Alaska oil fields and wildlife

Endangered species, such as grizzly bears, wolves, and other wildlife, can seriously impact the livestock industry. Ranchers manage their land to benefit wildlife, but have to put up with crop and livestock depredations, pressure from hunters, and habitat regulations.

Other industries also have to deal with wildlife issues. For example, the oil and gas fields on the North Slope of Alaska have been very controversial with regard to impacts on caribou.

The Central Arctic caribou herd ranges in and around the North Slope oil fields, where caribou cows give birth to calves in late May and early June. Government studies in the 1980s and 1990s reported fewer calving caribou within 1 to 4 kilometers (which is about 0.62 to 2.5 miles) of oil field roads than in areas farther from the roads. Wildlife advocates claim caribou avoided the roads with a negative impact on calf recruitment into the herd, and use it to oppose development in new areas such as the Arctic National Wildlife Refuge (ANWR).

However, calving caribou do not completely avoid the oilfield roads and 44 percent of the calves were within four kilometers of the road in the government studies. A published study by the oil industry in the 2000s actually found higher densities of calves within 1 kilometer of the roads than farther away from the roads. It makes sense that calving cows will be sensitive to human activity, but these studies show they might or might not avoid the oil field roads.

In late June and July after the calving period, caribou do not avoid the oil fields and regularly travel through them. Pipelines and roads can block or deflect caribou movements, but elevating pipelines above the ground, separating pipelines and roads, and other measures minimize this impact. Caribou will travel to the Beaufort Sea coast where wind provides relief from intense harassment by mosquitoes and flies. Caribou also congregate on oil field roads and gravel pads and in the shade of buildings and pipelines to escape the insects. There is no hunting allowed in the oil fields. Proper design and operation of oil fields has actually improved caribou habitat.

The caribou herd has grown since the oil fields were developed in the 1970s. The numbers have fluctuated (see the Figure), but not because of oil field impacts, as noted by the Alaska Department of Fish and Game: “The impact of oil infrastructure on Central Arctic herd has also been considered, but is not thought to be contributing to the decline since the herd grew substantially during peak oil development.”

Also, the number of caribou in the herd changes because of mixing with other herds with overlapping ranges. For example, movements between herds contributed to the decline of the Central Arctic herd between 2013 and 2016.  The numbers of caribou are affected by habitat, winter severity, inter-herd mixing, and other factors. Claims that the herd has been negatively impacted by the oil fields are not supported by the available information.

However, government reports still claim that the oil fields negatively affect caribou and ignore or downplay studies showing otherwise. For example, the draft Environmental Impact Statement for oil leasing in ANWR did not reference relevant industry-funded published papers and predicted displacement of calving caribou 2.5 miles from oil fields.

What you can do

Some of you produce oil and gas, timber, and minerals, in addition to livestock, and you might have to deal with claims that your operations negatively affect wildlife, such as sage grouse. You can tell government regulators that their impact assessments often ignore legitimate science, as with the Alaska oil fields and caribou. Tell the regulators and your elected officials what you know about positive and negative impacts on wildlife and your efforts to help wildlife while producing valuable resources. — Dr. Matthew Cronin

(Matthew Cronin was a research professor at the University of Alaska and is now at Northwest Biology Company LLC and an affiliate professor at Montana State University. He can be reached at


Load comments