seismic lines in the boreal and arctic ecosystems of north ......draft 1 1 seismic lines in the...

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Seismic lines in the boreal and arctic ecosystems of North

America: environmental impacts, challenges and opportunities

Journal: Environmental Reviews

Manuscript ID er-2017-0080.R1

Manuscript Type: Review

Date Submitted by the Author: 03-Feb-2018

Complete List of Authors: Dabros, Anna; Natural Resources Canada, Canadian Forest Service;

Natural Resources Canada, Northern Forestry Centre Pyper, Matthew; Fuse Consulting Ltd Castilla, Guillermo ; Natural Resources Canada, Northern Forestry Centre

Keyword: Linear disturbances, Low impact seismic lines, Conventional seismic lines, Environmental footprint, Regulations

https://mc06.manuscriptcentral.com/er-pubs

Environmental Reviews

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Seismic lines in the boreal and arctic ecosystems of North America: environmental impacts, 1

challenges and opportunities 2

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Anna Dabros, Matthew Pyper, and Guillermo Castilla 4

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A. Dabros. Natural Resources Canada, Canadian Forest Service, 580 Booth Street, Ottawa, ON K1A 0E4, 6

Canada. 7

M. Pyper. Fuse Consulting Ltd., Spruce Grove, AB T7X 3S2, Canada. 8

G. Castilla. Natural Resources Canada, Canadian Forest Service, 5320 122 Street NW, Edmonton, AB T6H 9

3S5, Canada. 10

Corresponding author: Anna Dabros, Natural Resources Canada, Canadian Forest Service, 580 Booth 11

Street, Ottawa, ON K1A 0E4, Canada. Tel.: +1 343 292 8540 (e-mail: [email protected]). 12

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Full word count with references: 16 702 16

Word count without references, figure captions and table: 11 977 17

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Abstract 22

The oil and gas industry has grown significantly throughout the boreal and arctic ecosystems of North 23

America. A major feature of the ecological footprint of oil and gas exploration is seismic lines - narrow 24

corridors used to transport and deploy geophysical survey equipment. These lines, which traverse 25

forests, tundra, uplands, and peatlands, were historically up to 10 m wide. Over the past decade, seismic 26

lines have decreased in width (in some cases down to 1.75 m – 3 m); however, their density has 27

increased drastically and their construction is expected to continue in regions of Canada and the United 28

States that are rich in oil and gas resources. We examine the literature related to the environmental 29

impacts of, and restoration and reclamation efforts associated with, seismic lines in the boreal and arctic 30

ecosystems of North America. With respect to conventional seismic lines, numerous studies report 31

significant and persistent environmental changes along these lines and slow recovery of vegetation that 32

translates into a lasting fragmentation of the landscape. This fragmentation has many ramifications for 33

biodiversity and ecosystem processes, including significant implications for threatened woodland 34

caribou herds. While modern, low impact seismic lines have comparatively lower ecological effects at 35

the site-level, their high density and associated potential edge effects suggest that their actual 36

environmental impact may be underestimated. Seismic line restoration is a critical aspect of future 37

integrated landscape management in hydrocarbon-rich regions of the boreal-arctic, and if widely 38

applied, has the potential to benefit a wide range of species and maintain or re-establish key ecosystem 39

services such as carbon sequestration and biodiversity. 40

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Keywords 42

Linear disturbances, low impact seismic lines, conventional seismic lines, environmental footprint, 43

regulations, restoration methods 44

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1. Introduction 46

Seismic lines, narrow linear clearings created during hydrocarbon exploration, are a common 47

feature in the hydrocarbon-rich boreal and tundra ecosystems of North America (Fig. 1). As of 1999, 48

Timoney and Lee (2001) estimated that the total length of seismic lines in Alberta, Canada, alone was 49

1.5-1.8 million km, while Lee and Boutin (2006) noted that in northeastern Alberta, the mean density of 50

conventional seismic lines was estimated to be 1.5 km/km2, and in some regions was as high as 10 51

km/km2. Based on Landsat imagery from 2008-2010, seismic lines accounted for 46% of all linear 52

features across the Canadian boreal ecosystem (Pasher et al. 2013). In a more recent study conducted 53

across an area of 4022 km2 of boreal forest in western Canada, it was estimated that the total length of 54

seismic lines was five times the length of roads and rail lines (Pattison et al. 2016). 55

Seismic exploration aims at delineating underground reservoirs of oil and natural gas by 56

analyzing the reflection of sound waves from subsurface geological structures (EMR 2006). The seismic 57

waves are generated by drilling a series of shot holes 6 to 20 m deep along the seismic line and then 58

detonating explosives, or by truck-mounted surface vibrators (also known as vibroseis), which create 59

seismic waves by vibrating a heavy plate on the ground surface (EMR 2006; Severson-Baker 2006). The 60

speed of seismic waves travelling from these sources to the subsurface rock formations is recorded by 61

geophones placed along the same line (two-dimensional [2D] seismic lines), or in receiver lines 62

perpendicular to the source lines (three-dimensional [3D] seismic lines), which eventually results in data 63

that are used to identify oil and gas reservoirs and guide further exploration and drilling programs 64

(Severson-Baker 2006). A typical seismic program involves various phases: planning and design, 65

obtaining permits, clearing lines, surveying the land, drilling shot holes, laying out geophones, shooting 66

and recording, and clean-up and closure (Government of Northwest Territories 2012) 67

Construction of conventional seismic lines up until the end of the 20th century typically involved 68

clearing vegetation along 5 to 10 m wide lines using bulldozers. Conventional seismic lines were typically 69

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straight and spaced at distances of 300 to 500 m (Figs. 2a, 2b, 3a). These seismic lines then provided 70

access for machinery required to complete the seismic program (MacFarlane 2003; EMR 2006). The 71

adverse environmental impact of conventional techniques was recognized as early as 1960, when 72

seismic operations were performed in the summer, a process that often removed roots and the top 73

layer of the soil (Bliss and Wein 1972). This recognition led to the introduction of some of the first “best 74

practices” for seismic surveys (AECOM 2009), with seismic operations being shifted to winter months. 75

These operations still produced considerable soil disturbance, and the procedure was further modified 76

by the early 1970s through elevation of the blade, so that only tussock tops and hummocks were 77

removed, and later on by the addition of mushroom shoes to the blade, which further raised the blade 78

to avoid damage to vegetation and the ground surface (Bliss and Wein 1972). 79

Further technological improvements followed gradually, with development of low-impact 80

seismic (LIS) lines in the mid-1990s, by which time the lines were becoming narrower (approximately 81

5 m), although heavy machinery was still used in their construction (MacFarlane 2003). In Alberta, it was 82

recognized that cutting seismic lines was significantly affecting existing and potential timber resources; 83

as such, the provincial government instituted a compensation fee for timber damage when a seismic line 84

dissected productive forestland (Dunnigan 1988). Starting in the 1990s, the Alberta provincial 85

government offered a financial incentive for narrowing the lines, namely, a 50% rebate in the timber 86

damage fee, which was sufficient to prompt reductions in width from 7–8 m to as low as 2 m. Soon 87

after, several studies and reviews began to shed light on the significant environmental impacts of oil and 88

gas exploration on the boreal forest of western Canada (Dyer et al. 2001; Schneider 2002; Lee and 89

Boutin 2006). 90

In the early 2000s, 3D seismic programs—in which tightly spaced grids of seismic lines were 91

applied at distances of 50-100 m apart—resulted in seismic lines that were on average 2–4 m wide and 92

meandering. The seismic lines were created with low ground pressure mulchers (Figs. 1b, 1c, 2c, and 3c) 93

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or other lightweight equipment with mushroom shoes or smear blades (Figs. 3b1 and 3b2, respectively) 94

to minimize ground layer disturbance (MacFarlane 2003; CAPP 2004; EMR 2006). Currently, receiver LIS 95

lines can be as narrow as 1.5 m, and source LIS lines are usually no more than 5.5 m (EMR 2006). Under 96

sensitive environmental conditions, where lines less than 3 m wide are required, “envirodrills” (Fig. 3d) 97

mounted on all-terrain vehicles can be used to further reduce the impact (EMR 2006; Severson-Baker 98

2006). In British Columbia, Alberta, Saskatchewan, Northwest Territories, and Yukon, construction of LIS 99

lines is a preferred management practice for seismic exploration (EMR 2006; AECOM 2009; Government 100

of Northwest Territories 2012 ). 101

Within Canada, which is poised to become the world’s fourth largest oil producer (IEA 2016), the 102

majority of reserves (an estimated 168 billion barrels of recoverable bitumen) are found in three oil sand 103

areas in Alberta, which constitute 97% of Canada’s proven oil reserves (CAPP 2017). Production of 104

natural gas is also prominent across North America, with an estimated 1087 trillion cubic feet of natural 105

gas potential in Canada (CAPP 2017), and about 2355 trillion cubic feet of technically recoverable 106

resources of dry natural gas in the United States (US Energy Information Administration 2017). Much of 107

these reserves overlap with the boreal and arctic ecosystems of Canada and Alaska. Thus, it can be 108

expected that linear infrastructure for the exploration and development of these vast hydrocarbon 109

reserves will continue to expand. 110

Growing resource demands also continue to stimulate an expanding interest in industrial 111

exploitation of high-latitude environments, such as the arctic tundra, with implications for ecosystem 112

disturbance and restoration needs (Forbes and Jefferies 1999). Hydrocarbon exploration commenced in 113

the 1940s in Alaska (Emers et al. 1995; Jorgenson et al. 2010), in the 1950s in the high Arctic of the 114

Northwest Territories (Kevan et al. 1995), and in the 1960s in the low Arctic (Bliss and Wein 1972; 115

Kemper and Macdonald 2009a; Kearns et al. 2015). Severe surface damage from early seismic 116

exploration in the Arctic is still detectable after many decades (Kemper and Macdonald 2009a; 117

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Jorgenson et al. 2010). Although seismic exploration practices have changed substantially, leading to 118

overall reduction of negative effect on soil and plants (Bliss and Wein 1972; Jorgenson et al. 2010), 119

recovery of tundra vegetation after disturbance is often very slow (Forbes et al. 2001; Kearns et al. 120

2015). 121

This review provides an overview of the environmental impacts of seismic lines in boreal and 122

arctic ecosystems. We document scientific evidence of the effect that these lines may have on various 123

environmental factors (soil conditions, permafrost, hydrology, carbon storage and fluxes, snowmelt, and 124

edge effects), and of the responses that plants and fauna may have to these altered environmental 125

conditions. We compare the patterns of seismic line recovery across various ecosystems, ranging from 126

drier uplands to wetter lowlands, as well as between conventional lines, which may be many decades 127

old, and LIS lines, many of which have been constructed within the past decade. We also consider 128

human use of seismic lines post-exploration (e.g., for recreation). After reviewing the ecological impacts, 129

we discuss the current state of regulatory and restoration practices. Finally, we list some of the 130

challenges and opportunities that may shape future research aimed at developing new approaches to 131

benefit on-the-ground programs for the restoration of seismic lines. 132

2. Environmental and ecological effects 133

Significant and persistent environmental changes after seismic operations, along with slow 134

recovery of vegetation, have been noted in boreal and mixedwood transitional forest zones (Revel et al. 135

1984; MacFarlane 2003; Lee and Boutin 2006; van Rensen et al. 2015; Finnegan et al. 2018) and in 136

arctic zones (Forbes et al. 2001; Kemper and Macdonald 2009a, 2009b; Jorgenson et al. 2010; Kearns et 137

al. 2015). For example, many conventional seismic lines in the boreal ecosystems of northern Alberta 138

have shown little recovery over the past 30–40 years (Lee and Boutin 2006; van Rensen et al. 2015). 139

Likewise, the impact of seismic activities in arctic ecosystems is still conspicuous 20–30 years later 140

(Emers et al. 1995; Kemper and Macdonald 2009a; Jorgenson et al. 2010). Despite the perceived 141

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benefits of a reduced footprint with the advent of LIS line techniques (AECOM 2009), there is still 142

uncertainty about the impact of LIS lines in terms of ecosystem recovery (Kemper and Macdonald 143

2009b) and also in terms of the extent and magnitude of associated edge effects (Dabros et al. 2017). 144

The machinery and practices used for creating the seismic line, the time of the year when the 145

line is cleared, and the type and characteristics of the disturbed habitat all contribute to a complex 146

network of environmental changes. This, in turn, affects a wide range of microclimatic, hydrological, and 147

biogeochemical factors. The initial physical damage to the ground surface and the removal of vegetation 148

have far-reaching and persistent effects on these environmental factors, altering overall ecosystem 149

functioning and often hindering recovery (van Rensen et al. 2015). To better asses the recovery 150

potential of seismic lines, it is helpful to first explore the extent and magnitude of environmental 151

changes brought on by seismic lines. 152

2.1. Environmental factors 153

2.1.1. Soil and permafrost 154

Removal of vegetation reduces water intake and decreases evapotranspiration (Vitt et al. 1975). 155

This effect may contribute to higher soil moisture conditions on seismic lines than on the adjacent 156

forest, as was observed by Dabros et al. (2017). Furthermore, compression and compaction of the soil 157

by equipment used during line construction and subsequent seismic operations may lead to pooling of 158

water near the surface, since water cannot easily infiltrate soil that is densely compacted, especially if it 159

is a mineral soil (Arnup 2000). High moisture makes soils are more prone to compaction and changes in 160

soil structure, which further affects moisture and thermal regimes. All of these factors lead to reduced 161

productivity and potentially reduced chances of vegetation recovery. 162

The implications of soil compaction are especially relevant in permafrost regions, which cover 163

about half of the Canadian land mass and about a quarter of the land surface in the northern 164

hemisphere (Zhang et al. 2000; Smith 2011). Unlike the active layer of the soil, which freezes and thaws 165

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every year, the permafrost layer remains frozen year-round. This permanently frozen layer is sensitive to 166

human footprint such as seismic lines, which can alter the energy balance and hydrology of northern 167

regions if the permafrost is disturbed (Smith 2011; Williams et al. 2013). Since almost 100% of Canadian 168

landmass above latitude 55°N consists of either continuous, extensive discontinuous, or sporadic 169

permafrost (Smith 2011), any seismic program performed in the Canadian arctic and northern boreal is 170

likely to overlap with permafrost. 171

Seismic operations within permafrost regions can also result in rutting and subsidence of the 172

ground surface, changes in albedo and net radiation, and changes in ground thermal and moisture 173

regimes, which all contribute to permafrost thaw and damage (Felix and Raynolds 1989; Emers et al. 174

1995; Jorgenson et al. 2010; Williams and Quinton 2013; Braverman and Quinton 2016). In the Arctic 175

National Wildlife Refuge of northeastern Alaska, Emers et al. (1995) found that an increase in the depth 176

of the active layer and severe soil compaction on seismic lines led to increased soil moisture and 177

subsequent ponding, which was still evident a decade later. By 2010, more than two decades after 178

seismic operations had ended, frequent trail subsidence was still observed in that region, especially at 179

sites with greater soil ice content (Jorgenson et al. 2010). 180

Degradation of permafrost is compounded and exacerbated by the cumulative effects of 181

anthropogenic disturbances and climate change (Lawrence and Slater 2005). Global warming introduces 182

a layer of uncertainty connected to potential positive feedbacks, leading to even more pronounced 183

permafrost thaw and to the release of soil carbon through greenhouse gas emissions, especially CO2 and 184

CH4 (Christensen et al. 2004; Lawrence and Slater 2005; Zhang et al. 2008; Dorrepaal et al. 2009; Kurz et 185

al. 2013). Permafrost degradation has been projected to continue under changing climatic conditions 186

(Lawrence and Slater 2005; Zhang et al. 2008). Northern peatlands in particular, where much of the 187

permafrost is found, have accumulated large C stock over millennia, so the impact of permafrost 188

degradation is predicted to be large, long-lasting, and fueled by a positive feedback from carbon 189

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emissions that further contribute to global climate change (Dorrepaal et al. 2009). By exacerbating 190

permafrost degradation, seismic activities in the arctic region may directly contribute to this effect. 191

The exact causes of permafrost thaw resulting from seismic exploration are complex, stemming 192

from the interaction of numerous factors, including changes in vegetation and the physical and 193

thermodynamic properties of soil. Soil structure and soil moisture-holding capacity appear to be major 194

factors directly controlling the soil thermal regime, which in turn affects the physical state of the 195

permafrost (Haag and Bliss 1974; Guan et al. 2010). The high water-holding capacity of organic soils, 196

such as peat, makes them prone to maintaining high moisture and thus high thermal conductivity, which 197

in turn creates conditions favourable to permafrost thaw (Guan et al. 2010). Removal of vegetation 198

during seismic operations decreases soil evapotranspiration capacity, which, when compounded by soil 199

compaction and subsidence of the ground layer, leads to increased soil moisture, decreased latent heat 200

loss, increased soil heat flux and soil temperature, and increased permafrost thaw (Haag and Bliss 1974). 201

2.1.2. Hydrology and permafrost 202

Degradation of permafrost below seismic lines can also alter water storage and flow processes, 203

with implications for the water balance at local and regional scales (Williams et al. 2013). Permafrost 204

controls water storage, drainage, and connectivity in the surrounding wetland terrains, as well as 205

hydrological interactions between near-surface water resources above the permafrost and deep 206

groundwater below (Quinton et al. 2011). 207

In the Scotty Creek region of the Northwest Territories, linear disturbances have resulted in 208

substantial permafrost thaw under the black spruce-dominated plateaus that rise above the surrounding 209

tree-less and permafrost-free wetland (Williams and Quinton 2013; Williams et al. 2013). The wetter 210

conditions resulting from permafrost thaw can lead to tree canopy dieback, and in locations where the 211

summer thaw exceeds winter freezing, regeneration of these permafrost plateaus is unlikely (Williams 212

and Quinton 2013; Williams et al. 2013). Given the high density of winter roads and seismic lines in the 213

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Scotty Creek region (0.875 km/km2), these changes to treed permafrost plateaus induced by linear 214

disturbance have a critical effect on the basin hydrology of the whole region (Quinton et al. 2011; 215

Williams and Quinton 2013; Williams et al. 2013). 216

Modelling studies in Canada also have predicted the disappearance of permafrost and the 217

development of a layer of year-round unfrozen ground (a.k.a. talik) above the permafrost (Zhang et al. 218

2008). These predictions were recently confirmed when Braverman and Quinton (2016) found that 219

seismic lines at Scotty Creek contributed to the development of talik layers between the overlying 220

active layer and the underlying permafrost. Unlike the active layer, which freezes during the winter 221

months, talik can convey water as a conduit throughout the year, connecting bogs and fens that 222

previously formed separate entities (Braverman and Quinton 2016). Overall, the presence of seismic 223

lines in permafrost regions has a profound impact on belowground processes. Seismic lines affect soil 224

thermal regimes and regional hydrology, which on a local scale may contribute to unfavourable 225

conditions for plant recolonization, and at a global scale, cause permafrost thaw and release of carbon, 226

contributing to global warming. 227

2.1.3. Snow cover impacts on soil and vegetation 228

Frozen ground and deep protective snow cover have been reported to reduce the degree of soil 229

disturbance and damage to permafrost (Felix and Reynolds 1989), which is why seismic operations in the 230

Arctic (and elsewhere) are now performed mostly in the winter season, when the ground is frozen. 231

However, the legacy and impact of early arctic seismic programs can still be seen 20–30 years after 232

operations, regardless of the season in which they were undertaken (Kemper and Macdonald 2009a; 233

Jorgenson et al. 2010). Furthermore, studies of seismic operations that made use of recent technological 234

improvements such as lighter vehicles, suggest that 2–3 years after the operations are complete, the 235

effects on soils and vegetation are still pronounced and comparable to the degree of disturbance 236

inflicted by seismic operations in the Arctic several decades ago (Kemper and Macdonald 2009b). 237

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Therefore, the apparent benefits of performing seismic operations in the winter months, with the snow 238

acting as a protective buffer zone, are not always evident. 239

Within boreal and arctic ecosystems, snow cover can last longer on linear disturbances such as 240

seismic lines, partially because the ground surface affected by subsidence acts as a snow catchment 241

basin (Haag and Bliss 1974). Delayed snowmelt may, in turn, delay plant phenology. Such changes have 242

important implications for plant growth and succession, because they shorten the already short growing 243

season for plants at higher latitudes (Dabros 2008; Bjorkman et al. 2015). 244

2.1.4. Solar radiation, air temperature and wind velocity 245

Regardless of the seismic program location and technology used, removal of the vegetation 246

layer, or of the vegetation and top soil layers, along with the longer presence of the snow layer on 247

seismic lines, affects albedo and radiation absorbance of the surface. The amount of solar radiation 248

reaching the ground surface depends on the width of the line and the height of the adjacent canopy 249

(Williams and Quinton 2013); the line’s orientation (Revel et al. 1984; van Rensen et al. 2015); variations 250

in topography (Braverman and Quinton 2016); level of initial disturbance; and degree of recovery (Haag 251

and Bliss 1974; Williams and Quinton 2013). 252

In the summer, removal of vegetation on linear disturbances can decrease the albedo of the 253

ground surface (Haag and Bliss 1974), which can be expected to increase heat absorbance and soil heat 254

flux, thus inducing permafrost thaw. However, relative to the effect of potential changes in near-surface 255

soil moisture, increases in solar radiation do not appear to be a major factor controlling permafrost thaw 256

along linear disturbances (Williams and Quinton 2013). On the other hand, in winter and early spring, 257

the longer presence of snow on the line (Haag and Bliss 1974) likely results in the lines having a higher 258

albedo, in comparison to sites adjacent to the lines. 259

Solar radiation also affects the environmental conditions on a linear disturbance. For example, 260

Haag and Bliss (1974) found that air temperature was significantly lower and wind velocity was higher 261

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up to 50 cm above an arctic winter road as compared to control plots. The authors attributed these 262

trends to a thicker atmospheric boundary layer due to the subsidence of the winter road. Increased 263

wind velocity and temperature also have been observed on seismic lines (S. Nielsen, personal 264

communication 2017). 265

2.1.5. Carbon dynamics 266

Given current projections for global climate change (IPCC 2014), the environmental footprint of 267

linear disturbances such as seismic lines may lead to cumulative and perpetuating effects on the 268

resilience of northern ecosystems (Kemper and Macdonald 2009a). Because of slow decomposition due 269

to cold temperatures and an often anoxic environment, northern ecosystems have accumulated large 270

carbon stock over millennia. In particular, global warming and increasing occurrence of disturbances 271

could turn certain parts of the northern regions into significant carbon sources in the near future (Kurz 272

et al. 2013), creating a positive feedback and contributing to further climate warming. 273

The removal of vegetation on seismic lines affects carbon storage and cycling in boreal 274

ecosystems. Even though enhanced tree growth along seismic line edges (Bella 1986) can offset a 275

portion of the carbon lost through tree removal, the net carbon balance can still shift from a sink to a 276

source in boreal treed ecosystems (Kurz et al. 2013, Strack et al. 2017). There is also evidence that global 277

warming promotes the release of ancient peatland carbon in northern peatland ecosystems, which have 278

accumulated one-third of Earth’s soil carbon stock since the last Ice Age (Walker et al. 2016). Increased 279

respiration has been observed with a 1°C increase in temperature, especially in the presence of dwarf 280

shrubs and graminoids (Walker et al. 2016), which are often more abundant on recovering seismic lines 281

than in the adjacent undisturbed sites (Emers et al. 1995; Jorgenson et al. 2010; Finnegan et al. 2018). 282

Permafrost thaw associated with construction of seismic lines may also lead to a shift of the ecosystem 283

from sink to source through the release of carbon (Schuur et al. 2009). 284

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In terms of carbon dynamics at the landscape scale, land-use changes caused by conventional oil 285

production and oil sands operations, including seismic surveys, were found to contribute relatively small 286

portions (no more than 4%) of greenhouse gases to lifecycle emissions when measured in California and 287

Alberta (Yeh et al. 2010). However, these estimates assumed only aboveground biomass removal, with 288

no disturbance of soil carbon, as well as 100% vegetation recovery, which has typically not been 289

achieved. Although Kurz et al. (2013) stated that the current rates of disturbances and forest 290

management are overall sustainable with regard to biomass and total ecosystem carbon stocks, they 291

recognized that within regions of high industrial development in the boreal zone, the cumulative impact 292

of human and natural disturbances may turn these areas from carbon sinks to carbon sources. Further 293

research is needed to determine whether both conventional and modern LIS lines might contribute to 294

such a shift. 295

Changes in hydrology associated with seismic line construction in boreal peatlands may also lead 296

to drawdown of the water table, which may change vegetation composition and consequently carbon 297

dynamics. For example, water table drawdown can lead to increased coverage of shrubs (carbon sink), 298

but an even more substantial decrease in Sphagnum L. cover (carbon source) (Munir et al. 2014). Strack 299

et al. (2014) concluded that under very dry conditions in peatlands, greenhouse gas emissions will 300

remain high, whereas under very wet conditions (often observed on seismic lines, relative to sites 301

adjacent to the line), abundant graminoid cover may increase CO2 uptake, but may also create areas of 302

high CH4 flux, potentially leading to the site becoming a carbon source. Clearly the removal of vegetation 303

during the construction of linear disturbances and its effects on soil moisture and water table position, 304

as well as the shifts in vegetation composition that occur during site recovery, will have effects on 305

carbon dynamics, but these effects are not easily predictable. 306

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2.2. Edge influence: complex dynamic of environmental and plant interactions 307

The extent of the environmental changes discussed often goes beyond the edges of the seismic 308

lines (and other disturbances) and into the adjacent ecosystem, effectively magnifying the impacts over 309

an area much larger than the seismic line (Porensky and Young 2013). The spatial accumulation of all 310

edges determines the total impact of edges in fragmented landscapes (Ewers and Banks-Leite 2013). The 311

ubiquity of seismic lines makes them the main source of anthropogenic edges. Indeed, in boreal regions 312

in western Canada, seismic lines accounted for 80% of all edges from linear disturbances (Pattison et al. 313

2016). 314

Edge effects are often neglected when assessing the impact of linear disturbances, as the 315

primary focus remains on the conditions and habitat changes on the cleared terrain (i.e., the line itself). 316

However, the indirect effects of linear disturbance spreading into adjacent areas may include changes in 317

physical and chemical conditions, plant growth, and wildlife behaviour, as well as interactions among 318

these factors (CAPP 2004). Given their elongated shape, linear disturbances such as seismic lines create 319

more edge per unit area than non-linear disturbances such as cutblocks (CAPP 2004), though the 320

magnitude of edge influence along linear disturbances may be no greater than for other edge types. 321

Manifestation of edge influence in plant responses is complex and will differ among vegetation 322

types according to climatic conditions and limiting environmental factors. Increased growth rates of 323

trees growing at edges have been reported for seismic line edges (e.g., Revel et al. 1984; Bella 1986; 324

MacFarlane 2003), although these growth responses depended on stand type. For instance, MacFarlane 325

(2003) found that the initial growth increase along the seismic line edges was observed for deciduous, 326

but not coniferous trees, whereas Revel et al. (1984) found that the mean height of coniferous tree 327

species adjacent to seismic lines was greater than the mean height of trees in the undisturbed interior 328

forest. 329

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With an increase in tree growth along line edges, the competitive balance may be shifted, 330

potentially to the disadvantage of understory vegetation such as low shrubs, herbaceous plants, and 331

bryophytes (Gignac and Dale 2007; Dabros et al. 2017). Competitive balance could be further affected 332

by an increase in opportunistic, disturbance-tolerant, often-invasive species at and near the edges 333

(Honnay et al. 2002; Finnegan et al. 2018). The presence and spread of these species could be related to 334

various factors, such as human and machinery traffic during construction of the linear disturbance 335

(Meunier and Lavoie 2012), certain wildlife species, which preferentially use seismic lines (Latham et al. 336

2011a; Tigner et al. 2014), and early reclamation attempts using agronomic mixes not native to forests 337

(Revel et al. 1984; MacFarlane 2003). 338

Wind conditions also are affected at the disturbance edge, with wind intensity potentially 339

decreasing exponentially as one moves into the adjacent forest (Chen et al. 1995). This may contribute 340

to increased windthrow and tree mortality along edges (Williams-Linera 1990; Laurance et al. 1998; 341

Burton 2002; Dabros et al. 2017). Increased tree mortality and the presence of deadwood along line 342

edges may in turn affect the abundance of certain species of fungi, lichens, and mosses, which often 343

grow on deadwood (Dittrich et al. 2014). Meanwhile, the creation of microsites and microhabitats may 344

attract many arthropod species, as well as small mammals, birds, and wildlife in general (Harper et al. 345

2014), whose presence and interactions will affect vegetation abundance and growth, contributing to 346

different species composition along seismic lines edges. 347

2.3. Plant responses to altered environmental conditions 348

2.3.1 Vascular plants: boreal ecosystems 349

After natural disturbances such as fires, boreal and arctic ecosystems usually start regenerating 350

within the next growing season, progressing through different stages of succession towards the pre-351

disturbance state. Seismic lines, which have no natural analog, often do not follow such successional 352

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trajectory, remaining instead in early successional stages (van Rensen et al. 2015). This implies the 353

presence of key factors that hinder the recovery of seismic lines to a pre-disturbance state. 354

The progression of regenerative processes and succession on conventional seismic lines has 355

been examined and evaluated on a landscape scale by Lee and Boutin (2006). They reported that even 356

after 35 years, more than 60% of the seismic lines showed little or no recovery back to a forested state. 357

Likewise, Finnegan et al. (2018) found that in the lower and upper foothills and subalpine regions of 358

Alberta, for understory vegetation, disturbance-tolerant species were more abundant on seismic lines 359

and line edges in comparison to interior forest, even decades after the line construction, with the lines 360

appearing to remain indefinitely in an early successional state. 361

On a finer scale, MacFarlane (2003) found that in the central mixedwood sub-region of Alberta, 362

the composition of the vascular understory on conventional seismic lines and early versions of LIS lines 363

was still significantly different from that of the interior forests after up to 30 years. This indicates 364

arrested succession, where the system does not seem to progress to what it used to be before the 365

disturbance. MacFarlane (2003) attributed competition from invasive species as a major factor 366

influencing these results. 367

The competitive advantage of non-native and invasive vegetation is a likely factor hindering 368

growth and recovery of native tree species on seismic lines, even those that are already established. 369

Indeed, although Revel et al. (1984) reported the presence of native vegetation, including tree seedlings, 370

on seismic lines in northeastern Alberta, they also noted that the growth of these seedlings was much 371

slower on the lines than in the adjacent and interior forest, with invasive vegetation on lines being one 372

of the factors contributing to that slow growth. Aggressive and fast-growing invasive graminoids often 373

establish abundantly on seismic lines in boreal regions of Alberta, growing to around 1 m in height, 374

which can result in the shading and smothering of small conifer seedlings. These include bluejoint 375

reedgrass (Calamagrostis canadensis (Michaux) Palisot de Beauvois) and water sedge (Carex 376

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aquatilis Wahlenberg) under drier and wetter conditions, respectively (A. Dabros, personal observation, 377

2014-2017). Furthermore, wind speed in seismic line corridors was seven times stronger than in the 378

adjacent control forest, resulting in five times further experimental dispersal of the seeds of weedy 379

species on seismic lines than in the forest (S. Nielsen, personal communication 2017). 380

Habitat type also plays a major role in plant recolonization and subsequent persistence and 381

growth of different plant species on seismic lines. van Rensen et al. (2015) concluded that for seismic 382

lines in northeastern Alberta, terrain wetness and the presence of adjacent fen ecosites had the 383

strongest negative effect on regeneration patterns, with the lines found in the wettest sites failing to 384

recover even 50 years after initial disturbance. 385

The degree of plant recovery on seismic lines will also affect interactions with wildlife. For 386

example, Kansas et al. (2015) found that, in comparison to other ecosite types, poor recovery on LIS 387

lines in bogs and poor fens in northeastern Alberta provided less visual obstruction for wolves (Canis 388

lupus L.) travelling on seismic lines to hunt woodland caribou (Rangifer tarandus caribou (Gmelin). Thus, 389

to reduce the negative impact of seismic lines on wolf–caribou predation dynamics, Kansas et al. (2015) 390

have suggested that restoration efforts focus on seismic lines showing poor recovery, namely those in 391

bogs and poor fens (see also van Rensen et al. 2015), which are also habitats preferred by caribou 392

(Neufeld 2006; Latham et al. 2011a). More recently, Dickie et al. (2017) suggested that since most of the 393

movement efficiency afforded to wolves by seismic lines is mediated when vegetation height exceeds 394

0.5 m, active restoration could be focused in areas that have not met this height. 395

Wildlife using seismic lines as corridors for easier movement may also contribute to line 396

regeneration by acting as dispersal vector for seeds of both desirable and undesirable plants (Tigner et 397

al. 2014), changing the competitive dynamics of plant species. An additional factor associated with 398

slower growth of trees on seismic lines in comparison to adjacent interior forest may be increased 399

browse damage by ungulates and other herbivores (Revel et al. 1984). 400

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Growing substrate also plays a major role in plant recolonization and subsequent persistence 401

and growth of different plant species on seismic lines. For example, lodgepole pine (Pinus 402

contorta Douglas ex Loudon) regeneration was better on exposed mineral soil and under dry conditions, 403

whereas black spruce (Picea mariana (Miller) Britton, Sterns & Poggenburgh) and white spruce (Picea 404

glauca (Moench) Voss) were the dominant conifers that regenerated on moist to wet sites on 405

conventional seismic lines in the boreal forests of Alberta (Revel et al. 1984). Such ecological knowledge 406

is crucial for application of silvicultural methods in restoration. 407

Post-disturbance regeneration relies on various factors, including dispersal capacity, habitat 408

conditions, and biotic and abiotic interactions (Baker et al. 2013). The characteristics of seismic lines and 409

their impacts on environmental factors will, therefore, affect natural regeneration and successional 410

trajectories. These processes can be further altered by human intervention, either negatively (e.g., 411

through the reuse of the lines for all-terrain vehicles or snowmobiles) or positively (e.g., through 412

reclamation and restoration activities, such as silvicultural practices to improve conditions for plant 413

establishment, or direct seeding and planting, respectively). 414

2.3.2. Vascular plants: tundra 415

In contrast to the situation in boreal regions, where wetlands are less resilient than uplands, 416

wetland ecosystems in the Arctic are more likely to recover faster, or the magnitude of seismic damage 417

is less intense, relative to Arctic uplands (Hernandez 1973; Emers et al. 1995; Jorgenson et al. 2010). For 418

example, Hernandez (1973) observed that wetter habitats had more roots and rhizomes, which during 419

winter seismic operations effectively reduced the degree of surface disturbance. Overall, regardless of 420

habitat type (drier or wetter), the commonly reported patterns of recovery on seismic lines in the Arctic 421

have been characterized by i) significantly increased cover of graminoids, forbs, and deciduous shrubs; 422

and, ii) frequent decreases in evergreen shrubs and/or bryophytes, relative to their respective 423

undisturbed sites (e.g., Emers et al. 1995; Kemper and Macdonald 2009b; Jorgenson et al. 2010). 424

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Rapid recolonization of disturbed sites by aggressive rhizomatous graminoids, especially at sites 425

severely disturbed by compression or subsidence of seismic trails, could lead to significant changes in 426

species composition. Such changes may occur partially through competitive exclusion of more damage-427

susceptible vegetation types, such as shrubs or bryophytes (Emers et al. 1995, Jorgenson et al. 2010). 428

The flush of nutrients released through a sharp increase in decomposition immediately after 429

disturbance, resulting from increased heat transfer under wetter conditions (Chapin and Shaver 1981), 430

may further benefit opportunistic graminoids (Emers et al. 1995). In the drier upland tundra, some grass 431

species have been similarly successful in taking advantage of nutrient-enriched conditions and 432

establishing dominance over other non-grass species after seismic line disturbances (Bliss and Wein 433

1972; Hernandez 1973; Emers et al. 1995; Kemper and Macdonald 2009a). On the other hand, forb 434

species show an initial reduction in cover following seismic disturbance in arctic environments, but then 435

rebound through opportunistic ruderal responses, successfully recolonizing lines in the early years and 436

often creating higher cover than occurs at undisturbed reference sites, though sometimes not 437

permanently (Emers et al. 1995; Jorgenson et al. 2010). 438

Exposure of mineral soil through blading and scuffing techniques, often more pronounced on 439

mesic sites than in wetter habitats, also created conditions advantageous for colonization by grasses and 440

forbs, which have been shown to replace original pre-disturbance vegetation types on seismic lines 441

(Jorgenson et al. 2010). Furthermore, at the drier sites, which were originally dominated by graminoids 442

and which remained relatively dry after seismic disturbance, certain grass species became much denser 443

in comparison to undisturbed areas, remaining visible for many years after disturbance (Jorgenson et al. 444

2010). 445

The cover of deciduous shrubs, such as birch (Betula spp L.), willow (Salix spp. L) and alder 446

(Alnus spp. L), has also been observed to increase on seismic lines in the low-arctic coastal plains tundra 447

of Alaska and Northwest Territories (Jorgenson et al. 2010; Kemper and Macdonald 2009a). These 448

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changes remained even 20-30 years after disturbance (Kemper and Macdonald 2009a). Jorgenson et al. 449

(2010) attributed this increased cover to general adaptation to disturbance (e.g., river flooding and 450

grazing) among deciduous shrubs such as willows. Potentially warmer soils and higher decomposition 451

rates leading to increased nutrient concentrations on seismic lines (Emers et al. 1995) may also be 452

advantageous and play a role in successful recolonization and growth of deciduous shrubs. Interestingly, 453

most research, with the exception of Kemper and Macdonald (2009a), indicates that this advantage 454

seemed less likely to extend to evergreen shrubs studied across seismic disturbances in the arctic (Bliss 455

and Wein 1972; Hernandez 1973; Felix and Raynolds 1989; Emers et al. 1995; Jorgenson et al. 2010). 456

Decreased abundance of evergreen shrubs on seismic lines in arctic plant communities has been 457

attributed to their low photosynthetic capacity and higher (relative to deciduous shrubs) nutritional 458

storage in the aboveground parts of the plant, which are more directly damaged during seismic 459

operations (Starr et al. 2008; Jorgenson et al. 2010). Overall, deciduous species, which are often 460

broadleaf, have been reported to grow faster because of their usually higher specific leaf area (Antúnez 461

et al. 2001), which could also contribute to their competitive advantage in recolonization of seismic 462

lines. 463

2.3.3. Non-vascular plants and lichens: boreal and tundra ecosystems 464

In forested lands, the canopy openings generally found at disturbed sites and the higher levels 465

of solar radiation usually found there may not be optimal for many bryophyte species, which are often 466

better adapted to shaded, cool, and moist conditions (Marschall and Proctor 2004). Indeed, in boreal 467

forests, lower bryophyte cover was found on both conventional seismic lines (Revel et al. 1984) and LIS 468

lines (Dabros et al. 2017). Likewise, increased light levels were observed on the lines and line edges by 469

Dabros et al. (2017), which parallels the increased light levels found on linear disturbances by Pohlman 470

et al. (2007). In comparison to the adjacent boreal forest, lower bryophyte cover was also observed on 471

other types of linear disturbances (e.g., at the edges of power line clearings in the boreal forests of 472

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Norway; Eldegard et al. 2015). However, these general trends were not observed in wide and open 473

conventional seismic lines in the treed peatlands of northwestern Alberta (A. Dabros, unpublished data, 474

2017; Fig. 1b), where species of Sphagnum L., were highly abundant. Despite higher light levels, the 475

higher moisture conditions found on the lines appeared to be the driving factor for the presence of 476

Sphagnum, which is an indicator of wet conditions. 477

Slow recovery to pre-disturbance conditions have also been reported for bryophytes on seismic 478

lines in arctic ecosystems (Hernandez 1973; Kemper and Macdonald 2009a, 2009b; Jorgenson et al. 479

2010). Low growth rates (especially for common northern species of late successional feathermosses) 480

and the competitive disadvantage for nutrients and moisture of bryophytes (which lack a vascular 481

system and depend on external hydration) are some of the factors that may contribute to this slow 482

recovery (Jorgenson et al. 2010). Early successional moss species and crustose lichens were more likely 483

to successfully recolonize exposed mineral soil after seismic operations (Jorgenson et al. 2010), but 484

other lichen species recovered much more slowly, in both the short term (Hernandez 1973; Babb and 485

Bliss 1974; Kemper and Macdonald 2009b) and the long term (Kemper and Macdonald 2009a; Jorgenson 486

et al. 2010). 487

2.4. Behavioural and population effects on fauna 488

The effects of seismic lines on wildlife are complex and multifaceted, and will vary with line 489

characteristics, such as width, age, and level of recovery, and with the wildlife species involved 490

(Ashenhurst and Hannon 2008; Bayne et al. 2011; Tigner et al. 2014, 2015). The effects may be direct, 491

such as habitat degradation because of vegetation clearing, or avoidance of the line by certain species 492

because of decreased habitat quality and food resources in the vicinity (CAPP 2004; Wilson 2011); or 493

indirect, such as increased risk of predation through facilitation of predator movement (CAPP 2004; 494

Ashenhurst and Hannon 2008; Latham et al. 2011a). 495

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The impact of seismic lines on wildlife also may differ on a temporal scale: immediate (e.g., 496

destruction of rabbit burrows during construction and operation of the lines (Wilson 2011)); 497

intermittent (e.g., noise disturbance by all-terrain vehicle traffic after the line closure (Pigeon et al. 498

2016)), or prolonged (e.g., changes in dynamics of predation, or behavioural changes connected to 499

territory size and intra-species competition (Latham et al. 2011b; Bayne et al. 2011; Machtans 2006)). 500

The impact also differs spatially, with effects more apparent at a local scale and less clear at a regional 501

scale (Bayne et al. 2011). 502

With respect to bird species, their behavioural responses to seismic lines may range from a total 503

avoidance and exclusion of lines from their territories (Ortega and Capen 1999; Machtans 2006, 504

Ashenhurst and Hannon 2008), to actually selecting for more open conditions found on seismic lines, or 505

not responding to this disturbance at all (Bayne et al. 2011; Machtans 2006). These responses may 506

depend on the type of seismic line, i.e., birds may perceive older conventional lines differently from 507

newer LIS lines. For example, Ovenbirds (Seiurus aurocapilla L.) used conventional lines as territory 508

boundaries, but incorporated LIS lines into their territories (Bayne et al. 2005). This may be partially 509

explained by the greater width of the conventional lines, as well as their straight nature, relative to the 510

narrower, meandering LIS lines. However, as canopy closure increased and amount of bare ground 511

decreased over time, conventional seismic lines were more frequently included within Ovenbird 512

territories (Bayne et al. 2011). 513

The regional abundance and density of species can also modulate behavioural responses to 514

seismic lines. For example, in high-quality habitats with high densities of Ovenbirds, conventional 515

seismic lines delimited the location and size of their territories, regardless of the level of vegetation 516

recovery. However, in low-quality Ovenbird habitat, seismic lines had a limited effect on territorial 517

behaviour (Bayne et al. 2011). Other boreal bird species, including the American Robin (Turdus 518

migratorius L.), Yellow Warbler (Dendroica petechia L.), and Warbling Vireo (Vireo gilvus Vieillot), 519

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experienced small increases in abundance with increased density of linear features, but the models had 520

low predictive power (Bayne et al. 2011). 521

Assessment of habitat quality and resource availability for birds on and around seismic lines has 522

led indirectly to research on another important group of organisms, the invertebrates. Lankau et al. 523

(2013) found there was less leaf litter on seismic lines, and hence reduced abundance of arthropods. On 524

the other hand, Riva et al. (2018) found higher butterfly abundance and diversity on 9 m wide seismic 525

lines, but not on low impact 3 m wide lines, which again shows that the line type is an important factor 526

in predicting the behaviour of fauna. Other than these studies, there appears to be no direct studies on 527

the effects of seismic lines on invertebrates, even if they are the largest and most diverse group of 528

organisms in most ecosystems, and despite the crucial ecological functions they play, including 529

decomposition, nutrient release, and carbon cycling (SFMN 1999; Abele 2014). Research is, however, 530

currently underway in northeastern Alberta to assess the cumulative effects of seismic lines and other 531

disturbances on beetles (D. Langor et al., personal communication, 2017), and spiders (J. Pinzon, 532

personal communication, 2017). 533

Presumably, small species such as invertebrates may be less affected by seismic lines in 534

comparison to bigger species with considerably larger territories. For example, insects may shift their 535

territories into the interior forest, away from the lines, but for large mammals the fragmented habitat 536

may not be suitable enough and they may choose to enlarge their territory and include the lower quality 537

habitat found on seismic lines (Ashenhurst and Hannon 2008). This, however, may result in increased 538

energetic costs, as a result of having to traverse a larger area in search for resources. On the other hand, 539

as was discussed earlier, certain species, including birds (Bayne et al. 2011) and butterflies (Riva et al. 540

2018), may actually find that the early seral stages found on seismic lines are more suitable in terms of 541

their resource requirements. 542

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Wide conventional seismic lines running through a dense forest often facilitate the movement 543

of some larger mammals. For example, Tigner et al. (2014) found that in general, black bears (Ursus 544

americanus Pallas) used seismic lines that were wider than 2 m more than forest interiors (though Linke 545

et al. (2005) found that seismic line density did not explain landscape use by grizzly bears (Ursus arctos 546

L.)). In contrast, smaller mammals such as martens (Martes americana (Turton)), avoided lines that were 547

open and wider than 2 m (Tigner et al. 2015). 548

Wolves have also shown a strong preference for conventional seismic lines, especially during the 549

snow-free season (Latham et al. 2011a). Furthermore, Dickie (2015) found that conventional seismic 550

lines significantly increased wolves’ rate of travel, relative to both LIS lines and the interior forest. Dickie 551

et al. (2017) also found that wolves selected seismic lines with shorter vegetation and traveled faster on 552

those with shorter, sparser vegetation and increased vegetation variability. 553

Preferential use of seismic lines by predators, such as bears and wolves, may alter their ability to 554

locate and capture prey, including caribou and other ungulates. Whittington et al. (2011) and McKenzie 555

et al. (2012) found evidence for increased encounters between wolves and caribou on seismic lines, 556

whereas James and Stuart-Smith (2000) found evidence for increased risk of wolf predation on caribou 557

close to linear corridors. Furthermore, DeMars and Boutin (2017) found that seismic lines increase 558

wolves’ and black bears’ selection of peatlands, which negatively impacted survival of caribou neonate 559

calves, since peatlands are highly used by females during the calving season. 560

These observations of changes in predator movement and predation have important 561

implications for woodland caribou. Woodland caribou populations are known to be declining across 562

most of their ranges and are currently considered threatened. Linear features are acknowledged as a 563

key limiting factor for populations in western Canada (Serrouya et al. 2017; Environment Canada 2011; 564

Hervieux et al. 2013). On their own, seismic lines may not have a direct or pronounced impact on 565

woodland caribou. For example, Dyer et al. (2002) determined that although roads with moderate traffic 566

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inhibited caribou movement to a certain extent, especially in winter, seismic lines did not present any 567

barrier effects. However, in the context of predator–prey dynamics, linear disturbances such as seismic 568

lines facilitate the movement of wolves, potentially making it easier for them to reach and hunt down 569

their prey (Latham et al. 2011a; McKenzie et al. 2012; Dickie 2015; Dickie et al. 2017). 570

Predation by wolves has been considered one of the most significant forces driving caribou 571

decline (McLoughlin et al. 2003; Hervieux et al. 2013). Linear disturbances create a maze of early seral 572

habitats that attract the primary prey of wolf, especially moose (Alces alces L.) and deer (Cervidae 573

Goldfuss), thus buoying wolf populations in caribou habitat (Hebblewhite et al. 2007). Perhaps not 574

coincidentally, woodland caribou have been found to use areas close to linear disturbances less often 575

than expected, especially in the snow-free season, which is where and when most caribou deaths occur 576

(Dyer et al. 2002; Neufeld 2006). 577

Deliberate avoidance of seismic lines by caribou leads to functional loss of otherwise suitable 578

habitat for caribou (Latham et al. 2011a). Using resource selection models for wolves, Latham et al. 579

(2011a) found positive selection for linear features. Seismic lines have also contributed to a shift in 580

spatial separation between wolves and caribou as a result of increased industrial activity and 581

disturbance (James et al. 2004; Latham et al. 2011b). In addition, behavioural responses to human 582

activities on linear features were clearly reflected through increased physiological and nutritional stress 583

of caribou when there was increased presence of humans on primary roads, as indicated by Wasser et 584

al. (2011). As a result of this wide body of literature, seismic lines have been highlighted as a key factor 585

to tackle in woodland caribou population recovery (Environment Canada 2011; 2012). Through these 586

various examples of mammal responses to seismic lines, it is clear that although the characteristics and 587

behavioural responses of wildlife species will influence how they are affected by seismic lines, the 588

characteristics of the lines themselves will inevitably play a major role. 589

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2.5. Effects of post-development human use 590

A key issue often hampering vegetation recovery along conventional seismic lines is their 591

continued use after the exploration program as access routes for trapping, hunting, and other activities. 592

The lack of legal obligations regarding line reclamation has resulted in many seismic lines providing 593

access for all-terrain vehicles and snowmobiles, which can lead to increased hunting and poaching, 594

indirect disturbance (due to human presence, noise, light, and air pollution), and spread of undesirable 595

plant species. All of these factors can have significant adverse effects on soil and vegetation, resulting in 596

delays to regeneration (EMR 2006; van Rensen et al. 2015). 597

Even a single pass by an all-terrain vehicle can result in substantial damage under some 598

conditions, as Revel et al. (1984) found while studying regeneration along conventional seismic lines in 599

northeastern Alberta. They observed little conifer regeneration on lines where all-terrain vehicles had 600

been used, because of both water channelization and subsequent erosion, and increased soil 601

compaction. Similarly, van Rensen et al. 2015 noted that the greatest impact on vegetation recovery 602

along seismic lines occurred near human access routes, which further emphasizes the impact of off-603

highway vehicle use on vegetation recovery. However, Pigeon et al. (2016) found that off-highway 604

vehicle use was mainly associated with local topography and vegetation attributes of seismic lines that 605

facilitated ease of travel, while broad-scale landscape attributes associated with industrial use, 606

recreational access, or hunting activities did not explain levels of off-highway vehicles use. Clearly, off-607

highway vehicles have significant impacts on the recovery potential of seismic lines, particularly in the 608

boreal forest. Any attempts to facilitate vegetation recovery along these lines must take into 609

consideration human access and use of seismic lines. 610

3. Regulatory aspects and reclamation practices 611

Regulations represent a potentially influential tool in seismic line development and reclamation, 612

as their progressive evolution attests. Early regulations (i.e., circa 1940 and 1950) focused largely on 613

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tracking exploration locations with little regard for ecological impacts other than disposal of refuse (e.g., 614

Government of Alberta 1941). These regulations were eventually updated to foster more advanced 615

planning to tackle adverse ecological effects (e.g. Government of Alberta 1978; Government of Alberta 616

1990). Currently, regulations generally encourage—but do not require—LIS practices and the use of 617

advanced planning and surveying techniques (e.g., British Columbia Oil & Gas Commission 2016; 618

Government of Alberta 2006; Yukon Government 2006). Current regulations also encourage reuse of 619

existing lines for oil and gas exploration where natural vegetation regrowth is low (Alberta Environment 620

2006; British Columbia Oil & Gas Commission 2016; Government of Northwest Territories 2012; Yukon 621

Government 2006). 622

Most provinces and territories have adopted similar best management practices and encourage 623

the use of LIS techniques; however, seismic lines up to 5 m wide are still permitted in most jurisdictions, 624

with appropriate justification (Alberta Environment 2006; British Columbia Oil & Gas Commission 2016; 625

Government of Northwest Territories 2012; Yukon Government 2006). In addition, few of the 626

regulations explicitly require reclamation of seismic lines to a forested ecosystem. Those regulations 627

that do discuss reclamation often focus on clean-up of refuse, limiting motorized access, or on slumping 628

and erosion along the lines (e.g. Government of Northwest Territories 2012). Although some regulations 629

do call for revegetation, they do not specify that the revegetation consist of woody species. In addition, 630

regulations explicitly focus on implementation monitoring (i.e., how closely treatments have followed 631

the standards), with little emphasis on effectiveness monitoring (i.e., how successful treatments have 632

been in re-establishing ecosystem services) (Machmer and Steeger 2002). 633

Recognizing the substantial backlog of legacy seismic lines that have not recovered back to 634

forest, many provinces have introduced initiatives that focus on restoration, with Alberta and British 635

Columbia having made the largest advances on this front. British Columbia has developed a framework 636

for restoration and associated monitoring for seismic lines within woodland caribou habitat (Golder 637

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Associates 2015) and is also testing alternative restoration techniques, such as snow fences to reduce 638

predator movement. In Alberta, the Alberta Land-use Framework (Government of Alberta 2008, 2016a) 639

and the Biodiversity Management Framework have emphasized restoration, introducing the topics of 640

conservation and biodiversity offsets (Habib et al. 2013). Also, Alberta has recently issued a new 641

framework for the restoration of Legacy Seismic Lines (Government of Alberta 2017), and has 642

committed to an ambitious restoration program focused on restoring 6000 km of seismic lines within 5 643

years as part of the draft plan for the Little Smoky and A La Peche caribou ranges (Government of 644

Alberta 2016b). Although these initiatives have not yet been fully implemented, they show the possible 645

policy arena within which seismic line restoration efforts are being designed. 646

3.1. Current practices for restoration of seismic lines 647

To address the significant backlog of seismic lines with stagnant recovery, several oil and gas 648

companies and provincial authorities, especially in British Columbia and Alberta, are implementing 649

restoration practices and monitoring their effectiveness (Golder Associates 2012; Pyper et al. 2014). 650

Introduction of the woodland caribou recovery strategy (Environment Canada 2012), which emphasized 651

the importance of restoration, has further contributed to on-the-ground linear restoration programs. 652

While different approaches to restoration are not discussed in the peer-reviewed literature, in 653

practice, there are two dominant approaches to restoration of seismic lines in forested landscapes: 654

habitat restoration and functional restoration (Pyper et al. 2014). Habitat restoration has the primary 655

goal of promoting vegetation recovery along seismic lines by addressing site-specific limitations, such as 656

the site being too wet or too dry, having its soil compacted, or lacking microsites suitable for 657

establishment and growth of seedlings (Lee and Boutin 2006; Golder Associates 2012; van Rensen et al. 658

2015). Functional restoration has the primary goal of reducing movement of predators along seismic 659

lines (Keim et al. 2014; Pyper et al. 2014). The latter approach is based on the fact that predators often 660

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use seismic lines as travel corridors, which increases the frequency of encounters between predators 661

such as wolves and prey such as woodland caribou (e.g., Latham et al. 2011a). 662

Given their aim of creating travel barriers, functional restoration treatments are often quite 663

different from habitat restoration methods, although there is obvious overlap between the two. For 664

example, placement of large piles of wood at irregular intervals along lines may be designed to reduce 665

use of lines by predators, but may also reduce human travel (especially with off-highway vehicles), 666

which can also be a key factor limiting recovery (van Rensen et al. 2015). It should be noted, however, 667

that functional restoration approaches show limited ability to recover forested habitat on seismic lines, 668

and thus may only prove beneficial for specific species such as wolves and woodland caribou. In 669

contrast, habitat restoration approaches that strive to re-establish forest vegetation have much broader 670

implications and benefits for a diverse suite of forest species. 671

Habitat restoration and functional restoration are defined in the context of woodland caribou 672

conservation, which has been the primary motivation for restoration efforts in western Canada. There 673

are at least three reasons for this. First, woodland caribou is a flagship and umbrella species for the 674

boreal forest, occurring at low densities in large patches of old-growth coniferous forests and boreal 675

peatland complexes (Environment Canada 2012); therefore, interventions fostering the recovery of 676

caribou habitat should also benefit the ecosystem at large. Second, boreal woodland caribou is a 677

threatened species, and many populations in western Canada face extirpation (COSEWIC 2011); seismic 678

lines significantly reduce the amount of undisturbed critical habitat available to caribou and increase 679

caribou predation, so seismic line restoration may play a crucial role in tackling this situation. Third, 680

provisions in the Canadian Species at Risk Act could lead to temporary prohibition of industrial activities 681

in caribou ranges where there is a risk of imminent extirpation, which would have dire economic 682

consequences (Hebblewhite 2017). 683

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A range of approaches has been developed to achieve restoration of seismic lines (e.g., Golder 684

Associates 2012; Pyper et al. 2014). This suite of techniques represents the typical restoration toolbox 685

that is currently available (Table 1). Most restoration programs use a subset of these methods, based on 686

the specific ecological conditions at sites (Golder Associates 2012; Pyper et al. 2014). These practices 687

continue to evolve—quite rapidly in some cases—as companies and agencies experiment with ways to 688

achieve restoration goals with maximum efficiency and effectiveness. Robust, replicated scientific trials 689

of the various restoration techniques are needed to enable an evaluation of their effectiveness and to 690

improve management practices over time. 691

4. Challenges and opportunities 692

The preceding sections have reviewed the literature on the impacts of seismic lines and the 693

approaches currently being used to restore these features to a functioning ecosystem. In the following 694

section, we examine some of the challenges and opportunities present in the successful restoration of 695

seismic lines. A more thorough understanding of these challenges and opportunities may help to shape 696

future research aimed at developing new approaches to benefit on-the-ground programs for the 697

restoration of seismic lines. 698

4.1. Definition of successful restoration 699

Despite substantial work on, and interest in, the restoration of legacy seismic lines, successful 700

restoration may be difficult to define, especially because different species have different habitat 701

requirements. The exact definition and objectives of restoration depends on the ecosystem in which the 702

line is found, the species that restoration is intended to benefit, and the processes and ecosystem 703

services that are being restored. While the definition of what constitutes successful restoration needs to 704

be tailored to the specific situation, shortening recovery to pre-existing conditions appears to be a 705

shared requisite. 706

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Defining and achieving restoration goals will also play an important role in future regulations. 707

For example, there is currently some debate about whether restoration should achieve purely functional 708

objectives (such as reducing movement efficiency of wolves) or whether a more habitat-based approach 709

(with a dual focus on re-establishing vegetation and reducing movement efficiency of wolves) is required 710

to deem restoration in woodland caribou habitat successful (Pyper et al. 2014). Similarly, there is a need 711

to better understand whether sites that may be on a trajectory toward a restored forest should count as 712

restored, or whether equivalence to adjacent forests must be achieved before restoration can be 713

deemed successful (Ray 2014). While recent efforts, such as the new restoration framework of the 714

province of Alberta (Government of Alberta 2017), reduce ambiguity in the definition of success, more 715

work is needed to advance this discussion in other jurisdictions and within the scientific community. 716

Similarly, determining whether successful restoration for one species, such as woodland caribou, 717

provides wide-ranging benefits for additional species is also a key area requiring future research. 718

4.2. Monitoring 719

Monitoring ensures that restoration programs do not devolve into “faith-based restoration,” 720

whereby the project is implemented with hopes of a positive outcome once the first segment of a 721

hypothetical recovery trajectory has been achieved (Hilderbrand et al. 2005). Credible monitoring 722

provides data to quantitatively assess whether ecological objectives have been achieved and over what 723

timeframes. Monitoring should not only provide a means to certify the effectiveness of treatments 724

applied, but should also enable the early detection of problematic areas where additional corrective 725

measures may be needed. A credible, consistent approach to monitoring has been identified as one of 726

the most pressing needs in seismic line restoration (Golder Associates 2012; Pyper et al. 2014). 727

Consequently, significant progress has been made on this topic in Alberta with the development of a 728

Provincial Restoration and Establishment Framework (Government of Alberta 2017). 729

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When designing a monitoring program, some of the typical questions that need to be asked 730

include: i) What components of the restored system will be measured and over what spatial scale, and 731

what metrics and benchmarks will be used to measure these components? ii) How will the data be 732

stored, managed, modelled, evaluated and analyzed? iii) How will the findings of monitoring affect the 733

management of the restoration program? iv) Who will communicate the results and to what audiences? 734

And last but not least v) Who will cover the monitoring costs? (Hooper et al. 2015). 735

A potential problem with monitoring is the cost, which may consume considerable resources 736

that could otherwise be applied to restoration. The use of new technologies, such as photogrammetry 737

with unmanned aerial vehicles (UAVs, commonly known as drones), whereby a detailed 3D model of the 738

ground and vegetation is generated from overlapping digital photographs captured at low altitude (<100 739

m above ground level), could help reduce monitoring costs (Zahawi et al. 2015). A recent study 740

comparing a point intercept survey of vegetation height on seismic lines with estimates derived from 741

UAV photogrammetry concluded that the latter can effectively replace the former, drastically reducing 742

the amount of time and effort required to complete a survey (Chen et al. 2017). Also, wireless sensor 743

networks (Mainwaring et al. 2002) based on inexpensive hardware connected to the Internet of Things 744

enabling two-way communication with the network (Atzori et al. 2010), can complement and enhance 745

remote sensing data. This possibility is being explored by the Boreal Ecosystem Recovery & Assessment 746

project (www.bera-project.org), which is also developing protocols to estimate survival and 747

establishment indicators of restoration success on seismic lines. Taking advantage of these rapidly 748

evolving technologies to improve monitoring effectiveness and efficiency is clearly an opportunity for 749

the scientific community. 750

Current monitoring efforts that rely on site-specific criteria may demonstrate the value of 751

“proof-of-concept” restoration projects; however, as restoration efforts are scaled up, more efficient 752

and repeatable techniques will be required. Again, remote sensing monitoring tools (e.g., Frolking et al. 753

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2009; Wulder and Franklin 2012; Lawley et al. 2016) could improve the speed and efficiency of 754

measuring habitat responses over time following restoration, and align with the identified need to 755

measure habitat response at large scales, rather than limiting monitoring to site-specific measurements 756

(Ray 2014). In addition, these tools can help to analyze variability within individual programs and 757

between different programs, to better assess which sites are succeeding and which are failing, and to 758

identify possible mechanisms for these responses. 759

4.3. Research needs 760

Substantial research has been conducted on seismic lines over the past 30 years or more, but 761

several significant knowledge gaps remain to be investigated. Firstly, more research into the landscape-762

level implications of LIS development is needed. Advances in LIS technology have significantly reduced 763

the footprint of individual seismic lines in boreal and tundra landscapes (e.g., Schneider et al. 2003), but 764

the relative number and density of seismic lines have increased dramatically (Latham and Boutin 2015). 765

For example, in some areas of Alberta’s oil sands deposits, seismic line grids with 45 × 45 m spacing are 766

common. As Kansas et al. (2015) noted, while there is an inherent assumption that LIS lines will recover 767

naturally because of lower disturbance and narrow width, the evidence to date is not clear. Thus, 768

research is still required to better understand the responses of understory vegetation to LIS programs, 769

the landscape implications of dense seismic line spacing, and to identify stand types that may be more 770

amenable to LIS development on the landscape. 771

Second, edge effects caused by seismic lines continue to be an area in need of research. For 772

example, research on the edge effects of seismic lines in different ecosystems, especially lowlands is 773

currently being initiated at a small scale for individual peatlands (Dabros unpublished data) and needs 774

further attention. Understanding the magnitude and extent of edge effects on different organisms and 775

processes, with consideration of different spatial scales (from site to landscape), would more accurately 776

reveal the actual level of disturbance that seismic lines cause for a range of species. In regions of dense 777

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3D seismic development, the footprint of disturbances may be much greater once edge effects are taken 778

into consideration (Dabros et al. 2017). Furthermore, on a temporal scale, short- and long-term effects 779

of cumulative disturbances across the landscape must be considered to assess the changes in edge 780

effect magnitude over time. 781

A third research need is to develop a better understanding of seismic line impacts on less 782

charismatic species. The effects of seismic lines on vegetation and charismatic wildlife has received 783

considerable attention in scientific and policy literature, but the effects of seismic lines on the most 784

diverse and abundant groups of living organisms, namely invertebrates, constitutes a significant 785

knowledge gap for which research is only now being initiated. These future studies should strive to 786

document and understand how individual responses at the site level translate into population and 787

ecosystem effects at the landscape level, as opposed to simply documenting patterns of fragmentation. 788

Fourth, prescribed burning, natural wildfire, and targeted forest harvesting are increasing in 789

their relevance to discussions about restoration of seismic lines. Seismic lines have no natural analog, 790

therefore the used of natural disturbance emulation may be more challenging than e.g., in forestry 791

practices. Nonetheless, practitioners and researchers have recently been advocating for more use of 792

fire, and even harvesting, in restoration programs. Specific to the use of fire as a restoration tool, 793

burning areas affected by dense seismic line development may reset the ecosystem to early successional 794

stages, thus effectively ‘erasing’ seismic lines. The effectiveness of fire as a restoration technique is 795

currently being evaluated through several research projects led by ecologists at the Canadian Forest 796

Service (within Natural Resources Canada) and the University of Alberta. Given how ubiquitous seismic 797

lines are in some parts of the boreal, the logistical and financial constraints, as well as the risk of fire 798

escape and human endangerment, should also be considered when evaluating this practice. Forest 799

harvesting, some have advocated, could also serve as a restoration tool by serving as a natural 800

disturbance analogue. Placement of such harvesting and prescribed burning events would need to 801

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consider the needs of species at a landscape scale, and the implications of a return to earlier 802

successional stages. This point of discussion is particularly relevant for woodland caribou ranges where 803

fragmentation and early successional habitats (Hebblewhite et al. 2007) are a key driver of population 804

decline (Environment Canada 2012). 805

Fifth, with respect to evaluating restoration success, one of the key limitations of current 806

monitoring programs is that most measurements are conducted at the site scale, with few 807

considerations for how habitat recovery may be measured at larger scales. While site-level monitoring 808

may be used to assess effectiveness of the restoration approach, remote sensing and spatial modelling 809

may be used to evaluate the broader landscape picture. Another obstacle is a lack of consistency in 810

monitoring efforts between programs (Golder Associates 2012; Pyper et al. 2014); in some cases, 811

monitoring goals are not clearly defined, or they lack a connection to larger goals for restoration of 812

woodland caribou (Pyper et al. 2014). These issues represent key obstacles to be overcome as programs 813

continue to evolve in support of efficiently monitoring habitat recovery. Developing monitoring 814

approaches that are applicable at multiple scales, and that enable learning based on past experiences, 815

represents a critical need in the field of seismic line restoration. 816

Finally, projecting future recovery probability based on current ecological conditions is also a 817

key area in need of research. For example, discussions have occurred about developing recovery 818

trajectories to help inform the possible paths that a recovering site may follow (Golder Associates 2015; 819

Ray 2014). In many ways, these recovery trajectories could emulate the growth-and-yield curves that 820

have been used by the forestry industry for many years to model and predict forest stand growth and 821

productivity over time (Davis et al. 2001). Ray (2014) also noted that “free-to-grow” metrics could be 822

used to help measure current recovery along seismic lines and as a predictive measure for future 823

outcomes of restoration efforts, especially at the sites where site recovery seems more probable, either 824

due to direct and deliberate actions such as tree planting, or where natural regeneration seems more 825

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probable. Free-to-grow metrics are regularly used in the forestry industry as short-term indicators that a 826

forest stand has reached sufficient height and vigour to be considered on a probable trajectory to a 827

mature forest. Although some limitations have been noted with respect to how accurately free-to-grow 828

systems represent growth of the target species (Lieffers et al. 2007), they remain an important tool that 829

could help in providing shorter-term indicators of the trajectory that a restored habitat may be on. 830

Development of such successional trajectories, or predictive models based on approaches like those of 831

free-to-grow metrics, could significantly benefit restoration programs. Such models should also take into 832

account how regeneration suitability may decline or improve for certain tree species as a result of 833

climate change (Erickson et al. 2015). 834

5. Conclusion 835

Seismic lines are the most pervasive linear disturbances in oil and gas rich areas in the boreal 836

and arctic regions of North America. This review has highlighted that by changing abiotic factors, these 837

ubiquitous linear features can lead to changes in ecosystem structure and function, affecting both plants 838

and fauna. At the landscape scale, the cumulative effects of seismic lines and other linear disturbances 839

also contribute heavily to landscape fragmentation. This fragmentation, paired with projected global 840

climatic changes for arctic and boreal regions, may eventually lead to imbalances of the ecosystem, 841

affecting its health and resilience. 842

To mediate these impacts, best practices have been adopted for seismic exploration in many 843

jurisdictions (AECOM 2009). In comparison to conventional seismic lines, the literature suggests that for 844

some species, narrower LIS lines do indeed have lower ecological effects at the site level (e.g., Bayne et 845

al. 2005; Tigner et al. 2015). However, considering the high density of LIS lines, and likely existence of 846

edge effects (Dabros et al. 2017), the actual environmental impact of these lines may be 847

underestimated. 848

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Given the amount of conventional seismic lines within boreal and arctic landscapes, large 849

restoration programs will be required to facilitate recovery of communities back to a natural pre-850

disturbance state (Finnegan et al 2018). This is particularly the case for sites that are either very wet, or 851

very dry (van Rensen et al. 2015). However, seismic lines represent site conditions that provide 852

additional challenges to restoration efforts, such as high shading, cold soils, high water tables, or in 853

some cases compacted soils. To be successful, restoration treatments must therefore clearly document 854

site limiting factors and address these factors through creation of microsites, facilitation of natural 855

regeneration, mechanical site preparation, and/or tree planting. 856

The costs, labour and logistical constrains necessary for restoration of all currently present 857

seismic lines may be a daunting and unrealistic undertaking. Given the scale of this challenge, 858

prioritization of seismic restoration efforts will be inevitable (van Rensen et al. 2015). As such, priority 859

must be established as to which areas need to be restored first, based on their ecological value in terms 860

of supporting biodiversity and/or vulnerable species, and provision of economic and ecosystem services. 861

One possibility could be to use of active restoration within woodland caribou ranges, and outside them, 862

use approaches to ‘erase’ seismic lines through forest harvesting or prescribed burning, which may 863

provide a more efficient means of achieving restoration objectives. 864

Preventative measures should also be taken to minimize future disturbances through integrated 865

land management and mitigation practices, which may reduce the overall footprint of cumulative 866

disturbances, including linear disturbances such as seismic lines. To facilitate more rapid recovery of LIS 867

lines, approaches should be tested which better create the necessary microsite conditions upon which 868

natural recovery may occur rapidly following the initial disturbance. 869

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Acknowledgements 870

The authors thank Dr. Erin Bayne, Dr. Scott Nielsen, and two anonymous reviewers for providing a 871

constructive review and thoughtful comments on this manuscript, Brenda Laishley and Marta Dabros for 872

thorough editorial work, and Sebastien Rodrigue for help with listing references and other formatting 873

issues. The authors also appreciate general support from the following management staff members at 874

Northern Forestry Centre (Canadian Forest Service): David Langor, Renée Lapointe, and Michael Norton. 875

This research was funded by NRCan project PERD 1C03.15. 876

877

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Figure 1. Seismic lines from above: (a) density of seismic lines in some woodland caribou ranges in 1262

northeastern Alberta (from Alberta Biodiversity Monitoring Institute 2016); (b) satellite image of an area 1263

corresponding to the high-density cells in Fig. 1a (Image was created using ArcGIS® software by Esri. 1264

ArcGIS® and ArcMap™ are the intellectual property of Esri and are used herein under license. Copyright 1265

© Esri. All rights reserved. (www.esri.com)); (c) close-up from a drone of the area enclosed by red 1266

rectangle in Fig. 1b (Photograph by Guillermo Castilla). 1267

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Figure 2. Examples of seismic lines: (a) conventional seismic line in coniferous boreal upland forest; (b) 1269

conventional seismic line in boreal peatlands; (c) low-impact seismic line in coniferous boreal upland 1270

forest. (Photographs by Anna Dabros). 1271

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Figure 3. Types of machinery used in the construction of seismic lines: (a) bulldozer from the 1950s 1273

(Edward Browning URL: https://classicdozers.files.wordpress.com/2013/03/caterpillar-no-7a-blade-on-1274

a-d-7-17a-tractor-edgar-browning-image.jpg); 1275

(b) implements to reduce or avoid scuffing the soil layer (b1, mushroom shoe; b2, smear blade) (GNWT 1276

2012); (c) modern mulcher http://ironwolf.com/products/mulcher/; (d) envirodrill 1277

(http://www.coredrillingcorp.com/). 1278

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Table 1. An inventory of current seismic line restoration techniques.

Treatment What is it? Why would you use it? Where would you use it?

Mounding

An excavator is used to

dig holes and place the

soil beside the hole

creating an elevated

mound.

Mounds create an elevated

microsite that increases soil

temperature and improves

growing conditions for natural

regeneration and/or planted

seedlings.

Mounds can help create an

access barrier for human use

and may impede predator

movement on lines.

Lowlands with high water

tables (moisture concerns).

Dry stands to improve

moisture availability (pooling

of water in mound holes).

Uplands to address

competition concerns (e.g.,

grasses).

Screefing

An excavator or other

implement removes

the organic layer,

exposing a mineral soil

microsite.

Can be used in areas where

organic layers would inhibit

seed germination. Can also

help create pockets of

moisture in dry sites.

May promote tree suckering.

Generally used on xeric sites

with thick duff or litter layers.

Ripping

A bulldozer with either

ripping teeth or a

specialized plow, used

to decompact soil.

Reduces site compaction,

improves moisture

availability, soil aeration and

potential for root

development.

Generally used on upland sites

with soil compaction issues.

Rollback and

coarse woody

material

Woody materials from

beside the line, or from

nearby operations, are

placed on the line.

Creates microsites for

vegetation establishment and

protection of seedlings

(natural and planted).

Creates a human access

barrier when applied at high

enough volumes.

May impede predator

movement.

Anywhere microsites would

help regeneration or where

access management is

required.

Tree felling or

tree hinging

Trees adjacent to the

seismic line are felled

across it.

Creates microsites for

vegetation establishment and

protection of seedlings

(natural and planted).

Creates a human access

barrier when applied at high

enough volumes.

May impede predator

movement.

Any sites where microsites

would benefit regeneration or

where access management is

required.

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Treatment What is it? Why would you use it? Where would you use it?

Tree tipping

A process by which

trees are pulled over

using winches or heavy

equipment.

Felling trees results in rapid

loss of needles. Tree tipping

maintains root contact with

soils and may extend the life

of the tree while still creating

a line-of-sight and movement

barrier for wolves and

humans.

Any sites where microsites

would benefit regeneration or

where access management is

required to reduce human

access and predator

movement.

Tree transplants

Established trees

adjacent to the

treatment lines are

excavated and moved

onto treatment lines.

Generally used in situations

where operators wish to

establish immediate tree

cover on a line.

Generally restricted to wet

areas where the root ball can

be excavated with minimal

damage to the root structure.

Summer planting

Seedlings are planted

to encourage

regeneration.

Can help ensure desirable

species mixes.

Puts vegetation on a long-

term recovery trajectory to a

restored condition.

Any sites where improving

regeneration is desirable.

Often used in combination

with site preparation.

Wetlands can be difficult to

plant in summer (access

challenges).

Winter planting

Seedlings are planted

to encourage

regeneration.

Establishes conifer cover on

sites and puts vegetation on a

long-term recovery trajectory

to a restored condition.

Generally used in treed

wetlands where site

preparation (mounding) has

occurred. Enables planting of

wetlands when access is

possible (i.e., frozen ground

conditions).

Seeding

Seeds are spread on

exposed microsites to

facilitate tree

recruitment.

Can reduce project costs and

in some cases may improve

tree establishment by

allowing trees to establish on

the most desirable microsites

as opposed to relying on a

planted tree plug.

Sites with sufficient exposed

microsites to enable seed

germination.

Natural

regeneration

Exposed microsites are

created and rely on

seed influx from the

adjacent stand.

Can reduce project costs and

in some cases may improve

tree establishment by

allowing trees to establish on

the most desirable microsites

as opposed to relying on a

planted tree plug.

Sites with sufficient exposed

microsites to enable seed

germination and with sufficient

seed sources of desired species

(e.g., white spruce) available

adjacent to the treated line.

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