How the proposed Ambler Road could impact the Western Arctic Caribou Herd
One of the biggest concerns over the proposed Ambler Road is how it would likely impact the Western Arctic caribou herd. If built, the Alaska Industrial Department and Export Authority (AIDEA) has insisted that the Ambler Road would be a 211-mile private industrial-access only road through the southern flanks of the Brooks Range used to develop an unknown number of foreign owned mines.
Caribou are incredibly important to locals and visiting hunters, other species of wildlife, and the land. The Bureau of Land Management’s (BLM) Supplemental Environmental Impact Statement identifies 66 communities whose subsistence activities could be potentially impacted by this road, finding that each of the proposed three routes may significantly restrict subsistence uses in nearly half of these communities.
Some people question if the Ambler Road would really be that bad for caribou and people. They point to the James Dalton Highway, where it’s pretty common to see caribou peacefully grazing nearby. We asked Jim Dau, a retired caribou biologist for the Alaska Department of Fish and Game, to help explain the difference.
Dau has lived in Kotzebue, in northwest Alaska, since 1988. He was the Alaska Department of Fish and Game area biologist for 15 years and then the Western Arctic caribou herd biologist for 10+ years.
Dau began looking at the effects roads have on caribou during graduate school at the University of Fairbanks Alaska, with a study running from 1982-1985. He studied caribou from the Central Arctic caribou herd in the Kuparuk River Oil Fields north of the Brooks Range on the arctic coastal plain. He found that during calving season, maternal females avoided roads, buildings, and other industrial footprints. A month later, under extreme duress from mosquitoes, warble flies and bot flies, caribou would form large aggregations and negotiate roads – even standing in the shade of buildings – to seek relief from these insects in coastal insect relief habitat. Once cool temperatures or high winds reduced insect harassment, roads, traffic and other industrial infrastructure again interfered with caribou movements as they attempted to travel from insect relief habitat to better feeding areas inland.
A2024 study shows that road traffic on the North Slope disrupts caribou more than previously believed. Heather Johnson, a U.S. Geological Survey biologist who coauthored the study was quoted in theAlaska Public Media.
“Caribou are really sensitive,” Johnson said. “They’re really sensitive to human activity. And we’ve seen from past studies that they’re also sensitive to human infrastructure, and they really respond to it. The key takeaway from the paper is they’re more sensitive to road activity than we had previously recognized.”
Dau points out that Alaska has decades of experience showing that caribou can survive roads. But herds that have roads through their range tend to be significantly smaller than herds in roadless areas, such as the Western Arctic caribou herd. Most caribou herds near roads have been intensively managed, often allowing a hunter bag limit of only one caribou—usually a bull with a permit requirement— during a short open season each year.
“Roads can be terrible barriers to caribou, especially when there’s hunting off them or if there’s lots of traffic and other human activities on or along them,” Dau says.
The projected peak daily traffic for the proposed Ambler Road is 168 trips. However, this may be a conservative estimate.
The Western Arctic caribou herd’s range
The Western Arctic caribou herd’s range encompasses around 140,000 square miles of northwest Alaska. Caribou from this herd have wintered as far south as the southern extent of the Nulato Hills west of the lower Yukon River. They calve in the early summer in the northern foothills of the Brooks Range. Dau points out that caribou from the Western Arctic herd have one of the longest migrations of any terrestrial mammal. Some people say caribou don’t know where they are going or travel by instinct, but Dau’s experience suggests otherwise.
“For caribou managers, one of the biggest challenges is giving caribou options for places to go. In any one year, caribou rarely use their entire range. But over the course of decades, they’re going to use—and need—every square inch of it.”
Jim Dau
“I don’t buy that at all,” Dau says. “These animals know movement areas where they’ve gone in the past; plus, they follow deeply embedded trails throughout their range. One of the remarkable things about this caribou herd is the long-term stability it has exhibited in its overall decadal movement pattern combined with shorter term annual and seasonal variability in movements and distribution. In some years, caribou begin moving toward specific portions of their winter range before the first snowflake ever falls.”
There are different variables in how caribou use their range. Caribou show their most fidelity to calving areas, and their least fidelity to winter range. Every 10 to 15 years, Dau has seen shifts in the Western Arctic herd’s winter range.
“Caribou need their entire range,” Dau says. “For caribou managers, one of the biggest challenges is giving caribou options for places to go. In any one year, caribou rarely use their entire range. But over the course of decades, they’re going to use—and need—every square inch of it.”
Differences Between the James Dalton Highway and the Proposed Ambler Road
One prominent difference between the two roads is that the Dalton is a north-south corridor. The Central Arctic caribou herd’s summer-winter migration pattern runs north-south as well. The proposed Ambler Road would run 211-miles east-west, which would bisect much of the Western Arctic caribou herd’s winter range. If caribou from this herd successfully cross the proposed Ambler Road during the fall migration, they would have to cross it again to migrate north during the spring migration. This, Dau and many others believe, could have serious consequences not just for caribou but also for the people that depend on them.
BLM’s Supplemental Environmental Impact Statement states that the Ambler Road would affect migrating caribou in “an expansive area beyond the specific project area. Changes in availability of caribou to subsistence users could be a high-magnitude impact for impacted communities. Population-level effects to caribou are less likely but could be large-magnitude effects and impact all subsistence harvesters throughout the annual range of the herd.”
Dau believes we have a good model of how the Ambler Road would affect the Western Arctic herd and local and visiting hunters. It comes from looking at how caribou have responded to the Red Dog Mine road in northwest Alaska.
Red Dog Mine Road Study
The Red Dog Mine has the world’s largest known zinc deposit and is located 80 miles north of Kotzebue, near the western extent of the Brooks Range. The mine’s road is used to haul ore 52 miles across the Western Arctic caribou herd’s range to a port 10 miles southeast of the village of Kivalina. The Red Dog Mine road is much smaller than the Ambler Road would be and is currently the only industrial mining road in Northwest Alaska of a remotely similar scale.
Dau looked at how the Red Dog Mine road affected caribou movements from the middle of August through November during 1990-2015. In many years, a significant portion of the Western Arctic caribou herd encountered the road during their fall migration to their wintering grounds. Before Dau plotted the data of satellite collared caribou, he thought they weren’t having much difficulty crossing the road based on aerial reconnaissance flights of the road during fall. The data showed otherwise.
“I was shocked. I couldn’t believe it,” Dau says. “The telemetry data clearly showed that caribou approached the road but were usually delayed before crossing it. It often took multiple attempts for delayed caribou to finally cross it. During the fall 2011 migration, on average it took caribou 33 days before they crossed; however, some caribou were delayed up to two months before they crossed the road. Some caribou backtracked up to a hundred straight-line miles while delayed by the road. Of course, caribou rarely travel via straight lines. Many caribou that were delayed by the road traveled several hundred miles during their attempts to cross it. Some caribou never crossed the road. Instead, they wintered north-northeast of it, or they went around it to the east.”
Dau estimated that during the fall 2011 migration, roughly 80,000 caribou were delayed by the road. He found the Red Dog Road affected caribou up to 30 miles away—animals were probably responding to other caribou who’d already bounced off the road. After the caribou finally crossed the road, they put on extra speed to make up for lost time and get to their wintering grounds.
Dau notes that the Red Dog road has negatively impacted hunters. Many villages used to count on at least two months to obtain caribou meat during fall. During years when caribou were delayed by the road, some communities downstream of Red Dog in the fall migration had substantially less than that, and caribou weren’t available until after the onset of rut caused subsistence hunters to shift from taking bulls to harvesting cows. The decline in caribou and hunting opportunities has led to controversial non-local caribou hunting closures on federal land.
The Western Arctic Caribou peaked at 490,000 caribou around 2003. Since then, it has steadily declined and, in 2023, the Alaska Department of Fish and Game reported it numbered 152,000 caribou. Like all wildlife populations, caribou numbers naturally fluctuate up and down. No one fully understands what is driving this current decline, but Dau thinks that warming temperatures are likely a major contributing factor.
“Winter icing events in northwest Alaska have become more frequent and severe since around 2000, and my observations during caribou surveys and while retrieving radio collars from hundreds of caribou carcasses suggested that these events were deadly,” Dau says. “There is never a good time to fragment caribou ranges, but this is a particularly bad time to do so given that climatologists predict that temperatures are going to continue to rise for decades to come, and considering the persistence and degree of this ongoing caribou decline.”
A Valid Concern
Since it went into production, the 52-mile-long Red Dog Road has supported about 80 trips/day by large ore trucks, with additional small-vehicle traffic and road maintenance equipment. Red Dog is the sole industrial mine that uses this road. In contrast, AIDEA has reported that the 211-mile-long Ambler Road will support multiple mines in the Ambler Mining District, and said that communities near the project will be able to connect to this road for commercial deliveries of goods and services. However, AIDEA has provided very little information regarding the maximum number of mines, their size, or the type that the Ambler Road will facilitate. BLM’s Supplemental EIS report for the Ambler Road assumed that this road would support four mines – one for each major mineral deposit – in the Ambler Mining District. This assumption is by no means a binding limitation on the maximum number of mines or level of mining activity in the Ambler Mining District, though. Thus, throughout the original EIS and subsequent Supplemental EIS processes, agencies and the public could only consider potential impacts of the proposed road on the land, wildlife, and people: impacts of a large and possibly ever-expanding industrial mining complex have been ignored.
The only infrastructure along the Red Dog Road is a modest port site located at the coast. The proposed Ambler Road will have multiple buildings, several airports, numerous gravel sites, many large bridges, and other infrastructure located along its length. Given these differences, the Ambler Road will have significantly higher levels of vehicular traffic and other human activity than the Red Dog Road. This will greatly increase the Ambler Road’s potential to delay and deflect caribou movements and magnify its impacts on other fish and wildlife in the project area.
You don’t have to be a biologist to predict that, if built, the Ambler Road would negatively affect the Western Arctic caribou herd. Dau thinks the Ambler Road will have effects similar to the Red Dog Mine road–except at a much larger scale. The project would change the biological and social character of northwest Alaska to the detriment of subsistence users and visiting hunters and anglers.
Caribou, Dau points out, are incredibly important to northwest Alaska. For visitors, a Western Arctic caribou hunt can be a trip of a lifetime. To local people, caribou provide their most important sources of terrestrial meat.
“But it goes beyond that,” Dau says. “Caribou are part and parcel of indigenous subsistence cultures. I cannot overemphasize the importance of caribou to people.”
Photo credit: Jim Dau and Bjorn Dihle
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