Monitoring Ecological Health
Soapberry, Buffa loberry, Sheperdia canadensis
© Parks Canada / R. Staley
Climate change and spruce bark beetles
Summary: Climate records starting in 1945 show that the average annual temperature and amount of precipitation have been increasing in the southwest Yukon. Winters show less frequent prolonged periods of severe cold, and early to mid-December is significantly warmer. The average amount of summer precipitation decreased in nine of the 15 years from 1989 to 2003. These climatic conditions have helped to promote a large infestation of spruce bark beetles in southwest Yukon and southern Alaska.
Berg and Henry (2003) assembled weather records for Haines Junction and Burwash since the mid-1940s. On an annual basis, temperature has increased in the southwestern Yukon during the past 40 years and precipitation has decreased at Burwash. At Haines Junction the temperature trend is similar but rainfall is increasing rather than decreasing (Carrier 2003).
A close-up view of a grizzly bear track in the sand
© Parks Canada / R. Staley
Paul Whitfield of Environment Canada analyzed five-day averages for temperature and precipitation over a 20-year period for the Kluane region. He compared temperature and precipitation between two decades (1976-1985 and 1986-1995). Although the average winter temperature did not become significantly warmer, in the latter decade there were successive winters without prolonged periods of severe cold, and early to mid-December was significantly warmer (Krebs, Boutin and Boonstra 2001). Whitfield also found warmer temperatures during the early spring and throughout the growing season.
These weather patterns likely have intensified the spruce bark beetle infestation in the Kluane region in several important ways (Berg and Henry 2003). Warmer summers probably promoted greater beetle reproduction: beetles that usually take two years to complete their life cycle took only one year. Warm summers also increased trees' moisture stress and reduced their ability to get rid of the beetles through a “pitching out” response. Furthermore, warmer early winters and the lack of severe cold probably means that fewer beetles die when they overwinter.
Rapid wasting of glaciers
Summary: Since the mid-1950s glaciers straddling the Alaska-Yukon border and in southern Alaska have been melting at an average rate of half a metre of thickness per year. Recently this rate has more than tripled.
© Parks Canada
Arendt et al. (2002) surveyed 67 glaciers in Alaska, southwestern Yukon and northeastern B.C; 11 of them span the U.S.-Canada border and one (Kaskawulsh) was entirely within the Yukon. The team used laser altimetry to estimate volume changes of these glaciers from the mid-1950s to the mid-1990s. The average change in rate of thickness was –0.52 m/year. Repeated measurements of 28 glaciers from the mid-1990s to 2000-2001 suggest an increased average rate of thinning of 1.8 m per year.
Extrapolation to all glaciers in Alaska yields an estimated total annual volume change during this past decade of –96±35 cubic km per year, equivalent to a rise in sea level of 0.27±0.10 mm per year. This is nearly double the estimated annual loss from the entire Greenland Ice Sheet during the same time period and is much higher than previously published loss estimates for Alaska glaciers. It is the largest glaciological contribution to rising sea level yet measured.
Summary: Monitoring of moose, bison, Dall's sheep and caribou by Kluane Regional Management, Yukon Department of Environment generally showed improved survival of calves and lambs. Early spring green-up and warm dry weather at birthing are believed to be factors.
A full view of a Dall Sheep Ewe on a mountain slope.
© Parks Canada / W. Lynch / Collection : knp/yfu
In advance of the new Aishihik Wildlife Management Planning Process, a moose census was carried out in an area of 3800 sq. km around Haines Junction in 2004. Initial analysis shows an estimated abundance of 577 moose, a density of 150 moose per 1000 sq. km (about average for the Yukon), and a calf to cow ratio of 32:100. While this ratio should promote some population growth, the census shows a decline in moose abundance since the previous census in 2000. Yearly composition surveys, looking at calf recruitment and distribution from 2000–2004, indicated a declining population. (Field observations in 2000 and 2001 showed that weather, not wolf predation, was the limiting factor in calf survival.)
Sheep were counted in the Ruby Range in late July 2004 on the east side of Talbot Arm, in an area that has been surveyed periodically since 1984. The survey was delayed and limited by forest fires, but 633 sheep were counted, including 104 lambs or 29 lambs per 100 nursery sheep. (Nursery sheep include ewes, yearling and some two-year-old rams.) Generally 25–30 lambs per 100 nursery sheep indicate a stable population. Note that wardens from Kluane National Park and Reserve survey sheep, moose and goat populations inside the park. Soon it will be possible to test if these patterns are occurring in the park as well.
The experimental Chisana caribou recovery project is in its third year and researchers are observing a significant improvement in calf survival. The project involves holding pregnant cows in a holding pen until their calves are at least two weeks old in order to protect the offspring from predators. Prior to the recovery project the Chisana had suffered at least 15 years of very poor calf survival, resulting in a herd of predominantly old cows and few bulls or younger animals. From an estimated herd size of over 2000 in the early 1980s, the herd had declined to about 700 animals in 2003.
In 2004 captive-reared calves accounted for about one-quarter of overall calf survival. Of the 29 calves released with their radio-collared mothers in June of 2004, 22 were still alive by October, a 76 percent survival rate. Eight calves born to radio-collared cows outside of the pen were also monitored; by mid-October only two of them were still alive. The higher survival rate for captive reared calves may be partially attributed to their higher body weight. On average, by the end of October, they weighed an additional 15.4 lb (almost 7.0 kg), compared to wild-born calves. This is likely an effect of the supplemental feeding their mothers received during captivity.
This international project provides valuable research for recovering small, threatened woodland caribou populations throughout North America, and its success hinges on considerable effort from both Canadian and American partners. For more information, e-mail firstname.lastname@example.org .
Arctic ground squirrels
Summary: Arctic ground squirrels are one of the most common small mammals in the Kluane region but have become relatively scarce since 2000. In the Kluane region their numbers continued to be low in 2004, although there is a trend to a slow recovery.
Because of shared predators the number of ground squirrels rises and falls with the ten-year cycle of snowshoe hares in the boreal forest. After the last hare peak in 1998, ground squirrel numbers fell to the lowest level in 20 years — about one per eight ha — and have been slow to make a comeback (see Figure 1).
Figure 1. Arctic ground squirrel and hare densities in Kluane's boreal forest, 1990–2004
Ground squirrel and hare densities follow a similar pattern: numbers decline from 1990 - 1994, then increase from 1994 - 1998. Numbers then make a sharp drop from 1998 - 2002 with a slight recovery starting in 2004.
© Parks Canada
The low density reached by ground squirrels was three times as extreme as the previous low in 1993. We do not know why, but since predation is the major limiting factor with ground squirrels, severe predation was probably the cause. A possible alternative explanation is poor overwinter survival.
Because of the severity of the latest population crash, they will take longer to recover. As of 2004, ground squirrel numbers had reached about one per 3-4 ha. They will likely continue to increase and regain their former abundance during the next three years.
It is interesting to compare the ground squirrels in the boreal forest with those at higher elevations. In alpine areas in the Ruby Ranges ground squirrel numbers reached their lowest level in 1999 and rose slowly over the next three years (Gillis et al. 2005). By 2003, alpine ground squirrels had reached relatively high numbers, while the number of ground squirrels in the boreal forests of the valley remained very low.
Arendt, A.A., K.A. Echelmeyer, W.D. Harrison, C.S. Lingle and V.B. Valentine. 2002. “Rapid wastage of Alaska glaciers and their contribution to rising sea level.” Science 297: 382-386.
Berg, E.E. and J.D. Henry. 2003. The history of spruce bark beetle outbreak in the Kluane region as determined from the dendrochronology of selected forest stands. Parks Canada Report. 46 pp.
( http://kenai.fws.gov/science/studies.htm ).
Carrier, P. 2003. Effects of water addition on biotic and abiotic components of a dry boreal forest in the Yukon. PhD thesis, University of British Columbia, Department of Zoology. 134 pp.
Cruikshank, Julie. 2005. Do Glaciers Listen? Local Knowledge, Colonial Encounters, and Social Imagination. University of British Columbia Press, Vancouver. 288 pp.
Gillis, E.A., D.S. Hik, R.Boonstra, T.J. Karels and C.J. Krebs. 2005. “Being high is better: effects of elevation and habitat on arctic ground squirrel demography.” Oikos 108: 231-240.
Garbutt, R. 2005. 2004 Yukon Report. Canadian Forest Service, Victoria, B.C. 11 pp.
Henry, J.D. 2002. Canada's Boreal Forest. Smith-sonian Institution Press. Washington, D.C. 194 pp.
Krebs, C.J., S. Boutin and R. Boonstra (eds.). 2001. Ecosystem Dynamics of the Boreal Forest: The Kluane Project. Oxford University Press, Oxford. 511 pp.
This report describes some issues related to the ecological health of Kluane National Park and Reserve and the Kluane region. The findings come from the Kluane Ecological Monitoring Project ( KEMP ) and other relevant research. KEMP is a partnership between the Arctic Institute Research Station at Kluane Lake, Parks Canada, Yukon Department of Environment, Canadian Wildlife Service and Yukon College. For more information, see: http://www.taiga.net/top/reports.html .
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