By Deborah Jacobs
As politicians debate oil exploration in the Arctic National Wildlife Refuge (ANWR), public attention has turned to the caribou. Due to their large numbers, lengthy migrations, and importance to traditional Alaskan cultures, these ruminants are probably the most prominent animal species on the North Slope of Alaska.
Opponents of oil exploration often evoke the image of migrating herds of caribou. On its Web site, the National Audubon Society (2001) warns that "no suitable alternative habitat exists for the Porcupine Caribou Herd if they are driven from their calving grounds by oil development." It even says that the Department of the Interior predicts that oil development will "contribute to" a 20 to 40 percent decline in the caribou population, although it does not give a source for this claim.
Oil exploration since 1968 around Prudhoe Bay on the North Slope does not seem to have negatively affected the Central Arctic caribou herd. And there is little evidence that the Porcupine herd, which journeys through the area proposed for oil drilling in ANWR, will suffer harm.
Nestled in Alaska's northeast corner, ANWR covers 19.6 million acres of the state's 365 million acres. In 1980, Congress divided the refuge into three parts: 8 million acres of wilderness, 10 million acres of wildlife refuge that would remain off limits to oil drilling, and 1.5 million acres, known as section 1002, which can be explored for oil if Congress approves. Section 1002 represents only 8 percent of the total refuge, and less than 4 percent of Alaska's total coastal plain and foothills zone (U.S. Fish and Wildlife Service 2001).
In many years, the Porcupine herd of 130,000 caribou migrates through section 1002, where cows give birth to their calves. Opponents of oil development in ANWR contend that exploration and development threaten the herd. They point to evidence that some individual caribou in the Central Arctic herd have been harmed and contend that the Porcupine is more vulnerable because it is a much larger herd affecting a smaller area.
The Central Arctic herd migrates annually from the foothills of the Brooks Range, where it spends the fall and winter, north to the Beaufort Sea coast in the spring and summer. It inhabits the Prudhoe Bay oil field during summer and early fall as cows calve and suckle their young (Maki 1992, 1702).
In terms of overall health, the Central Arctic herd has prospered (Cronin et al. 1998; Maki 1992; Pollard et al. 1996). In 1972, according to the Alaska Department of Fish and Game, the herd numbered 3,000 animals. Since then it has increased to between 25,000 and 27,000 (Maki 1992, 1703). The caribou population fluctuates naturally, reflecting factors such as predation, parasites, habitat condition, hunting, and weather (Cronin et al. 1998, 201).
Several studies conclude, however, that the oil facilities have displaced some Central Arctic caribou, especially females (Nelleman and Cameron 1996; Whitten and Cameron 1983; Whitten et al. 1992). In 1996 Nellemann and Cameron concluded that the oil facilities have displaced many maternal females from a zone within 4 km of development structures. They also found that the number of males and females in the area surrounding the infrastructure declined by 52 percent, with a 43 percent increase in use of terrain that was 4Ð 10 km from surface development (Nellemann and Cameron 1996, 23). Thus, they suggest that the caribou are staying away from the surface development, and this may lead them to overeat the vegetation further away, possibly leading to a reduction in nutrients.
Another hypothesis is that oil field developments impede the females' typical eastwest movement during late summer. The Alaska Department of Fish and Game studied caribou movements from 1975Ð1978 in the Prudhoe Bay region. Individual caribou were collared and their movements tracked. The study found a higher percentage of bulls near the road system. Away from the roads there was no significant difference in the percentages of bull and cow sightings. From this the researchers concluded that cows avoid the oil-related facilities (Whitten and Cameron 1983, 145).
However, the authors acknowledge that "this comparison may be misleading, since cows apparently retained collars longer than did bulls" (144). With a disproportionately larger total number of cows sighted, the number of cows near the development represents a smaller percentage than the percentage of bulls nearby. If the females do avoid certain structures, it has had no measurable impact on the herd.
Challenging the claim of individual displacement is the well-documented fact that during the herd's summer migration route the caribou walk under pipelines, which are five feet above ground-"to spare the animals a limbo-bar maneuver" (Newsweek 2000). Aerial studies of the Prudhoe Bay oil fields have shown many caribou on and around surface structures (Cronin et al. 1998, 197). Noel et al. (1998, 408) observed that "even when disturbed by moving vehicles, caribou most commonly just move to another location on the pad rather than leaving the pad."
The oil fields help relieve the caribou from insects that harass them. Studies have shown that gravel pads and roadbeds keep some insects away. In the absence of these surfaces, the caribou move to the coast, using energy in the process and moving farther away from their inland grazing grounds (Pollard et al. 1996, 649).
The Porcupine herd is much larger than the Central Arctic herd. Section 1002 is one-fifth the size of the Central Arctic herd's calving grounds but is used by six times as many animals (U.S. Fish and Wildlife Service 2001). The caribou roam through ANWR during a 930- mile yearly migration that stretches across Alaska and Canada. They visit section 1002 for only two months, similar to the time spent by the Central Arctic herd at Prudhoe Bay.
Some argue that if maternal females are displaced, suitable alternative habitat might not be available (Urquhart 2001). Scientists at the University of Alaska at Fairbanks say that caribou cows and calves are sensitive to human disturbances. Thus, oil development could disrupt calving patterns and decrease the number of surviving young (Pearce 2000).
Other evidence casts doubt on this view. The U.S. Fish and Wildlife Service has been investigating the impacts of potential oil development on wildlife in section 1002 for the past fifteen years. Fish and Wildlife officials point out that the herd roams over a vast expanse of territory, and calving has historically occurred over a fairly large area of the North Slope and the Yukon Territory (Urquhart 2001).
Even if oil development could disrupt the migration of females, improvements in technology in the last thirty years make the surface footprint of the facilities very small. The facilities at Prudhoe Bay cover 5,000 acres, or 2 percent of the oil field surface area. The 1.5 million acres of section 1002 can be explored and developed on less than 2,000 acres, or 0.14 percent of the section (Arctic Power 2001). Joseph Hegna of ARCO Alaska states: "We can explore without leaving footprints. And the footprint required for new developments is a tenth of what it once was" (quoted in Revkin 2001).
Improved three-dimensional underground survey technology and directional drilling allow for more precise, efficient, and far-reaching discovery and extraction of oil and gas reserves. Surface reserve pits, the core of environmental damage in the past, can now be eliminated through the use of waste re-injection. New ice chip roads will melt in the summer, when caribou inhabit the area. Pipelines will be elevated, as at Prudhoe Bay, and punctuated by elbows to allow for caribou movement around the field and to reduce accidental oil spills (Revkin 2001).
Companies know more about caribou management, too. They can limit exploration to the nine to ten months of the year when the caribou are hundreds of miles away.
The weight of evidence suggests that the oil facilities built in the late 1960s have not visibly harmed the caribou that migrate through the Prudhoe Bay area. While there are speculative reasons to be concerned about the larger herd of caribou migrating in ANWR, the evidence of likely harm is weak.
Arctic Power. 2001. ANWR Information Brief: Technology. February. Available: www.anwr.org. Cited May 7, 2001.
Cronin, Matthew A., Warren B. Ballard, James D. Bryan, Barbara J. Pierson, and Jay D. McKendrick. 1998. Northern Alaska Oil Fields and Caribou: A Commentary. Biological Conservation 83(2): 195Ð208.
Maki, Alan. 1992. Of Measured Risks: The Environmental Impacts of the Prudhoe Bay, Alaska, Oil Field. Environmental Toxicology and Chemistry 11: 1691Ð706.
National Audubon Society. 2001. Protect the Arctic from Oil Drilling. Available: www.protectthe arctic.com/history.asp. Cited May 7, 2001. Nellemann, Christian, and Raymond Cameron. 1996. Effects of Petroleum Development on Terrain Preferences of Calving Caribou. Arctic 49(1): 23Ð28.
Newsweek. 2000. An Arctic Battlefield: Billions of Barrels of Oil Lie beneath a Pristine Wildlife Refuge. July 10, 46.
Noel, Lynn E., Robert H. Pollard, Warren B. Ballard, and Matthew A. Cronin. 1998. Activity and Use of Active Gravel Pads and Tundra by Caribou within the Prudhoe Bay Oil Field. Canadian Field-Naturalist 112(3): 400Ð409.
Pearce, Fred. 2000. Sink or Swim. New Scientist 167(2250): 16.
Pollard, Robert H., 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): 649Ð58.
Revkin, Andrew C. 2001. Hunting for Oil: New Precision, Less Pollution. New York Times, January 30.
Urquhart, Doug. 2001. Oil Development and Caribou Science: The Porcupine Caribou Range in Alaska's National Wildlife Refuge. Available: arcticcircle.uconn.edu/ArcticCircle/ANWR/ anwrcaribouscience.html. Cited May 7, 2001.
U.S. Fish and Wildlife Service. 2001. Potential Impacts of Proposed Oil and Gas Development on the Arctic Refuge's Coastal Plain: Historical Overview and Issues of Concern. January 17, 2001. Available: arctic.fws.gov/issues1.html. Cited May 7, 2001.
Whitten, Kenneth, and Raymond Cameron. 1983. Movements of Collared Caribou in Relation to Petroleum Development on the Arctic Slope of Alaska. Canadian Field-Naturalist 97(3): 143Ð45.
Whitten, Kenneth R., Gerald W. Garner, Francis J. Mauer, and Richard B. Harris. 1992. Productivity and Early Calf Survival in The Porcupine Caribou Herd. Journal of Wildlife Management 56(2): 201Ð11.
Deborah Jacobs was a research assistant at PERC during the past academic year. She begins work as a commodity merchandiser for Archer Daniels Midland in July.