No Job Name


Decrease of lichens in Arctic ecosystems: the role of
wildfire, caribou, reindeer, competition and climate in
north-western Alaskapor_113 433..442
Kyle Joly,1,2 Randi R. Jandt3 & David R. Klein4

1 National Park Service, Gates of the Arctic National Park and Preserve, 4175 Geist Road Fairbanks, AK 99709, USA

2 Department of Biology and Wildlife, 211 Irving 1, University of Alaska Fairbanks, Fairbanks, AK 99775, USA

3 Bureau of Land Management, Alaska Fire Service, 1541 Gaffney Road, Fort Wainwright, AK 99703, USA

4 Institute of Arctic Biology, University of Alaska Fairbanks, P.O. Box 757000, Fairbanks, AK 99775, USA

Abstract

We review and present a synthesis of the existing research dealing with
changing Arctic tundra ecosystems, in relation to caribou and reindeer winter
ranges. Whereas pan-Arctic studies have documented the effects on tundra
vegetation from simulated climate change, we draw upon recent long-term
regional studies in Alaska that have documented the actual, on-the-ground
effects. Our review reveals signs of marked change in Arctic tundra ecosystems.
Factors known to be affecting these changes include wildfire, disturbance by
caribou and reindeer, differential growth responses of vascular plants and
lichens, and associated competition under climate warming scenarios. These
factors are interrelated, and, we posit, unidirectional: that is, they are all
implicated in the significant reduction of terricolous lichen ground cover and
biomass during recent decades. Lichens constitute the primary winter forage
for large, migratory caribou and reindeer herds, which in turn are a critical
subsistence resource for rural residents in Alaska. Thus, declines in these
lichens are a major concern for rural people who harvest caribou and reindeer
for subsistence, as well as for sport hunters, reindeer herders, wildlife enthu-
siasts and land managers. We believe a more widely distributed and better
integrated research programme is warranted to quantify the magnitude and
extent of the decline in lichen communities across the Arctic.

Keywords
Climate warming; disturbance; fire; grazing;

lichens; Rangifer tarandus.

Correspondence
Kyle Joly, National Park Service, 4175 Geist

Road, Fairbanks, AK 99709, USA. E-mail:

kyle_joly@nps.gov

doi:10.1111/j.1751-8369.2009.00113.x

Climate warming is predicted to cause unprecedented
change in the future (Parry et al. 2007). Rapid and dra-
matic changes in both terrestrial and aquatic ecosystems
were already evident throughout much of the Arctic
several years ago (Symon et al. 2005). The Arctic is now
experiencing the warmest temperatures it has seen over
the past 400 years, and the rate of temperature rise is
predicted to increase (Hinzman et al. 2005; Symon et al.
2005). These climatic changes will have, and indeed are
already having, a dramatic effect on the flora and fauna of
the Arctic.

A comprehensive review of the effects of climate
change on the winter range of reindeer (Rangifer tarandus
tarandus) in Norway was conducted by Heggberget et al.
(2002). Their review focused on how climate warming
could affect the quality, distribution and availability of
winter forage, with lichens being of specific interest

(Heggberget et al. 2002). Terricolous (ground-dwelling)
lichens are the preferred winter forage, where available,
for Rangifer populations, with specific species of interest
that include Cladina mitis, Cladina rangiferina, Cladina
stellaris, Cladonia amaurocraea, Cladonia gracilis, Cladonia
uncialis, Cetraria cucullata, Cetraria ericetorum, Cetraria
islandica and Cetraria nivalis (Ahti 1959; Scotter 1967;
Pegau 1968; Holleman & Luick 1977; Thomas & Hervieux
1986; Thomas & Kiliaan 1998; Brodo et al. 2001). Hegg-
berget et al. (2002) also reviewed the impacts of climate
warming on alternative, vascular forage, and the impacts
of grazing on lichens, whereas the role of wildfire,
uncommon in Norwegian reindeer ranges, was only
briefly covered.

The intent with our review is to build upon past
reviews, highlighting the major driving factors altering
Arctic flora, while focusing on the winter ranges of

Polar Research 28 2009 433–442 © 2009 The Authors 433

mailto:joly@nps.gov


caribou (Rangifer tarandus granti) and reindeer (Rangifer,
collectively) in Alaska. By expanding the scope of the
review to include the findings of recent long-term field
and experimental studies on changes in the tundra eco-
systems in Alaska, we believe that the possibility of pan-
Arctic changes should be considered.

There is strong agreement in climate change models
with regards to temperature changes, and the rate of
climate warming in Alaska is predicted to accelerate
(Chapin et al. 2005; Symon et al. 2005; Parry et al. 2007).
Wildfires, a primary ecosystem driver in the boreal forest
regions of Alaska, have increased in frequency and extent
in recent years (Kasischke & Turetsky 2006; Shulski &
Wendler 2007). Though more common in boreal forest
ecosystems, fires do occur within the tundra winter
ranges of Rangifer (Jandt et al. 2008), and are expected
to continue to increase in frequency (Higuera et al.
2008).

Although there is little agreement on how the moisture
regime will be affected by climate change, it plays an
important role in the ecology of the Arctic (Rouse et al.
1997), especially for lichens. The reliance of lichens on
atmospheric moisture and nutrients, and their slow
growth, make them vulnerable to the disturbance and
environmental changes driven by climate warming and
drying. Summer warming and drying, with increased
evaporative loss, would lead to decreased growth rates in
lichens if there was not an increase in precipitation, be it
rain, fog or dew. Continued climate warming is expected
to have a direct impact on lichens in Arctic and sub-
Arctic plant communities, and to indirectly impact them
through industrial development activities (Klein &
Vlasova 1991), leading to concern that declining lichen
communities could lead to reduced Rangifer populations.
Rangifer populations are heavily utilized by rural residents
in Alaska, and are therefore important in their
subsistence-dominated economies. Caribou are sought
after by sport hunters, and are appreciated by wildlife
enthusiasts: groups that are important to the broader
economy of Alaska.

Because of the importance of lichens in tundra ecosys-
tem dynamics in Alaska, investigators have used long-
term monitoring studies to understand their response to
disturbance factors that affect their presence and distri-
bution within the northern landscape. We highlight four
recent long-term studies in this review. On St. Matthew
Island (Fig. 1), in the northern Bering Sea, permanent
plots were originally established in 1957, in conjunction
with a study of feral reindeer (Klein 1968). On the
eastern Seward Peninsula, permanent plots were estab-
lished in 1981 to monitor caribou grazing pressure and
changes in vegetative cover within the core winter range
of the Western Arctic Herd (WAH; Fig. 1; Joly, Jandt et al.

2007). Jandt et al. (2008) monitored post-fire succession
from 1981 to 2006 using adjacent, paired burned and
unburned transects within the same region. Holt et al.
(2008) investigated plots on the western Seward Penin-
sula: a region used by both caribou and reindeer.

Twenty-nine reindeer were introduced to St. Matthew
Island in 1944, as an emergency source of human food for
personnel at a navigational station that was abandoned
only two years later (Klein 1968). Much of the vegetated
portion of the island was initially blanketed with dense
lichen mats. The herd faced no predation pressure, and in
the absence of humans the reindeer population rapidly
increased, reaching 6000 animals in 1963. By that time,
the herd had decimated the lichen community, and, in
conjunction with severe weather, a population crash
occurred during the late winter of 1964 (Klein 1968). The
population expired shortly after the crash, as no viable
males survived that winter, and the island has remained
free of reindeer and other large herbivores ever since.
Lichen re-growth on the island was tracked during sub-
sequent studies (Klein 1987; Klein & Shulski 2009)

The WAH, Alaska’s largest caribou herd, reached a
population of nearly 500 000 in 2003 (Dau 2005a). It
occupies a total range of about 363 000 km2 in north-
western Alaska. The centre of the herd’s wintering area
lies just east of the Seward Peninsula, and is dominated
by tussock tundra, but also contains extensive areas of
boreal forest and alpine ecosystems. The herd is highly
migratory, and faces predation from wolves (Canis lupus),
bears (primarily Ursus arctos), other carnivores and golden
eagles (Aquila chrysaetos). The WAH remains an important
resource in the subsistence-dominated lifestyle of the
people of the region, which emphasizes the need for an
increased understanding of caribou–habitat relationships
for the effective management and conservation of the
herd. In recent years there has been an increased focus on
changes in plant community structure within the winter
range of the herd, primarily associated with the influ-
ences of wildfire and climate change, and their effects on
habitat quality for Rangifer and other herbivores (Racine
et al. 1985; Racine et al. 1987; Sturm et al. 2001; Joly
et al. 2007; Jandt et al. 2008). The role of terricolous
lichens, which constitute the majority (60–80%) of the
diet of WAH caribou in winter (Saperstein 1996), in the
ecosystem dynamics of tundra and boreal forest habitats,
remains poorly understood.

Reindeer were first introduced to the Seward Peninsula
in 1892 through the efforts of Sheldon Jackson, then
Commissioner for Education in Alaska, for the purpose of
providing a stable supply of food for the native inhabit-
ants (Stern et al. 1980). Reindeer herding on the Seward
Peninsula was at its apex in the 1930s, when more than
100 000 animals were present, but numbers since have

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Polar Research 28 2009 433–442 © 2009 The Authors434



greatly declined (Stern et al. 1980). With the expansion
of the WAH in recent decades making herding of reindeer
no longer feasible over all but the westernmost portion of
the peninsula, the industry has been reduced to less than
10 000 reindeer (Dau 2000). Studies of the effects of
wildfire and grazing by both Rangifer species on the
Seward Peninsula have been carried out by Holt et al.
(2008).

Wildfire

The role of wildfire in boreal forest succession is relatively
well studied. In Alaska, the burn area correlates strongly
with increased summer temperature (Duffy et al. 2005).
The frequency and extent of wildfires in North American
boreal ecosystems have increased in recent decades
(Kasischke & Turetsky 2006). Caribou forage lichens are
especially vulnerable to being consumed by fire during

dry summers (Auclair 1983; Dunford et al. 2006),
because of their growth form and rapid loss of moisture
content in response to decreases in relative humidity that
proceed a fire front. Caribou are known to avoid recently
burned areas in the boreal forest: that is, areas burned
within the last 50 years (Thomas et al. 1996; Thomas
et al. 1998; Joly et al. 2003; Dalerum et al. 2007).

Less is known about the role of fire in Arctic tundra
ecosystems. Fires are relatively uncommon, and are of
limited extent, in tundra ecosystems (Wein 1976; Payette
et al. 1989), although they are somewhat more common
in the Noatak River valley and the Seward Peninsula
(Racine et al. 1985; Racine et al. 1987)—both are areas
within the range of the WAH. Similarly, the incidence of
fires is increasing within the range of the WAH (Fig. 2;
this study). However, a corresponding trend in the
acreage burned has not yet been identified, which may be
because of improved firefighting capabilities. In 2007, a

Fig. 1 Total annual range of the Western Arctic Caribou Herd, shown outlined by the thick, solid black line, within which the dark-grey shaded area is
the core winter range, in north-western Alaska (courtesy of the Alaska Department of Fish and Game). Areas shaded black within the range of the herd

depict recent burns (< 55 years old) in boreal forest habitats while stippled areas depict burns within tundra habitats, for the period 1950–2007 (courtesy
of the Alaska Fire Service).

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single fire burned over 100 000 ha of tundra, making it
the largest fire on record north of the Arctic Circle in
Alaska (the north-easternmost fire in Fig. 1; this study).
In addition to the unusual size of this tundra fire, the fact
that it burned so late into the season (e.g., late September,
when small lakes had already frozen) was remarkable.
This fire elicited concern from local rural residents that
Arctic tundra fires may become an issue in the future.

Caribou forage lichens are also vulnerable to being
consumed by wildfire in tundra habitats, and are a major
component of these ecosystems. The response of caribou
to burned tundra habitat has received much less attention
than in boreal ecosystems. In fact, only one regional
study of these effects has been undertaken so far. This
recent analysis using satellite telemetry data determined
that caribou avoided burned tundra habitat in mid-winter
for up to 55 years (Joly, Bente et al. 2007). In comple-
mentary studies, it was shown that the lichen cover in
burned tundra areas was less than 5% at 30 or 35 years
post-fire (Holt et al. 2008; Jandt et al. 2008, respectively).
This level of lichen cover is not likely to be great enough
for caribou to seek it out as foraging habitat (Arseneault
et al. 1997; Joly, Jandt et al. 2007). Wildfires reduce the
abundance of lichens, especially the late-succession fru-
ticose lichens that are the primary caribou forage lichens,
for decades in tundra ecosystems (Morneau & Payette
1989; Arseneault et al. 1997; Racine et al. 2004; Holt
et al. 2006; Holt et al. 2008; Jandt et al. 2008). Further-
more, post-fire lichen recovery is taking longer than has
been predicted (Jandt et al. 2008). The Natural Resource

Conservation Service forecasted lichen cover of >20% at
10 years post-fire, and of >30% at 20 years post-fire, on
the Seward Peninsula (Swanson et al. 1985), whereas
lichen cover has remained at under 5% for 20–35 years
post-fire on the plots examined by Jandt et al. (2008).

Caribou and reindeer

Rangifer directly affect lichen abundance through grazing
and trampling (Ahti 1959; Klein 1968, 1982, 1987; Pegau
1969; Moser et al. 1979; Helle & Aspi 1983; van der Wal
et al. 2001; van der Wal 2006). These effects can occur at
local and regional levels (Moser et al. 1979; Morneau &
Payette 1989; Arseneault et al. 1997). On St. Matthew
Island, Klein (1968, 1987) reported on the population
increase and crash of the introduced reindeer, and their
impact on the island flora. Heavy grazing pressure
exerted by reindeer on St. Matthew Island as the popu-
lation increased to its peak, without the option for
dispersal or movement from the island, resulted in the
near total removal of lichens, with few live fragments
from which forage lichen species could regenerate (Klein
& Shulski 2009). Although lichen cover and biomass
recovered somewhat from 1985 to 2005, it was still below
historic levels (Klein & Shulski 2009). Lichen biomass on
St. Matthew Island was just 12% of that on neighbouring
Hall Island, which had not been populated by reindeer
(Klein & Shulski 2009).

The WAH reached a record high population level
(490 000 caribou) by 2003, causing the general public and

Fig. 2 The incidence of reported fires from
1950 to 2007 occurring within the range of the

Western Arctic Caribou Herd, north-western

Alaska (compiled from Alaska Fire Service

data). The solid black line represents the

5-year moving average, and the dashed grey

line is a best-fit trend polynomial.

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Polar Research 28 2009 433–442 © 2009 The Authors436



land managers to become concerned about the possibility
of deteriorating winter ranges through heavy grazing
pressure (Dau 2005a). In fact, lichen cover had declined
by more than 50% (Joly, Jandt et al. 2007) on permanent
unburned transects in the winter range between 1981 and
2005, coincident with the population rise. Joly, Jandt et al.
(2007) determined that the decline in lichen cover was
significantly related to the amount of caribou utilization:
31% of the variation in the decline of lichens was
explained by caribou utilization. On the Seward Penin-
sula, areas that were heavily grazed by reindeer had lower
lichen cover and shorter thallus heights than areas that
were lightly grazed (Holt et al. 2008). The recovery of
lichen communities from heavy grazing by caribou and
reindeer can take a few to many decades, depending on the
intensity and duration of grazing, past history of grazing,
the suite of lichen species present, characteristics of snow
cover at the time of use by the caribou or reindeer, and the
duration of the growth season and its favourability for
lichen growth (Pegau 1969; Thing 1984; Messier et al.
1988; Henry & Gunn 1990).

Competition with vascular plants

Graminoids (grasses and sedges) are known to increase
under heavy grazing pressure from reindeer and caribou
in lichen-dominated plant communities (Klein 1968;
Thing 1984; Post & Klein 1999), and are also predicted to
increase under global warming scenarios (Chapin et al.
1995; Walker et al. 2006). These taxa rapidly increased in
the WAH winter range over a 25-year period, more than
doubling their percentage cover (Joly, Jandt et al. 2007).
Holt et al. (2008) revealed a strong negative correlation
between lichen and graminoid cover. Shrub height and
cover extent is also expected to increase with climate
warming (Chapin et al. 1995; van Wijk et al. 2003;
Walker et al. 2006), and studies using aerial photography
indicate that shrub expansion is already occurring in
Arctic and sub-Arctic Alaska (Sturm et al. 2001; Tape
et al. 2006). Dwarf shrub cover has increased by more
than 35% in north-western Alaska over the past 25 years
(Joly, Jandt et al. 2007). Tall shrubs (e.g., Alnus spp.) have
noticeably increased within the WAH winter range, based
on time-paired photos (Bureau of Land Management,
unpubl. data). Vascular plant species compete with
lichens for sunlight and available ground surface sub-
strate. This competition can lead to declining lichen cover
in Arctic tundra ecosystems. These vascular taxa not only
directly compete with lichens, but they also alter the
snow-melt patterns, which could lead to even greater
shrub cover (Sturm et al. 2005). Although the shrubs
may interfere with the winter grazing of lichens by Rangi-
fer, the smothering (by shed leaves of deciduous shrubs)

and shading effects of the shrubs may be more detrimen-
tal to the lichens. The expansion of vascular plants has
also come at the expense of some mosses, which have
declined by 67% in the WAH winter range (Joly, Jandt
et al. 2007). This may prove to be important regionally, as
Holt et al. (2008) determined that there was a positive
correlation between lichen and moss cover.

Climate change

The observed reduction in lichen cover in north-western
Alaska over the past 25 years cannot be attributed solely
to wildfire and the effects of Rangifer grazing. The slow
rate of the re-establishment of lichens on St. Matthew
Island, and their subsequent growth, has been further
retarded by pronounced climate warming in recent
decades, with associated atmospheric drying (Klein &
Shulski 2009). In areas that contain high densities of
Rangifer or other animal populations in summer, atmo-
spheric drying could result in increased damage to lichen
communities by trampling (Cooper et al. 2001).

Lichen cover has declined on some unburned Seward
Peninsula transects that have only experienced light
caribou grazing (Joly, Jandt et al. 2007). Jandt et al.
(2008) also revealed that lichen cover dropped from 20 to
6% on unburned transects with low caribou use. Further-
more, the recovery of lichen communities after wildfire
has regressed on transects on the Seward Peninsula over
the past decade (Jandt et al. 2008). Analyses of the impli-
cations of climate change on tundra ecosystems as well as
experimental warming studies predict that lichens and
mosses will be negatively affected as a result of warming
and drying (Chapin et al. 1995; Robinson et al. 1998;
Cornelissen et al. 2001; van Wijk et al. 2003; Epstein
et al. 2004; Hollister et al. 2005; Walker et al. 2006;
Wiedermann et al. 2007), and we posit that recent obser-
vations from north-western Alaska augment this body of
evidence. Furthermore, decreases in lichen and moss
cover have also been detected on the North Slope
of northern central Alaska between 1984 and 2002
(Jorgensen & Buchholtz 2003). Alternatively, lichens in
alpine habitats may benefit from increased temperatures
if there is little competition with vascular species (Molau
& Alatalo 1998) and sufficient atmospheric moisture
(Cooper et al. 2001). The effects of climate change on
Arctic ecosystems will not, however, be easy to predict,
especially changes in the moisture regime (Rouse et al.
1997; Wookey 2007).

Snow is a critical factor in determining the accessibility
of winter forage for Rangifer (Heggberget et al. 2002).
Rangifer prefer to forage in areas where the snow is less
hard and shallow (Collins & Smith 1991). Exceptionally
deep snow, in conjunction with depleted lichens, was a

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factor in the crash of the reindeer herd on St. Matthew
Island. In the Arctic, warming will be especially pro-
nounced during winter (Hinzman et al. 2005; Symon
et al. 2005). Warmer winters could be accompanied by
increased rain-on-snow events that form ice crusts, or
engulf vegetation, at ground level on Rangifer winter
ranges. Within the winter range of the WAH, two of these
events have been documented, along with the associated
caribou die-offs (Dau 2005b).

Interactions

Wildfire, disturbance by Rangifer, competition with vas-
cular plants and climate change all independently act to
reduce lichen cover in Arctic tundra ecosystems. These
factors, however, are also interactive. Wildfires consume
lichens, but also facilitate rapid increases in shrub and
graminoid cover through nutrient release and soil
warming (Racine et al. 2004; Jandt et al. 2008). Darker
surfaces left by wildfire charring may reduce surface
albedo, leading to more melting, which would give com-
petitive advantage to vascular taxa over lichens. Deep
burns also expose suitable mineral soil seedbeds for the
establishment of new shrubs: particularly willows, which
have efficient wind-aided seed dispersal. The establish-
ment of new willows (Salix pulchra) following fire on the
Seward Peninsula has been documented (Racine et al.
2004). Greater shrub cover could also reduce the surface
albedo, over that of the pre-burn tundra vegetation
(Chapin et al. 2005).

Herbivory can also induce fairly rapid changes in
tundra plant community structure, both directly and indi-
rectly (Thing 1984; Arseneault et al. 1997; van der Wal
2006; Klein & Shulski 2009). Areas heavily grazed by
reindeer had 26% higher vascular plant cover than areas
that were lightly grazed (Holt et al. 2008). The reduction
of lichens by grazing Rangifer may also affect the surface
albedo and plant community structure, which could lead
into a feedback loop with further declines in lichens.

Climate warming induces change more slowly, and is
the most difficult factor to document with field studies.
However, longer growing seasons, increased photosyn-
thetic activity and accelerated leaf tissue maturation
have all been detected in tundra ecosystems (Goetz et al.
2005). Climate warming could lead to more dwarf birch
(Betula nana) across tundra ecosystems in northern
Alaska (van Wijk et al. 2003), which was the primary fuel
when this region had significantly more frequent fires
(Higuera et al. 2008). Thus, climate warming may induce
changes in shrub species dominance and cover, which, in
conjunction with warmer temperatures, could increase
fire frequency (Higuera et al. 2008). Climate warming
and summer drought are correlated with more frequent

and extensive wildfires in Alaska, northern Canada and
Siberia (Wein 1976; Duffy et al. 2005; McCoy & Burn
2005; Soja et al. 2007), which could accelerate lichen
declines and the potential disappearance of old-growth
lichen tussock tundra communities in north-west Alaska
(Rupp et al. 2000), thereby further degrading the caribou
winter range (see Rupp et al. 2006). The decline in lichen
biomass within plant communities that previously had a
major lichen component appears to result from the
warmer summers of recent decades, which favour
vascular plant growth. Moreover, the associated dryer
conditions at the ground surface inhibit lichen re-growth
following either wildfire or moderate to heavy winter
grazing by Rangifer species. In other words, climate
change may extend the lichen regeneration time lines
following disturbance by either wildfire or Rangifer
grazing (Gough et al. 2008; Jandt et al. 2008; Klein &
Shulski 2009).

The negative effects of climate warming on the Rangifer
winter range may be partially offset by the improved
spring forage quality resulting from earlier snowmelt
(Cebrian et al. 2008). However, as spring forage quality
and availability are temperature dependent, whereas
caribou migration and calving are cued by changes in day
length, a trophic mismatch may arise (Post & Forchham-
mer 2008). In West Greenland, this trophic mismatch has
resulted in decreased calf production and increased calf
mortality (Post & Forchhammer 2008).

Conclusions

Our review of the theoretical, experimental and actual
outcomes of climate warming reveals a decrease in the
extent and biomass of fruticose lichens over recent
decades in north-western Alaska. Our current under-
standing of the primary factors influencing Arctic tundra
ecosystems, inclusive of wildfire, grazing by Rangifer
species, competition with vascular plants and climate
change, leads us to conclude that these factors are unidi-
rectional, interrelated and most likely have led to a
marked decline in lichens among plant communities at
high latitudes across Alaska. Changes in Arctic and
sub-Arctic lichen communities in Alaska may be repre-
sentative of changes elsewhere in the Arctic (Shaver &
Jonasson 1999), with the possible exception of the Fen-
noscandian Arctic (Callaghan et al. 1999). Our review, in
concert with others (e.g., Heggberget et al. 2002), leads us
to question if these changes may well be pan-Arctic in
nature, and may foreshadow major changes in plant com-
munity structure throughout the world’s circumpolar
regions.

Lichens are considered to be critical winter forage for
the large, migratory herds of caribou in North America,

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for the wild reindeer in Eurasia, as well as for the
semi-domesticated reindeer throughout the Arctic,
particularly for herds that face predation (White et al.
1981; Klein 1982; Syroechkovskii 1995; Heggberget
et al. 2002). Thus, the decline of lichens in Arctic and
sub-Arctic plant communities should concern land
managers, subsistence and sport hunters, reindeer
herders and wildlife enthusiasts.

Some researchers have postulated that the transition
from a lichen-rich winter diet to one dominated by
graminoids may not adversely affect Rangifer populations
(Bergerud 1974; Heggberget et al. 2002; van der Wal
2006). This postulation, however, is based on ad libitum
feeding trials with individual animals in captivity (Jacob-
sen & Skjenneberg 1975), and extrapolation from High-
Arctic, low-density populations of Peary caribou (Rangifer
tarandus pearyi; Thomas & Edmonds 1983) and the Sval-
bard caribou (Rangifer tarandus platyrhynchus). The latter,
in the absence of predators, with little winter snow
accumulation and with little need for efficient mobility,
acquired morphological, physiological and behavioural
adaptations that, unlike other caribou, equip them for
winter survival through low energy expenditure, a
greater capacity for fat storage, and an increased effi-
ciency in the digestion of graminoids and mosses (Tyler
1987). On predator-free, High-Arctic islands, low-density
populations of Rangifer can survive without abundant
fruticose lichens (van der Wal et al. 2001; Heggberget
et al. 2002). Lichens, as a component of the winter diet of
the continental WAH, have declined during the past
decade, with corresponding increases in graminoids (Joly,
Cole et al. 2007). Therefore, the WAH may serve as a test
case for assessing the importance of lichens for large,
migratory caribou herds that face predation. Declining
recruitment in the herd (Dau 2005a) concurrent with the
decline in lichens on the landscape and in the diet, and
the avoidance of recently (within 55 years) burned areas
on the winter range (Joly, Bente et al. 2007), despite the
quick and vigorous regrowth of graminoids (Jandt et al.
2008), appear to be initial evidence supporting the impor-
tance of climate warming and a lichen-rich winter diet for
this herd. Furthermore, the initial population estimate for
the WAH in 2007 revealed a 20% decline from the popu-
lation high of 490 000 in 2003 (Dau, pers. comm.). It has
been hypothesized that Rangifer herds may become
smaller, more sedentary and utilize mountainous habitat
more, as a result of climate warming and declining lichen
communities (Heggberget et al. 2002). The work of Holle-
man et al. (1979) also supports the theory that more
mobile Rangifer utilize greater proportions of lichen in
their diets. Thus, the potential loss of dense and extensive
lichen communities in the Arctic could lead to declines in
herd sizes, and changes in distribution, behaviour and

diet of Rangifer, rather than leading towards their
extirpation.

The role of wildfire in caribou winter ecology has long
been debated (Leopold & Darling 1953; Scotter 1970;
Klein 1982). However, of the four factors affecting lichen
abundance, wildfire appears to be the one that land man-
agers have the most control over, and thus garners the
most attention. We promote the idea of improving the
synthesis of existing research, supporting new research
projects to address knowledge gaps and using this infor-
mation to develop fire management plans for the winter
ranges of large, migratory Rangifer herds. In addition, an
integrated, international effort is needed to investigate
the role of lichens in Arctic and sub-Arctic ecosystems,
and the responses of lichens to changes in the environ-
ment: changes that have accelerated in recent decades
(Symon et al. 2005). Such an effort should encompass:
climate change detection and modelling; the assessment
of the long-term impacts of boreal forest and tundra wild-
fires, and the related soil dynamics; determining the
competitive feedbacks between lichens, shrubs and
graminoids in plant community structure; and impacts on
caribou ecology. Furthermore, dramatic changes in sea-
ice dynamics, which strongly influence Arctic weather
patterns, may lead to even more pronounced changes on
terrestrial Arctic ecosystems. Land managers throughout
the Arctic could use such data to guide strategies for fire
and resource management that fit with the changing
climate.

Acknowledgements

We thank all the Bureau of Land Management employees
that have worked on the various projects mentioned in
this paper, especially R. Meyers and J. Cole. J. Allen,
T. Chapin, K. Kielland, R. Meyers, G. Theisen, R. van
der Wal and anonymous reviewers provided comments
and discussions that were helpful for developing this
manuscript.

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