Human impacts on George River Caribou : An Overview

H u m a n activit ies have had , h is tor ica l ly , v a r y i n g degrees o f effect o n c a r i b o u (Rangifer tarandus). I n n o r t h e r n E u r o p e , c a r i b o u have b e e n m o u l d e d i n t o the s emi -domes t i c re indeer . I n N o r t h A m e r i c a , m a n y sedentary w o o d l a n d popu la t ions have b e e n e l i m i n a t e d o r severely r e d u c e d i n n u m b e r . M i g r a t o r y , b a r r e n g r o u n d popu la t ions , o n the o ther hand , have recen t ly e x p e r i e n c e d p o p u l a t i o n h ighs r emin i scen t o f levels est imated to have o c c u r r e d p r i o r to the last cen tu ry o f increased e x p l o i t a t i o n (Berge rud , 1988) . T h e G e o r g e R i v e r p o p u l a t i o n is n o e x c e p t i o n and , i n fact, m a y serve as a m o d e l o f this recent expans ion . F o r m u c h o f this cen tury , the p o p u l a t i o n appeared to be o f l i t t le consequence , c o m p a r e d to its i m p o r t a n c e i n the late 1800s. B e g i n n i n g i n the 1950s, an increase f r o m perhaps less than 10 ,000 ind iv idua l s to o v e r 600 ,000 b y the m i d 1 9 8 0 s p r o p e l l e d the p o p u l a t i o n i n t o a centra l p o s i t i o n r ega rd ing h u m a n act ivi t ies i n n o r t h e r n Q u e b e c and Labrador . A l t h o u g h there is o f yet n o clear ev idence that h u m a n ac t iv i ty has h a d m u c h to d o w i t h e i ther the popula t ion ' s increase o r the i n i t i a t i on o f its cur ren t dec l ine , the issue o f po ten t i a l impacts b y humans is n o w a major c o n c e r n . D e c i s i o n s made n o w c o n c e r n i n g these impacts m a y de te rmine the u l t imate l e v e l o f the nex t p o p u l a t i o n l o w , its du ra t i on , and the p e r i o d to the nex t p o p u l a t i o n peak.

Migratory, barren-ground populations, on the other hand, have recently experienced population highs reminiscent of levels estimated to have occurred prior to the last century of increased exploitation (Bergerud, 1988).The George River population is no exception and, in fact, may serve as a model of this recent expansion.For much of this century, the population appeared to be of little consequence, compared to its importance in the late 1800s.
Beginning in the 1950s, an increase from perhaps less than 10,000 individuals to over 600,000 by the mid-1980s propelled the population into a central position regarding human activities in northern Quebec and Labrador.Although there is of yet no clear evidence that human activity has had much to do with either the population's increase or the initiation of its current decline, the issue of potential impacts by humans is now a major concern.
Decisions made now concerning these impacts may determine the ultimate level of the next population low, its duration, and the period to the next population peak.
The nature of human impacts varies along a number of dimensions.Influences can be direct or indirect.Hunting represents the most direct of influences; ultimately, its impact of the population may be either positive or negative.Global warming, on the other hand, may be among the most indirect, acting through effects on vegetation or snow conditions.Impacts may also be permanent or transient.Loss of habitat through development, whether for mining, hydroelectric power, or human habitation, may exert relatively long-term effects.Low-level aircraft flights may cause relatively transient effects that may be easily reversible.Ultimately, it is the cumulative impact of these various influences that is of greatest concern.Below I will focus on three forms of human impact that are of most immediate concern.
Hunting is an activity with the potential for both positive and negative effects (Harrington, 1988(Harrington, , 1991)).Over-hunting may send a population into an early decline; under-hunting may allow it to peak relatively early.Judicious hunting, on the other hand, may sustain a population peak.
However, a sustained population high may not be beneficial in the long term, if other negative effects rare circumstances (Harrington & Veitch, 1991).
On the other hand, low-level jet overpasses may have important although largely indirect negative impacts on caribou population dynamics.Calves overflown more often during the first two weeks postcalving survive for shorter periods of time (Harrington & Veitch, 1992).Females overflow by jets during the post calving period move longer distances during the next 24-hours than they normally do (Murphy et ai, 1993), perhaps making their calves more accessible to predators.The vulnerability of caribou to negative impacts from low-level jet activity likely varies dramatically depending on season.In addition, although the high frequency of jet flights makes them an important concern, helicopters on a per flight basis have a greater potential for negative effects than either fixed-wing or jet aircraft.
Hydro-electric development is the third source of potential human impacts of caribou (Harrington, 1991).Habitat alteration and habitat loss are two of the potential effects of such development.Some of these impacts would be permanent, as in winter range flooded under reservoirs; others would be long term, such as return of vegetation following humancaused wildfires, and still others might be short-term, such as changes to river drainage patterns or lake ice conditions caused by lowering of reservoirs for power overwinter.In addition, the opening up of previously inaccessible areas will increase the vulnerability of caribou to hunting activity.
Habitat loss exerts its influence by lowering the carrying capacity of the habitat.Loss of critical habitat, therefore, is of most concern.The fact that calving range is the one "constant" in the caribou's migratory movements, and that summer range appears to be overgrazed at present and may be limiting the population, indicates that protection of habitat in or about calving and summer range is a priority.
No one factor is likely to be the key element.
Rather, the effects of various factors will be additive, multiplicative, or compensatory.In the end, it may not be possible to construct a model that adequately characterizes the influence of these factors and the relationship among them.But it is important to monitor human influences of the population, so that changes in the relative magnitudes, at least, of these variables can be detected before their impacts become serious.Until a fuller understanding of the impacts of these various activities is acquired, it may be more appropriate to accept the alternative hypothesis that there is an impact, rather than the null hypothesis that there is none.

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fighter training has been another recent area of concern.Low-level flying does not likely exert a significant direct effect on caribou.Caribou may be startled by low-level overpasses and may run briefly, but these effects are short-lived and unlikely to have important population-wide effects except under