TL: Caribou and Climate Change SO: Greenpeace (GP) DT: 1998 INTRODUCTION Caribou, Rangifer tarandus, also called reindeer in Europe, are the most common large land mammal of the Arctic and Subarctic. Most caribou gather in large herds of tens of thousands to more than one hundred thousand animals on their calving grounds in the brief Arctic summer, and scatter widely in small groups for the rest of the year. Because of their numbers, caribou are the foundation of the traditional economy for many northern peoples, including the Gwich'in of Alaska and northwestern Canada, the Saami and Komi peoples of Scandinavia and the Russian western Arctic, and numerous peoples of Siberia and the Russian Far East. Eurasian reindeer are the same species as North American caribou - the primary difference is that many Eurasian reindeer are semi-domesticated and are herded and protected more often than their North American counterparts. Caribou provided much of the food for traditional northern societies, and their hides became clothing and material for tents and other shelters. Today, Arctic peoples like the Gwich'in identify closely with the caribou they hunt and are dependent on them for nutritious, affordable "country food" to supplement supplies imported from the south. Even the Inuit, while also hunters of marine mammals, often depend upon the caribou as their primary source of traditional food. Caribou are also important prey for Arctic predators, especially the Arctic wolf and, on the calving grounds, grizzly bears and golden eagles.[1] Caribou form numerous, distinct herds with separate calving grounds. Amongst the major herds of the western Arctic are the Bathurst, Porcupine, Western Arctic, Central Arctic and Teshekpuk Lake caribou herds. Much rarer than their mainland cousins, the Peary caribou are a white, smaller subspecies found only in western Greenland and Canada's Arctic Islands. Unlike most caribou, the Peary caribou do not gather in large herds but remain scattered in small island groups. ------------------------------------------------------------------------ [1] Ed Hall, (ed.), 1989. People and Caribou in the Northwest Territories, Government of the Northwest Territories, Yellowknife, Canada. CLIMATE IMPACTS It may seem paradoxical that climate change and warmer temperatures would harm the caribou. After all, similar deer species thrive in many different habitats on the planet - from the boreal forests of Canada to the savannas of Africa. Why would warmer temperatures threaten such adaptable creatures? The two key climate-related factors influencing caribou are snow and insects. Caribou, although usually successful in their harsh habitat, must often work hard to forage for the moss and lichen that is their main food source during the long Arctic winters, and must make the most of the small tundra shrubs they feed on during the brief summer. Any changes that make foraging more difficult on a consistent basis would threaten the herds. Almost all climate models project more precipitation in a greenhouse future, particularly in the Arctic.[2] The Arctic is dry, receiving an average of 4 cm of annual precipitation, mostly in the form of snow.[3] Models suggest that doubling the levels of greenhouse gases in the atmosphere would cause a 30 to 50 increase in Arctic snowfall.[4] Snowfall and other precipitation is already increasing in the Mackenzie Valley region in northwestern Canada[5] and in much of Alaska.[6] Caribou often dig through snow to find moss and lichen, a process called "cratering". In areas of shallow or patchy snow, it may take only a few minutes to expose enough food for the day. On the other hand, cratering may occur for approximately 2 hours per day where snow is deep or is covered with a crust of ice from freezing rain. The energy required per cratering stroke varies from 118 joules in light uncrusted snow, to 219 joules in denser snow with a thin, hard crust.[7] A study of Greenland caribou on Coates Island in Canada's Northwest Territories found that, in harsh winter conditions with an unusually thick snow pack averaging 50-80 centimetres, the animals cratered only in highland areas where the snow was 10-20 centimetres thick. Forage available under these winter conditions was drastically reduced and there was high calf mortality.[8] Increased energy consumption and decreased food availability would increase winter starvation and decrease spring body fat, significantly reducing lactation and calf survival rates.[9] A deeper winter snow pack may also make caribou more vulnerable to wolf attack since lighter wolves can travel on snow crusts that caribou would sink through.[10] During the summer, caribou feed on small tundra shrubs, including willow, and fatten themselves in preparation for the coming winter. The summer is also a crucial period for calving and lactation. Insect harrassment by mosquitoes and parasitic flies may significantly decrease foraging time.[11] In particular insect harassment is associated with temperatures of 13 degrees Celsius or higher, and wind speeds of less than 6 meters per second.[12] Insect harrassment prevents foraging and increases energy requirements. As a result, warmer summers and more insect harrassment can cause significant declines in body fat.[13] The average temperature in the western Arctic in Canada and Alaska has been warming at a rate of at least 0.5 degrees per decade over the last 30 years, a rate 3-5 times faster than the planet as a whole.Most of this warming has occurred in the winter and spring, but warming has also occurred in the summer.[14] This warming suggests that insect harrassment may already be increasing. Models also suggest a 2-4 week earlier period of snow melt.[15] Caribou tend to frequent melting snowpatches in the summer. Several reasons have been proposed for this, including decreased insect harrassment because of lower air temperatures and higher wind speeds, or because of the availability of cotton grass.[16] Cotton grass, an important food source for caribou, has its highest nutritional when it emerges from melting snow. Its nutritional value declines significantly within a few days following its emergence. Earlier snowmelt made sharply reduce the availablility of cotton grass in its most nutritious form, especially if caribou migration times do not change accordingly.[17] Increased insect harrassment and decreased food quality because of earlier and more extensive snow melt would put increased stress on caribou herds. A computer model of a Porcupine Caribou Herd female suggests that the combination of a deeper winter snow and increased insect harrassment could significantly decrease the female's body fat. Since there is a strong correlation between autumn body fat and successful spring births, the projected climate change could reduce caribou birth rates by about 40 percent.[18] An examination of four climate models suggests that increased winter snow depth and summer insect harassment may be detrimental to the Bathurst Caribou Herd.[19] Caribou population declines are cyclical and, to some degree, self correcting. For example, a temporary decline in caribou populations allows increased growth of moss and lichen, allowing a major population increase should favourable conditions return.[20] Nevertheless, the IPCC projects that continued climate change may lead to the extinction of the high Arctic Peary caribou and the IPCC, along with several previously cited researchers, concludes that other caribou population may also be reduced.[21] Recent climate change may already be contributing to the severe decline of the Peary caribou on Canada's Arctic Islands. Peary caribou populations on the western Arctic Islands declined from 24,320 animals in 1961 to 1100 animals in 1997 - a 95 percent decrease. Populations on the eastern Arctic Islands are unknown.[22] This decline appears to have been caused largely by increased snowfall and ice conditions associated with warmer winters. After heavy snow and ice conditions developed on the Arctic Islands during the winter of 1973-4, Peary caribou populations declined by 45 percent on the western Arctic Islands and by 69 percent on Bathurst Island.[23] More recent Peary caribou decline on Banks Island appears to be correlated with snow pack depth.[24] The unusually warm winter of 1996-7 was associated with a deep snowpack and icing, causing about 10,000 reindeer to die of starvation on Russia's far northeast Chukotsk peninsula.[25] Peary caribou populations also dropped severely on Bathurst Island during the same winter.[26] ------------------------------------------------------------------------ [2] IPCC Regional Impacts Special Report, Final Draft, Chapter 3, Arctic/Antarctica, p 1. October 1997. [3] Walter Skinner, et.al., 1995. The State of Canada's Climate: Monitoring Variability and Change, SOE Report No. 95-1, Atmospheric Environment Service, Environment Canada. [4] Don E. Russell, 1993. "Effects of global warming on the biology and management of the Porcupine caribou herd", in G. Wall (ed.), Impacts of Climate Change on Resource Management in the North, Dept. of Geography, Occasional Paper No. 16, University of Waterloo, pp. 91-97. [5] Skinner 1995, op.cit. [6] Bering Sea Impact Study (BESIS), 1996. The Impacts of Global Climate Change in the Bering Sea Region, Conference Proceedings, Girdwood, Alaska, 18-21 September 1996, BESIS Project Office, University of Alaska-Fairbanks. [7] Steve G. Fancy and Robert G. White, "Energy expenditures by caribou while cratering in snow", Journal of Wildlife Management, 49(4):987-993, 1985. [8] J.Z. Adamczewski, C.C. Gates, B.M. Soutar, and R.J. Hudson, "Limiting effects of snow on seasonal habitat use and diets of caribou (Rangifer tarandus groenlandicus) on Coats Island, Northwest Territories", Canadian Journal of Zoology 66:1986-1996, 1988. [9] Caribou birth rates and calf survival ratesare very sensitive to female body fat. See Raymond D. Cameron, Walter T. Smith, Steven G. Fancy, Karen L. Gerhart, and Robert G. White, 1992. "Calving success of female caribou in relation to body weight", Can. J. Zool. 71:480-486; and Raymond D. Cameron and Jay M. Ver Hoef, 1994. "Predicting parturition rate of caribou from autumn body mass". J. Wildl. Manage. 58(4):674-679. [10] Janet Brotton and Geoffrey Wall, 1997. "Climate change and the Bathurst Caribou Herd in the Northwest Territories, Canada", Climatic Change 35: 35-52. [11] Robert H. Pollard, Warren B. Ballard, Lynn E. Noel and Matthew A. Cronin, 1996. "Parasitic insect abundance and microclimate of gravel pads and tundra within the Prudhoe Bay Oil Field, Alaska, in relation to use by caribou, Rangifer tarandus granti", Canadian Field-Naturalist 110(4):649-658. [12] Noreen E. Walsh, Steven G. Fancy, Thomas R. McCabe and Larry F. Pank, 1992. "Habitat use by the Porcupine caribou herd during predicted insect harrassment", Journal of Wildlife Management 56(3):465-473. [13] Anne Gunn and Terje Skogland, 1997. "Responses of caribou and reindeer to global warming", in Walter C. Oechl, et.al. (eds.), Global Change and Arctic Terrestial Ecosystems, Springer-Verlag, New York, p. 191. [14] Stewart Cohen (ed.), 1997. The Mackenzie Basin Impact Study, Environment Canada, Ottawa; and BESIS 1996. [15] Russell 1993, op.cit. [16] Peter G. Ion and G. Peter Kershaw, 1989. "The selection of snowpatches as relief habitat by woodland caribou (Rangifer tarandus caribou), Macmillan Pass, Selwyn/Mackenzie Mountains, N.W.T., Canada", Arctic and Alpine Research 21(2):203-211; and Warren G. Eastland, R. Terry Bowyer, and Steven G. Fancy, 1989. "Effects of snow cover on selection of calving sites by caribou", J. Mamm. 70(4):824-828. [17] Warren G. Eastland and Robert G. White, 1990. "Potential effects of global warming on calving caribou", in International Conference on the Role of the Polar Regions in Global Change, June 11-15, 1990, University of Alaska-Fairbanks, pp. 460-464. [18] Russell 1993, op.cit. [19] Brotton and Wall 1997 [20] Michael A.D. Ferguson, 1996. "Arctic tundra caribou and climatic change: questions of temporal and spatial scales", Geoscience Canada 23(4):245-252. [21] IPCC 1997, Eastland and White 1990, Russell 1993, Brotton and Wall 1997, Gunn and Skogland 1997 [22] Anne Gunn, Frank Miller and John Nishi, 1998. "Status of endangered and threatened caribou on Canada's Arctic Islands", abstract, Eighth North American Caribou Conference, Whitehorse, Yukon, Canada, March 1998. [23] Ferguson 1996 [24] A. Gunn, 1995. "Responses of Arctic ungulates to climate change", in David L. Peterson and Darryll R. Johnson (eds.), Human Ecology and Climate Change: People and Resources in the Far North, Taylor and Francis, Washington D.C., pp. 90-106. [25] Jay R. Malcolm, 1996. The Demise of an Ecosystem: Arctic Wildlife in a Changing Climate, World Wildlife Fund Report, Washington, D.C., p. 5. [26] Anne Gunn, personal communication, January 1998 CONCLUSION Increased winter snow depth and summer insect harrassment are likely to reduce food availability, increase energy requirements, and make caribou more vulnerable to predators such as wolves. These projected impacts suggest that continued climate change is likely to reduce caribou populations, and may cause the extinction of vulnerable subspecies such as the Peary caribou. A caribou decline would reduce the availability of food for predators such as wolves and damage a traditional foundation of the northern native economy.