant caribou population as it has the highest density of any population in southern British Columbia. Maintaining undisturbed caribou calving range with minimal access will be essential for meeting provincial caribou objectives.
In the Cariboo, wolf populations are sustained by a variety of prey species including moose, caribou, mule deer, mountain sheep and mountain goat. As a multiple prey - predator system exists it is possible for wolf numbers to remain relatively high even if predation (or human harvest) has drastically reduced one of the prey species. Caribou are extremely vulnerable to wolf predation compared to most other ungulates (Seip 1991). Caribou usually occur at much lower densities than either moose or deer and occupy very large home ranges. They do not use escape terrain as efficiently as mountain sheep or mountain goats and they have a low reproductive rate as compared to moose or mule deer. Therefore, caribou are usually the most vulnerable species in a multiple prey - predator system, the first to decline and the last to recover (Seip 1991).
Strategies such as seasonal migrations of caribou to alpine areas and habitat segregation between different ungulate species allow caribou to coexist through spatial separation from wolves and alternate prey (Bergerud et al. 1984; Seip 1990). However, changes to habitat through timber harvesting or fire, which enhance moose populations may negatively effect caribou populations. Seip (1992b) suggests wolf predation can eliminate caribou from areas where the wolf population is sustained by other prey species because there is no negative feedback on the number of wolves as caribou decline in numbers. Wolves can persist on moose or deer as they drive caribou populations to extinction. As predation and human harvest are usually important limiting factors to caribou populations, they can respond quickly to changes in harvest rate or to the use of wolf control (Gasaway et al. 1983; Bergerud and Elliot 1986 and Farnell and McDonald 1988). As such, curtailment of hunting and implementation of predator control programs may, under circumstances of steep population decline, become necessary to ensure the maximum probability of maintaining eastern and Itcha-Ilgachuz caribou.
SECTION III: INTERIM STRATEGY FOR EASTERN CARIBOU
The Cariboo-Chilcotin Land Use Plan recognizes that mountain caribou in the eastern portion of the Cariboo Region are of provincial significance and are a species at risk. Maintaining habitat values for mountain caribou has been identified as an overriding objective within the plan.
The mountain caribou population occurs from Prince George to the U.S. border with the regional population in the Quesnel Highland and Cariboo Mountains. Continuous, extensive high elevation caribou winter ranges occur on rounded subalpine mountain tops throughout the Quesnel Highland. Within the more rugged mountainous terrain of the Cariboo Mountains high elevation caribou winter ranges are present but are more restricted and discontinuous in nature. Figures 3 and 4 show areas used in summer and winter based on existing radio telemetry information.
The population once was much larger and herds roamed as far west as Horsefly. These herds largely disappeared as the area became settled and developed. The remaining population in the eastern mountains then declined during the mid-1980’s soon after the initiation of logging in the area. This recent decline has been linked to high levels of wolf predation but the population now appears to have stabilized at approximately 200-300 animals. There is a risk that further logging within caribou habitat areas will increase the wolf population and increase predation rates on caribou if conventional logging practices are utilized. This is because with conventional harvest practices understory shrub and forb production is enhanced in early seral stages, consequently enhancing moose productivity in the area. Higher moose population levels in these areas will result in a larger wolf population. Logging also creates access which can contribute to higher predation, harassment and poaching.
Most of the winter range habitat for eastern caribou is located outside of protected areas and will be subject to logging development. Herds that summer in higher elevation parks will also be at increased risk with logging development because the wintering areas that support these caribou are located outside parks. During the 1980’s extensive areas of important habitat for caribou, generally above 1500 meters, were deferred from timber harvesting in the short and medium terms. The CCLUP has established that 65% of the forest land base within these previously deferred areas will not be available for timber harvest and that 35% will be available under modified harvesting practices. The current deferrals will remain in place until after 1999 when the caribou strategy has been completed and has produced satisfactory integrated resource management solutions. In addition, the CCLUP has established that provisions of the Forest Practices Code will be applied to manage lower elevation habitats including winter range and travel corridors.
CCLUP Targets for Eastern Caribou The CCLUP defines timber harvest targets for the polygons that eastern caribou inhabit by percentages that translate into areas (in hectares) as indicated in Table 1.
Table 1. Summary Of Eastern Caribou CCLUP Targets By Polygon
The CCLUP caribou targets for no harvest and modified harvest by polygon were followed in determining an interim strategy for locating modified harvest that would have least impact on caribou. At the landscape level, the identification of modified harvest areas for eastern caribou utilized the following criteria:
Following these criteria, a detailed assessment of the impacts of proposed logging areas (from the STTAA proposal) on Eastern caribou was made by landscape unit at the request of the IAMC Integration Committee (Table 3).
Figure 5 depicts one option (Option A) for the location of the 35% modified harvest (35% of the forested land base) that would have least impact on caribou habitat and meet individual polygon targets. Generally the no harvest and modified harvest areas identified in Figure 2 are close to the CCLUP targets for eastern caribou (see Table 1 and Table 2). The intent of the Caribou Strategy Committee is to refine the size of these areas to meet the CCLUP targets exactly once the area of the productive forest land base has been confirmed.
Table 2. Eastern Caribou Strategy Interim Map Area (Option A) Summaries By Polygon For Caribou No Harvest and Modified Harvest Areas
Figure 6 depicts a second option (Option B) for locating the 35% modified harvest if individual polygon targets were relaxed and the caribou no harvest and modified harvest targets were applied within the deferral area independent of individual polygon targets. This option would concentrate the modified harvest in a geographical area that is utilized by one herd of caribou (Barkerville sub-population) rather than dispersing the harvest throughout the habitat of all three sub-populations that occur in the eastern part of the region. Although this approach increases the risk for this one herd of 30-40 caribou, the risk to the rest of the population would be greatly reduced. Also, this approach would allow for the modified harvest stand level prescription to be tested over the majority of the range of one herd. Over time, this would allow us to better understand whether the prescription actually is maintaining the habitat values that we hope it will. In the other option (following individual polygon targets), caribou may continue to survive in the short term by avoiding the areas of modified harvest. If this is the case it will not be immediately clear whether the prescription is actually maintaining caribou habitat as mandated by the land use plan. Although this second option does not meet individual polygon targets for caribou, we believe it does follow the spirit of the plan in that overall targets for eastern caribou are still met. Therefore, Option B is the preferred option recommended by the Caribou Strategy Committee.
At the stand management level, the Caribou Strategy Committee has used the best information available at this time to recommend a suitable integrated management harvesting approach for eastern caribou. Further research is required to refine this methodology over the next four years. Group selection involving 33 percent volume removal with long cutting cycles (80 years) is the most promising stand level approach. This translates to an equivalent of an extended rotation of 240 years to manage for arboreal lichen and maintain suitable habitat. Larger (selective) cutblocks would also be favorable because this would reduce long term access problems and habitat fragmentation. This silvicultural system relates to the ESSF; a slightly different approach would probably be taken in the ICH.
In the modified harvest areas, the Caribou Strategy Committee recommends the following timber management approach within the first 20 year period:
Issues Specific To Strategy Development
There are several key issues related to development of the interim caribou strategy that are fundamental in determining how well the objective of maintaining caribou is met.
The impacts of forest harvest patterns, access and predation, and options for addressing these impacts, have been described previously in SECTION II.
Rotation Age To Manage Stands For Lichens
To manage for arboreal lichen production in harvested forest stands in the eastern caribou area will require, in effect, a doubling of the rotation to 240 years, with 3 cutting cycles removing 33% gross volume every 80 years.
Group selection with 33% volume removal every 80 years will eventually produce a multi-aged stand made up of 1/3 trees 0 to 80 years, 1/3 trees 81 to 160 years, and 1/3 trees 161 to 240 years of age. The 0 to 80 year old trees will not have significant lichen present. This is clear from looking at lichen distribution on younger trees. The 81 to 160 year old trees will start to have some suitable substrates for lichen so fragments can securely attach and grow. Since lichen is slow growing, trees of this age range have less lichen biomass than older stands. The 161 to 240 year old trees will have the substrates necessary for lichens and will be in this condition for sufficient time for lichen biomass to build to usable levels for caribou. It is important to remember that these are tree age distributions within stands and do not reflect stand ages as is used to assess seral stage distribution.
A stand managed in this way will have less lichen biomass than an uncut old forest; less than half the biomass given the age distribution of the trees (Table 4). It is our hope that this will still be acceptable habitat for caribou, however, we acknowledge a considerable level of uncertainty about this. We would describe this stand level management as a moderate risk of not maintaining caribou habitat.
Table 4. The estimated proportion of ‘old’ stand lichen biomass in forest stands managed on a 240 year rotation with 33 % volume every 80 years.
Why limit volume removal to 33%? It is our technical assessment that any change to the volume removal per entry is unacceptable both from the caribou habitat and from the windfirmness standpoints.
Higher levels of volume removal would produce corresponding higher rates of lichen loss within the stand. Also, with higher volume removals the growth rate of lichen will probably decline as micro-climatic conditions less favourable to arboreal lichen are created. Additionally, research conducted in the Prince George region has shown that wind scouring of arboreal lichens increases with greater volume removal (Stevenson et al. 1994). Harvest entries of more than 33% volume removal have a much greater risk of blowdown which not only impacts caribou habitat but also harvest opportunities.
Why not shorten the cutting cycle to less than 80 years? It is important to remember that the integrated management prescription being advocated (33% removal every 80 years; 100% volume available in 240 years) is still quite risky and is estimated to reduce the stand lichen biomass to 33-45% of the lichen biomass of an uncut stand (Table 4).
To shorten the cutting cycle to less than 80 years would not allow trees to reach a sufficient age for lichen establishment and remain long enough for lichen to grow to usable quantities. For example, Table 5 shows that reducing the cutting cycle to 70 years (100% volume available in 210 years) would produce a stand with approximately 24-36% of the lichen biomass of an uncut old stand.
Table 5. The estimated proportion of ‘old’ stand lichen biomass in forest stands managed on a 210 year rotation with 33 % volume every 70 years.
Impacts of the 70-30 Zonal Target The recent interpretation of achieving the 70-30 target for the SRDZ has major ramifications to the amount of forest land that can have extended rotations, to manage for non-timber values, while still meeting the timber area-equivalent targets. A doubling of the normal rotation for non-pine stands from 120 to 240 years would be required to maintain some level of arboreal lichens if the forests are to be managed for caribou. As such, the amount of forest area designated for modified harvest for caribou within each SRDZ polygon requires the management approach indicated in column 2 of Table 6. Following the current 70-30 interpretation and assuming that the percent of the forest land within the SRDZ no harvest category is maintained, the amount of forest area that can have double rotations in the eastern caribou SRDZ polygons is limited to the percentages indicated in column 3 of Table 6.
Table 6. Percent of area available to meet caribou habitat requirements with extended (double) rotations (applying the current 70-30 interpretation to Special Resource Development Areas).
Initial comparison suggests that the designated targets can be attained within the Quesnel Lake polygon but there is a slight shortfall within the Boss/Deception and Quesnel Highland polygons. However, other non-timber resource values also likely require forests being managed at extended rotations (ie. biodiversity concerns). Until full integration is completed it is not clear how much of the caribou habitat within the modified harvest category can be managed at double the normal rotation.
Mount Tom
Recent telemetry work has identified several key areas utilized by caribou that are outside the historic deferral area. One area of concern is Mount Tom, northwest of Wells. During the last three years, this area has been consistently used by caribou during summer and winter. At times, as many as half the caribou that are resident to this general area have been observed on this ridge. In contrast, some of the presently deferred area further to the south in the vicinity of Cariboo Mountain has received limited use based on recent telemetry work. The Caribou Strategy Committee proposes that the areas of low use be exchanged for the habitat in the vicinity of Mount Tom, staying within the designated area targets for the two affected CCLUP polygons (Cottonwood and Quesnel Highland).
Early Winter Ranges
Mountain caribou throughout south-east and east-central B.C. utilize low elevation early winter range within the Interior Cedar Hemlock (ICH) biogeoclimatic zone. The CCLUP allows for the delineation and management of mountain caribou early winter range under the provisions of the Forest Practices Code. For mountain caribou in the eastern part of the Cariboo Region, concentrated use in the ICH (in addition to stands within protected areas) has been observed in five areas (hatched areas in Figure 5). Additional areas may be identified in the future. Research in these areas to identify the stand attributes important to caribou is ongoing. Because few logging trials have occurred in the ICH zone, it is difficult at this time to determine appropriate stand management techniques that would maintain caribou habitat values. The Caribou Strategy Committee feels, where possible and compatible with other conservation needs, these areas should be incorporated into Forest Ecosystem Networks or old growth reserve requirements within each Landscape Unit. The forest area within the five identified early winter ranges is approximately 4500 hectares.
Research Requirements to Refine Interim Strategy
The following research is deemed necessary in order to adequately determine caribou habitat requirements and modified harvest regimes that have least impact on caribou habitat and to aid in refining an integrated caribou-forestry solution:
Habitat Use Studies
Macro-Habitat Use
Macro-habitat use can be defined as the broad scale habitat use patterns of caribou at the landscape level. Additional radiotelemetry studies are required on macro-habitat use of eastern caribou in order to better define their annual ranges and seasonal habitat use patterns. Twenty to twenty-five radio-collars will be maintained on caribou in the study area over the four-year period. The radio-collared caribou will be monitored weekly during winter and a minimum of monthly during the rest of the year. Specific objectives of this monitoring include:
GIS analyses will be undertaken to examine radiotelemetry information, timber types, road and trail densities, traffic timing and volume and human use (particularly snowmobiles) patterns in relation to caribou habitat. It should be possible to accomplish most of these analyses in-house on B.C. Environment or Ministry of Forests GIS.
Micro-Habitat Use
Micro-habitat use can be defined as animal habitat use at the stand level of selection. More information is required on micro-habitat use for eastern caribou, particularly in regard to early winter use in the ICH biogeoclimatic zone, to identify what stand level factors are influencing habitat selection. Information on stand level habitat requirements for caribou is required in order to develop detailed management strategies in the Quesnel Highland. Caribou micro-habitat will be measured through the establishment of caribou trailing transects. A more detailed, research working plan will be developed for this work.
Lichen Ecology Work
Lichen ecology in harvested stands has been studied in this region and Prince George for 10 years (Stevenson 1986). Currently the impacts of selective harvest on lichen growth rates is being monitored; this work will continue over the next four years.
Silvicultural Systems Research
Logging of a pilot block to develop a silvicultural system more compatible with the maintenance of caribou habitat occurred in the winter of 1990-91. Initial results of this trial were incorporated into the development of replicated prescriptions. An experiment involving three replicates of three treatments were logged in the winter of 1992-93. An additional site was logged with the same three treatments in the summer of 1992. All treatments involve group selection with 30% removal using feller-bunchers and grapple skidders. The treatments differ in the size of openings created (0.03, 0.13, and 1 ha). Arboreal lichen and a range of other forest attributes are being monitored. A variety of natural and artificial regeneration methods will test silvicultural options in these high elevation forests.
Adaptive Management Research
Adaptive management is being investigated as a component of the overall provincial adaptive management strategy. The silvicultural systems research is a likely candidate but options for adaptive management research trials for eastern caribou need to be further explored. To date, no adaptive management research logging blocks have been identified.
Inventory Requirements to Refine Interim Strategy
The following inventory is deemed necessary in order to adequately determine caribou habitat requirements and modified harvest regimes that have least impact on caribou habitat:
Population Surveys
Annual population surveys are necessary to monitor trends in caribou numbers and to examine seasonal distribution patterns of the herd. This population information will be important to examine in relation to habitat use patterns and predation trends. The annual survey will be conducted in March. A population estimate will be derived from the survey based on a sightability index obtained from collared caribou.
Predation Monitoring
Minimum wolf density estimates have been established for the Quesnel Highland based on current radiotelemetry studies. Further wolf population monitoring is a low priority because much additional effort in collaring and monitoring would be required to get useful data in terms of caribou-wolf interactions. Existing radiocollared wolves will continue to be monitored in conjunction with caribou monitoring but additional radiocollars will not be placed on wolves.
Ecosystem Mapping
There is a need to quantify the distribution, abundance and importance of various habitats to caribou, within the Quesnel Highland, through the use of ecosystem mapping (formerly referred to as biophysical mapping). Some 1:50,000 ecosystem mapping has been initiated in 1995 in the Quesnel TSA portion of the eastern caribou range. In total the mapping work will require the completion of a minimum of ten 1:50,000 ecosystem maps for the area, with an emphasis on caribou and other species at risk. In addition, more detailed ecosystem mapping (1:20,000 scale) will be completed for one watershed within the Quesnel Highland; this watershed will be the Penfold. With completion of detailed 1:50,000 maps, the existing deferral area will be stratified into no harvest and modified harvest zones. Landscape level zoning will take into consideration attributes such as:
Due to the short time frame available to conduct the research necessary to develop an integrated management strategy, and recognizing the need for research trials that will monitor lichens that have a relatively slow growth rate, there is some risk that the final recommended strategy developed within a four year timeframe will not achieve the desired objective over the long term. Given this, it is imperative that the available four year timeframe to conduct the research not be shortened.
This project schedule is based on the fiscal year of the provincial government, with year end on March 31 and the new year starting April 1. Table 7 outlines a 5-year schedule, recognizing that 1995/96 and 1999/2000 do not represent complete years in terms of available timelines for initiation and completion of this work.
Table 7. Project Schedule for Eastern Caribou.
SECTION IV: INTERIM STRATEGY FOR ITCHA-ILGACHUZ CARIBOU
The Itcha-Ilgachuz caribou herd, which consists of approximately 1500 caribou, summers primarily in alpine and subalpine habitat in the Itcha and Ilgachuz Mountains, and winters in low elevation forested areas east of the Itcha Mountains and north of the Ilgachuz Mountains, as well as in windswept alpine habitat in the Ilgachuz and Itcha Mountains (Cichowski 1993). Two components of caribou habitat are essential for ensuring viable caribou populations: summer calving habitat and winter habitat. During calving, caribou require undisturbed mountainous terrain where they can distance themselves away from other prey and predators. During winter, caribou require large areas of suitable habitat (space) which contains adequate forage availability and security cover. Figures 7 and 8 show areas used in summer and winter based on existing radio telemetry information.
Most of the winter range habitat for Itcha-Ilgachuz caribou is located outside of protected areas and will be subject to logging development. Most of the herds summer in high elevation areas that are protected by parks, however, these caribou will be at increased risk with logging development because the wintering areas that support these caribou are primarily located outside of these parks.
CCLUP Targets for Itcha-Ilgachuz Caribou The CCLUP defines timber harvest targets for the polygons that Itcha-Ilgachuz caribou inhabit by percentages that translate into areas (in hectares) as indicated in Table 8.
Table 8. Summary of western caribou CCLUP targets by polygon
The CCLUP targets for no harvest and modified harvest for caribou by polygon were followed in determining an interim strategy for locating modified harvest that would least impact on caribou. At the landscape level, the identification of modified harvest areas within the Itcha-Ilgachuz caribou range utilized the following criteria:
Following these criteria, a detailed assessment of the impacts of proposed logging areas (from the STTAA proposal) on Itcha-Ilgachuz caribou was made by landscape unit (Table 10) at the request of the IAMC Integration Committee.
Figure 9 shows the moderate risk option for the Itcha-Ilgachuz caribou herd as developed by the Western Caribou Working group in 1992. Figure 10 depicts one option (Option A) for the location of the ‘no harvest’ and ‘modified harvest’ areas that would have the least impact on caribou habitat and still meet the individual CCLUP polygon targets. Generally the ‘no harvest’ and ‘modified harvest’ areas identified in Figure 10 are close to the CCLUP targets for Itcha-Ilgachuz caribou (see Table 8 and Table 9). The intent of the Caribou Strategy Committee is to refine the size of these areas to meet the targets exactly once the area of the productive forest land base has been confirmed.
Figure 11 depicts a second option (Option B) for locating the 35% modified harvest if individual polygon targets were relaxed and the caribou no harvest and modified harvest targets were applied within the deferral area independent of individual polygon targets. This option allows flexibility to ensure no harvest and modified areas can be placed in the most appropriate locations for caribou rather than being restricted to individual polygons. In option A (Figure 10), following the individual polygon targets results in winter range that receives low caribou use (area in Upper Blackwater polygon) receiving no harvest areas while other areas that receive much more extensive caribou use (in the Itcha-Ilgachuz polygon) receive modified or conventional harvest (due to the limited amount of no harvest area available in the polygon).
Although Option B does not meet individual polygon targets for caribou, we believe that it follows the intent of the plan in that overall targets for Itcha-Ilgachuz caribou are still met. Based on our current knowledge, we would propose shifting portions of the no harvest and modified harvest between polygons. For example, it would be more effective from a caribou perspective to shift portions of the no harvest targets out of the Upper Blackwater and Baezaeko polygons and into the Itcha-Ilgachuz polygon. This would allow the no harvest areas to overlap the most heavily utilized winter range (based on existing radiotelemetry data). This would allow areas receiving modified harvest to be intermediate or peripheral to the winter range. Therefore, Option B is the preferred option recommended by the Caribou Strategy Committee.
Table 9. Area summaries by polygon for caribou no harvest and modified harvest areas based on Itcha-Ilgachuz caribou interim strategy map. (Option A)
At the stand management level, the Caribou Strategy Committee has used the best available information to recommend a suitable integrated management harvesting approach at this time. The silvicultural systems research applicable to this caribou population is not as far along as that for eastern caribou. As this research continues over the next four years it may be necessary to refine this methodology. Based on preliminary results of pilot trials, two treatments are suggested which have the highest probability of minimizing impact on caribou habitat while harvesting timber:
TABLE 10. A detailed assessment of the impacts of proposed logging areas (from the STTAA proposal) on Itcha-Ilgachuz caribou assuming the harvest prescriptions recommended by the Caribou Committee are utilized. The assessment is generalized by landscape unit.
In the modified harvest areas, the Caribou Strategy Committee recommends the following timber management approach within the first 20 year period:
It is important to recognize that this selection harvest system has been chosen to mimic the large size of natural disturbance patterns while maintaining lichens and lichen regenerating capacity within stands over each cutting cycle and the entire rotation period (ie. selective harvest is intended to maintain suitable conditions for lichen growth). In both of these systems, sufficiently long cutting cycles would be required to maintain a suitable microclimate for lichens. On terrestrial lichen sites, the cutting cycle should be 70 years minimum. On arboreal lichen sites, the cutting cycle should be 80 years minimum. Where appropriate on the land base, large treatment areas (up to 1000 hectares) should be used. This approach would aggregate logging and access impacts to specific parts of the winter range and more closely mimic natural disturbance size.
Issues Specific To Strategy Development
The impacts of forest harvest patterns, access and predation, and measures to address these impacts, have been previously described in SECTION II.
Rotation Age To Manage For Lichens
To manage for lichen production in forest stands in Itcha-Ilgachuz winter range it will be necessary to manage stands differently for arboreal and terrestrial lichens. In stands that are important for arboreal lichen production (rough estimate is 20% of area), group selection with 33% volume removal and an 80 year cutting cycle (rotation age of 240 years) would likely be required to maintain lichen production in these stands over time. In stands that are important for terrestrial lichen production, rotation ages of 140 to 150 years with 2 entries (50% partial retention) would likely be required to maintain lichen production. However, if the required stand attributes can be achieved within a shorter rotation, these times could be reduced.
A rotation age of 80 years for pine stands in the MSxv is biologically inappropriate because pine regeneration is significantly slower than in other parts of the Cariboo Forest Region due to the extremely dry and cold climate experienced in this area (Ordell Steen, Research Ecologist; Appendix C). Steen has predicted, based on VDYP, that a more appropriate rotation age for pine in the MSxv would be 140 years (this would produce trees with an average DBH of 20 cm and height of 18m).
On terrestrial lichen sites, in western caribou range, partial retention with 50% volume removal every 70 years would produce stands made up of 1/2 trees 0 to 70 years and 1/2 trees 71 to 140 years of age. Considering this area has the harshest growing conditions in the region, hopefully 70 years will produce trees large enough to provide the amelioration of micro-climate necessary for terrestrial lichen to flourish. We would describe this stand level management as a moderate risk of not maintaining caribou habitat.
Why not remove more than 50 % volume?
A pilot trial of 70 % volume removal was harvested in 1995 in the Satah Mountain area. Initial indications revealed damage to terrestrial lichens within months of timber harvest. Trevor Goward, a leading lichenologist, has also assessed the site and predicts significant impact to the lichen community. As part of the same trial, 30 % volume removal was tested. The terrestrial lichen community, at least initially, seemed quite healthy. This provided some of the background which led to the 50 % volume removal prescription that is being advocated as an integrated management approach. Clearly, even 50 % removal does not come without risks and would be described as a moderate risk of not maintaining caribou habitat.
Why not shorten the cutting cycle to less than 70 years?
The objective with this cutting cycle is to produce trees of sufficient size to ameliorate the micro-climate so that when the remaining 50 % of the original forest is harvested the lichen community will continue to flourish.
Very few growth and yield data are available from the MSxv in the Itcha-Ilgachuz area. Using data from a single growth and yield plot near Thunder Mountain and increasing its site index to allow for increased growth rate in a managed stand, VDYP predicted an average DBH of approximately 13 cm at 70 years. Given even normal regeneration delays, the size of trees 70 years from harvesting would be even smaller. It is questionable whether trees of this size would be sufficient for maintenance of micro-climatic conditions necessary for terrestrial lichens. Any re-entry less than 70 years is even less likely to produce trees of adequate size because of the regeneration delays and the very slow growth rates in this area. For these reasons, any re-entry less than 70 years would have to be described as a high risk of not maintaining caribou habitat.
Impacts of the 70-30 Zonal Target
Within the western caribou population, only one SRDZ polygon (the Itcha/Ilgachuz unit) has designated modified harvest area targets for caribou. The CCLUP 90-Day Implementation Process Final Report states that 39% of the forest land base within this unit is to be managed for caribou under the ‘modified harvest’ category. We assume approximately 20% of the caribou ‘modified harvest’ area (20% of 39%) would need to be managed at a 240 year rotation to produce arboreal lichens and 80% would be managed at a 140 year rotation to produce terrestrial lichens. The assumed normal rotation for pine stands within this area has a major bearing on whether any of the caribou habitat targets will be met. Based on the present assumption that pine stands within this polygon would be normally managed at a 80 year rotation these targets can not be achieved due to the requirement to extend the rotation in both cases; tripling the normal rotation age to manage arboreal lichen stands to 240 years and almost doubling the normal rotation age to manage terrestrial lichen stands to 140 years. This scenario would allow for 20% of the forest land area to be managed to 240 years but only approximately 20% of the remaining area could only be managed to a 140 year rotation. This would leave approximately 60% of the designated caribou habitat within the modified harvest category to be managed at normal rotations (80 years). These assumptions assume that all the modified harvest in extended rotations within the Itcha/Ilgachuz SRDZ polygon is dedicated to caribou which will likely not be the case.
However, if the normal rotation age was considered to be 140 years (which better reflects ecological realities) for this area, modified harvest targets for caribou could be met as this assumption would only require extended rotations when managing stands to 240 years for arboreal lichens. Managing stands for terrestrial lichens could be achieved within the normal rotation of 140 years, resulting in no impact on the required 30% net down.
Polygon B1
Polygon B1, located in the central, core area of the Itcha-Ilgachuz caribou winter range (east of the Ilgachuz Range), is currently believed to be the most critical habitat area for caribou and was originally identified as part of the proposed protected area in recognition of that concern. As indicated in Table 10, observed caribou use, present caribou suitability and access concerns in relation to calving habitat and winter habitat are all high for this area (Punky/Moore Landscape Unit). Figure 8, showing radio-collared caribou locations in the Itcha-Ilgachuz during winter, highlights the importance of this area to caribou by the clustering of animal locations seen here. Based on current knowledge of caribou use in this area, the Caribou Strategy Committee considers that any harvest in this area at this time will place the herd at a risk well above the moderate level mandated in the land use plan. Additionally, all the required modified harvest specified in the CCLUP can be found within the caribou deferral area without harvesting in this polygon.
Research and habitat inventory done over the next four years on the Itcha-Ilgachuz caribou winter range will not change the factors contributing to the determination of risk to caribou of logging development in polygon B1. This research and inventory will collect information on caribou habitat use in modified harvest stands outside of polygon B1, gather further caribou winter habitat use information and map out areas of high and low value caribou habitat based on lichen abundance. However, collection of this additional information will not allow the Caribou Strategy Committee to assure maintenance of the caribou herd because the main concerns are related to the uncertainty and risk associated with the development of access into this critical habitat area (central part of the winter range). Development of access into critical caribou areas carries a high risk of increased poaching, harassment and interactions with predators. Even with an extensive access management plan including single or few access points, gates and road closures the concern still exists. Any road development increases snowmobile, motorcycle and ATV access even if these motor vehicle uses are discouraged or even prohibited. Evidence throughout North America shows that when caribou habitat is roaded and developed, then the caribou value is degraded.
Research Requirements to Refine Interim Strategy The following research is deemed necessary in order to adequately determine caribou habitat requirements and modified harvest regimes that have least impact on caribou habitat and to aid in refining an integrated caribou-forestry solution:
Habitat Use Studies
Radiotelemetry studies on Itcha-Ilgachuz caribou were initiated in 1995/96 and will be continued for four years in order to collect information on caribou landscape and stand-level habitat use patterns in relation to: recent logging in the area, adaptive management prescriptions, ongoing logging research trials and benchmark habitat use information collected in the mid-1980’s. Up to 30 conventional radiocollars will be maintained on caribou for monitoring purposes during this time period. Caribou will be monitored weekly except where opportunities arise to monitor collared caribou in trial or research logging areas, then the frequency of relocation will be increased to twice or three times weekly. GPS (Geographic Positioning System) radiocollars will be employed on a trial basis, likely in 1996 or 1997, in relation to adaptive management research areas. This type of collar may provide substantially more information on stand-level habitat use patterns of caribou. A more detailed work plan will be prepared for the proposed GPS radiocollar/habitat use research work.
GIS analyses will be undertaken to examine radiotelemetry information, timber types, road and trail densities and human use (particularly snowmobiles) patterns in relation to caribou habitat. It should be possible to accomplish most of these analyses in-house on B.C. Environment or Ministry of Forests GIS.
Lichen Ecology Work
Ecological dynamics of lichen communities will be further examined through analysis of data collected on a previous study in the western caribou winter range (Brulisauer and Pitt 1992). This analysis was initiated in 1995. Lichen monitoring plots established by B.C. Environment in 1990 (Enns 1990) will be resurveyed in 1997.
Silvicultural Systems Research
Logging of a pilot block to develop a silvicultural system more compatible with the maintenance of caribou habitat occurred in the late winter of 1995. Initial assessments of this trial were incorporated into the development of replicated prescriptions. An experiment involving five replicates of three treatments was logged in the mid winter of 1996. The treatments include: group selection involving 30% volume removal in groups of approximately 20m diameter using a feller buncher, a processor at the stump and a forwarder, group retention of 50% volume in variable sized groups using a feller-buncher, a processor at the stump and a forwarder, and group retention of 50% volume in variable sized groups using a feller-buncher, grapple skidders and roadside processing. Impacts on the terrestrial and arboreal lichen communities will be monitored along with a range of other forest attributes.
Adaptive Management Research
Two large adaptive management logging blocks will be initiated on the winter range by 1997 or 1998. In order to maintain some habitat values within modified harvest blocks and provide meaningful research results, the blocks should be 300 hectares or greater and winter harvested on snowpack for terrestrial lichen sites. The Caribou Strategy Committee anticipates removal levels somewhere between 30 and 50 percent, with the actual level and prescription based on preliminary research results.
Inventory Requirement to Refine Interim Strategy
The following inventory information is deemed necessary in order to adequately determine caribou habitat requirements and modified harvest regimes that have least impact on caribou habitat:
Population Surveys
Annual population surveys are necessary to monitor trends in caribou numbers and to examine seasonal distribution patterns of the herd. This population information will be important to examine in relation to habitat use patterns and predation trends. Surveys will be conducted in June, October and March. A population estimate will be derived from these surveys based on a sightability index obtained from collared caribou.
Predation Monitoring
Minimum wolf density estimates and home ranges will be determined for the area based on wolf radiocollaring and monitoring work to be initiated in 1996. Wolf monitoring is required to understand how habitat changes influence their foraging habits with respect to potential additional impacts to caribou.
Ecosystem Mapping
There is a need to quantify the distribution, abundance and importance of various habitats to caribou, within the Itcha-Ilgachuz winter range, through the use of ecosystem mapping (formerly referred to as biophysical mapping). In total the mapping work will require the completion of a minimum of ten 1:50,000 ecosystem maps for the area, with an emphasis on caribou and other species at risk. In addition, more detailed ecosystem mapping (1:20,000 scale) will be completed for one watershed within the area; this watershed will be the Punkutlaenkut. With completion of detailed 1:50,000 maps, the existing deferral area will be stratified into no harvest and modified harvest zones. Landscape level zoning will take into consideration attributes such as:
Due to the short time frame available to conduct the research necessary to develop an integrated management strategy, and recognizing the need for research trials that will monitor lichens that have a relatively slow growth rate, there is some risk that the final recommended strategy developed within a four year timeframe will not achieve the desired objective over the long term. Given this, it is imperative that the available four year timeframe to conduct the research not be shortened.
Table 11. Project Schedule for Itcha-Ilgachuz Caribou.
SECTION V: INTEGRATION ISSUES RELATED TO CARIBOU
STTAA Approach To Caribou Management
The Caribou Strategy Committee met five times with the Short Term Timber Availability (STTAA) Committee to address integration of the two strategies.
Some agreement between strategies was reached in regard to stand level management, with the STTAA indicating some flexibility in terms of selective harvest, if necessary for caribou. The STTAA prefers clearcut over group selection harvest prescriptions. The Caribou Strategy Committee has indicated that clearcut harvesting may be an option on steep slopes because these are generally of lower capability for eastern caribou but in order to maintain caribou habitat values over the majority of the 35% modified harvest within the caribou ranges (east and west) more sensitive selection systems will be required.
There is also some agreement between the Caribou Strategy Committee and the STTAA that access management is a major issue related to minimizing impacts on caribou populations, however the details of how to accomplish this are unresolved. The STTAA view access as "problematic" but feel that there are options to mitigate adverse effects. The solution proposed by the Caribou Strategy Committee is to aggregate modified harvest areas and locate large no harvest areas where there is critical caribou habitat. The aggregated modified harvest areas should have strict access controls such as single access points, gates, road deactivation, no motorized hunting access and no snowmobile or ATV activity. Although this aggressive approach may not be popular with all, and will not eliminate all access problems, it will give the maintenance of caribou the best chance of success. This approach will lead to the least access development across the caribou range.
Outstanding, unresolved issues with the STTAA include the following:
Regional Biodiversity Strategy The Caribou Strategy Committee met once with the Biodiversity Strategy Committee. Most integration issues involving targets are unresolved because the information required to assess modified or no harvest requirements for biodiversity by polygon were not yet available. However, the following integration issues were raised:
The Caribou Strategy Committee has not met with the Mule Deer Strategy Committee. However, based on the 70-30 interpretation for the SRDZ, there appears to be minimal conflicts between strategies. Quesnel Lake is the only SRDZ polygon in the east that has mule deer targets; there appears to be enough modified harvest to address a 240 year rotation for both caribou and mule deer. However, we are uncertain as to how much forest in extended rotations other non-forest resource values require. In the west, there are no deer winter ranges in the SRDZ polygons. In the Chezacut and Bazaeko polygons there is no 70-30 interpretation that would limit the Mule Deer Strategy from meeting their targets.
The Caribou Strategy Committee has not met with the Access Strategy Committee. However, there are several access issues that the Caribou Strategy Committee feels need to be addressed:
To have the best chance of conserving caribou, we need to manage a whole ‘package’ of issues, not separately, but in concert within both eastern and Itcha-Ilgachuz caribou ranges. These issues include access, forest harvest patterns and silviculture, poaching, predation and snowmobiling.
Flexibility in the application of polygon-specific targets may help to ensure that the timber supply and caribou habitat are maintained as mandated in the land use plan.
Bergerud, A.T., H.E. Butler and D.R. Miller. 1984. Antipredator tactics of calving caribou: dispersion in mountains. Can. J. Zool. 62:1566-1575.
Bergerud, A.T. and J.P. Elliot. 1986. Dynamics of caribou and wolves in northern British Columbia. Can. J. Zool. 64:1515-1529.
Bergerud, A.T. and R.E. Page. 1987. Displacement and dispersion of parturient caribou at calving as antipredator tactics. Can. J. Zool. 65:1597-1606.
Brulisauer, A.R. and M.D. Pitt. 1992. Ecology and successional status of terrestrial and arboreal lichens in the winter habitat area of the Itcha-Ilgachuz caribou. Prog. Report. Dept. of Plant Science. Faculty of Agriculture Sciences. Univ. of British Columbia. 100pp.
Cichowski, D.B. 1993. Seasonal movements, habitat use, and winter feeding ecology of woodland caribou in west-central British Columbia. B.C. Ministry of Forests, Land Management Report No.79. 54pp.
Edmonds, E.J. 1988. Population status, distribution and movements of woodland caribou in westcentral Alberta. Can. J. Zool. 66:817-826.
Edwards, R.Y. 1954. Fire and the decline of a mountain caribou herd. J. wildl. Manage. 18:521- 526.
Enns, K.A. 1990. Terrestrial forage lichen enhancement in the Itcha-Ilgachuz: treatment trials and working plan. Unpublished report. Prepared for: Minist. of Environ., Williams Lake, B.C. 33pp.
Farnell, R. and J. McDonald. 1987. The demography of Yukon’s Finlayson caribou herd, 1982-1987. Yukon Renewable Resources, Whitehorse. Prog. Rep. 54 pp.
Farnell, R. and J. McDonald. 1988. The influence of wolf predation on caribou mortality in Yukon’s Finlayson caribou herd. In: Proceedings of the Third North American Caribou Workshop, Alaska Dept. Fish and Game, Juneau. Wildlife Technical Bulletin. No. 8:52-70.
Gasaway, W.C., Stephenson, R.O., Davis, J.L., Shepherd, P.E.K. and Burris, O.E. 1983. Interrelationships between wolves, prey and man in interior Alaska. Wildlife Monograph 84.
Klein, D.R. 1982. Fire, lichens and caribou. J. Range Manage. 35:390-395. Ontario Ministry of Natural Resources. 1994. [Draft] Management guidelines for woodland caribou habitat. OMNR Northwest Region. Recommendations of NWR Caribou Task Team on behalf of Policy and Program Division. 17pp. Province of British Columbia. 1995. The Cariboo-Chilcotin Land-Use Plan. 90-Day Implementation Process Final Report, Victoria, B.C.
Seip, D.R. 1990. Ecology of woodland caribou in Wells Gray Provincial Park. B.C. Minist. of Environ. Wildlife Bulletin No. B-68. 43 pp.
Seip, D.R. 1991. Predation and caribou populations. Rangifer Spec. Issue No.7:46-52
Seip, D.R. 1992a. Factors limiting woodland caribou populations and their interrelationships with wolves and moose in southeastern British Columbia. Can J. Zool. 70:1494-1503.
Seip, D.R. 1992b. Habitat Use and Population Status of Woodland Caribou in the Quesnel Highlands, British Columbia. B.C. Minist. of Environ. Wildlife Bulletin No. B-71. 50pp.
Seip, D.R. and D.B. Cichowski. in press. Population ecology of caribou in British Columbia. Proceedings of 6th North American Caribou Conference.
Stevenson, S.K. 1986. Review of forestry practices in caribou habitat in southeastern British Columbia, Canada. Rangifer, Spec. Issue No. 1: 289-295.
Stevenson, S.K., H.M. Armleder, M.J. Jull, D.G. King, E.L. Terry, G.S. Watts, B.N. McLellan and K.N. Child. 1994. Mountain caribou in managed forests: preliminary recommendations for managers. Research Branch, Ministry of Forests, Victoria, B.C. 33pp.
APPENDIX B
The following methodology was used to determine the maximum forest area available to meet caribou habitat requirements incorporating extended rotations and applying governments 70-30 interpretation to Special Resource Development Areas. For the modified harvest category within the SRDZ subunits the following formulas were utilized; x + a (b - x) = c
y = b - x where; x = the amount of area within the modified harvest category with normal rotation y = the amount of area within the modified harvest category with extended rotation a = rotation equivalent factor b = SRDZ subunit target for area accessible within the modified harvest category c = SRDZ subunit target for area equivalent within the modified harvest category Example Subunit is Boss/Deception; a = 0.5 as the normal rotation was doubled to 240 years b = 51% which equates to the proportion of productive forest land base accessible under the modified harvest category target c = 44% which equates to the area equivalent of the productive forest land base which will be harvested based on governments interpretation of the 70-30 agreement therefore: x + 0.5 (51 - x) = 44 x + 25.5 - 0.5x = 44 0.5 x = 18.5 x =37
y = 51 -37 y = 14 therefore to meet the area equivalent target based on the current interpretation of the 70-30 agreement, of the 51% of the productive forest land base that is within the modified harvest category for the Boss/Deception polygon 37 of the 51% would be managed at normal rotations (120 year rotation) and 14 of the 51% would be managed at double the normal rotation (240 year rotation). All or a portion of the area dedicated to double rotation could be placed in areas being managed for caribou. Changing the length of the rotation age for the forest with extended rotations would vary the proportion of modified harvest with normal rotation or extended rotation for the polygon.
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