OVERVIEW AND SUMMARY OF CARIBOU-OIL FIELD RELATIONSHIPS IN ALASKA'S ARCTIC
John W. Schoen, Ph.D.
Senior Scientist
Audubon Alaska
Although the significance of observed short-term effects on Arctic caribou from oil exploration and development is debated by the oil industry because some caribou still use habitats within the Prudhoe Bay and Kuparuk oil fields, particularly during the post-calving period (Cronin et al. 2000), the potential long-term and cumulative effects on caribou nutrition, reproduction, and mortality may be significant. Wolfe et al. (2000) have reviewed the extensive scientific literature regarding the response of reindeer and caribou to human activities.
In the Central Arctic Herd (around Prudhoe Bay), where oil development has occurred on a portion of the calving grounds, cows in the late stage of pregnancy and with newborn calves avoided and shifted concentrated calving away from developed areas, including prime calving and foraging habitat (Whitten and Cameron 1983; Dau and Cameron 1986; Cameron et al. 1992; Nelleman and Cameron 1996, 1998; Murphy and Lawhead 2000; Wolfe 2000). Displacement from calving grounds can result in overcrowding and competition on suboptimal habitat. Decreased forage availability and lower nutrient intake can reduce reproductive rates (Cameron 1995, Nelleman and Cameron 1998). Caribou cows within oil fields gained less weight and exhibited lower calving and calf survival rates than cows outside oil fields (Cameron 1995). Displacement from prime calving grounds may also increase predation (Whitten al al. 1992, Nelleman and Cameron 1998, Griffith et al. 2002, Young et al. 2002).
Generally, some caribou appear to habituate to the presence of structures in oil fields (Ballard et al. 2000) but not to human presence and vehicular traffic (Nelleman and Cameron 1998). Caribou of the CAH avoided areas within 2.5 mi (4 km) of roads and pipelines, functionally increasing habitat loss from 2% (the immediate footprint of roads and gravel pads) to 29% (Wolfe 2000). The sensitivity of caribou to human activity and structures is greater during calving than during insect seasons, greater for maternal than nonmaternal caribou during the calving period, and greater during periods of intense insect harassment versus no insect harassment during summer (J. Dau, ADF&G, Kotzebue, AK, personal communication 2002). For example, Dau and Cameron (1986) clearly showed maternal caribou avoided roads during calving even when traffic levels were low, but nonmaternal caribou did not. During periods of intense insect harassment, some caribou have selected the elevated gravel of roads and shade from pipelines and buildings (Ballard et al. 2000). At Prudhoe Bay, large groups of caribou often crossed roads with traffic and feeder pipelines during intense insect harassment but were reluctant to cross the same areas after insect harassment abated (Dau, personal communication 2002). Air traffic also has stressed parturient and postpartum cows and calves (Yokel 1997). Roads and pipelines and the snowdrifts they cause may impede caribou movements between foraging and insect-relief areas or disrupt normal movements, especially if perpendicular to routes (Gilliam and Lent 1982). Groups of >100 caribou, common when under insect harassment and attempting to move to insect-relief areas at the coast, have greater difficulty crossing roads and pipelines than smaller groups (Smith and Cameron 1985). Raising pipelines and separating them from roads, however, appears to enhance crossing (Curatolo and Murphy 1986). Measures to mitigate oil development impacts that appeared to work during exploration and onset of development may have become less effective as the cumulative effects of expanding development increased and the oil fields became operational (Whitten, personal communication 2002).
Demonstrable development related effects on the portion of the CAH occurring within the oil fields were observed during 1980-2000, despite masking effects of relatively low caribou densities and highly favorable weather on the calving grounds (Wolfe 2000, Griffith et al. 2002). Effects included shifting of concentrated calving from the Kuparuk oil field to the southwest of the field and delayed and deflected movement to and from coastal insect-relief areas (Whitten and Cameron 1983; Dau and Cameron 1986; Cameron et al. 1992; Nelleman and Cameron 1996, 1998; Murphy and Lawhead 2000; Wolfe 2000). Although the CAH increased from about 5,000 animals in 1978 to an estimated 27,000 in 2000, a population decline occurred from 1992 to 1995, followed by a rebound (Cameron et al. 2002). Cronin et al. (2000) argued that population-level impacts from oil field development have not occurred for the CAH. However, comparing the higher growth rate of the TCH to the growth rate of the CAH, Griffith et al. (2002) suggested that the CAH population may have been influenced by development infrastructure after approximately 1987. It appears that although oil field development has had a negative effect on the CAH, favorable environmental conditions, a low density of animals on the calving and post-calving grounds, and available calving area outside the oil fields on the broad coastal plain may have minimized the population-level impacts at this time. If displacement were to occur on a much larger herd like the WACH or PCH, both of which migrate long distances, the population-level impacts could be much higher. Griffith et al. (2002), in fact, have predicted significant population-level impacts to the PCH from industrial development of the concentrated calving ground.
Literature Cited:
Ballard, W.B., M.A. Cronin, and H.A. Whitlaw. 2000. Caribou and oil fields. Pages 85-104 in J.C., Truett and S.R. Johnson, editors. The natural history of an Arctic oil field. Academic Press, San Diego, CA.
Cameron, R.D. 1995. Can petroleum development depress the productivity of Arctic caribou? Proceedings of the 2nd Int. Arctic Caribou Conference 36. University of Alaska Fairbanks, AK .
_____, D.J. Reed, J.R. Dau, and W.T. Smith. 1992. Redistribution of calving caribou in response to oil-field development on the Arctic slope of Alaska. Arctic 45:338-342.
_____, W. T. Smith, R. G. White, and B. Griffith. 2002. The Central Arctic caribou herd. Pages 38-45 in D. C. Douglas, P. E. Reynolds, and E. B. Rhode, editors. Arctic Refuge coastal plain terrestrial wildlife research summaries. U. S. Geological Survey, Biological Resources Division, Biological Science Report USGS/BRD BSR-2002-0001.
Cronin, M., H. Whitlaw, and W. Ballard. 2000. Northern Alaska oil fields and caribou. Wildlife Society Bulletin 28:919-922.
Curatolo, J. and S. Murphy. 1986. The effects of pipelines, roads, and traffic on the movement of caribou (Rangifer terandus). Canadian Field Naturalist 100:218-225.
Dau, J.R., and R.D. Cameron. 1986. Effects of a road system on caribou distribution during calving. Rangifer Spec. Iss. 1:950101.
Gilliam, J.K., and P.C. Lent, editors. 1982. Proceedings of NPR-A caribou/waterbird impact analysis workshop. Bureau of Land Management, Anchorage, AK.
Griffith, B., D. Douglas, N. Walsh, D. Young, T. McCabe, D. Russell, R. White, R. Cameron, and K. Whitten. 2002. The Porcupine caribou herd. In D. Douglas, P. Reynolds, and E. Rhode, editors. Arctic Refuge coastal plain terrestrial wildlife research summaries. U.S. Geological Survey, Biological Resources Division, Biological Science Report BSR-2002-0001.
Murphy, S.M., and B.E. Lawhead. 2000. Caribou. Pages 59-84 in J.C. Truett and S.R. Johnson, editors. The natural history of an Arctic oil field. Academic Press, San Diego, CA.
Nellemann, C. and R. Cameron. 1996. Effects of petroleum development on terrain preferences of calving caribou. Arctic 49:23-28.
_____. and R. Cameron. 1998. Cumulative impacts of an evolving oil-field complex on the distribution of calving caribou. Canadian Journal of Zoology 76:1425-1430.
Smith, W.T., and R.D. Cameron. 1985. Reactions of large groups of caribou to a pipeline corridor on the Arctic coastal plain of Alaska. Arctic 38:53-57.
Whitten, K. and R. Cameron. 1983. Movements of collared caribou, Rangifer tarandus, in relation to petroleum development on the Aarctic slope of Alaska. Canadian Field-Naturalist. 97:143-146.
_____, G. Garner, F. Mauer, and R. Harris. 1992. Productivity and early calf survival in the Porcupine caribou herd. Journal of Wildlife Management 56:201-212.
Wolfe, S.A. 2000. Habitat selection by the calving caribou of the Central Arctic Herd, 1980-1995. M.S. Thesis. University of Alaska Fairbanks, AK.
_____, B. Griffith, and C. Gray. 2000. Response of reindeer and caribou to human activities. Polar Research 19:63-73.
Yokel, D.A., editor. 1997. Proceedings of Teshekpuk Lake Area Caribou/Waterfowl Analysis Workshop. Bureau of Land Management, Fairbanks, AK.
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