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Resource Roads and Grizzly Bears in British Columbia and Alberta, Canada

Authors:
  • The Foothills Research Institute

Abstract and Figures

Here we reviewed the scientific literature on the relationship between grizzly bears, human motorized access, and the efficacy of motorized access control as a tool to benefit grizzly bear conservation in western Canada. We suggest landscape road targets that will benefit bear conservation.
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Effects of roads and motorized human access on grizzly bear
populations in British Columbia and Alberta, Canada
Michael F. Proctor1,6, Bruce N. McLellan2, Gordon B. Stenhouse3, Garth Mowat4, Clayton T. Lamb5,
and Mark S. Boyce5
1Birchdale Ecological, P.O. Box 606, Kaslo, British Columbia, V0G 1M0, Canada
2Ministry of Forest, Lands, & Natural Resource Operations, P.O. Box 1732, D’Arcy, British Columbia, V0N 1L0,
Canada
3fRi Research, 1176b Switzer Drive, Hinton, Alberta, T7V 1V3, Canada
4Ministry of Forest, Lands, Natural Resource Operations & Rural Development, Nelson, British Columbia, V1L 4K3,
Canada
5Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
Abstract: The growing human footprint has placed unprecedented stressors on ecosystems in recent
decades resulting in losses of biodiversity and ecosystem function around the world. Roads are influential
through their direct footprint and facilitating human access; however, their influence can be mitigated.
Here, we review the scientific literature on the relationship between grizzly bears (Ursus arctos), hu-
man motorized access, and the efficacy of motorized access control as a tool to benefit grizzly bear
conservation in western Canada. We found that motorized access affected grizzly bears at the individual
and population levels through effects on bears’ habitat use, home range selection, movements, popula-
tion fragmentation, survival, and reproductive rates that ultimately were reflected in population density,
trend, and conservation status. Motorized access management was effective in mitigating these effects.
Our review of the scientific literature suggests that industrial road management would be a useful tool if
(a) roads exist in high-quality grizzly bear habitats with population-energy-rich food resources; (b) open
road densities exceed 0.6 km/km2; (c) less than at least 60% of the unit’s area is >500 m from an open
road in patch sizes of 10 km2. Motorized access management would be most beneficial in threatened
populations, in areas where roads occur in the highest quality habitats, within and adjacent to identi-
fied linkage areas between population units, and in areas that are expected to exceed motorized route
thresholds as a result of resource extraction activities. Evidence suggests benefits of motorized access
management are more likely to be realized if habitat quality is integrated and is best if managed at scales
that optimize the benefit of distribution, survival, reproduction, and density of female grizzly bears. We
encourage land use managers developing access rules to consider a wider spectrum of biodiversity and
overall habitat conservation, and suggest landscape road targets that will benefit bear conservation.
Key words: access management, Alberta, British Columbia, grizzly bear, motorized access, review, roads, Ursus arctos
DOI: 10.2192/URSUS-D-18-00016.2 Ursus 30: article e2 (2019)
Natural systems and wildlife have faced unprecedented
challenges in recent decades resulting in accelerated loss
of biodiversity and ecosystem function across the globe
(Sala et al. 2010, Barnosky et al. 2011, van der Ree et al.
2011, Hooper et al. 2012), resulting in extinction rates
approximately 100 times natural rates (Celabos et al.
2015). These trends are occurring while a decades-long
environmental mitigation effort sweeps the globe (Sec-
retariat of the Convention on Biological Diversity 2014,
6email: mproctor@netidea.com
Wilson 2016). This conundrum clearly suggests that pro-
tected areas are not mitigating the ever-expanding and
intensifying human footprint (Sanderson et al. 2002,
Venter et al. 2016, Wilson 2016, Dinerstein et al. 2017).
The corollary is that if we want to maintain biodiver-
sity and sustainable supportive ecosystems, we either
need to increase and diversify the protected area system
(Wilson 2016, Dinerstein et al. 2017), ensure the varied
types of protected areas are linked by functional connec-
tivity networks (Dinerstein et al. 2017), manage the inter-
vening matrix of multiple-use lands to a higher standard,
or some combination of the above (Lamb et al. 2018a).
16
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 17
Table 1. A glossary of terms applicable to our review of the scientific literature on the relationship between
grizzlybears(Ursus arctos), human motorized access, and the efficacy of motorized access control as a tool
to benefit grizzly bear conservation in western Canada.
Term Definition
Motorized access management A term reflecting restrictions to motorized traffic on roads in the backcountry for the benefit of
wildlife and ecosystems.
Road A track- or gravel-paved road traversable by pickup trucks or Off Highway Vehicles (OHVs).
Off Highway Vehicle A motorized vehicle capable of operating off highways, including but not limited to quads,
side-by-sides, tracked vehicles, or motorcycles.
Road density A measure of roads traversable by pickup trucks or OHVs in km/km2.
Open road A road that is open to everyone, industry and the public.
Restricted road A road that is not open to the public, but allows industrial use.
Closed road A road that is closed to everyone.
Seasonally closed road A road that is closed during a certain season, for instance the late summer–early autumn berry
season when bears feed intensively to store energy for hibernation.
One sphere within the increasing human footprint is the
ubiquitous presence of roads, which can have unintended
negative effects on natural systems and wildlife popu-
lations (McLellan 1990, Forman and Alexander 1998,
Fahrig and Rytwinski 2009, Basille et al. 2013, Ibisch
et al. 2016, Ceia-Hasse et al. 2017).
Although this document is focused on one large car-
nivore species, the grizzly bear (Ursus arctos) in British
Columbia (BC) and Alberta, Canada, it also is a reflection
of our modern world. We are not alone with the issues pre-
sented here. Although biodiversity loss in Canada is less
than in many other parts of the world, we do have signif-
icant extinction risk for several endemic species and ex-
tirpation risk within BC and Alberta for several species
with broader distributions (Rainer et al. 2017). Finally,
Canada is a stronghold for 24% of the planet’s remaining
wilderness, but ongoing resource extraction is reducing
Canada’s wilderness, compromising grizzly bear popula-
tions and furthering the loss of biodiversity (Lamb et al.
2018a).
After protected areas, motorized access controls
(MACs, on routes that include roads and Off Highway Ve-
hicles [OHV] tracks; Table 1) have been the cornerstone
of the recovery of threatened grizzly bear populations for
the past 3 decades in the contiguous United States, where
grizzly bears in the Yellowstone and Northern Continen-
tal Divide ecosystems have all but recovered (though legal
debates are ongoing [Schwartz et al. 2006, Kendall et al.
2009, Mace et al. 2012]). Populations have increased sig-
nificantly and geographic expansion has occurred in both
ecosystems from historic lows prior to 1970 (Schwartz
et al. 2006, Kendall et al. 2009). In the lower 48 states,
mortality reduction has been implemented intensively,
including motorized access management on public lands
and mitigation efforts to reduce front-country (human-
settled valleys), conflict-related deaths. These successes
are lessons for grizzly bear management in Canada, where
there is extensive and increasing human–bear overlap.
Alberta grizzly bear populations were first designated
threatened in 2010 and management of road densities (ex-
cluding OHV tracks) is a key strategy in the province’s
newest “draft” Recovery Plan (Alberta Environment and
Parks 2016). Although BC has almost 10 times as many
grizzly bears as there are in the lower 48 states or Alberta,
there are a few population units in BC that are either of-
concern (“threatened”) or well below their potential num-
bers (Hamilton and Austin 2004, BC Ministry of Envi-
ronment 2012, McLellan et al. 2016). British Columbia
has no provincial-scale road management strategy and
road building has been extensive, although some regional
MAC initiatives have existed for decades (Fig. 1).
We reviewed the scientific literature on the relationship
between grizzly bear ecology, human motorized access,
and the efficacy of MACs as a tool in grizzly bear man-
agement to answer 3 questions:
1) What are the effects of motorized access on griz-
zly bear populations?
2) Is motorized access management effective to re-
duce any negative effects of roads?
3) If yes, how should it be implemented to maximize
efficacy?
There are many economic and social benefits of road
networks in our backcountry ecosystems. Roads are the
backbone of our forestry, mining, and energy industries,
and enable people to easily recreate in remote natural
environments. The road network, however, is potentially
costly to our natural systems. The goal of this report is
to assess these costs and the tools that can help mitigate
them.
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18 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
Fig. 1. Grizzly bear (Ursus arctos) distribution and resource roads across Alberta and British Columbia,
Canada. Resource roads are non-highway, dirt or gravel roads used to access timber and mining resources.
This map does not reflect all Off Highway Vehicle tracks. The upper right inset displays topographic relief and
the lower left inset provides a close up to show variation in road densities within southeast British Columbia.
We begin by discussing some of the mechanisms in-
volved between grizzly bears and motorized access with
grizzly bear response to roads, mortality, displacement,
habitat loss, and fragmentation. This is followed by an ex-
ploration into beneficial access controls for grizzly bear
conservation, including what metrics (road density, se-
cure habitat—habitat >500 m from an open road) and
thresholds exist. We then look at where MACs are useful
(i.e., in what types of populations and habitats are they
beneficial). We finish with how they might be applied
within Alberta and British Columbia.
Grizzly bear response to roads
Grizzly bear response to motorized human access gen-
erally occurs via 4 mechanisms. In the likely order of their
influence on grizzly bear populations in Alberta and BC
they are (1) increased human-caused mortality, (2) habi-
tat displacement, (3) fragmentation, and (4) direct habitat
loss (Fig. 2).
Mortality—top-down versus bottom-up influ-
ence
When trying to understand grizzly bear population dy-
namics and the role of mortality, it is useful to consider
the relationship between food resources (bottom-up influ-
ence) and mortality (top-down influence). Food resources
drive animal abundance (McLellan 1994, 2011, 2015;
Hilderbrand et al. 1999; Carbone and Gittleman 2002;
Sinclair and Krebs 2002; Brasher et al. 2007; Lamb et al.
2017, 2018b; Proctor et al. 2017). However, mortality rate
can determine how close a population comes to its food-
limited density and can have a significant influence on
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 19
Fig. 2. Schematic of mechanisms of grizzly bear
(Ursus arctos) response to roads. The main effect
is mortality, which ultimately reduces density. Sec-
ondarily, displacement and direct habitat loss poten-
tially affect reproductive output and density.
conservation status (Ciarniello et al. 2007a, Lamb et al.
2017, Proctor et al. 2017). Conservation status is not nec-
essarily determined by bear density because it can natu-
rally range by 2 orders of magnitude (100×) across North
America (McLellan 1994, Hilderbrand et al. 1999, Mowat
et al. 2013). Even though measuring potential grizzly bear
density or carrying capacity is challenging, conservation
status has been partly predicated on how far a population
is below their potential density as a result of excessive
human influence. A population may be at low density be-
cause food is naturally limited, whereas a higher density
population may be well below its potential because of
human mortality, often as a result of high road densities
(Mowat and Lamb 2016; Lamb et al. 2017, 2018b).
Top down—mortality and roads
In areas with human–bear overlap, a large majority of
grizzly bears over the age of 2 are eventually killed by
people and almost all are killed near roads (shot, not hit by
vehicles). Studies from across west-central North Amer-
ica report that humans cause between 77% and 90% of
grizzly bear mortalities (McLellan 1989, 2015; McLellan
et al. 1999; Garshelis et al. 2005; Schwartz et al. 2006;
Mace et al. 2012). Where humans and bears overlap, adult
bear survival decreases (Gunther et al. 2004; Schwartz
et al. 2006, 2010; Boulanger et al. 2013; Boulanger
and Stenhouse 2014; Lamb et al. 2017). Most bears are
killed near a road (Benn and Herrero 2002, McLellan
2015); therefore, there is a strong positive association
between motorized access into grizzly bear habitat and
bear mortality (Nielsen et al. 2004a, Schwartz et al. 2010,
Boulanger and Stenhouse 2014, Proctor et al. 2017).
The most important mechanism influencing grizzly
bear population growth emanates from the combination
of 2 factors. First, female survival has the greatest influ-
ence on population trend (McLellan 1989, Eberhardt et al.
1994, Garshelis et al. 2005, Harris et al. 2006, Mace et al.
2012), and second, female survival is reduced in habitats
with higher road densities where people use the roads
(Schwartz et al. 2010, Boulanger and Stenhouse 2014).
Open road density and the amount of secure habitat in
female home ranges are important predictors of female
survival and both contribute different yet important com-
ponents influencing survival (Mace et al. 1996, Wakkinen
and Kasworm 1997, Schwartz et al. 2010).
Taking the link between high road densities and ele-
vated female mortality rates further, Alberta researchers
found female survival was not only inversely related to
road density, but low female survival also resulted in lo-
cal population declines when road densities exceeded
0.75 km/km2(Fig. 3; Boulanger and Stenhouse 2014).
The specificity of this effect will vary across Alberta
and BC as a result of variation in traffic volumes, human
lethality (tendency to kill bears), and habitat quality, but
Boulanger and Stenhouse (2014) demonstrated the link
between road density, female survival, and the potential
for population decline.
Excessive human-caused mortality is the main cause
of current grizzly bear conservation issues in several, but
not all, population units in Alberta and BC. For example,
motorized-access–related mortality was the most impor-
tant limiting factor in the plateau portion of a central BC
study area near Prince George, but food was the most im-
portant limiting factor in the mountainous section (Cia-
rniello et al. 2007a). Mortality was thought to be a major
factor in a population decline in the South Rockies Griz-
zly Bear Population Unit (GBPU) of southeastern BC,
which was likely initiated by a multi-year food shortage
(Mowat and Lamb 2016, Lamb et al. 2017) as was docu-
mented in the adjacent Flathead Valley (McLellan 2015).
Although food resources likely set the potential density
of these populations, conservation issues arose from ex-
cessive human-caused mortality.
In Alberta, a mortality risk analysis supported the
hypothesis that human access (indexed by distance to
roads) and edge habitats near water sources were im-
portant predictors of reported grizzly bear mortality
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20 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
Fig. 3. Road density threshold for stable population
growth relative to female grizzly bear (Ursus arctos)
survival in western Alberta, Canada between 1999
and 2012. The reproductive state of females was con-
sidered as a variable when developing this curve.
Females with dependent offspring had lower sur-
vival, relative to road density, than females without
offspring. Adapted from Boulanger and Stenhouse
(2014). Areas with road densities >0.75 km/km2cor-
respondingly had Lambda (population growth), val-
ues <1.0, representing population decline. ‘CI’ is
confidence interval.
(Nielsen et al. 2004a). A similar analysis in southeast-
ern BC examined a combination of reported and unre-
ported mortalities and found similar results, where road
density, distance to roads, highways, and lower eleva-
tion open habitats near riparian areas (often valley bot-
toms) best predicted grizzly bear mortality (Proctor et al.
2018). Both these studies used mortality databases that
were skewed toward reported mortalities, which are likely
biased toward front-country mortalities. Therefore their
results may not accurately reflect unreported mortalities
that occur in backcountry settings. Including a better sam-
ple of unreported mortalities in southeastern BC, McLel-
lan (2015) found 86% of the 26 radiocollared bears killed
by people were within 120 m of a backcountry road when
killed. Similarly, 20 years of radiocollared bear data from
across Alberta found 100% of all human-caused mortal-
ities were within 100 m of all-weather gravel roads or
highways (G.B. Stenhouse, unpublished data). The cu-
mulative evidence is compelling; motorized road access
into grizzly bear habitat does reduce grizzly bear survival,
particularly of females, and will usually affect density and
sometimes conservation status.
Bottom up—food resources, habitat quality,
and roads
To understand the relationship between human motor-
ized access and grizzly bear habitat, it is useful to ex-
plore the relationship to habitat quality, important food
resources, human motorized access, and the seasonality
of human-caused mortality.
How are habitat and food resources related to
road densities?
As mentioned above, population dynamics of grizzly
bears are driven by interrelated top-down and bottom-up
forces. Food abundance and quality affect individual and
population productivity (Carbone and Gittleman 2002,
Sinclair and Krebs 2002, Mattson et al. 2004, Rode et al.
2006, McLellan 2015, Hertel et al. 2017, Proctor et al.
2017) and density (Hilderbrand et al. 1999, Mowat et al.
2013). Researchers brought these forces together to iden-
tity source and sink habitats across Alberta and eventually
incorporated food resources and human-caused mortality
risk into habitat models. They argued that understanding
and integrating these functional drivers are required to
better inform management (Nielsen et al. 2006, 2010;
Boulanger et al. 2018). In other research, grizzly bears
in the foothills of central Alberta that used mixed ages
of young regenerating forests were found to gain more
weight than bears using older forests, but those advan-
tages were offset by lower survival rates associated with
higher road densities (Boulanger et al. 2013). In the south-
ern Rocky Mountains of southeastern BC, higher grizzly
bear densities occurred in an area with higher overall road
density, but with large, unroaded huckleberry (Vaccinium
membranaceum) fields (see Flathead example discussed
below; McLellan 2015). These results showed that abun-
dant and secure food in late summer–autumn habitats reg-
ulated this population.
Inspired by these insights, 2 efforts linked food and
mortality risk in different analyses in southeastern BC.
First, in the southern Rocky Mountains, researchers
linked important foods with mortality risk and found
that berry resources, kokanee salmon (Oncorhynchus
nerka), and anthropogenic food sources (fruit trees, live-
stock, garbage, and ungulate carcasses) likely acted to
bring bears and humans into direct contact, increasing
bear mortality and contributing to a population decline
(Lamb et al. 2017).
Second, in BC’s southern Selkirk and Purcell Moun-
tains, researchers developed predictive models for grizzly
bear seasonal habitat use, density, and fitness from a com-
bination of a spatialized food-patch layer using the re-
gion’s primary hyperphagia food resource—huckleberry
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 21
patches—and human motorized access layers (Proctor
et al. 2017). They found that, across all individual and
population-level scales tested, food patch variables were
the most influential predictors, whereas road density was
also a significant and additive contributor to predicting
realized habitat effectiveness, density, and fitness.
Although not a direct assessment of foods and mor-
tality risk, recent work in Alberta linked habitat quality
(as a surrogate for food resources) to mortality risk. That
pan-Alberta meta-analysis found that habitat quality was
most important in the northern population units and mor-
tality risk was the key driver in southern units. These
results demonstrate that the spatial (and likely temporal)
drivers of density differ by area and landscape conditions
(Boulanger et al. 2018). All the above studies reveal the
complex and intertwined relationships between food re-
sources and mortality risk. Their relative influence varies
spatially and temporally and suggests that to benefit bears,
food and motorized access are better kept apart.
Although berries are important in many areas, vari-
ous energy-rich foods drive the productivity of bears in
other ecosystems across British Columbia and Alberta,
including salmon (Oncorynchus spp.), ungulates, white-
bark pine nuts (Pinus albicaulis), buffalo berries (Shep-
herdia canadensis), sweet vetch (Hedysarum spp.), and
combinations of these and other important foods. To de-
posit fat needed for successful reproduction and hiberna-
tion, these foods are eaten in late summer and autumn,
concurrent with the ungulate hunting season. In the BC
population unit with the highest legal hunter-kill density
in BC (Flathead), as many female grizzlies were killed
in the autumn by ungulate hunters as a result of human–
bear conflict as were by grizzly bear hunters in the spring.
Keeping roads away from important energy-rich food
sources not only enables females to focus on getting fat
for hibernation, but also reduces the number of ungulate
hunters, who sometimes kill these bears as a result of real
or perceived self-defense (McLellan 2015).
The proximity between humans and bears can also vary
by season. For example, spring green-up, summer and
autumn natural-food fluctuations, and autumn ungulate-
hunting seasons can all bring bears to lower elevation val-
ley bottoms, where they are closer to people and roads,
resulting in high mortality rates. Finally in some areas,
timber harvest can improve foraging resources for bears,
and may require post-harvest access management to re-
alize this benefit for bears (Boulanger et al. 2013).
Displacement
Displacement from habitat near roads has the poten-
tial to reduce grizzly bear habitat effectiveness, body
condition, reproductive rates, and ultimately population
density, due to habitat loss (McLellan and Shackleton
1988, Mace et al. 1996, Hertel et al. 2016). Brown bears
(U. arctos) in Scandinavia decrease foraging on berries in
response to hunting pressure, causing a measurable nu-
tritional cost that likely results in poorer body condition
and reduced reproductive success (Hertel et al. 2016).
However, the full story on grizzly bear habitat use near
roads is complex, because roads can be both attractive
and disruptive.
Roadside foods can attract bears under several cir-
cumstances. Roads are often associated with logging or
oil–gas development, where seeded roadside forage pro-
vides high-quality nutrition for grizzly bears, particularly
in spring (Nielsen et al. 2004b). Although these sea-
sonally attractive foods can potentially improve female
body condition and reproductive success, the benefits
of roadsides are offset by reductions in survival (Matt-
son et al. 1987, Boulanger et al. 2013). To offset this
mortality risk, some bears use roadside habitats at night
(McLellan and Shackleton 1988, Martin et al. 2010, Or-
diz et al. 2011, Northrup et al. 2012, Cristescu et al.
2013) or become habituated to nutritious food sources
near roads and human developments in protected areas
(Mattson et al. 1987).
Roads can be disruptive because bears generally avoid
traffic (McLellan and Shackleton 1988, Berland et al.
2008, Graham et al. 2010, Roever et al. 2010, Northrup
et al. 2012, Proctor et al. 2017, Lamb et al. 2018b). How-
ever, the degree to which habitat selection studies demon-
strate “some degree of avoidance” of roads, as opposed to
a sample of bears that have succeeded in not dying near
roads, remains unknown. Consequently, road avoidance
remains difficult to discern from survival in the absence of
a manipulative or before–after study (see below for more
on this topic). Nevertheless, on average it appears that
bears avoid roads with vehicular traffic, but exceptions
exist to this rule.
Although grizzly bears tend to avoid roads at the indi-
vidual level, especially those that receive moderate–high
traffic volumes (Northrup et al. 2012), there are important
caveats to road influence at the population level. Roadside
habitats do not usually provide energy-rich food resources
during some seasons (spring and late autumn) and bears
may avoid roads more when their populations are below
carrying capacity and when alternative and unused habi-
tats are available, thus dampening any population-level
effects (McLellan 2015). We conclude that grizzly bears
avoid open roads, but the evidence of individual (body
condition and reproduction) and population level (den-
sity, trend) effects are less certain.
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22 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
In the literature, the spatial extent of road effects on
female survival is variable. The quality of foods along
roadsides also influences roadside habitat use and such
use can vary by bear sex and age. The spatial scale at
which roads and associated human presence affect grizzly
bear survival and behavior varies across studies, but is at
a minimum 100 m (McLellan and Shackleton 1989), and
extends up to 1,000 m (Kasworm and Manley 1990). Most
commonly, researchers reported that the effects of roads
extended to 500 m; bears avoided habitat and/or were
killed within this distance (Mattson et al. 1987, Mace
et al. 1996, Benn and Herrero 2002, Schwartz et al. 2010,
van Manen et al. 2016).
There are approximately 750,000 km of resource roads
(not including all OHV tracks) in BC. Assuming a road
width of approximately 10 m, there is somewhere in the
range of 7,500 km2of vegetative habitat loss across BC
due to road footprint (although some areas eventually
re-vegetate). This represents approximately 1% of the
750,000 km2of occupied grizzly bear territory within
BC. Likewise, in Alberta, the approximately 43,000 km
of roads (not including all OHV tracks) in potential griz-
zly bear habitat (Boulanger and Stenhouse 2014) repre-
sents 0.25% of the 173,000 km2of grizzly bear range in
Alberta. It is challenging to translate this habitat loss into
an estimate of the number of bears lost, but is certainly
greater than zero.
Fragmentation
Roads have been shown to disrupt bear movements, in-
fluencing natal dispersal and ultimately population-level
fragmentation. In northwestern Montana, USA (Graves
et al. 2014), and Scandinavia (Steyaert et al. 2016, Bischof
et al. 2017), backcountry forestry roads imposed resis-
tance to dispersal, although no links were identified to
population-level consequences. In a large landscape in-
vestigation, researchers found that human-caused mortal-
ity, when combined with settlement patterns and highway
traffic, was responsible for extensive population fragmen-
tation across much of southeastern BC, western Alberta,
and northwestern United States in occupied bear terri-
tory (Proctor et al. 2012): road densities were an influen-
tial variable in mortality risk of grizzly bears across their
study area (Proctor et al. 2018). Further work in BC went
on to reveal mechanisms that included human settlement
patterns and excessive human-caused mortality, to which
high road densities and human settlement were likely
contributors (Mowat and Lamb 2016, Lamb et al. 2017);
this corroborated and further explained population-level
fragmentation caused by Highway 3 through the Cana-
dian Rockies (Proctor et al. 2012). In other work, detailed
analyses of movements of 38 Global Positioning System–
collared grizzly bears in the BC Highway 3 area of the
Rocky Mountains found that the main highway reduced
the odds of crossing movements by 44%, whereas in-
dustrial main lines (forestry and energy sector roads) re-
duced the odds of crossing movements by 9–20% (Apps
et al. 2013). Only the main highway (approx. 3,700 vehi-
cles/day) blocked movements of about half the collared
bears, although all bears crossed less busy roads (Apps
et al. 2013). These examples reveal the link between ex-
cessive road densities and fragmentation.
When are access controls a beneficial
tool for grizzly bear conservation?
Both BC and Alberta have public policies to ensure the
long-term sustainability of grizzly bear populations in
their current distribution. Alberta has an official Provin-
cial Recovery Plan (Alberta Environment and Parks
2016), and BC has a Provincial Conservation Strategy
and Wildlife Program Plan (BC Ministry of Environment
1995, 2010). To realize those policies, the science sug-
gests that both provinces should apply MACs where road
densities are high and grizzly bear conservation is a con-
cern. There are large areas of grizzly bear distribution,
particularly in northwestern BC, where motorized access
management may not be necessary because of current
low road densities; but, considering trends in resource
extraction, road development, and increasing human
populations, motorized access management should be
considered by managers, even in those areas. Much of
southern and central BC and all of Alberta’s provincial
lands have high road densities, and bears would benefit
from increased motorized access management. We
recognize that MACs have been applied effectively in
some areas of each province. However, whereas much
has been done, large tracts of heavily roaded bear habitat
still exist. In this section we discuss the evidence behind
our conclusions by looking into grizzly bear response to
variation in human motorized access.
Female home-range selection, bear density, and
the 0.6-km/km2threshold
The United States has used MACs as a cornerstone
of their threatened population recovery effort in the
lower 48 states for 30 years; it has largely worked
within their larger conservation management toolbox
(Mealey 1986, USFWS 1993) and is supported by a
body of science (Mace et al. 1996, 2012; Kendall et al.
2009; Schwartz et al. 2010). Other mortality reduction
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 23
actions also were undertaken, so it is difficult to tease
apart the proportional influence of each concurrent ac-
tion. Prior to 1993, there were 237 grizzly bears
across 23,300 km2in the Greater Yellowstone Ecosystem
(USFWS 1993, 136 in 1975, U.S. Fish and Wildlife Ser-
vice [USFWS] website https://www.fws.gov/mountain-
prairie/es/GYE%20Grizzly-FAQs.pdf). That estimate
has since grown to a minimum of 700 bears
over 50,280 km2(van Manen et al. 2016, US-
FWS website https://www.fws.gov/mountain-prairie/es/
GYE%20Grizzly-FAQs.pdf). The U.S. Northern Conti-
nental Divide Ecosystem population grew from a crudely
estimated 440–680 animals across 24,800 km2prior to
1993 (Mace et al. 2012; minimum estimates of 300 bears
[USFWS 1993]) to a DNA-derived estimate of 765 in
2004 across 33,480 km2(Kendall et al. 2009), and has
been increasing at a rate of approximately 3% annually
(Mace et al. 2012).
Managers in the United States applied a motorized-
access management system that allows for varying pro-
portions of the planning area to have different road den-
sities, ranging from no roads, to minimal roads, to unre-
stricted road densities (regulations include OHV trails).
Approximately 55–68% of the planning area must be
>500 m from an open road (i.e., roadless or 0 km/km2),
approximately 19–33% should have a road density of
<0.6 km/km2, and 19–26% may have >1.2 km/km2total
road density (both closed and open roads; these percent-
ages do not sum to 100 because their categories over-
lap). Landscape application of these rules and spatial
patterns are flexible, but it is suggested that these areas
have at least a 10-year window of consistency to allow
bears to adjust to, and benefit from, secure habitat (W.
Kasworm, USFWS Cabinet–Yaak Recovery Coordina-
tor, personal communication). These rules were derived
based on work by Mace et al. (1996) and Wakkinen and
Kasworm (1997), who found these were the approximate
conditions that surviving and reproducing female bears
selected for in their home ranges within otherwise dimin-
ished remnant populations in northwestern Montana.
The 0.6-km/km2road-density threshold, first identi-
fied by Mace et al. (1996), has been roughly observed by
other researchers in multiple study areas. However, note
that not all researchers calculated road densities in ex-
actly the same way; variation often depended on what
digitized roads layers were available, with several re-
searchers including all motorized routes, which included
roads traversable by pickup trucks and trails suitable for
only OHVs, whereas a few excluded OHV trails. Despite
this variation, we feel the resulting patterns are mean-
ingful. Mace et al. (1996) found that females were sur-
viving and reproducing in areas with road densities <0.6
km/km2. The surrounding landscape where females were
not found had road densities of 1.1 km/km2. Similarly,
work in Alberta found lower female survival and popula-
tion declines in areas with road densities >0.75 km/km2
(Fig. 3; Boulanger and Stenhouse [2014]). In the BC
Granby–Kettle population, researchers found that the
optimal threshold road density was approximately 0.5
km/km2(range =0.4–0.6) and that grizzly bear den-
sity was approximately 3–4 times higher in habitats with
road densities <0.6 km/km2than in habitats with >0.6
km/km2(Fig. 4; Lamb et al. 2018b). Across the south
Selkirk and Purcell Mountains of southeastern BC, re-
searchers that found radiocollared females selected and
survived in home ranges with average road densities of
0.5 km/km2(Proctor et al. 2017). Similar to Lamb et al.
(2017), Proctor et al. (2017) also found grizzly bear den-
sities to be approximately 3 times higher in habitats with
road densities <0.6 km/km2relative to habitats with road
densities of >0.6 km/km2(Fig. 5).
Female choice of home range, as reported by Mace
et al. (1996), Wakkinen and Kasworm (1997), Lamb et al.
(2018b), and Proctor et al. (2017) is likely more a function
of survival than active selection. That is, female bears tend
to have higher survival rates in habitats with lower road
densities (Schwartz et al. 2010, Boulanger and Stenhouse
2014); therefore, some portion of apparent home-range
selection reflects bears surviving longer in habitats with
fewer roads. In a multi-scaled analysis, assessing daily
use areas versus female home ranges, researchers found
that bears used habitats with higher road densities on a
daily basis, yet their home ranges contained lower road
densities on average (Apps et al. 2013). These results
suggested that survival was more important than avoiding
roads. So rather than refer to this as “selection of home
range,” a more appropriately descriptive term might be
“selection of home ranges considering survival.”
Although road densities matter to grizzly bears,
thresholds can be population-specific. For example, the
threatened Stein–Nahatlatch population in southwest-
ern BC—a small (10 adults), isolated, low-density,
and threatened population—declined from 7.4 to 6.5
bears/1,000 km2between 2005 and 2015, even though
there are only 0.2 km/km2of open roads (M. McLel-
lan, Victoria University of Wellington, unpublished data).
This area has generally poor habitat quality that limits
bear reproduction to a level that only compensates for
minimal human-caused mortality. Thus, a road network
of 0.6 km/km2does not guarantee recovery or a sustain-
able population. When food is a limiting factor, as sus-
pected in the Stein–Nahatlatch bear population, even road
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24 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
Fig. 4. (a) Optimal road density threshold (0.5 km/km2) in the Kettle–Granby Grizzly Bear Population Unit
of south-central British Columbia, Canada, in 2015. The threshold was derived from the distribution of log
likelihood values and cumulative model weights used to find an optimal road-density breakpoint (best fit of the
data when grizzly bear (Ursus arctos) density was classified into 2 groups, above and below each breakpoint)
for grizzly bear density; and (b) Evidence of the positive relationship between habitat quality and bear density
in the Kettle–Granby population as determined from the predicted responses of the most supported model.
Road density was fixed to >0.6 km/km2; and (c) Grizzly bear density in habitats with road densities >and <0.6
km/km2. Adapted from Lamb et al. (2018b).
density of 0.6 km/km2may facilitate too much mortality
risk for that population to recover or be sustainable until
habitat management can yield a better food supply.
Another example is from the Flathead Valley (Wildlife
Management Units 4-01) of southeastern BC. A DNA-
based survey in 2007 yielded an estimated density of
65 bears/1,000 km2across the 1,585-km2management
unit. Unit 4-01 is a small area with a high density of
bears, where the open and restricted road density is ap-
proximately 1.2 km/km2. In the southern half of this
unit, where bear densities are the highest, there were
0.74 km/km2of 2-wheel drive roads plus 0.9 km/km2of
smaller ephemeral roads (McLellan 2015). This is a very
productive area, and bear reproductive rates can compen-
sate for a higher level of human-caused mortality than
in most other areas; the Flathead population unit had
the highest density of human-caused deaths of grizzly
bears in BC between 1979 and 2010 (McLellan 2015).
Fig. 5. (a) Differential grizzly bear (GB; Ursus arctos) density in the South Selkirk and Purcell Mountain habi-
tats, British Columbia, Canada, between 2004 and 2017 with open road densities >and <0.6 km/km2; and (b)
Female grizzly response to open road density, used (telemetry locations of bears, blue line) versus available
habitat (all habitat in area, red line). Adapted from Proctor et al. (2017).
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 25
Fig. 6. Schematic of how landscape-level motorized-access controls might look when applied relative to griz-
zly bear (Ursus arctos) habitats. Berry fields and salmon streams represent important energy-rich hyperphagia
food habitats, which contain very few or no roads. Areas of medium-quality habitat would be associated with
<0.6 km/km2open road densities and >60% secure habitat >500 m from open roads wherein some roads might
be restricted or temporarily closed (brown lines), and lower quality habitats are associated with road densities
>0.6 km/km2. These areas could be managed to control access such that the overall area has patches of >60%
secure habitat and <0.6 km/km2road density.
Furthermore, in this management unit, a natural separa-
tion of critical foods and roads, coupled with decades
of strategic motorized access management, have helped
to enable continued resource development and a high
density of bears. The most important summer and early
autumn habitat for grizzly bears was higher elevation,
post–forest-fire areas, where huckleberries were plenti-
ful and the habitat was essentially roadless. The most im-
portant spring habitats in this area are riparian areas and
avalanche chutes, where some roads have been closed
or have naturally grown over. Areas of high road densi-
ties were restricted to the broad, lodgepole pine (Pinus
contorta) and clearcut-dominated valley bottom that is
generally of less value to grizzly bears (McLellan 2015).
Also of importance, the entire area is more than an hour’s
drive from the nearest permanent human settlement, so
the roads see little public use except during the autumn
hunting season.
The Flathead Valley is a relevant and well-documented
example of how the relationship between roads and
habitat quality is important when setting open-road
motorized-access targets. First, having no or very few
roads in the higher quality habitats with important food
resources (in this case, large huckleberry fields) across
the late summer and autumn (i.e., ungulate hunting sea-
son) hyperphagia season has been very beneficial to griz-
zly bear reproductive rates, survival, and ultimately bear
densities (McLellan 2015). This supports our conclusion
that management consider no or low road densities around
the best habitats when possible. Second, the Flathead ex-
ample supports a moderate density of roads in medium-
quality habitats, especially during non-limiting seasons,
such as spring. And third, in areas of less productive habi-
tats, there has been little MAC (Fig. 6). Such a motorized-
access management strategy, where there is no motorized
access to very important habitat, would likely work in
other areas with outstanding food sources, such as along
the limited stretches of salmon spawning streams where
bears can more easily catch fish.
Grizzly bear response to secure habitat
In addition to road densities, female home-range se-
lection and/or survival also has related to the propor-
tion of habitat >500 m from an open road (Fig. 7; often
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26 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
Fig. 7. Schematic of the relationship between road density and the proportion of secure grizzly bear (Ursus
arctos) habitat. Evenly spaced roads across a unit can result in small patches of secure habitat (i.e., areas >500
m from an open road) that require female bears to cross roads often during a day (panels on left). Managing
road distribution to yield larger patches of secure habitat (panels on right), even at similar road densities,
should benefit females and result in healthier grizzly bear populations.
termed ‘secure habitat’). Studies in northwestern Mon-
tana’s Rocky Mountains found that female grizzly bears
selected for, and survived better in, home ranges with
56% secure habitat as compared with 30% secure habitat
outside the composite female home range (Mace et al.
1996). Female grizzly bears selected for, and survived
better in, home ranges with 55% secure habitat, relative
to 23–34% secure habitats, in the Yaak and Selkirk Moun-
tains in Montana (Wakkinen and Kasworm 1997). Across
the border in Canada, researchers found that female griz-
zly bears selected for, and survived better in, areas with
56% secure habitat as compared with available areas with
46% secure habitat (M. F. Proctor, unpublished data). The
Canadian study measured secure habitats in patch sizes
>9km
2, as suggested by Gibeau et al. (2001) to provide
females with lower mortality risk within their average
daily movement areas. In the U.S. Greater Yellowstone
Ecosystem, road densities and the amount of secure habi-
tat within female home ranges had a large influence on
their survival (Schwartz et al. 2010). Both road density
and the proportion of secure habitat contributed differ-
ent, yet important, components influencing survival; road
density had more influence on survival as the proportion
of secure habitat within female home ranges decreased.
The distribution and configuration of roads can in-
fluence secure habitat patch sizes significantly (Fig. 7;
Jaeger 2000, Jaeger et al. 2006). Evenly spaced roads,
even at an otherwise acceptable road density, can provide
very little security in patches within the range of average
daily movements, requiring that bears cross roads multi-
ple times daily to meet their needs. These patterns suggest
that road density and secure habitat with minimum patch
size should be included in motorized access targets.
Restricted roads versus totally closed roads
Researchers in southern BC found that female bears
did not avoid restricted roads (roads only open to the
forest industry), whereas they avoided roads open to the
forest industry and the public (Wielgus et al. 2002). In
southern Alberta, researchers found that roads closed to
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 27
the public were not avoided by bears, and habitats near
those roads were used at similar levels to unroaded areas
(Northrup et al. 2012). Another study looking at grizzly
bear habitat use and response to mining activity, during
and post-mining, found that females with cubs were more
likely to tolerate mining activities than other cohorts of
bears (Cristescu et al. 2016). These examples suggest that
industrial use of roads may not be as detrimental to grizzly
bears as recreational use of roads that are open to the pub-
lic. Indeed, areas with total road densities >0.6 km/km2
can sustain grizzly bear numbers representative of the
overall habitat quality if some proportion of roads are
closed (or restricted) to the public (Lamb et al. 2018b).
Where to apply motorized access
controls
In this section we consider where MACs might be ap-
plied. First, we look at the conservation status of pop-
ulation units. Second, we examine geographic scale at
which it is most efficient and effective to monitor and ap-
ply road management. Third, we look at specific habitats
that would be most beneficial for application of MACs.
Conservation status
Although it is important to manage all population
units for long-term sustainability, different ecological
or anthropogenic factors influence conservation risks
among populations. We therefore view threatened pop-
ulations or those of conservation concern (declines,
unsustainable mortality rates, or high human footprints)
as a first priority for motorized-access management
consideration. Managers should examine the causes for
threatened status: long-term food resource declines, ex-
cessive human-caused mortality related to front-country
conflicts, backcountry-road–related mortality, and habi-
tat security declines, or some combination of the four.
When backcountry mortalities and habitat displacement
are involved and population recovery is a management
goal, closing roads that enter any of the higher quality
habitats should be a priority. If the overall road density
is >0.6 km/km2and there is <60% secure habitat, then
efforts should be made to continue to eliminate roads in
the better habitats until these targets are met.
A second priority would be population units that are
partially or well-connected to adjacent units. Some units
may be population sinks for a larger region (Lamb et al.
2017), providing greater incentive to consider access con-
trols to improve habitat security and recover these areas.
Further, linkage areas (e.g., Proctor et al. 2015) that have
the potential to allow genetic and demographic exchange
between neighboring populations should be candidates
for MACs. In all cases, threatened status is exacerbated
by lack of inter-area connectivity, and occasionally might
be the sole cause of their threatened status. Managing for
improving secure habitats in linkage areas will improve
the chances of successful inter-area connectivity leading
to more sustainable populations.
Finally, we recommend that areas where significant
resource extraction is planned, but that otherwise have a
relatively robust wilderness character, would benefit from
motorized access planning as resource industries develop.
Public acceptance of MACs will be easier on new roads
than those that have a tradition of use.
Scale of motorized access management
The scientific literature is less clear on which scale
is most appropriate when applying road management.
The distribution of quality habitats and important food
resources will influence, to some degree, the spatial con-
figuration of management strategies. Motorized access
monitoring and control management may best be carried
out at scales that optimize the protection of important
habitats to benefit the distribution, survival, reproduction,
and density of females across a broad area.
Both Alberta and the lower 48 states of the United
States have chosen to manage road density within geo-
graphic areas that approximate the size of several over-
lapping adult female home ranges (approx. 200–500 km2;
USFWS 1993, Alberta Environment and Parks 2016).
Their logic is to partition road density targets across larger
population units, so as to not cluster low road densi-
ties within only one portion of a larger population unit,
thereby conferring some habitat security for most females
across the larger population unit. The U.S. example has
the strength of a successful decades-long recovery pro-
gram behind it.
British Columbia is not currently managing for road
density across the province, but has several local ini-
tiatives. Within BC, several scales are typically used to
manage wildlife and ecosystems. Grizzly Bear Popula-
tion Units (GBPUs, average size approx. 13,500 km2)are
the legal units in which grizzly bears are assessed for con-
servation status. Although this scale is useful at a coarse
level, our experience suggests that this scale is too large
for effective motorized access management. Conserva-
tion benefits may accrue when MACs are monitored and
applied at scales small enough to benefit female grizzly
bears across the larger GBPUs. In many cases the Wildlife
Management Unit (WMU, average size 3,800 km2)may
be more appropriately sized and in some cases the
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28 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
Fig. 8. Types of motorized access controls relative to ease of implementation and benefit to grizzly bears
(Ursus arctos).
Landscape Unit scale (average size 800 km2) may be best.
This decision will depend on local conditions. Smaller
geographic areas may benefit grizzly bears, as managers
spread out MACs to the benefit of more females. On the
other hand, geographic areas that are too small can create
excessive workloads on managers. This issue might re-
solve itself because habitat-structured motorized-access
plans will require assessments at the scale of the drainage
and many drainages make up a WMU, so ultimately man-
agers must work at several scales.
Prioritizing habitats for motorized access man-
agement across British Columbia and Alberta
In parts of BC and Alberta, high-quality habitats
have been identified through telemetry studies and local
knowledge, but mapping of specific food sources varies
across these provinces. Habitat-quality maps have been
created by several researchers for a variety of areas in-
cluding Alberta (Nielsen et al. 2006, 2010), southeast-
ern BC (McLellan and Hovey 2001; Proctor et al. 2015,
2017), southwestern BC (Apps et al. 2014; M. McLel-
lan, Victoria University of Wellington, unpublished data);
central BC (Ciarniello et al. 2007a,b), northern BC (Mi-
lakovic et al. 2012), and the interior-side of the Coast
Mountains (Iredale 2016). Food layers have been devel-
oped for portions of Alberta (Nielsen et al. 2010) and
a small portion of BC (Lamb et al. 2017, Proctor et al.
2017). In large areas of BC, these types of data are miss-
ing, although regional biologists and foresters often know
the location of the major berry fields, salmon-spawning
areas, whitebark pine stands, and/or areas of high ungu-
late density.
How might motorized access controls
be applied?
Although the relationship of grizzly bears to their basic
food requirements and response to human pressures are
similar across ecosystems, differences in ecology, natu-
ral resource industries, and land-use decision traditions
make it inevitable that management approaches will dif-
fer among political jurisdictions. There are several road-
control designations that may be used in MAC systems.
Roads may be revegetated, closed by a gate or their equiv-
alent, restricted to certain segments of society (hunters, or
the public, for example), or completely open. From a so-
cietal perspective, there is a balance between human use,
ease of implementation, and what benefits grizzly bears
(Fig. 8). Although there is no consistent science-based
estimate of what total road (open and closed) density
might be conducive to grizzly bear, habitat, and biodi-
versity conservation, we suspect that there is a threshold
beyond which there are measurable negative impacts to
grizzly bears (and other species) at both the individual and
population level. A landscape saturated with roads would
not be conductive to productive grizzly bear populations,
even if the roads were closed. We encourage land-use
managers developing access rules to consider total roads
(open, restricted, and closed), which includes the ecolog-
ical needs of grizzly bears but also a wider spectrum of
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 29
Fig. 9. (a) Grizzly Bear Management Areas (BMAs) across western Alberta, Canada (AEP 2016); (b) Core and
Secondary habitats across grizzly bear distribution in western Alberta (adapted from Nielsen et al. 2009); and
(c) Road density by Grizzly Bear Watershed Units across 7 BMAs in western Alberta (AEP 2016).
Synthesis on how motorized access manage-
ment could be improved in British Columbia
and Alberta
In the following sections, we discuss options for access
management in Alberta and BC separately, while recog-
nizing that both provinces have some level of motorized
access management already in place. For this discussion,
we intend road density to mean open-road density.
Alberta. Grizzly bears are considered threatened in
Alberta, with an approximate estimate of <900 bears
across 173,000 km2of occupied grizzly bear habitat
(Festa-Bianchet 2010, Alberta Environment and Parks
2016). Alberta has developed a province-wide Recovery
Plan (Alberta Environment and Parks 2016) and man-
ages grizzly bears within a series of 7 Grizzly Bear
Management Areas (BMAs; Fig 9a) with a mean size
of 24,762 km2. The average density of grizzly bears in
Alberta is approximately 4.3/1,000 km2. The BMAs are
separated by genetic discontinuities through Alberta me-
diated by major east–west highways (Proctor et al. 2012),
but are all connected with populations in BC.
Road networks in Alberta grizzly bear habitat mainly
exist outside the mountain parks along the east front of the
Rocky Mountains (Fig. 1). Road management is applied
in Alberta in response to, and accordance with, results of
considerable province-wide research into the relationship
between road density, female survival, localized popula-
tion trend, and source–sink population dynamics (Nielsen
et al. 2004a, 2006, 2009, 2010; Boulanger et al. 2013;
Boulanger and Stenhouse 2014).
Road density management is planned at the scale of
Grizzly Bear Watershed Units (Fig. 9c: GBWUs, ap-
prox. 500 km2; Alberta Environment and Parks 2016),
the approximate size of several overlapping female home
ranges, to partition road density management across the
larger BMAs. Alberta has developed a habitat-structured
access management system by delineating its provincial
grizzly bear range into Core and Secondary areas (Fig.
9b; Nielsen et al. 2009), except in the northern BMA 1
where data were insufficient.
Core areas were identified within each BMA as areas
of higher habitat quality (as indexed by high scores within
ecological models) and security (as indexed by low road
densities). Secondary areas were identified to connect or
buffer Core areas. Road densities in identified Core area
watersheds on provincial lands outside of national parks
have a target road density of <0.6 km/km2, although
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biodiversity (Trombulak and Frissell 2000, Ibisch et al.
2016), including amphibians and reptiles (Hels and Buch-
wald 2001, Fahrig and Rytwinski 2009), fish, birds and
mammals (Fahrig and Rytwinski 2009, Beneitz-Lopez
et al. 2010), and carnivores (Basille et al. 2013, Ceia-
Hasse et al. 2017), in addition to overall habitat (erosion,
terrain stability, water pollution, etc.) conservation (For-
man and Alexander 1998, Daigle 2010).
30 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
several GBWUs exceed this target (Fig. 9b,c; Nielsen
et al. 2009). Core grizzly bear areas are spatially linked
and contiguous along the eastern slopes of the Rocky
Mountains in Alberta. This system was designed so Core
areas maintained high-quality grizzly bear habitats with
lower human-caused mortality risk.
Secondary areas, generally to the east of Core areas,
were also delineated using a combination of medium-
quality habitat (medium scores within ecological mod-
els) and somewhat higher open road densities. Recent
work suggested that open road densities >0.75 km/km2
were associated with sink habitats, the current target in
Alberta’s Draft Recovery Plan (AEP 2016). Currently,
a large proportion of GBWUs exceed the new target
road density of 0.75 km/km2(Boulanger and Stenhouse
2014; Fig. 9c). Grizzly bear population inventory data
collected within the Alberta provincial BMAs (2004–
2008 and 2014) have shown that the majority of griz-
zly bears were found within Core areas and lower num-
bers were found within Secondary areas (G.B. Stenhouse,
unpublished data).
Although there are open-road density thresholds for
grizzly bear conservation areas in Alberta, there are re-
gional differences in how these are being implemented.
Currently within Alberta, OHVs are not excluded (as
pickup trucks and cars are on restricted roads). There also
is a lack of clarity on what should constitute a “closed or
restricted” road that will not be counted within open-road
density calculations within watersheds inside each BMA.
However, many resource extraction industries are chang-
ing access management practices related to road planning
within grizzly bear conservation areas in the province.
In addition to these challenges, there remains the need
to develop and implement strategies to reduce current
open-road densities in identified watersheds (Boulanger
and Stenhouse 2014), and this will be more challenging
with the new open-road density standard (0.75 km/km2)
in secondary conservation areas.
Examples of road management include units in south-
ern and central Alberta. In 2017, the Alberta govern-
ment announced the creation of 2 new conservation ar-
eas within BMA 6 in the southwestern corner of the
province, the Castle Wildland Provincial Park and the
Castle Provincial Park. A key element in the manage-
ment of these areas is restrictions on motorized access to
reduce open motorized road densities and, thus, human-
caused mortality. The Swan Hills (BMA 7) population
unit in central Alberta is geographically connected to
BMA 2 (Fig. 9a) and current genetic data suggest a
weak genetic break between these 2 management areas
(Proctor et al. 2012). This is cause for concern, and the
current Secondary area—essentially a linkage between
these 2 units—has open road densities that exceed the
0.75 km/km2target. Industrial development and associ-
ated road building continues in this linkage area and mo-
torized access management planning is needed to reduce
current open-road densities and develop coordinated mo-
torized access management plans with industry to ensure
the BMA 7 grizzly bear population unit does not become
an “island” population of bears.
British Columbia. The relationship between griz-
zly bear habitats and roads in BC is more complex than
in Alberta. In BC there are an estimated 15,000 grizzly
bears across an area of approximately 750,000 km2,or
>16 times as many bears across >4 times the occupied
area of Alberta. The average grizzly bear density across
BC is approximately 23 bears/1,000 km2(BC Ministry
of Environment 2012), >5 times as high as Alberta bear
densities. British Columbia’s grizzly bears are managed
within 55 diverse Grizzly Bear Population Units (GB-
PUs) that average approximately 13,500 km2in size. The
GBPUs contain smaller designations, Wildlife Manage-
ment Units (WMUs), of which there are 183 contain-
ing grizzly bears with an average area of approximately
3,800 km2. Landscape Units are a yet smaller designa-
tion and the 940 in BC are approximately the size of sev-
eral overlapping female home ranges (approx. 800 km2),
similar to Alberta’s GBWUs. Although the greater spatial
area and diversity of habitat types in BC mean that man-
agement also may be more variable than in Alberta, we
expect that the response of female grizzly bear survival
and displacement due to open roads to be similar in both
provinces.
Road densities in north-central and northwestern BC
are generally <0.6 km/km2(Fig. 10a), but the locations
of critical food resources for grizzly bears are generally
undocumented, and thus likely unprotected. Much of cen-
tral, southern, and northeastern BC have road densities
that exceed 0.6 km/km2(Fig. 10a), and critical food re-
sources are mapped for only a small portion of these areas.
There is no overarching grizzly bear management plan
across BC that includes road densities and motorized ac-
cess targets; however, there have been several regional
initiatives.
Examples of “threatened” population units in BC in-
clude the Granby–Kettle, the South Rockies, and the
South Selkirk (Fig. 11). The Granby Kettle unit has
an average road density of approximately 1.6 km/km2
(Lamb et al. 2018b). This population has doubled in
size over the past 20 years, likely influenced by re-
duced mortality rates, as a result of a recently cre-
ated Provincial park that has no roads and includes an
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 31
Fig. 10. (a) Road density across British Columbia (BC), Canada, by Landscape Unit (LU mean area approx.
800 km2) adapted from a BC government initiative to assess Cumulative Effects in BC; and (b) Grizzly Bear
Population Units (GBPU) in BC. Conservation status determined through NatureServe ranking by BC Ministry
of Environment & Climate Change Strategy. Draft designations are ranked 1–5, with 1 being the highest con-
servation concern and 5 the least.
associated motorized-access management buffer (Lamb
et al. 2018b). By far, the highest densities of bears in
this unit are in areas of road densities <0.6 km/km2
(Fig. 4b).
The South Rockies have been a focal—and often
contentious—area for motorized access management for
several decades, and until recently had a relatively high
density of bears (35–50 grizzly bears/1,000 km2; Apps
et al. 2016, Mowat and Lamb 2016). This is an exam-
ple of a population unit in BC that is not threatened that
could benefit from additional motorized access manage-
ment. The unit experienced an approximate 2% annual
population decline over a recent 7-year period that was
likely initiated by a multiple-year food shortage (Lamb
et al. 2019), although it has been increasing for the past
3–4 years (C.T. Lamb, personal communication). The
area has an average road density of 1.0 km/km2,some
of which are seasonally closed, and a relatively large
human footprint. Unreported mortality from front- and
backcountry sources and highway and railway kills all
contributed to what may be a recent excessive unre-
ported mortality issue (Mowat and Lamb 2016). The
authors suggest motorized access management would
be an appropriate management action to rebuild this
population.
Central and northern BC are regions of the province
that could benefit from motorized access management.
Trends for resource extraction expansion and the associ-
ated increase in road building in central and northern BC
is cause for concern. Road densities in areas are already
high (many landscape units already exceed 0.6 km/km2)
and, given the expected increase in resource extraction,
we recommend increased consideration of MACs be in-
tegrated into resource development activities in northern
BC. Our experience has taught us that it is easier to man-
age motorized access before road densities become too
high. Limiting motorized access to roads that have been
traditionally used for recreation creates significant social
challenges.
To meet the goals concerning grizzly bear conservation
outlined in BC’s Wildlife Program Plan (BC Ministry of
Environment 2010) and the Grizzly Bear Conservation
Strategy (BC Ministry of Environment 1995; see BC Au-
ditor General Report 2017), our review of the scientific
literature suggests that industrial road management would
be a useful tool if
rroads exist within 500 m of the highest quality
habitats or energy-rich food resources for hyper-
phagia (salmon, berries, etc.); or,
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32 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
Fig. 11. Habitat-structured motorized-access management: an example in the South Selkirk population unit,
southernmost British Columbia (BC), Canada, is an example of how motorized access management might
work in BC. It contains 2 Wildlife Management Units, each approximately 2,000 km2. The Nature Conservancy
of Canada (NCC) owns a large parcel (550 km2) that holds extensive huckleberry fields; and they continue
a decades-long public motorized-access management policy applied by the previous owners, a timber com-
pany. This “threatened” population unit has been increasing for a decade or more and is in slow recovery.
The trans-border Grizzly Bear Project (Proctor et al. 2017) has been radiocollaring and doing DNA-based pop-
ulation surveys in this unit for over a decade. Their research shows that the areas with low road densities
and abundant huckleberry patches have provided well for female grizzly bears, being the best predictors of
habitat use, reproductive success, and density. Some closed roads are being revegetated. Habitat quality is
medium in other areas of the unit where road densities are correspondingly higher than in the NCC property.
Areas of medium-quality habitat (i.e., some huckleberry patches and other attractive attributes) have modest
road densities. Another area of lower quality habitat for grizzly bears has high road densities. Although refine-
ments may be necessary (application within smaller geographic units), this example has the components of
an access management strategy that has worked reasonably well for industry, the public, and grizzly bears. It
has allowed areas of very low road density in the highest quality food patches, areas of medium road densities
in medium-quality habitats, and areas of higher road densities in lower quality habitats.
r<60% of the vegetated land base in each Wildlife
Management Unit (or Landscape Unit in some
cases) is >500 m from an open road with a mini-
mum patch size of 10 km2;or
rthere is >0.6 km/km2of open roads across the
vegetated occupied habitat in the monitored unit
(Fig. 10).
As a recent BC Auditor General Report (BC Auditor
General 2017) concluded, habitat considerations are at
the forefront of grizzly bear management and conserva-
tion, with or without a legal hunt. The grizzly bear hunt
was closed in BC in November of 2017 and in Alberta
in 2006. Motorized-access management considerations
are still relevant across grizzly bear distribution because
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RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al. 33
many population units across BC and Alberta are at some
level of risk, regardless of the hunt, as a result of habitat
insecurity and mortality risk.
Within both BC and Alberta, non-usable land-cover
types within broader bear habitat (rock, icefields, lakes,
etc.) should be removed before calculating road density
and the proportion of secure habitat. Both metrics should
be standardized (e.g., recently developed methods by BC
Ministry of Forests, Lands, Natural Resource Operations
& Rural Development for a wildlife-ecosystem–oriented
Cumulative Effects Analysis). We also realize these sug-
gestions may not apply to some coastal road networks,
where the general public has no ability to reach because
they are accessed through ocean travel.
Tools for managing motorized access
Conclusions
Motorized access has been shown to influence griz-
zly bears at the individual and population levels. Peo-
ple in motorized vehicles affect grizzly bear habitat use,
home-range selection, movements, population fragmen-
tation, and demography including survival and repro-
duction, which ultimately affects bear density, popula-
Table 2. Research needs for Alberta and British
Columbia, Canada, relative to roads and grizzly bears
(Ursus arctos).
Research topic
Improved digitized maps of usable roads across both
provinces.
Updated unreported grizzly bear mortality estimates.
Assessment of habitat quality across much of the provinces.
Assessment of important energy-rich hyperphagia foods.
Evaluation of road trends over time for both BC and Alberta
(i.e., roads layer map then vs. now).
Analysis of North America grizzly bear distribution patterns
relative to road density patterns.
Specific studies on the spatial extent of disturbance of open
roads.
Controlled studies that examine the effects of road traffic on
both bear mortality and behavior.
Studies on the link between people’s attitudes toward bears
and roads.
tion trends, and conservation status. Integrating habitat
quality into road management improves the efficiency
and effectiveness in reaching management goals, such
as managing for few or no roads within 500 m of habitats
containing late summer and autumn hyperphagia food re-
sources, such as major berry fields, salmon streams where
bears can effectively catch fish, and high-quality white-
bark pine stands. Further, in populations with moderate
habitat quality and close to human settlements, road den-
sities near 0.6 km/km2with >60% secure habitat (i.e.,
>500 m from an open road) are meaningful thresholds
that, if not exceeded, may allow female grizzly bears to
have sustainable survival rates. In other areas, population-
specific thresholds may be appropriate, such as where
conservation is a major concern, because poor habitat
quality limits reproductive rates and very little human-
caused mortality can be sustained. In areas that are further
from human population centers and have large patches of
high-quality habitat, the bear population could tolerate
higher overall road densities provided large, high-quality
patches have no roads.
Our consensus of prioritizing the use of motorized ac-
cess management across occupied grizzly bear terrain
was that “Threatened” populations, or populations of
conservation concern (documented or suspected popu-
lation declines, excessive reported mortality, and areas
with high human footprints), were a first priority. Next,
we conclude that habitat quality is an integral part of
understanding grizzly bear responses to roads and, if in-
tegrated, will increase the efficiency and effectiveness of
road management programs. Therefore, managers should
allow for habitat security with zero or low road densities
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We will not make specific recommendations on meth-
ods for closing roads at this time, but suggest the
development of a guidebook of motorized access man-
agement methods. Such a manual could be funded by
government, nongovernmental organizations, or industry.
However, after considering many years of voluntary clo-
sures and their ineffectiveness over time, we suggest that
when MACs are applied, that they be regulatory rather
than voluntary. We also recognize that administrative use
and some level of industrial use may be allowed on re-
stricted roads (Wielgus et al. 2002, Northrup et al. 2012,
Cristescu et al. 2016). We also note that managing mo-
torized access for grizzly bears is but one environmental
concern relative to many other potential negative effects
of roads faced by other species and habitats (runoff, pol-
lution, disturbance, mortality, etc.). For a more compre-
hensive assessment, see Daigle (2010). There are also
more research needs to fully understand the relationship
between, and implement and monitor, MACs and griz-
zly bears (Table 2). This includes the need to integrate
monitoring the efficacy of implementing MACs where
they are applied to inform adaptive management strate-
gies that improve optimization of landscape use for hu-
man endeavors and wildlife conservation (Robinson et al.
2010, van der Grift et al. 2013).
34 RESOURCE ROADS AND GRIZZLY BEARS IN CANADA rProctor et al.
in high-quality foraging habitats where major summer–
autumn hyperphagia energy-rich food sources are used
heavily. This could entail maintaining low road densities
in currently safe habitats (where habitat quality is high
and mortality risk is low) and applying motorized access
controls in areas of sink habitats (where habitat quality
and road densities are high). In some instances, when
lower elevation spring or autumn habitats have high mor-
tality risk, access controls should be considered. Also, in
some habitats, timber harvest can temporarily improve
the foraging resources for bears. When this is the case,
post-harvest MACs may be necessary to provide habitat
security for females to realize this benefit. The third pri-
ority is protection for areas within and adjacent to identi-
fied linkage areas between population units to allow bears
to move safely among occupied habitats, including con-
nected sink habitats that may be affecting a larger area.
Given that it is much easier to manage motorized ac-
cess before the public begins using the road, the final
priority is areas with increasing road densities due to re-
cent or planned industrial activities, such as increased
resource extraction in northeastern BC and portions of
Alberta.
We conclude that motorized access is best monitored
and applied across smaller geographic areas to optimize
the protection of important habitats to benefit the distribu-
tion, survival, reproduction, and density of females across
a broad area. Most jurisdictions manage motorized access
across areas approximately 500–800 km2, the approxi-
mate size of several overlapping female home ranges.
Incorporating habitat quality into management strategies
will require working at these smaller scales; but across
BC, larger units may be more practical in some cases.
Final statement
In much of their range, particularly in southern BC and
Alberta, grizzly bears live in close proximity to humans
and are what Scott et al. (2005) refer to as a “conservation-
reliant species”; that is, a species that is at risk from threats
so persistent that it requires continuous management to
maintain population levels. This sentiment was echoed
in Schwartz et al. (2006:62) discussing the approaching-
recovered populations, at that time, in the lower 48 states
of the United States.
“We are optimistic that, with continued vigilance,
these populations can persist indefinitely. But normal
management, in the sense we have grown to expect from
our experience with ungulate or black bear populations
in the western United States over the past few decades, is
not a term we associate with grizzly bear conservation.”
The point is that others have realized that grizzly bears
have a special place in wildlife management. They require
special attention and management to coexist with humans
where they overlap significantly. That type of overlap is
occurring in most of the Alberta grizzly bear distribution
and in the southern, central, and northeastern distribution
of BC.
Acknowledgments
We thank both W. Kasworm and C. Servheen of
the U.S. Fish and Wildlife Service, who reviewed this
manuscript and provided very useful input, which we
heeded. Both individuals have extensive (>3 decades
each) experience in developing and implementing a
motorized-access management program in the U.S. re-
covery zones of the lower 48 states. We also thank A.
Morehouse for her very useful review and the Ursus As-
sociate Editor and reviewers of this article. We thank the
National Fish & Wildlife Foundation, Wilburforce Foun-
dation, and the Liz Claiborne Art Ortenberg Foundation
for providing support to M. Proctor. We also extend our
wholehearted appreciation and thanks to K. Broadley for
her help in creating clear figures.
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Technical Report
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The objective of this research is to identify areas of population connectivity between the South-Chilcotin, Squamish-Lillooet, Garibaldi-Pitt, and Stein Nahatlatch grizzly bear populations in southwestern British Columbia. These populations of conservation concern are at the southwestern extent of grizzly bear range in North America and have varying degrees of genetic, demographic, and geographic isolation between them. Fragmentation is a key threat to population recovery in the region and is the result of high levels of historic human-caused mortality and persecution in the valley bottoms that separate populations, contemporary mortality resulting from conflict with humans, and geographic features including large lakes, rugged mountains, and icefields. Connectivity increases the resilience of each population to demographic and environmental fluctuations and protects populations from loss of genetic diversity and the deleterious effects of inbreeding. Restoring historic connectivity and maintaining existing interpopulation connectivity is essential for the long-term persistence of grizzly bears in the region. Based on 239,283 daytime locations from 57 bears wearing GPS collars across a 51,624 km 2 area, we used seasonal resource selection functions to identify core habitat areas in the region and to identify pathways of connectivity between them. We evaluated connectivity by identifying the natural and human-caused barriers preventing it and estimated the least-cost-paths among core habitat areas and across population fractures. Resistance to movement across the landscape was a function of inverse habitat quality and permanent human infrastructure density. We used this information to identify pinch points in connectivity by applying the principles of circuit theory to areas where movement is constrained by human or geographic factors. The resulting models identify areas where grizzly bear movement is constricted into pinch points where interpopulation connectivity is most likely because of geographic and human-caused barriers to connectivity. Conserving the small and isolated Stein-Nahatlatch and the nearly extirpated Garibaldi-Pitt populations will require conservation efforts within the population as well as in the fractures that separate them from neighbouring recovering populations. As a result, the most important fractures to restore are the South Chilcotin-Stein-Nahatlatch fracture between Lil'wat/Mount Currie, and N'Quatqua/D'Arcy and the Squamish-Lillooet-Garibaldi-Pitt between Squamish and Pemberton. Maintaining connectivity and low mortality risk between the South Chilcotin and Squamish-Lillooet is important for regional population resilience and long-term population persistence. Connectivity models can be applied to compare alternative conservation actions and used as a decision-making tool to guide the establishment of secure movement corridors for grizzly bears. Population connectivity at the pinch point scale across partial and complete population fractures can be compared and weighted using the resulting connectivity models. Connectivity models can also be applied to intrapopulation connectivity and assessing the impacts of potential developments for industry or recreation on the connectivity between extant core habitat areas.
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Winter recreation and tourism continue to expand worldwide, and where these activities overlap with valuable wildlife habitat, there is greater potential for conservation concerns. Wildlife populations can be particularly vulnerable to disturbance in alpine habitats as helicopters and snowmachines are increasingly used to access remote backcountry terrain. Brown bears (Ursus arctos) have adapted hibernation strategies to survive this period when resources and energy reserves are limited, and disturbance could negatively impact fitness and survival. To help identify areas of potential conflict between helicopter skiing and den-ning brown bears in Alaska, we developed a model to predict alpine denning habitat and an associated data-based framework for mitigating disturbance activities. Following den emergence in spring, we conducted three annual aerial surveys (2015-2017) and used locations from three GPS-collared bears (2008-2014) to identify 89 brown bear dens above the forest line. We evaluated brown bear den site selection of land cover, terrain, and climate factors using resource selection function (RSF) models. Our top model supported the hypothesis that bears selected dens based on terrain and climate factors that maximized thermal efficiency. Brown bears selected den sites characterized by steep slopes at moderate elevations in smooth, well-drained topographies that promoted vegetation and deep snow. We used the RSF model to map relative probability of den selection and found 85% of dens occurred within terrain predicted as prime denning habitat. Brown bear exposure to helicopter disturbance was evident as moderate to high intensities of helicopter flight tracking data overlapped prime denning habitat, and we quantified where the risk of these impact was greatest. We also documented evidence of late season den abandonment due to disturbance from helicopter skiing. The results from this study provide valuable insights into bear denning habitat requirements in subalpine and alpine landscapes. Our quantitative framework can be used to support conservation planning for winter recreation industries operating in habitats occupied by denning brown bears.
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The Anthropocene is an era of marked human impact on the world. Quantifying these impacts has become central to understanding the dynamics of coupled human‐natural systems, resource‐dependent livelihoods, and biodiversity conservation. Ecologists are facing growing pressure to quantify the size, distribution, and trajectory of wild populations in a cost‐effective and socially acceptable manner. Genetic tagging, combined with modern computational and genetic analyses, is an under‐utilized tool to meet this demand, especially for wide‐ranging, elusive, sensitive, and low‐density species. Genetic tagging studies are now revealing unprecedented insight into the mechanisms that control the density, trajectory, connectivity, and patterns of human–wildlife interaction for populations over vast spatial extents. Here, we outline the application of, and ecological inferences from, new analytical techniques applied to genetically tagged individuals, contrast this approach with conventional methods, and describe how genetic tagging can be better applied to address outstanding questions in ecology. We provide example analyses using a long‐term genetic tagging dataset of grizzly bears in the Canadian Rockies. The genetic tagging toolbox is a powerful and overlooked ensemble that ecologists and conservation biologists can leverage to generate evidence and meet the challenges of the Anthropocene.
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Increasing levels of human activity threaten wildlife populations through direct mortality, habitat degradation, and habitat fragmentation. Area closures can improve habitat quality for wildlife, but may be difficult to achieve where tourism or other economic drivers are a priority. Temporal closures that limit human use during specific times of day have potential to increase habitat quality for wildlife, while continuing to provide opportunities for human use. However, the effectiveness of daily temporal closures has not been tested. We assessed how implementation of a temporal road closure affected wildlife movements in Banff National Park. Parks Canada closed a popular 17 km stretch of road between 2000 and 0800 hours to improve habitat quality for wildlife. We assessed the effectiveness of the closure on nine mammal species using three sets of data: remote cameras, road surveys, and grizzly bear (Ursus arctos) GPS data. In all three analyses, wildlife detection rates on the road doubled during the closure while remaining unchanged in reference areas. Our strong and consistent results suggest temporal closures are an important conservation tool that can increase habitat quality for wildlife while minimizing effects on people.
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One of the challenges in conservation is determining patterns and responses in population density and distribution as it relates to habitat and changes in anthropogenic activities. We applied spatially explicit capture recapture (SECR) methods, combined with density surface modelling from five grizzly bear (Ursus arctos) management areas (BMAs) in Alberta, Canada, to assess SECR methods and to explore factors influencing bear distribution. Here we used models of grizzly bear habitat and mortality risk to test local density associations using density surface modelling. Results demonstrated BMA-specific factors influenced density, as well as the effects of habitat and topography on detections and movements of bears. Estimates from SECR were similar to those from closed population models and telemetry data, but with similar or higher levels of precision. Habitat was most associated with areas of higher bear density in the north, whereas mortality risk was most associated (negatively) with density of bears in the south. Comparisons of the distribution of mortality risk and habitat revealed differences by BMA that in turn influenced local abundance of bears. Combining SECR methods with density surface modelling increases the resolution of mark-recapture methods by directly inferring the effect of spatial factors on regulating local densities of animals.
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Increasing global demand for Canada’s re-sources is eroding the country’s iconic wilderness, intact ecosystems, and rich megafaunal diversity (1, 2). To meet its 2020 commitments to the United Nations Convention on Biological Diversity (CBD), Canada must protect 17% of its terrestrial area and 10% of its marine area (3); cur-rently, only 10% and 1%, respectively, are protected (4). Polls suggest that 87% of Canadians support increased landscape protection (5). On 8 January, 116 Canadi-an politicians called for a historic $1.4 bil-lion in government funding to conserve Canada's exceptional wilderness and bio-diversity between 2018 and 2020, with $470 million per year to support efforts after 2020 (3). This investment is essen-tial to enact the land and water protection Canadians want. We support this call to action. However, even if Canada meets its CBD commitment to protect 17% of its terrestrial area, wildlife conservation will fail if Canada neglects the other 83%, which will remain unprotected. In western Canada, 35% of the provincially managed landscape has been affected by industrial activity (6). These effects are gradually compromising the persistence of many high-profile species, including the grizzly bear, caribou, elk, wolverine, and moun-tain goat (6). The growing threats to Cana-da’s functional ecosystems are not matched by increasing funds to manage and conserve wildlife and habitats. Funds provided to wildlife management agen-cies in western Canada pale in compari-son to neighboring jurisdictions and are in decline (7). We strongly urge provincial governments to honor their promise to address this wide funding deficit (8) to ensure the effective management and conservation of Canada's species outside protected areas. Canadian governments have a responsibility not only to their citizens, who overwhelmingly support conservation, but also to the world as stewards of 24% of the planet’s remaining wilderness (2). Increased investment in both protected and unprotected areas is vital to safe-guard Canada's immense wilderness and wildlife capital.
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Human activities have dramatic effects on the distribution and abundance of wildlife. Increased road densities and human presence in wilderness areas have elevated human-caused mortality of grizzly bears and reduced bears' use. Management agencies frequently attempt to reduce human-caused mortality by managing road density and thus human access, but the effectiveness of these actions is rarely assessed. We combined systematic, DNA-based mark-recapture techniques with spatially explicit capture-recapture models to estimate population size of a threatened grizzly bear population (Kettle-Granby), following management actions to recover this population. We tested the effects of habitat and road density on grizzly bear population density. We tested both a linear and threshold-based road density metric and investigated the effect of current access management (closing roads to the public). Road closures resulted in an c. 50% increase in bear density since 1997 suggesting increased landscape and species conservation from management agencies played a significant role in that increase. However, bear density was lower where road densities exceeded 0.6 km/km² and higher where motorised vehicle access had been restricted. The highest bear densities were in areas with large tracts of few or no roads and high habitat quality. Access management bolstered bear density in small areas by 27%. Synthesis and applications. Our spatially explicit capture-recapture analysis demonstrates that population recovery is possible in a multi-use landscape when management actions target priority areas. We suggest that road density is a useful surrogate for the negative effects of human land use on grizzly bear populations, but spatial configuration of roads must still be considered. Reducing roads will increase grizzly bear density, but restricting vehicle access can also achieve this goal. We demonstrate that a policy target of reducing human access by managing road density below 0.6 km/km², while ensuring areas of high habitat quality have no roads, is a reasonable compromise between the need for road access and population recovery goals. Targeting closures to areas of highest habitat quality would benefit grizzly bear population recovery the most.
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We assess progress toward the protection of 50% of the terrestrial biosphere to address the species-extinction crisis and conserve a global ecological heritage for future generations. Using a map of Earth's 846 terrestrial ecoregions, we show that 98 ecoregions (12%) exceed Half Protected; 313 ecoregions (37%) fall short of Half Protected but have sufficient unaltered habitat remaining to reach the target; and 207 ecoregions (24%) are in peril, where an average of only 4% of natural habitat remains. We propose a Global Deal for Nature—a companion to the Paris Climate Deal—to promote increased habitat protection and restoration, national-and ecoregion-scale conservation strategies, and the empowerment of indigenous peoples to protect their sovereign lands. The goal of such an accord would be to protect half the terrestrial realm by 2050 to halt the extinction crisis while sustaining human livelihoods.
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Land-use change is a major threat to biodiversity globally. Roads cause direct mortality and limitation of individual movements, which may isolate populations and affect their viability in the long term. Here we provide the first comprehensive global assessment of the exposure of terrestrial mammalian carnivores to roads using an integrated modelling framework. Global. We estimated critical road densities and critical patch sizes for each species based on a spatially explicit model and life-history traits. We calculated the distribution of landscape fragment sizes for each carnivore species by intersecting global road density with each species range. The proportion of a species’ geographical range with fragments below the critical patch size is used as an index of the vulnerability to roads. We found that the carnivores expected to be most exposed to roads belong to families Felidae, Ursidae, Mustelidae, Canidae and Procyonidae. Approximately one-third of the species most affected have not been identified by the IUCN as threatened by roads. Our model projects time to extinction that may be as low as one century for some species, such as the endangered Iberian lynx. Species are expected to be more exposed in areas with medium to high road density but, surprisingly, also in areas where road density is relatively low. Hotspots of the number of species locally endangered by roads occur in North America and Asia. Our results suggest the need to reassess the status and threats of those species that have not been previously recognized as strongly affected by roads. Our framework can be applied at different spatial scales, to assess the effects of the development of the road network and inform prioritization schemes for road building, and to identify areas for conservation, and species requiring particular mitigation and restoration measures.
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Too many roads Roads have done much to help humanity spread across the planet and maintain global movement and trade. However, roads also damage wild areas and rapidly contribute to habitat degradation and species loss. Ibisch et al. cataloged the world's roads. Though most of the world is not covered by roads, it is fragmented by them, with only 7% of land patches created by roads being greater than 100 km ² . Furthermore, environmental protection of roadless areas is insufficient, which could lead to further degradation of the world's remaining wildernesses. Science , this issue p. 1423
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Roads have a pervasive multi-faceted influence on ecosystems, including pronounced impacts on wildlife movements. In recognition of the scale-transcending impacts of transportation infrastructure, ecologists have been encouraged to extend the study of barrier impacts from individual roads and animals to networks and populations. In this study, we adopt an analytical representation of road networks as mosaics of landscape tiles, separated by roads. We then adapt spatial capture-recapture analysis to estimate the propensity of wildlife to stay within the boundaries of the road network tiles (RNTs) that hold their activity centres. We fit the model to national non-invasive genetic monitoring data for brown bears (Ursus arctos) in Sweden and show that bears had up to 73% lower odds of using areas outside the network tile of their home range centre, even after accounting for the effect of natural barriers (major rivers) and the decrease in utilization with increasing distance from a bear's activity centre. Our study highlights the pronounced landscape-level barrier effect on wildlife mobility and, in doing so, introduces a novel and flexible approach for quantifying contemporary fragmentation from the scale of RNTs and individual animals to transportation networks and populations. This article is protected by copyright. All rights reserved.