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Effectiveness of above-ground pipeline mitigation for moose (Alces alces) and other large mammals
B I O L O G I C A L C O N S E RVAT I O N
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Effectiveness of above-ground pipeline mitigation for moose (Alces alces) and other large mammals Bridget M. Dunne, Michael S. Quinn* Faculty of Environmental Design, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, Canada T2N 1N4
A R T I C L E I N F O
A B S T R A C T
Article history:
Above-ground pipelines for in situ oil sands development are potentially significant vectors
Received 8 February 2008
of habitat fragmentation for large mammals. We evaluated the use of elevated pipeline
Received in revised form
clearances (distance between the ground and the bottom of the pipeline) and pipeline
28 July 2008
crossing structures, the two primary methods of mitigating the barrier effect of above-
Accepted 18 October 2008
ground pipelines on large mammals, with a particular emphasis on moose (Alces alces),
Available online 10 December 2008
in northern Alberta, Canada. Winter snow tracking and remote cameras were employed for one year to monitor large mammal interactions with a 5.5 km stretch of pipeline miti-
Keywords:
gated with five pipeline crossing structures and a 1.6 km control area of unmitigated pipe-
Habitat fragmentation
line. A minimum threshold pipeline clearance of 140 cm was critical in allowing adult
Crossing structure
moose to cross underneath the pipeline. Pipeline crossing structures facilitated movement
Pipeline mitigation
across the pipeline and were used more than sections of elevated pipelines by all species.
Oil sands
1.
Introduction
The infrastructure associated with energy development results in a broad array of environmental effects (Dincer, 1998; Balat, 2005). Increasing demand for energy, coupled with the depletion of conventional petroleum reserves, is leading to the development of unconventional oil resources such as bitumen occurring as oil sands (Greene et al., 2004). Recovery of this heavy oil is generating a novel set of environmental impacts beyond those associated with conventional petroleum exploitation. Terrestrial bitumen reserves are widespread and are estimated to occur in over 65 countries (Soderbergh et al., 2007). Bitumen extraction occurs through surface mining of shallow deposits, or in situ withdrawal of deeper (>75 m) deposits. The landscape disturbance associated with such oil sands development is large and growing. Methods are required to manage and mitigate the environmental effects of oil sands development. One of the largest bitumen reserves in the world is found in the oil sand deposits of Alberta, Canada. Approximately 80% of the estimated 174 billion barrels of oil in the Alberta
Ó 2008 Elsevier Ltd. All rights reserved.
oil sands will require in situ recovery (Hopwood et al., 2004). The current in situ recovery method of choice is steam assisted gravity drainage (SAGD), which involves placing two horizontal wells into a bitumen formation. The top well injects steam to decrease the viscosity of the bitumen, while the bottom well captures the bitumen and returns it to the surface for processing (Chow et al., 2008). Extensive networks of above-ground pipelines are used to transport steam to the extraction site, and bitumen from the extraction site to a processing facility. High and variable temperatures result in pipeline expansion and contraction, thus preventing the pipelines from being buried underground. The pipeline clearance (distance between ground and bottom of pipeline) is typically 1 m, although this varies with topography. Pipelines generally consist of two or more parallel pipes 30–60 cm in diameter separated by 50–200 cm. The resultant a horizontal barrier is two to several metres wide. Smaller gas lines and other cables may also be associated with the pipeline structure. In situ development and associated above-ground pipelines have the potential to cover 138,000 km2 of northern Alberta (Schneider and Dyer, 2006).
* Corresponding author: Tel.: +1 403 220 7013; fax: +1 403 284 4399. E-mail addresses: [email protected] (B.M. Dunne), [email protected] (M.S. Quinn). 0006-3207/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2008.10.029
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Habitat fragmentation, especially for large mammals, is a predicted consequence of such extensive development (Noel et al., 2006; Schneider and Dyer, 2006). Habitat fragmentation occurs when smaller, isolated patches of habitat are created due to a disturbance; often a linear development such as a pipeline, road, railway or power line (Andren, 1994; Alexander et al., 2004; Reimers et al., 2007). Such disturbances reduce or prevent individuals from moving between patches of habitat and result in a barrier effect (Ng et al., 2004; Alexander et al., 2005; Cushman 2006). Habitat loss, reduced patch size, and more isolated habitat patches are the primary components of fragmentation. All of these result in lower biological diversity and altered ecosystem processes (Hobbs, 1993; Andren, 1994; Van Wieren and Worm, 2001; Castelletta et al., 2005). Species that display a low resilience to habitat fragmentation include those with life history traits such as late age of first reproduction, low population densities, low reproductive rates, large home-range requirements, and low fecundity (Weaver et al., 1996; Van Wieren and Worm, 2001; Alexander et al., 2004; Ng et al., 2004). Species that move over great distances to disperse, find food, and mate are also most threatened by linear developments (Clevenger et al., 2001; Ng et al., 2004). As a result, the species of interest for this project included moose (Alces alces), black bear (Ursus americanus), lynx (Lynx canadensis), gray wolf (Canis lupus), coyote (Canis latrans), white-tailed deer (Odocoileus virginianus), and mule deer (Odocoileus hemionus). Pipelines pose a significant barrier to moose as the largest mammal in the study area, with large home ranges, low reproductive rates, low population densities, and extended parental care (Franzmann and Schwartz, 1997). There are two primary means of mitigating the physical barrier created by above-ground pipelines: (1) elevating the pipeline clearance to facilitate movement underneath, and (2) constructing pipeline crossing structures to facilitate movement over the pipeline. Elevated pipelines with a pipeline clearance of at least 180 cm have proven effective in facilitating wildlife movement, particularly for moose (Van Ballenberghe, 1978; Eide and Miller, 1979; Sopuck and Vernam, 1986; Golder Associates Limited, 2000; AXYS Environmental Consulting Limited, 2003; Golder Associates Limited, 2004). However, local ground conditions, engineering requirements, and human safety issues may limit the application of elevated pipelines. Pipeline crossing structures that facilitate the movement of wildlife over pipelines have been proffered as a mitigation alternative. However, few such structures have been installed and there is a dearth of published research on their effectiveness or optimal design characteristics. Our research provides a unique and valuable examination of pipeline crossing structures and an assessment of required pipeline clearances for large mammals in a boreal context. The purpose of this paper is to examine pipeline crossing structures and elevated pipeline clearances as means of mitigating the effects of above-ground pipelines in areas of in situ bitumen extraction. The focus of our research was on the movement of large mammals, with a particular emphasis on moose. Three research questions were used to guide our inquiry: (1) How do large mammals interact with aboveground pipelines? (2) How do large mammals interact with pipeline crossing structures?, and (3) How do the crossing
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rates at pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals? Our results are used to provide recommendations for future above-ground pipelines and pipeline crossing structures in order to facilitate wildlife movement.
2.
Methods
2.1.
Study area
In March 2006, five pipeline crossing structures (structures) were built by Shell Canada at its Peace River Complex, 55 km northeast of Peace River in the boreal mixed-wood region of northern Alberta, Canada (Fig. 1). These structures were built by placing steel sleeves over a section of pipeline, compacting gravel over these sections, adding a layer of topsoil, and then seeding the structure to provide vegetation and cover. Structure locations were chosen by Shell Canada based on surrounding habitat, and existing cut lines and trails. Structures were built 19.8–25.0 m long (i.e., span perpendicular to the direction of the pipeline) with a height of 2.0–3.0 m. Width at the top of the structures ranged from 3.7 to 4.0 m and width at the bottom of the structures was 11.9–14.9 m. Elevated pipelines were defined as locations with a pipeline clearance (distance between the ground and the bottom of the pipeline) of at least 180 cm (Van Ballenberghe, 1978; Eide and Miller, 1979; Sopuck and Vernam, 1986; Golder Associates Limited, 2000; AXYS Environmental Consulting Limited, 2003; Golder Associates Limited, 2004). Pipeline clearance is primarily a function of local changes in topography. The term pipeline refers to locations with a clearance less than 180 cm. Two sections of pipeline were studied for this project (Fig. 1). One section (pipeline crossing structure area) was a 5.5 km stretch of pipeline with five pipeline crossing structures. This pipeline was built at the beginning of the study in March 2006. The second was a 1.6 km section of pipeline with no pipeline crossing structures (control area) built in 2000. Pipeline clearance ranged from 32 to 234 cm (mean = 130 cm) in the crossing structure area and 53–256 cm (mean = 127 cm) in the control area. Large mammal movement was monitored using remote cameras during the entire study period and snow tracking in winter. Animal movements were classified as crossings (movement across the pipeline or structure from one side to the other), deflections (movement indicating a definite approach towards the pipeline or structure followed by a change in direction away) or parallel movements (movement parallel to the pipeline or structure). Approaches to the pipeline or structure were considered to be active attempts to cross, and were calculated by summing crossings and deflections for that species or location. Data were combined for mule deer and white-tailed deer. Methods to address each of the research questions are presented below.
2.2. How do large mammals interact with above-ground pipelines? 2.2.1.
Winter snow tracking
Three tracking sessions occurred during the first winter (9 February 2006 to 23 March 2006) primarily to identify study
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4
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5
2 3
1
Pipeline Crossing Structure Area
Control Area
Peace River Study Area
Fig. 1 – Location of study area with pipeline crossing structure and control areas outlined.
areas, and appropriate locations for remote cameras. The second winter (22 November 2006 to 3 April 2007) consisted of a full season of winter snow tracking with seven tracking sessions along the pipeline crossing structure and control areas. Winter snow tracking was conducted every three weeks following the establishment of a consistent snow layer. The 20 m pipeline right-of-way (ROW) on each side of the pipeline was assessed for tracks by two researchers; one walked along the pipeline while the other walked along the forest edge (Young, 1989). This allowed us to record the tracks of any animal approaching the pipeline from either side, thus ensuring complete coverage of the ROW. Five environmental variables were recorded or calculated for all track sequences: snow depth, pipeline clearance, distance to preferred moose habitat (defined by an existing habitat classification), distance to water, and distance to road. Analysis of Variance (ANOVA) was conducted to assess these environmental factors in relation to moose crossings, deflections or parallel movements to the pipeline, for the structure and control areas combined. t-Tests were used to compare these variables at pipeline crossing and deflection locations by moose separately for each study area. Logistic regression was employed to determine which of the five variables had the greatest predictive capability for moose crossing and deflection locations in each study area. A t-test was used to analyze the null hypothesis that the means of the five environmental variables were similar at moose crossing sites in each study area.
2.2.2.
Remote camera monitoring
Four digital infrared cameras (Reconyx, 2004) were placed next to the pipeline in both the pipeline crossing structure and control areas to monitor wildlife movement. Cameras were checked every three weeks during the full year of oper-
ation at which time the digital media cards and batteries were changed. An interval of two minutes between digital image capture was chosen to distinguish between unique wildlife events (Morgantini, 1981). Data were standardized by dividing the number of wildlife movements observed by the number of functional camera days. This allowed for the direct comparison of wildlife movements at each camera location. The camera data were a series of non-normal, independent, random events with no replicate samples, making chi square analysis most appropriate. Relative indices for crossings, deflections, and parallel movements next to the pipeline by moose, deer, and carnivores (bear, coyote, lynx, and wolf) were analyzed using one-sample chi square tests. The frequency distributions of pipeline crossings by moose, deer, and carnivores at different pipeline clearances were graphed with available pipeline clearances to identify preferences for crossing at particular pipeline clearances.
2.3. How do large mammals interact with pipeline crossing structures? Two digital infrared cameras were placed at each of the five structures to monitor wildlife movement for a period of 12 months (mounted on posts; one on each side of the structure). Cameras were positioned to capture movement along the pipeline right-of-way as well as on the structure. Wildlife movements were defined as crossing, deflecting or paralleling the structure. Relative indices were calculated for wildlife movements by functional camera day, species, season, day versus night, and weekday versus weekend. Environmental variables collected in association with each structure included: pipeline clearance, ecosite (as identified in an existing vegetation assessment), structure dimensions, distance to water, distance to preferred moose habitat, distance to roads,
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and distance to the next structure. Chi square tests were used to test for differences in use between the pipeline crossing structures.
2.4. How does the crossing rate of pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals? Relative indices for crossings by all species at the pipeline, elevated pipeline and pipeline crossing structures were compared. In other words, the relative indices calculated for the cameras at the pipeline and elevated pipeline locations were compared to the pipeline crossing structure cameras for each species over the year of monitoring.
3.
Results
3.1. How do large mammals interact with above-ground pipelines? 3.1.1.
Winter snow tracking: moose
To calculate successful pipeline crossing rates for each species, 57 (first winter), and 563 (second winter) wildlife track sequences were pooled. Although a higher number of wildlife tracks were encountered along the pipeline crossing structure area, the density of tracks per 100 m was much higher in the control area (28.9 compared to 9.4; Table 1). Of the 86 moose track sequences observed in both study areas combined, 56 crossed the pipeline, 21 deflected away from the pipeline, and 9 moved parallel to the pipeline. Moose was the only species observed more frequently in the control area. Moose also crossed the control area pipeline more frequently and with a higher rate of success (77.1% compared to 65.5%) compared to the pipeline crossing structure area.
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Fewer moose deflections were observed along the control pipeline (20%) than the pipeline crossing structure area (31%). The mean pipeline clearance for the entire study area was 128.5 cm while the mean pipeline clearance at moose crossing locations was 169.7 cm (N = 56). The majority of moose crossings (43.5%) occurred at a pipeline clearance of 185– 256 cm (Fig. 2). Pipeline clearances of 143–256 cm were used more than available. Although 84.8% of moose crossings occurred at locations with a pipeline clearance above 140 cm, only 30.4% of the pipeline had a clearance over 140 cm. There was only one instance where a moose crossed directly. This event occurred at a location with a pipeline clearance of 32– 43 cm (top of the pipeline 75–87 cm). The mean pipeline clearance where moose deflected from the pipeline over the entire study area was 110.7 cm (N = 21). Locations where moose deflected from the pipeline occurred at significantly higher snow depths (F(2, 72) = 5.384, p < 0.01) and further from water (F(2, 72) = 4.585, p = 0.013) than moose crossing locations. Moose crossing sites occurred at significantly higher pipeline clearances (F(2, 72) = 16.948, p < 0.01) than deflections or parallel movements. Distance to preferred moose habitat and roads were not significantly different for moose crossings, deflections or parallel movements next to the pipeline. Parallel movements (N = 9) did not show any significant results and were not included in further analysis as they provide no information on wildlife interactions with above-ground pipelines. Moose crossing sites within the pipeline crossing structure area occurred at significantly higher pipeline clearances (t = 3.08, df = 22, p < 0.01) and closer to water (t = 2.26, df = 22, p = 0.03) than moose deflection sites. Pipeline clearance had a predictive capability of 83.3% for moose crossing locations [Y = 2.859 + 0.026 (pipeline clearance)].
Table 1 – Pipeline crossing rates by species in the pipeline crossing structure and control areas based on winter snow track results. Species
Movement
Pipeline crossing structure area
Control area
Moose Crossings/approaches Percent cross
19/29 65.5
37/48 77.1
Crossings/approaches Percent cross
327/341 95.9
262/290 90.3
Crossings/approaches Percent cross
68/72 94.4
32/32 100.0
Crossings/approaches Percent cross
4/6 66.7
1/1 100.0
Crossings/approaches Percent cross
17/20 85.0
5/5 100.0
Animals recorded Pipeline length (m) Animals recorded/100 m
5195 5500 9.4
462 1600 28.9
Deer
Coyote
Lynx
Wolf
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Moose 50
16
45
Deer
14
40
12
30
10
25
8
20
6
15
4
10
2
0
0 082 83 -9 1 92 -9 9 10 010 5 10 611 7 11 812 9 13 014 2 14 315 4 15 518 4 18 525 6
5 082 83 -9 1 92 -9 9 10 010 5 10 611 7 11 812 9 13 014 2 14 315 4 15 518 4 18 525 6
Pipeline Crossings (Percent)
35
Pipeline Clearance (cm)
Pipeline Clearance (cm)
Carnivore
16 14 12
Available Pipeline
10
Moose (N=46)
8
Deer (N=312)
6 4
Carnivore (N=113)
2 6
4 18
5-
25
18
4 15
515
2 314
9
14 013
7
12 811
5
11
10
610
9
1
-9
010
92
-9 83
0-
82
0
Pipeline Clearance (cm)
Fig. 2 – Comparison of pipeline clearances where moose (Alces alces), deer (O. virginianus and O. hemionus), and carnivores (Canis lupus, Canis latrans, Lynx canadensis) crossed underneath the pipeline, with available pipeline clearances based on winter snow tracking data.
In the control area, the majority of moose tracks (30 of 37) were observed next to elevated pipelines. Of the 30 encounters at these locations, 86.7% were successful crossings (v21 ¼ 162:000), p = 0.05. Pipeline clearance (t = 4.16, df = 40, p < 0.01) and distance to water (t = 2.28, df = 40, p = 0.028) were significantly different for moose crossing and deflecting locations, as was observed in the structure area. Pipeline clearance was also the best predictor of pipeline crossing locations by moose at 85.7% [Y = 4.062 + 0.035 (pipeline clearance)]. Nineteen moose (15 track sequences) were observed at the pipeline crossing structure area and 37 (32 track sequences) along the control area. Moose crossing locations at each of the study areas were not significantly different in terms of snow depth (t = 0.95 df = 45, p = 0.35), pipeline clearance (t = 0.60, df = 19, p = 0.59), or distance to road (t = 1.84, df = 19.7, p = 0.08). There was a significant difference between distance to preferred moose habitat (t = 4.88, df = 15.8, p = <0.01), and distance to water (t = 7.23, df = 45, p < 0.01), with pipeline crossings being closer to moose habitat and water in the control area. The mean distance from crossing locations to moose habitat was 249 m in the control area, and 566 m in the pipeline crossing structure area, with the mean distance to water being 210 m and 587 m, respectively.
3.1.2.
Winter snow tracking: deer
Deer were recorded most frequently and had a 5.6% higher successful crossing rate at the pipeline crossing structure area (Table 1). One deer jumped over a cluster of three pipelines at the control area (pipeline clearance of 59–72 cm), where the top of the pipeline reached 100–110 cm from the ground. Winter snow track data indicated deer crossings (N = 312) occurring at pipeline clearances of 70–256 cm, with an average of 121 cm. Deer movement was almost uniform across all pipeline clearances with 0–91 cm, 100–105 cm, 118–129 cm and 155–184 cm pipeline clearances used more than expected, while 92–99 cm, 106–117 cm, 130–154 cm, and 185–256 cm pipeline clearances were used less than expected (Fig. 2).
3.1.3.
Winter snow tracking: carnivore
More carnivores were observed along the pipeline crossing structure area. However, all attempted pipeline crossings at the control area were successful and no deflections were observed here (Table 1). The average carnivore crossing (N = 113) occurred at a pipeline clearance of 115 cm, with a range of 53– 56 cm (Fig. 2). Carnivores crossed locations with lower pipeline clearances more frequently than moose or deer, with 83.2% of carnivore crossings at pipeline clearances less than 140 cm. Carnivores crossed pipelines with a clearance less
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than 129 cm more than available, except for clearances of 92– 99 cm.
3.1.4.
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3.3. How does the crossing rate of pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals?
Remote camera monitoring: all species
Camera data indicated moose crossing the pipeline with a mean clearance of 190 cm (N = 47), ranging from 115 to 200 cm (Fig. 3), again showing a clear preference by moose to cross at higher pipeline clearances. Camera data (N = 300) recorded deer crossing the pipeline with an average clearance of 156 cm and with a range of 80–200 cm (Fig. 3). Deer did not show a clear preference for crossing at specific pipeline clearances. The camera data showed carnivore crossing locations (N = 11) ranging from 47 to 200 cm, with an average pipeline clearance of 132 cm. The 200 cm location in the control area received the highest number of successful pipeline crossings for all species.
During the 12 months of camera monitoring at pipelines, elevated pipelines, and pipeline crossing structures, the highest successful crossing rate was observed at the structures (Fig. 3). As with all species combined, moose exhibit a preference to use pipeline crossing structures more frequently than crossing underneath pipelines or elevated pipelines (Fig. 3).
3.2. How do large mammals interact with pipeline crossing structures?
Moose deflected from the pipeline at locations with significantly higher snow depths, and further from water than at crossing or parallel movement locations. Snow depth can influence wildlife movement under a pipeline as the clearance between the ground and the bottom of the pipeline decreases. In deep snow, wildlife, particularly ungulates, will use different movement patterns in order to follow the path of least energetic resistance (Bergerud et al., 1984; Dyer et al., 2002). Snow depths up to 85 cm were observed during this study. As snow depth increases to levels greater than 70–80 cm, moose home range use, movements, and migrations decrease (Van Ballenberghe, 1978; Hamilton et al., 1980; Hauge and Keith, 1981; Sopuck and Vernam, 1986; Franzmann and Schwartz, 1997; Garrett and Conway, 1999; Keech et al., 2000), resulting in fewer attempted pipeline crossings. It was expected that locations farther from water would have fewer moose (Sopuck and Vernam, 1986; Clevenger et al., 2001). The mean distance from water ranged from 330 m at crossing sites, to 543 m at deflection sites. Although moose can easily traverse both of these distances, deflection sites were found significantly farther from water than pipeline crossing locations.
4.
4.1. How do large mammals interact with above-ground pipelines? 4.1.1.
Table 2 provides the environmental and physical characteristics of each of the five pipeline crossing structures. Structures were crossed by deer (N = 746), moose (N = 157), coyote (N = 52), bear (N = 2), lynx (N = 2) and wolves (N = 1) (Table 3). Moose had the highest successful crossing rate overall (88.2%) based on total approaches to the structure. Coyote and deer had very high overall crossing rates as well, with 88.1% and 82.5%, respectively. Wildlife crossings for all species were significantly higher at Structure 4 than any other structure (v21 ¼ 164:995, p = 0.05). Coyotes (v21 ¼ 15:211, p = 0.05), and moose (v21 ¼ 172:165, p = 0.05) crossed this structure significantly more. The fourth structure was the most frequently crossed by moose and coyotes, with 91.7 and 90.9%, respectively. The third structure had the highest proportion of successful crossings by deer, with 91.1%. Two bears and two lynx crossed the fifth structure, while one wolf crossed the second structure. Although their numbers are low, all black bear, lynx, and wolf approaches to the structures were successful crossings.
Discussion and conclusions
Moose
Pipeline Crossings (Percent)
60 50 40
Moose Crossings (N=47)
30
Deer Crossings (N=300) Carnivore Crossings (N=11)
20 10
Pipeline Clearance (cm)
l on
tro
20 0 20 0
C
14 9
14 0
13 0
11 5
10 0
95
86
80
47
0
Fig. 3 – Moose (Alces alces), carnivore (Ursus americanus and Canis latrans), and deer (O. virginianus and O. hemionus) crossings based on stationary camera data at specific pipeline clearances.
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Table 2 – Environmental variable information for pipeline crossing structures. Structure 1 Height (m) Length (m) Width at top (m) Average width on bottom (m) Surrounding pipeline clearance (cm) Distance to water (m) Distance to moose Habitat (m) Distance to road (m) Distance to next Structure (m) Ecosite phase
Structure 2
Structure 3
Structure 4
Structure 5
3.0 25.0 4.0 11.9 125 519
3.0 21.5 3.8 12.3 114 702
2.0 20.2 3.8 13.4 70 1070
2.0 19.8 3.8 13.4 64 300
2.5 22.1 3.7 14.9 127 284
326 255
0 76
381 67
0 125
582 416
455 Low bush cranberry
544 Shrubby rich fen
764 Low bush cranberry
878 Shrubby rich fen
862 Shrubby poor fen
Table 3 – Structure crossing rates by species based on remote camera results. Moose
Deer
Coyote
Lynx
Wolf
Bear
Structure 1 Crossings/approaches Percent cross
5/7 71.4
177/197 89.8
8/9 88.9
0/0 0.0
0/0 0.0
0/0 0.0
Structure 2 Crossings/approaches Percent cross
4/5 80.0
99/152 65.1
3/4 75.0
0/0 0.0
1/1 100.0
0/0 0.0
Structure 3 Crossings/approaches Percent cross
6/10 60.0
164/180 91.1
11/13 84.6
0/0 0.0
0/0 0.0
0/0 0.0
Structure 4 Crossings/approaches Percent cross
132/144 91.7
294/353 83.3
30/33 90.9
0/0 0.0
0/0 0.0
0/0 0.0
Structure 5 Crossings/approaches Percent cross
10/12 83.3
12/22 54.5
0/0 0.0
2/2 100.0
0/0 0.0
2/2 100.0
Average for all structures Crossings/approaches Percent cross
157/178 88.2
746/904 82.5
52/59 88.1
2/2 100.0
1/1 100.0
2/2 100.0
Moose crossing sites occurred at significantly higher pipeline clearances than at deflection or parallel movement locations. In addition, pipeline clearance was the best predictor of moose pipeline crossing locations in both study areas. This emphasizes the barrier effect that low pipeline clearances have on moose movement. These findings are consistent with Kansas and Raine (1988) and Golder Associates Limited (2000), where pipeline characteristics have a greater influence on pipeline crossing locations than environmental conditions. Moose crossing sites occur at locations significantly closer to preferred moose habitat and water in the control area, than along the pipeline crossing structure area. The higher use of the control area by moose can be partly explained by proximity to moose habitat and water. Snow depth, pipeline clearance, and distance to road were not significantly different for moose crossings between study areas, suggesting that moose crossing locations follow similar trends for these three parameters. The control pipeline does not parallel a road at any point; therefore, in order for pipeline crossings to occur at similar distances from roads in both study areas, moose)
are choosing to cross the pipeline at locations farther from the road at the pipeline crossing structure area. The more frequent observation of moose (A. alces) at the control area, and the higher proportion of moose crossings at elevated pipelines, suggests that moose have become habituated to elevated pipeline locations, as found by Child (1973) and Young et al. (1989). It is possible that the high number of successful pipeline crossings at elevated sections of the control pipeline (30 of 37) is due to one animal repeatedly using that area. However, the lower proportion of deflections along the control area suggests that moose have habituated to locations where they can easily cross underneath the pipeline. The higher frequency of moose crossings along the control area appears to be a result of proximity to moose habitat and water, along with moose habituating to elevated pipeline locations.
4.1.2.
Pipeline clearance required for moose
Moose deflections occurred at an average pipeline clearance of 110.7 cm, based on winter snow tracking data. Pipeline
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clearances less than 120 cm could physically impede moose from crossing the pipeline (Morgantini, 1985; Skinner and Westworth, 1990). Penner (1985) found pipeline clearances ranging between 70 and 140 cm impede moose movement. Other studies have reported moose crossing underneath pipelines with clearances of 130–140 cm (Eide et al., 1986; Kansas and Raine, 1988; Skinner and Westworth, 1990). Our research found 84.8% of moose crossings occurring at locations with a pipeline clearance above 140 cm, while only 30.4% of the pipeline had a clearance of that amount. A pipeline clearance of 140 cm appears to be a critical threshold height in allowing moose movement under the pipeline. Deer and carnivores were shown to easily cross underneath pipelines of this height, confirming that above-ground pipelines are a greater barrier to moose than other species in the study. Moose rarely cross over obstructions such as snow berms or above-ground pipelines, and even buried sections of pipeline are used significantly less than available (Van Ballenberghe, 1978; Eide et al., 1986). We observed only one instance of a moose walking over five adjacent, parallel pipelines (pipeline clearance of 32–47 cm, and ground to top of pipeline height of 75–87 cm).
4.1.3.
Pipeline clearance required for carnivores
Carnivores crossed the pipeline with less than 129 cm clearance more than available, except for the 92–99 cm locations. The average pipeline clearance for carnivore crossings was 113 cm, with pipeline clearances less than 91 cm being crossed far more than was available. Golder Associates Limited (2004) found carnivores crossing pipelines with an average height of 108 cm. However, further research is required to determine if carnivores avoid sections of elevated pipeline or exhibit other behavioural changes.
4.2.
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tions below is expected to meet the needs of all large boreal mammals found in the study area.
4.2.1.
Moose require a minimum pipeline clearance of 140 cm
Moose movement can be facilitated by constructing pipelines with a clearance of at least 140 cm and/or by using pipeline mitigations when this clearance is not met. The majority of pipeline crossings by moose (84.8%) occurred at locations with a clearance of at least 140 cm. Small gas pipelines and steel cables are sometimes associated with above-ground pipelines and should be kept at the same clearance as the rest of the pipeline. A pipeline clearance of 140 cm may not be sufficient during times of deep snow or flooding and the use of pipeline crossing structures or elevated pipelines should be used in these situations. A pipeline clearance of 140 cm can be achieved at existing pipelines by modifying the ground underneath (Young, 1989). Physically removing the soil beneath a section of pipeline will increase the clearance between the ground and the bottom of the pipeline, allowing wildlife to cross underneath. This is only feasible in dry locations; otherwise the excavated area may flood. The priority here is to create sections of pipeline that facilitate wildlife movement underneath the pipeline.
Pipeline clearance required for deer
Deer crossed the pipeline in locations with an average pipeline clearance of 121 cm. Kansas and Raine (1988) observed deer crossing underneath pipelines with a mean clearance of 120 cm. Deer movement was relatively uniform across all pipeline clearances with an increase in deer crossings at pipeline clearances of 100–105 cm. Other studies have also observed deer crossing underneath pipelines with a clearance of 100 cm (Morgantini, 1981; Penner, 1985; Golder Associates Limited, 2000; AXYS Environmental Consulting Limited, 2003). Only one deer was observed jumping over a pipeline (59– 72 cm clearance and ground to top of pipeline distance of 100–110 cm). The tracks indicate that the deer was being chased by a predator resulting in the deer jumping the pipeline. As was found by Golder Associates Limited (2000), deer rarely jump over and prefer to cross underneath pipelines with a minimum clearance of 100 cm.
4.1.4.
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Recommendations for pipeline design
The following recommendations are predominantly focussed on moose and recommendations can be used in locations where the movement of large ungulate populations are potentially hindered by above-ground pipelines. Deer and carnivores demonstrated less of an aversion to crossing above-ground pipelines and adhering to the recommenda-
4.2.2. The pipeline should not be lowered to facilitate movement over top Pipelines should not be constructed low to the ground as neither deer nor moose show a preference for crossing over them. There was only one instance, each of a deer and a moose, going over the pipeline during 12 months of monitoring, despite the abundance of locations with relatively low pipeline clearances.
4.3. How do large mammals interact with pipeline crossing structures? Remote camera data indicated that large mammal species are regularly using the above-ground pipeline crossing structures with successful crossings varying by species. Moose successfully crossed structures more often than any other species (88.2% of approaches). Pipelines pose a greater barrier to moose (as previously discussed), emphasizing the importance of this finding. Lower use rates by deer and carnivores were likely a result of their ability to cross underneath a larger range of pipeline clearances, and so they do not need to use the structures as often. All approaches to the structures by carnivores (bear, coyote, lynx, and wolf) were successful. Coyote and moose crossed significantly more at Structure 4 than at any other structure. Individual behavioural responses to features can greatly influence successful crossing rates (Morgantini, 1985). One moose cow and calf were observed using Structure 4 frequently – almost everyday – accounting for a large proportion of the successful crossings. This shows that individual moose may become habituated to certain structures and are using them on a frequent basis. This may have resulted in a disproportionately high number of moose crossings being observed at this location. However, Structure 4 is located in high quality moose habitat and very close to water, which corresponds to the t test results where
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moose crossed pipelines significantly closer to water than at deflection locations. Structure 1 had the most wildlife movement adjacent to it, and was used more during the day and on weekdays, despite being only 255 m from a road and 165 m from a well pad. The presence of well pads is a constant stimulus of low intensity, which moose habituate to (Tennessen, 1979; Sopuck and Vernam, 1986). Well pads were found to be less of an influence on wildlife movement than roads. The distance and alignment of roads to crossing structures influenced the timing and overall crossing success. Structures 1, 2, and 5 (further from a road) were used more frequently during the day than Structures 3 and 4. Structures 3 and 4 were used more frequently on weekends when traffic volumes were lower. The very high success rate of Structure 4, despite being located close (126 m) to the road, appears to be due to the parallel placement next to the road, and lower pipeline clearance adjacent to it (64 cm). An animal is less likely to cross a structure that takes it directly onto a road when compared to a structure perpendicular to a road. At Structure 4, the vast majority of wildlife movements were successful crossings; this was not the case at Structures 2 and 3, which facilitate movement toward the road. This indicates the need to consider alignment of the crossing structures as well as distance to roads. Clevenger and Waltho (2005) reported that after human activity, physical attributes were most important in determining a successful crossing over road structures. Structure 4 had the lowest adjacent pipeline clearance it (64 cm), which acted to funnel wildlife toward the structure in the same way fences funnel wildlife toward road crossing structures. Despite Structure 5 being the farthest from a road, it had relatively low crossing rates due to the high adjacent pipeline clearance (127 cm). Most wildlife can cross underneath the pipeline at this height, limiting the need for an animal to use the pipeline crossing structure.
4.4.
Recommendations for pipeline mitigations
More research in more environments and over longer periods of time is required to improve the mitigation methods for facilitating wildlife movement across above-ground pipelines. However, the following recommendations demonstrate the practical application of conservation research to facilitate wildlife movement using pipeline crossing structures and elevated pipelines.
4.4.1.
Pipeline crossing structure design
The pipeline clearance on either side of a pipeline crossing structure greatly influences the number of successful crossings. If the pipeline clearance on either side of the structure is low (<100 cm), carnivores and deer can cross underneath, while moose are funnelled toward the pipeline crossing structure. A lower pipeline clearance adjacent to the structure also results in a smaller gradient and increased visibility across the structure. The pipeline crossing structures in the current study were constructed with a slope of 6:1, and a width of 4 m at the top. The structures should be planted with local vegetation to pro-
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vide habitat and proximity to cover. Research has not been undertaken to determine the most effective pipeline crossing structure design (Golder Associates Limited, 2004). Monitoring the efficacy of different structure designs for particular target species over the long-term would be very valuable.
4.4.2. Elevated pipeline (pipeline clearance greater than 180 cm) The results of this study and previous studies indicate that moose freely cross underneath elevated pipelines with a clearance of at least 180 cm and will cross under pipelines as low as 140 cm. Elevated pipelines can be used in addition to pipeline crossing structures to facilitate wildlife movement. More research is required to determine the necessary length of elevated pipeline sections to facilitate moose movement.
4.4.3.
Placement of pipeline mitigations
If pipeline mitigations must be placed near a road, they should be situated so that movement across the structure or under the elevated pipeline moves parallel and not directly perpendicular to the road. In addition, mitigation measures are most effective if placed in known movement corridors and areas of high habitat quality for the focal species. An assessment of the optimal density of pipeline crossing structures or elevated pipelines was not within the framework of this study. Golder Associates Limited (2004) used a distance of 400 m between pipeline crossing structures, while an average distance of 700 m (455–878 m) was used in this study. More research is needed to determine the optimal spatial coverage of mitigation measures.
4.5. How does the crossing rate of pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals? Relative indices represent the number of crossings by all animals during the time the remote cameras were running at that location. When the relative indices are totalled for crossings by all species (moose, deer, coyote, lynx, wolf, and black bear), the results show that pipeline crossing structures were used more than pipelines or elevated pipelines (Fig. 4). It is noteworthy that the pipeline crossing structures were still used given that carnivores show a preference for lower pipeline clearances, and deer are capable of crossing the majority of pipeline clearances. As expected, lower pipeline clearances (47 to 149 cm) were used the least for all species combined. When analyzed separately, moose also show a preference to use structures more than pipelines or elevated pipelines. The locations for elevated pipelines were not specifically chosen for wildlife mitigation and are simply a result of changing topography. As a result, wildlife may not be using the areas adjacent to elevated pipelines as frequently, partially accounting for this difference in use. Effective structures permit wildlife to cross anthropogenic barriers to fulfill biological needs, and to move between habitats (Clevenger, 1997). The pipeline crossing structures in this study were used regularly and by all species of interest. By facilitating movement across the pipeline, both structures and elevated pipelines are assumed to have conservation value in mitigating the effects of fragmentation.
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Relative Indices *1000
450
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All Species Combined
400 350 300 250 200 150 100 50 0 Cameras at Structures
Cameras at 200 cm Pipeline Clearance
Relative Indices *1000
70
Cameras at 47-149 cm Pipeline Clearanc
Moose Only
60 50 40 30 20 10 0 Cameras at Structures
Cameras at 200 cm Pipeline Clearance
Cameras at 47-149cm Pipeline Clearance
Fig. 4 – Relative indices for successful crossings at structures, elevated pipelines and pipelines for all species combined, and separately for moose (Alces alces), based on remote camera data.
5.
Conclusions
The results of this project are the first to use longer-term quantitative data to assess the effectiveness of pipeline crossing structures in facilitating wildlife movement. This study found that pipeline crossing structures were utilized more frequently than elevated pipelines for moose and for all species combined. In the 12 months following pipeline construction, these structures facilitated wildlife movement across the pipeline. Wildlife, especially moose, showed habituation to pipeline crossing structures and sections of elevated pipeline. This indicates that such mitigation efforts will likely be used more with time. The inclusion of pipeline crossing structures and elevated pipelines in future developments is essential to lessen the negative impacts of habitat fragmentation. Our research provides quantitative information on wildlife interactions with above-ground pipelines and associated structures, with special attention paid to moose. Natural fluctuations in resident wildlife populations occur due to changes in weather patterns, vegetation, snow depth, and disease, requiring long-term monitoring to determine the optimal use of pipeline crossing structures. Continued monitoring and adaptive management will ensure that the structures remain functional over time, while allowing for improved design and evaluation. The potential extent of future in situ oil sand development in Canada and elsewhere is substantial. Such landscapes must be managed through regional collaboration with industry and regulators, in order for pipeline mitigations such as these to be effective.
Acknowledgements We would like to thank Roger Creasey, and Fred West at Shell Canada for funding this study and providing the opportunity to work on such a project. Conrad Pilon, Ken Zaitsoff, Greg Gordey, Moss Giasson, and Sarah Laughton, also at Shell Canada, were crucial in providing administrative and logistic support. A special thank you to the staff of the Miistakis Institute for the Rockies, especially Danah Duke and Greg Chernoff.
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available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/biocon
Effectiveness of above-ground pipeline mitigation for moose (Alces alces) and other large mammals Bridget M. Dunne, Michael S. Quinn* Faculty of Environmental Design, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, Canada T2N 1N4
A R T I C L E I N F O
A B S T R A C T
Article history:
Above-ground pipelines for in situ oil sands development are potentially significant vectors
Received 8 February 2008
of habitat fragmentation for large mammals. We evaluated the use of elevated pipeline
Received in revised form
clearances (distance between the ground and the bottom of the pipeline) and pipeline
28 July 2008
crossing structures, the two primary methods of mitigating the barrier effect of above-
Accepted 18 October 2008
ground pipelines on large mammals, with a particular emphasis on moose (Alces alces),
Available online 10 December 2008
in northern Alberta, Canada. Winter snow tracking and remote cameras were employed for one year to monitor large mammal interactions with a 5.5 km stretch of pipeline miti-
Keywords:
gated with five pipeline crossing structures and a 1.6 km control area of unmitigated pipe-
Habitat fragmentation
line. A minimum threshold pipeline clearance of 140 cm was critical in allowing adult
Crossing structure
moose to cross underneath the pipeline. Pipeline crossing structures facilitated movement
Pipeline mitigation
across the pipeline and were used more than sections of elevated pipelines by all species.
Oil sands
1.
Introduction
The infrastructure associated with energy development results in a broad array of environmental effects (Dincer, 1998; Balat, 2005). Increasing demand for energy, coupled with the depletion of conventional petroleum reserves, is leading to the development of unconventional oil resources such as bitumen occurring as oil sands (Greene et al., 2004). Recovery of this heavy oil is generating a novel set of environmental impacts beyond those associated with conventional petroleum exploitation. Terrestrial bitumen reserves are widespread and are estimated to occur in over 65 countries (Soderbergh et al., 2007). Bitumen extraction occurs through surface mining of shallow deposits, or in situ withdrawal of deeper (>75 m) deposits. The landscape disturbance associated with such oil sands development is large and growing. Methods are required to manage and mitigate the environmental effects of oil sands development. One of the largest bitumen reserves in the world is found in the oil sand deposits of Alberta, Canada. Approximately 80% of the estimated 174 billion barrels of oil in the Alberta
Ó 2008 Elsevier Ltd. All rights reserved.
oil sands will require in situ recovery (Hopwood et al., 2004). The current in situ recovery method of choice is steam assisted gravity drainage (SAGD), which involves placing two horizontal wells into a bitumen formation. The top well injects steam to decrease the viscosity of the bitumen, while the bottom well captures the bitumen and returns it to the surface for processing (Chow et al., 2008). Extensive networks of above-ground pipelines are used to transport steam to the extraction site, and bitumen from the extraction site to a processing facility. High and variable temperatures result in pipeline expansion and contraction, thus preventing the pipelines from being buried underground. The pipeline clearance (distance between ground and bottom of pipeline) is typically 1 m, although this varies with topography. Pipelines generally consist of two or more parallel pipes 30–60 cm in diameter separated by 50–200 cm. The resultant a horizontal barrier is two to several metres wide. Smaller gas lines and other cables may also be associated with the pipeline structure. In situ development and associated above-ground pipelines have the potential to cover 138,000 km2 of northern Alberta (Schneider and Dyer, 2006).
* Corresponding author: Tel.: +1 403 220 7013; fax: +1 403 284 4399. E-mail addresses: [email protected] (B.M. Dunne), [email protected] (M.S. Quinn). 0006-3207/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2008.10.029
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Habitat fragmentation, especially for large mammals, is a predicted consequence of such extensive development (Noel et al., 2006; Schneider and Dyer, 2006). Habitat fragmentation occurs when smaller, isolated patches of habitat are created due to a disturbance; often a linear development such as a pipeline, road, railway or power line (Andren, 1994; Alexander et al., 2004; Reimers et al., 2007). Such disturbances reduce or prevent individuals from moving between patches of habitat and result in a barrier effect (Ng et al., 2004; Alexander et al., 2005; Cushman 2006). Habitat loss, reduced patch size, and more isolated habitat patches are the primary components of fragmentation. All of these result in lower biological diversity and altered ecosystem processes (Hobbs, 1993; Andren, 1994; Van Wieren and Worm, 2001; Castelletta et al., 2005). Species that display a low resilience to habitat fragmentation include those with life history traits such as late age of first reproduction, low population densities, low reproductive rates, large home-range requirements, and low fecundity (Weaver et al., 1996; Van Wieren and Worm, 2001; Alexander et al., 2004; Ng et al., 2004). Species that move over great distances to disperse, find food, and mate are also most threatened by linear developments (Clevenger et al., 2001; Ng et al., 2004). As a result, the species of interest for this project included moose (Alces alces), black bear (Ursus americanus), lynx (Lynx canadensis), gray wolf (Canis lupus), coyote (Canis latrans), white-tailed deer (Odocoileus virginianus), and mule deer (Odocoileus hemionus). Pipelines pose a significant barrier to moose as the largest mammal in the study area, with large home ranges, low reproductive rates, low population densities, and extended parental care (Franzmann and Schwartz, 1997). There are two primary means of mitigating the physical barrier created by above-ground pipelines: (1) elevating the pipeline clearance to facilitate movement underneath, and (2) constructing pipeline crossing structures to facilitate movement over the pipeline. Elevated pipelines with a pipeline clearance of at least 180 cm have proven effective in facilitating wildlife movement, particularly for moose (Van Ballenberghe, 1978; Eide and Miller, 1979; Sopuck and Vernam, 1986; Golder Associates Limited, 2000; AXYS Environmental Consulting Limited, 2003; Golder Associates Limited, 2004). However, local ground conditions, engineering requirements, and human safety issues may limit the application of elevated pipelines. Pipeline crossing structures that facilitate the movement of wildlife over pipelines have been proffered as a mitigation alternative. However, few such structures have been installed and there is a dearth of published research on their effectiveness or optimal design characteristics. Our research provides a unique and valuable examination of pipeline crossing structures and an assessment of required pipeline clearances for large mammals in a boreal context. The purpose of this paper is to examine pipeline crossing structures and elevated pipeline clearances as means of mitigating the effects of above-ground pipelines in areas of in situ bitumen extraction. The focus of our research was on the movement of large mammals, with a particular emphasis on moose. Three research questions were used to guide our inquiry: (1) How do large mammals interact with aboveground pipelines? (2) How do large mammals interact with pipeline crossing structures?, and (3) How do the crossing
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rates at pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals? Our results are used to provide recommendations for future above-ground pipelines and pipeline crossing structures in order to facilitate wildlife movement.
2.
Methods
2.1.
Study area
In March 2006, five pipeline crossing structures (structures) were built by Shell Canada at its Peace River Complex, 55 km northeast of Peace River in the boreal mixed-wood region of northern Alberta, Canada (Fig. 1). These structures were built by placing steel sleeves over a section of pipeline, compacting gravel over these sections, adding a layer of topsoil, and then seeding the structure to provide vegetation and cover. Structure locations were chosen by Shell Canada based on surrounding habitat, and existing cut lines and trails. Structures were built 19.8–25.0 m long (i.e., span perpendicular to the direction of the pipeline) with a height of 2.0–3.0 m. Width at the top of the structures ranged from 3.7 to 4.0 m and width at the bottom of the structures was 11.9–14.9 m. Elevated pipelines were defined as locations with a pipeline clearance (distance between the ground and the bottom of the pipeline) of at least 180 cm (Van Ballenberghe, 1978; Eide and Miller, 1979; Sopuck and Vernam, 1986; Golder Associates Limited, 2000; AXYS Environmental Consulting Limited, 2003; Golder Associates Limited, 2004). Pipeline clearance is primarily a function of local changes in topography. The term pipeline refers to locations with a clearance less than 180 cm. Two sections of pipeline were studied for this project (Fig. 1). One section (pipeline crossing structure area) was a 5.5 km stretch of pipeline with five pipeline crossing structures. This pipeline was built at the beginning of the study in March 2006. The second was a 1.6 km section of pipeline with no pipeline crossing structures (control area) built in 2000. Pipeline clearance ranged from 32 to 234 cm (mean = 130 cm) in the crossing structure area and 53–256 cm (mean = 127 cm) in the control area. Large mammal movement was monitored using remote cameras during the entire study period and snow tracking in winter. Animal movements were classified as crossings (movement across the pipeline or structure from one side to the other), deflections (movement indicating a definite approach towards the pipeline or structure followed by a change in direction away) or parallel movements (movement parallel to the pipeline or structure). Approaches to the pipeline or structure were considered to be active attempts to cross, and were calculated by summing crossings and deflections for that species or location. Data were combined for mule deer and white-tailed deer. Methods to address each of the research questions are presented below.
2.2. How do large mammals interact with above-ground pipelines? 2.2.1.
Winter snow tracking
Three tracking sessions occurred during the first winter (9 February 2006 to 23 March 2006) primarily to identify study
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4
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5
2 3
1
Pipeline Crossing Structure Area
Control Area
Peace River Study Area
Fig. 1 – Location of study area with pipeline crossing structure and control areas outlined.
areas, and appropriate locations for remote cameras. The second winter (22 November 2006 to 3 April 2007) consisted of a full season of winter snow tracking with seven tracking sessions along the pipeline crossing structure and control areas. Winter snow tracking was conducted every three weeks following the establishment of a consistent snow layer. The 20 m pipeline right-of-way (ROW) on each side of the pipeline was assessed for tracks by two researchers; one walked along the pipeline while the other walked along the forest edge (Young, 1989). This allowed us to record the tracks of any animal approaching the pipeline from either side, thus ensuring complete coverage of the ROW. Five environmental variables were recorded or calculated for all track sequences: snow depth, pipeline clearance, distance to preferred moose habitat (defined by an existing habitat classification), distance to water, and distance to road. Analysis of Variance (ANOVA) was conducted to assess these environmental factors in relation to moose crossings, deflections or parallel movements to the pipeline, for the structure and control areas combined. t-Tests were used to compare these variables at pipeline crossing and deflection locations by moose separately for each study area. Logistic regression was employed to determine which of the five variables had the greatest predictive capability for moose crossing and deflection locations in each study area. A t-test was used to analyze the null hypothesis that the means of the five environmental variables were similar at moose crossing sites in each study area.
2.2.2.
Remote camera monitoring
Four digital infrared cameras (Reconyx, 2004) were placed next to the pipeline in both the pipeline crossing structure and control areas to monitor wildlife movement. Cameras were checked every three weeks during the full year of oper-
ation at which time the digital media cards and batteries were changed. An interval of two minutes between digital image capture was chosen to distinguish between unique wildlife events (Morgantini, 1981). Data were standardized by dividing the number of wildlife movements observed by the number of functional camera days. This allowed for the direct comparison of wildlife movements at each camera location. The camera data were a series of non-normal, independent, random events with no replicate samples, making chi square analysis most appropriate. Relative indices for crossings, deflections, and parallel movements next to the pipeline by moose, deer, and carnivores (bear, coyote, lynx, and wolf) were analyzed using one-sample chi square tests. The frequency distributions of pipeline crossings by moose, deer, and carnivores at different pipeline clearances were graphed with available pipeline clearances to identify preferences for crossing at particular pipeline clearances.
2.3. How do large mammals interact with pipeline crossing structures? Two digital infrared cameras were placed at each of the five structures to monitor wildlife movement for a period of 12 months (mounted on posts; one on each side of the structure). Cameras were positioned to capture movement along the pipeline right-of-way as well as on the structure. Wildlife movements were defined as crossing, deflecting or paralleling the structure. Relative indices were calculated for wildlife movements by functional camera day, species, season, day versus night, and weekday versus weekend. Environmental variables collected in association with each structure included: pipeline clearance, ecosite (as identified in an existing vegetation assessment), structure dimensions, distance to water, distance to preferred moose habitat, distance to roads,
B I O L O G I C A L C O N S E RVAT I O N
and distance to the next structure. Chi square tests were used to test for differences in use between the pipeline crossing structures.
2.4. How does the crossing rate of pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals? Relative indices for crossings by all species at the pipeline, elevated pipeline and pipeline crossing structures were compared. In other words, the relative indices calculated for the cameras at the pipeline and elevated pipeline locations were compared to the pipeline crossing structure cameras for each species over the year of monitoring.
3.
Results
3.1. How do large mammals interact with above-ground pipelines? 3.1.1.
Winter snow tracking: moose
To calculate successful pipeline crossing rates for each species, 57 (first winter), and 563 (second winter) wildlife track sequences were pooled. Although a higher number of wildlife tracks were encountered along the pipeline crossing structure area, the density of tracks per 100 m was much higher in the control area (28.9 compared to 9.4; Table 1). Of the 86 moose track sequences observed in both study areas combined, 56 crossed the pipeline, 21 deflected away from the pipeline, and 9 moved parallel to the pipeline. Moose was the only species observed more frequently in the control area. Moose also crossed the control area pipeline more frequently and with a higher rate of success (77.1% compared to 65.5%) compared to the pipeline crossing structure area.
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Fewer moose deflections were observed along the control pipeline (20%) than the pipeline crossing structure area (31%). The mean pipeline clearance for the entire study area was 128.5 cm while the mean pipeline clearance at moose crossing locations was 169.7 cm (N = 56). The majority of moose crossings (43.5%) occurred at a pipeline clearance of 185– 256 cm (Fig. 2). Pipeline clearances of 143–256 cm were used more than available. Although 84.8% of moose crossings occurred at locations with a pipeline clearance above 140 cm, only 30.4% of the pipeline had a clearance over 140 cm. There was only one instance where a moose crossed directly. This event occurred at a location with a pipeline clearance of 32– 43 cm (top of the pipeline 75–87 cm). The mean pipeline clearance where moose deflected from the pipeline over the entire study area was 110.7 cm (N = 21). Locations where moose deflected from the pipeline occurred at significantly higher snow depths (F(2, 72) = 5.384, p < 0.01) and further from water (F(2, 72) = 4.585, p = 0.013) than moose crossing locations. Moose crossing sites occurred at significantly higher pipeline clearances (F(2, 72) = 16.948, p < 0.01) than deflections or parallel movements. Distance to preferred moose habitat and roads were not significantly different for moose crossings, deflections or parallel movements next to the pipeline. Parallel movements (N = 9) did not show any significant results and were not included in further analysis as they provide no information on wildlife interactions with above-ground pipelines. Moose crossing sites within the pipeline crossing structure area occurred at significantly higher pipeline clearances (t = 3.08, df = 22, p < 0.01) and closer to water (t = 2.26, df = 22, p = 0.03) than moose deflection sites. Pipeline clearance had a predictive capability of 83.3% for moose crossing locations [Y = 2.859 + 0.026 (pipeline clearance)].
Table 1 – Pipeline crossing rates by species in the pipeline crossing structure and control areas based on winter snow track results. Species
Movement
Pipeline crossing structure area
Control area
Moose Crossings/approaches Percent cross
19/29 65.5
37/48 77.1
Crossings/approaches Percent cross
327/341 95.9
262/290 90.3
Crossings/approaches Percent cross
68/72 94.4
32/32 100.0
Crossings/approaches Percent cross
4/6 66.7
1/1 100.0
Crossings/approaches Percent cross
17/20 85.0
5/5 100.0
Animals recorded Pipeline length (m) Animals recorded/100 m
5195 5500 9.4
462 1600 28.9
Deer
Coyote
Lynx
Wolf
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1 4 2 ( 2 0 0 9 ) 3 3 2 –3 4 3
Moose 50
16
45
Deer
14
40
12
30
10
25
8
20
6
15
4
10
2
0
0 082 83 -9 1 92 -9 9 10 010 5 10 611 7 11 812 9 13 014 2 14 315 4 15 518 4 18 525 6
5 082 83 -9 1 92 -9 9 10 010 5 10 611 7 11 812 9 13 014 2 14 315 4 15 518 4 18 525 6
Pipeline Crossings (Percent)
35
Pipeline Clearance (cm)
Pipeline Clearance (cm)
Carnivore
16 14 12
Available Pipeline
10
Moose (N=46)
8
Deer (N=312)
6 4
Carnivore (N=113)
2 6
4 18
5-
25
18
4 15
515
2 314
9
14 013
7
12 811
5
11
10
610
9
1
-9
010
92
-9 83
0-
82
0
Pipeline Clearance (cm)
Fig. 2 – Comparison of pipeline clearances where moose (Alces alces), deer (O. virginianus and O. hemionus), and carnivores (Canis lupus, Canis latrans, Lynx canadensis) crossed underneath the pipeline, with available pipeline clearances based on winter snow tracking data.
In the control area, the majority of moose tracks (30 of 37) were observed next to elevated pipelines. Of the 30 encounters at these locations, 86.7% were successful crossings (v21 ¼ 162:000), p = 0.05. Pipeline clearance (t = 4.16, df = 40, p < 0.01) and distance to water (t = 2.28, df = 40, p = 0.028) were significantly different for moose crossing and deflecting locations, as was observed in the structure area. Pipeline clearance was also the best predictor of pipeline crossing locations by moose at 85.7% [Y = 4.062 + 0.035 (pipeline clearance)]. Nineteen moose (15 track sequences) were observed at the pipeline crossing structure area and 37 (32 track sequences) along the control area. Moose crossing locations at each of the study areas were not significantly different in terms of snow depth (t = 0.95 df = 45, p = 0.35), pipeline clearance (t = 0.60, df = 19, p = 0.59), or distance to road (t = 1.84, df = 19.7, p = 0.08). There was a significant difference between distance to preferred moose habitat (t = 4.88, df = 15.8, p = <0.01), and distance to water (t = 7.23, df = 45, p < 0.01), with pipeline crossings being closer to moose habitat and water in the control area. The mean distance from crossing locations to moose habitat was 249 m in the control area, and 566 m in the pipeline crossing structure area, with the mean distance to water being 210 m and 587 m, respectively.
3.1.2.
Winter snow tracking: deer
Deer were recorded most frequently and had a 5.6% higher successful crossing rate at the pipeline crossing structure area (Table 1). One deer jumped over a cluster of three pipelines at the control area (pipeline clearance of 59–72 cm), where the top of the pipeline reached 100–110 cm from the ground. Winter snow track data indicated deer crossings (N = 312) occurring at pipeline clearances of 70–256 cm, with an average of 121 cm. Deer movement was almost uniform across all pipeline clearances with 0–91 cm, 100–105 cm, 118–129 cm and 155–184 cm pipeline clearances used more than expected, while 92–99 cm, 106–117 cm, 130–154 cm, and 185–256 cm pipeline clearances were used less than expected (Fig. 2).
3.1.3.
Winter snow tracking: carnivore
More carnivores were observed along the pipeline crossing structure area. However, all attempted pipeline crossings at the control area were successful and no deflections were observed here (Table 1). The average carnivore crossing (N = 113) occurred at a pipeline clearance of 115 cm, with a range of 53– 56 cm (Fig. 2). Carnivores crossed locations with lower pipeline clearances more frequently than moose or deer, with 83.2% of carnivore crossings at pipeline clearances less than 140 cm. Carnivores crossed pipelines with a clearance less
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than 129 cm more than available, except for clearances of 92– 99 cm.
3.1.4.
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3.3. How does the crossing rate of pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals?
Remote camera monitoring: all species
Camera data indicated moose crossing the pipeline with a mean clearance of 190 cm (N = 47), ranging from 115 to 200 cm (Fig. 3), again showing a clear preference by moose to cross at higher pipeline clearances. Camera data (N = 300) recorded deer crossing the pipeline with an average clearance of 156 cm and with a range of 80–200 cm (Fig. 3). Deer did not show a clear preference for crossing at specific pipeline clearances. The camera data showed carnivore crossing locations (N = 11) ranging from 47 to 200 cm, with an average pipeline clearance of 132 cm. The 200 cm location in the control area received the highest number of successful pipeline crossings for all species.
During the 12 months of camera monitoring at pipelines, elevated pipelines, and pipeline crossing structures, the highest successful crossing rate was observed at the structures (Fig. 3). As with all species combined, moose exhibit a preference to use pipeline crossing structures more frequently than crossing underneath pipelines or elevated pipelines (Fig. 3).
3.2. How do large mammals interact with pipeline crossing structures?
Moose deflected from the pipeline at locations with significantly higher snow depths, and further from water than at crossing or parallel movement locations. Snow depth can influence wildlife movement under a pipeline as the clearance between the ground and the bottom of the pipeline decreases. In deep snow, wildlife, particularly ungulates, will use different movement patterns in order to follow the path of least energetic resistance (Bergerud et al., 1984; Dyer et al., 2002). Snow depths up to 85 cm were observed during this study. As snow depth increases to levels greater than 70–80 cm, moose home range use, movements, and migrations decrease (Van Ballenberghe, 1978; Hamilton et al., 1980; Hauge and Keith, 1981; Sopuck and Vernam, 1986; Franzmann and Schwartz, 1997; Garrett and Conway, 1999; Keech et al., 2000), resulting in fewer attempted pipeline crossings. It was expected that locations farther from water would have fewer moose (Sopuck and Vernam, 1986; Clevenger et al., 2001). The mean distance from water ranged from 330 m at crossing sites, to 543 m at deflection sites. Although moose can easily traverse both of these distances, deflection sites were found significantly farther from water than pipeline crossing locations.
4.
4.1. How do large mammals interact with above-ground pipelines? 4.1.1.
Table 2 provides the environmental and physical characteristics of each of the five pipeline crossing structures. Structures were crossed by deer (N = 746), moose (N = 157), coyote (N = 52), bear (N = 2), lynx (N = 2) and wolves (N = 1) (Table 3). Moose had the highest successful crossing rate overall (88.2%) based on total approaches to the structure. Coyote and deer had very high overall crossing rates as well, with 88.1% and 82.5%, respectively. Wildlife crossings for all species were significantly higher at Structure 4 than any other structure (v21 ¼ 164:995, p = 0.05). Coyotes (v21 ¼ 15:211, p = 0.05), and moose (v21 ¼ 172:165, p = 0.05) crossed this structure significantly more. The fourth structure was the most frequently crossed by moose and coyotes, with 91.7 and 90.9%, respectively. The third structure had the highest proportion of successful crossings by deer, with 91.1%. Two bears and two lynx crossed the fifth structure, while one wolf crossed the second structure. Although their numbers are low, all black bear, lynx, and wolf approaches to the structures were successful crossings.
Discussion and conclusions
Moose
Pipeline Crossings (Percent)
60 50 40
Moose Crossings (N=47)
30
Deer Crossings (N=300) Carnivore Crossings (N=11)
20 10
Pipeline Clearance (cm)
l on
tro
20 0 20 0
C
14 9
14 0
13 0
11 5
10 0
95
86
80
47
0
Fig. 3 – Moose (Alces alces), carnivore (Ursus americanus and Canis latrans), and deer (O. virginianus and O. hemionus) crossings based on stationary camera data at specific pipeline clearances.
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1 4 2 ( 2 0 0 9 ) 3 3 2 –3 4 3
Table 2 – Environmental variable information for pipeline crossing structures. Structure 1 Height (m) Length (m) Width at top (m) Average width on bottom (m) Surrounding pipeline clearance (cm) Distance to water (m) Distance to moose Habitat (m) Distance to road (m) Distance to next Structure (m) Ecosite phase
Structure 2
Structure 3
Structure 4
Structure 5
3.0 25.0 4.0 11.9 125 519
3.0 21.5 3.8 12.3 114 702
2.0 20.2 3.8 13.4 70 1070
2.0 19.8 3.8 13.4 64 300
2.5 22.1 3.7 14.9 127 284
326 255
0 76
381 67
0 125
582 416
455 Low bush cranberry
544 Shrubby rich fen
764 Low bush cranberry
878 Shrubby rich fen
862 Shrubby poor fen
Table 3 – Structure crossing rates by species based on remote camera results. Moose
Deer
Coyote
Lynx
Wolf
Bear
Structure 1 Crossings/approaches Percent cross
5/7 71.4
177/197 89.8
8/9 88.9
0/0 0.0
0/0 0.0
0/0 0.0
Structure 2 Crossings/approaches Percent cross
4/5 80.0
99/152 65.1
3/4 75.0
0/0 0.0
1/1 100.0
0/0 0.0
Structure 3 Crossings/approaches Percent cross
6/10 60.0
164/180 91.1
11/13 84.6
0/0 0.0
0/0 0.0
0/0 0.0
Structure 4 Crossings/approaches Percent cross
132/144 91.7
294/353 83.3
30/33 90.9
0/0 0.0
0/0 0.0
0/0 0.0
Structure 5 Crossings/approaches Percent cross
10/12 83.3
12/22 54.5
0/0 0.0
2/2 100.0
0/0 0.0
2/2 100.0
Average for all structures Crossings/approaches Percent cross
157/178 88.2
746/904 82.5
52/59 88.1
2/2 100.0
1/1 100.0
2/2 100.0
Moose crossing sites occurred at significantly higher pipeline clearances than at deflection or parallel movement locations. In addition, pipeline clearance was the best predictor of moose pipeline crossing locations in both study areas. This emphasizes the barrier effect that low pipeline clearances have on moose movement. These findings are consistent with Kansas and Raine (1988) and Golder Associates Limited (2000), where pipeline characteristics have a greater influence on pipeline crossing locations than environmental conditions. Moose crossing sites occur at locations significantly closer to preferred moose habitat and water in the control area, than along the pipeline crossing structure area. The higher use of the control area by moose can be partly explained by proximity to moose habitat and water. Snow depth, pipeline clearance, and distance to road were not significantly different for moose crossings between study areas, suggesting that moose crossing locations follow similar trends for these three parameters. The control pipeline does not parallel a road at any point; therefore, in order for pipeline crossings to occur at similar distances from roads in both study areas, moose)
are choosing to cross the pipeline at locations farther from the road at the pipeline crossing structure area. The more frequent observation of moose (A. alces) at the control area, and the higher proportion of moose crossings at elevated pipelines, suggests that moose have become habituated to elevated pipeline locations, as found by Child (1973) and Young et al. (1989). It is possible that the high number of successful pipeline crossings at elevated sections of the control pipeline (30 of 37) is due to one animal repeatedly using that area. However, the lower proportion of deflections along the control area suggests that moose have habituated to locations where they can easily cross underneath the pipeline. The higher frequency of moose crossings along the control area appears to be a result of proximity to moose habitat and water, along with moose habituating to elevated pipeline locations.
4.1.2.
Pipeline clearance required for moose
Moose deflections occurred at an average pipeline clearance of 110.7 cm, based on winter snow tracking data. Pipeline
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clearances less than 120 cm could physically impede moose from crossing the pipeline (Morgantini, 1985; Skinner and Westworth, 1990). Penner (1985) found pipeline clearances ranging between 70 and 140 cm impede moose movement. Other studies have reported moose crossing underneath pipelines with clearances of 130–140 cm (Eide et al., 1986; Kansas and Raine, 1988; Skinner and Westworth, 1990). Our research found 84.8% of moose crossings occurring at locations with a pipeline clearance above 140 cm, while only 30.4% of the pipeline had a clearance of that amount. A pipeline clearance of 140 cm appears to be a critical threshold height in allowing moose movement under the pipeline. Deer and carnivores were shown to easily cross underneath pipelines of this height, confirming that above-ground pipelines are a greater barrier to moose than other species in the study. Moose rarely cross over obstructions such as snow berms or above-ground pipelines, and even buried sections of pipeline are used significantly less than available (Van Ballenberghe, 1978; Eide et al., 1986). We observed only one instance of a moose walking over five adjacent, parallel pipelines (pipeline clearance of 32–47 cm, and ground to top of pipeline height of 75–87 cm).
4.1.3.
Pipeline clearance required for carnivores
Carnivores crossed the pipeline with less than 129 cm clearance more than available, except for the 92–99 cm locations. The average pipeline clearance for carnivore crossings was 113 cm, with pipeline clearances less than 91 cm being crossed far more than was available. Golder Associates Limited (2004) found carnivores crossing pipelines with an average height of 108 cm. However, further research is required to determine if carnivores avoid sections of elevated pipeline or exhibit other behavioural changes.
4.2.
339
tions below is expected to meet the needs of all large boreal mammals found in the study area.
4.2.1.
Moose require a minimum pipeline clearance of 140 cm
Moose movement can be facilitated by constructing pipelines with a clearance of at least 140 cm and/or by using pipeline mitigations when this clearance is not met. The majority of pipeline crossings by moose (84.8%) occurred at locations with a clearance of at least 140 cm. Small gas pipelines and steel cables are sometimes associated with above-ground pipelines and should be kept at the same clearance as the rest of the pipeline. A pipeline clearance of 140 cm may not be sufficient during times of deep snow or flooding and the use of pipeline crossing structures or elevated pipelines should be used in these situations. A pipeline clearance of 140 cm can be achieved at existing pipelines by modifying the ground underneath (Young, 1989). Physically removing the soil beneath a section of pipeline will increase the clearance between the ground and the bottom of the pipeline, allowing wildlife to cross underneath. This is only feasible in dry locations; otherwise the excavated area may flood. The priority here is to create sections of pipeline that facilitate wildlife movement underneath the pipeline.
Pipeline clearance required for deer
Deer crossed the pipeline in locations with an average pipeline clearance of 121 cm. Kansas and Raine (1988) observed deer crossing underneath pipelines with a mean clearance of 120 cm. Deer movement was relatively uniform across all pipeline clearances with an increase in deer crossings at pipeline clearances of 100–105 cm. Other studies have also observed deer crossing underneath pipelines with a clearance of 100 cm (Morgantini, 1981; Penner, 1985; Golder Associates Limited, 2000; AXYS Environmental Consulting Limited, 2003). Only one deer was observed jumping over a pipeline (59– 72 cm clearance and ground to top of pipeline distance of 100–110 cm). The tracks indicate that the deer was being chased by a predator resulting in the deer jumping the pipeline. As was found by Golder Associates Limited (2000), deer rarely jump over and prefer to cross underneath pipelines with a minimum clearance of 100 cm.
4.1.4.
1 4 2 ( 2 0 0 9 ) 3 3 2 –3 4 3
Recommendations for pipeline design
The following recommendations are predominantly focussed on moose and recommendations can be used in locations where the movement of large ungulate populations are potentially hindered by above-ground pipelines. Deer and carnivores demonstrated less of an aversion to crossing above-ground pipelines and adhering to the recommenda-
4.2.2. The pipeline should not be lowered to facilitate movement over top Pipelines should not be constructed low to the ground as neither deer nor moose show a preference for crossing over them. There was only one instance, each of a deer and a moose, going over the pipeline during 12 months of monitoring, despite the abundance of locations with relatively low pipeline clearances.
4.3. How do large mammals interact with pipeline crossing structures? Remote camera data indicated that large mammal species are regularly using the above-ground pipeline crossing structures with successful crossings varying by species. Moose successfully crossed structures more often than any other species (88.2% of approaches). Pipelines pose a greater barrier to moose (as previously discussed), emphasizing the importance of this finding. Lower use rates by deer and carnivores were likely a result of their ability to cross underneath a larger range of pipeline clearances, and so they do not need to use the structures as often. All approaches to the structures by carnivores (bear, coyote, lynx, and wolf) were successful. Coyote and moose crossed significantly more at Structure 4 than at any other structure. Individual behavioural responses to features can greatly influence successful crossing rates (Morgantini, 1985). One moose cow and calf were observed using Structure 4 frequently – almost everyday – accounting for a large proportion of the successful crossings. This shows that individual moose may become habituated to certain structures and are using them on a frequent basis. This may have resulted in a disproportionately high number of moose crossings being observed at this location. However, Structure 4 is located in high quality moose habitat and very close to water, which corresponds to the t test results where
340
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moose crossed pipelines significantly closer to water than at deflection locations. Structure 1 had the most wildlife movement adjacent to it, and was used more during the day and on weekdays, despite being only 255 m from a road and 165 m from a well pad. The presence of well pads is a constant stimulus of low intensity, which moose habituate to (Tennessen, 1979; Sopuck and Vernam, 1986). Well pads were found to be less of an influence on wildlife movement than roads. The distance and alignment of roads to crossing structures influenced the timing and overall crossing success. Structures 1, 2, and 5 (further from a road) were used more frequently during the day than Structures 3 and 4. Structures 3 and 4 were used more frequently on weekends when traffic volumes were lower. The very high success rate of Structure 4, despite being located close (126 m) to the road, appears to be due to the parallel placement next to the road, and lower pipeline clearance adjacent to it (64 cm). An animal is less likely to cross a structure that takes it directly onto a road when compared to a structure perpendicular to a road. At Structure 4, the vast majority of wildlife movements were successful crossings; this was not the case at Structures 2 and 3, which facilitate movement toward the road. This indicates the need to consider alignment of the crossing structures as well as distance to roads. Clevenger and Waltho (2005) reported that after human activity, physical attributes were most important in determining a successful crossing over road structures. Structure 4 had the lowest adjacent pipeline clearance it (64 cm), which acted to funnel wildlife toward the structure in the same way fences funnel wildlife toward road crossing structures. Despite Structure 5 being the farthest from a road, it had relatively low crossing rates due to the high adjacent pipeline clearance (127 cm). Most wildlife can cross underneath the pipeline at this height, limiting the need for an animal to use the pipeline crossing structure.
4.4.
Recommendations for pipeline mitigations
More research in more environments and over longer periods of time is required to improve the mitigation methods for facilitating wildlife movement across above-ground pipelines. However, the following recommendations demonstrate the practical application of conservation research to facilitate wildlife movement using pipeline crossing structures and elevated pipelines.
4.4.1.
Pipeline crossing structure design
The pipeline clearance on either side of a pipeline crossing structure greatly influences the number of successful crossings. If the pipeline clearance on either side of the structure is low (<100 cm), carnivores and deer can cross underneath, while moose are funnelled toward the pipeline crossing structure. A lower pipeline clearance adjacent to the structure also results in a smaller gradient and increased visibility across the structure. The pipeline crossing structures in the current study were constructed with a slope of 6:1, and a width of 4 m at the top. The structures should be planted with local vegetation to pro-
1 4 2 ( 2 0 0 9 ) 3 3 2 –3 4 3
vide habitat and proximity to cover. Research has not been undertaken to determine the most effective pipeline crossing structure design (Golder Associates Limited, 2004). Monitoring the efficacy of different structure designs for particular target species over the long-term would be very valuable.
4.4.2. Elevated pipeline (pipeline clearance greater than 180 cm) The results of this study and previous studies indicate that moose freely cross underneath elevated pipelines with a clearance of at least 180 cm and will cross under pipelines as low as 140 cm. Elevated pipelines can be used in addition to pipeline crossing structures to facilitate wildlife movement. More research is required to determine the necessary length of elevated pipeline sections to facilitate moose movement.
4.4.3.
Placement of pipeline mitigations
If pipeline mitigations must be placed near a road, they should be situated so that movement across the structure or under the elevated pipeline moves parallel and not directly perpendicular to the road. In addition, mitigation measures are most effective if placed in known movement corridors and areas of high habitat quality for the focal species. An assessment of the optimal density of pipeline crossing structures or elevated pipelines was not within the framework of this study. Golder Associates Limited (2004) used a distance of 400 m between pipeline crossing structures, while an average distance of 700 m (455–878 m) was used in this study. More research is needed to determine the optimal spatial coverage of mitigation measures.
4.5. How does the crossing rate of pipelines, elevated pipelines, and pipeline crossing structures compare for large mammals? Relative indices represent the number of crossings by all animals during the time the remote cameras were running at that location. When the relative indices are totalled for crossings by all species (moose, deer, coyote, lynx, wolf, and black bear), the results show that pipeline crossing structures were used more than pipelines or elevated pipelines (Fig. 4). It is noteworthy that the pipeline crossing structures were still used given that carnivores show a preference for lower pipeline clearances, and deer are capable of crossing the majority of pipeline clearances. As expected, lower pipeline clearances (47 to 149 cm) were used the least for all species combined. When analyzed separately, moose also show a preference to use structures more than pipelines or elevated pipelines. The locations for elevated pipelines were not specifically chosen for wildlife mitigation and are simply a result of changing topography. As a result, wildlife may not be using the areas adjacent to elevated pipelines as frequently, partially accounting for this difference in use. Effective structures permit wildlife to cross anthropogenic barriers to fulfill biological needs, and to move between habitats (Clevenger, 1997). The pipeline crossing structures in this study were used regularly and by all species of interest. By facilitating movement across the pipeline, both structures and elevated pipelines are assumed to have conservation value in mitigating the effects of fragmentation.
B I O L O G I C A L C O N S E RVAT I O N
Relative Indices *1000
450
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341
All Species Combined
400 350 300 250 200 150 100 50 0 Cameras at Structures
Cameras at 200 cm Pipeline Clearance
Relative Indices *1000
70
Cameras at 47-149 cm Pipeline Clearanc
Moose Only
60 50 40 30 20 10 0 Cameras at Structures
Cameras at 200 cm Pipeline Clearance
Cameras at 47-149cm Pipeline Clearance
Fig. 4 – Relative indices for successful crossings at structures, elevated pipelines and pipelines for all species combined, and separately for moose (Alces alces), based on remote camera data.
5.
Conclusions
The results of this project are the first to use longer-term quantitative data to assess the effectiveness of pipeline crossing structures in facilitating wildlife movement. This study found that pipeline crossing structures were utilized more frequently than elevated pipelines for moose and for all species combined. In the 12 months following pipeline construction, these structures facilitated wildlife movement across the pipeline. Wildlife, especially moose, showed habituation to pipeline crossing structures and sections of elevated pipeline. This indicates that such mitigation efforts will likely be used more with time. The inclusion of pipeline crossing structures and elevated pipelines in future developments is essential to lessen the negative impacts of habitat fragmentation. Our research provides quantitative information on wildlife interactions with above-ground pipelines and associated structures, with special attention paid to moose. Natural fluctuations in resident wildlife populations occur due to changes in weather patterns, vegetation, snow depth, and disease, requiring long-term monitoring to determine the optimal use of pipeline crossing structures. Continued monitoring and adaptive management will ensure that the structures remain functional over time, while allowing for improved design and evaluation. The potential extent of future in situ oil sand development in Canada and elsewhere is substantial. Such landscapes must be managed through regional collaboration with industry and regulators, in order for pipeline mitigations such as these to be effective.
Acknowledgements We would like to thank Roger Creasey, and Fred West at Shell Canada for funding this study and providing the opportunity to work on such a project. Conrad Pilon, Ken Zaitsoff, Greg Gordey, Moss Giasson, and Sarah Laughton, also at Shell Canada, were crucial in providing administrative and logistic support. A special thank you to the staff of the Miistakis Institute for the Rockies, especially Danah Duke and Greg Chernoff.
R E F E R E N C E S
Alexander, S.M., Water, N.M., Paquet, P.C., 2004. A probabilitybased GIS model for identifying focal species linkage zones across highways in the Canadian Rocky Mountains. In: Clarke, G., Stillwell, J. (Eds.), Applied GIS and Spatial Analysis. John Wiley and Sons, West Sussex, England, pp. 233–255. Alexander, S.M., Water, N.M., Paquet, P.C., 2005. Traffic volume and highway permeability for a mammalian community in the Canadian Rocky Mountains. Canadian Geographer 49, 321–331. Andren, H., 1994. Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: a review. Oikos 71, 355–366. AXYS (AXYS Environmental Consulting Limited), 2003. 2003 Winter Wildlife Surveys Field Technical Report: Cold Lake Expansion Projects – Nabiye and Mahihkan North. Prepared for Imperial Oil Resources Limited, Calgary, Alberta. Balat, M., 2005. Usage of energy sources and environmental problems. Energy Exploration & Exploitation 23, 141–167.
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