Bernadette Demientieff says it is a "very scary time" for the Gwich'in indigenous nation as proposed US budget legislation would open a key section of a nearly 20-million acre wildlife refuge in the Arctic up to oil-and-gas development.

The coastal plain of the Arctic National Wildlife Refuge (ANWR), a largely protected wilderness reserve in northeastern Alaska, is a key point on the migratory route of porcupine caribou herds: it is where female caribou give birth and nurse their young.

The Gwich'in - about 9,000 indigenous peoples living in more than a dozen communities in northern Canada and the United States - fear oil-and-gas drilling will threaten that delicate habitat.

"Eighty percent of our diet is the porcupine caribou herd," said Demientieff, executive director of the Gwich'in Steering Committee, which represents the Gwich'in on both sides of the US-Canada border.

Porcupine caribou herds can number as many as 170,000 animals, and up to 40,000 calves are born every year on the coastal plain, according to the committee.

Demientieff said the Gwich'in have a spiritual and cultural connection to the herds and depend on them to maintain their way of life. The Gwich'in even refer to the coastal plain as the "The sacred place where life begins".

"An attack on the Arctic refuge is an attack on the Gwich'in nation," Demientieff told Al Jazeera. "We will stand firm and we will not let this happen."

A partisan fight

The US Senate Committee on Energy and Natural Resources was recently directed to propose a way to lower the federal deficit.

Last week, Republican Senator Lisa Murkowski of Alaska, who chairs the committee, brought forward a motion that would open up the coastal plain "for the leasing, development, production, and transportation of oil and gas".

Murkowski said the plan would generate more than $1bn in the first decade.

She also said it would create jobs, keep energy affordable for families and businesses, and generate new sources of wealth for Alaska and the US as a whole.

"[It] is a tremendous opportunity both for our committee and our country," Murkowski said in a statement.

A meeting to discuss the legislation is scheduled for November 15.

Will put AK&nation on path toward greater prosperity by creating jobs, keeping energy affordable & reducing deficit. https://t.co/0DTGH8mRHQ — Sen. Lisa Murkowski (@lisamurkowski) November 9, 2017

However, critics have accused lawmakers of trying to sneak Arctic drilling - a longstanding and strongly contested issue - into budget legislation.

Since it is technically a budgetary measure, known as reconciliation legislation, Murkowski's proposal can be passed with a simple majority in the US House of Representatives and the US Senate.

Republican Senator James Inhofe of Oklahoma recently told Bloomberg that drilling in the ANWR is only the first step.

"We begin there," Inhofe told Bloomberg. "Anything else we can get in there with a simple majority vote we ought to do."

Senate Democrats, meanwhile, say they will fight the proposal with a budget measure of their own to protect the ecological area, The Hill reported last week.

Senator Ed Markey of Massachusetts called the Republicans' proposal a "heartless ... budgetary scam" and "nothing more than a Big Oil polar payout".

19.4 million acres

An Arctic National Wildlife Range was first established in northeastern Alaska in 1960. That area was incorporated into a larger swathe of land, the ANWR, in 1980.

Today, the ANWR extends over 19.4 million acres (about 7.8 million hectares) of land and water, roughly equivalent to the size of the state of South Carolina.

The area was given federal wilderness status as part of an effort to conserve fish and wildlife populations and habitats, protect the subsistence of local residents and safeguard water quality and supplies.

The ANWR is home to muskoxen and sheep, figures within the migratory route of many waterfowl species, serves as a breeding ground for golden eagles, and black, grizzly and polar bears make their dens within the refuge every year.

It also contains more than 160 rivers and streams, and several lakes.

{articleGUID}

The 1.5 million-acre coastal plain, also known as the "1002 area", sits off the coast of the Beaufort Sea and is the country's "largest unexplored, potentially productive geological onshore basin", according to the US Department of the Interior.

Between 4.3 and 11.8 billion barrels of recoverable oil are believed to lie beneath the plain, according to an environmental assessment dating back to 1998.

However, the coastal plain was not included among the areas designated as protected wilderness in 1980 and "was left in legislative limbo", explained historian Finis Dunaway from Trent University in Ontario, who has studied the political history of the refuge.

"Essentially what they did is they said it would be up to a future Congress to decide whether the coastal plain could be given wilderness status, or whether it could be opened up for development," Dunaway told Al Jazeera.

Caribou face 'decimation'

Porcupine caribou herds migrate through the refuge and northwestern Canada.

Oil and gas exploration on the plain would threaten the herds' delicate migratory route, said Eduardo Sousa, a forest campaigner with Greenpeace Canada based in British Columbia.

"We're really concerned," Sousa told Al Jazeera.

He said oil and gas exploration work, like what is being proposed, would involve drilling into the tundra, bringing in rigs and building roads and other infrastructure.

"That starts to create a sort of fragmenting situation on a habitat that needs to remain whole," he said.

If oil deposits are found and larger projects eventually go ahead, a risk of an oil spill then comes up.

Sousa said that could threaten the caribou herds with a "massive decimation".

"They live in very delicate environments ... If we destroy the calving grounds like that, that's it. Kaput. We're done," he said.

Long-running debate

The fate of the coastal plain is the "longest running, frequently recurring, public land debate in US history", Dunaway said.

A major US government push for oil drilling in the refuge came up during the Ronald Reagan administration in the late 1980s, Dunaway explained, but the Exxon Valdez oil spill in Alaska in 1989, when George HW Bush was newly president, put a temporary stop to any plans.

{articleGUID}

In 1991, the Bush Sr administration put oil exploration in the ANWR into a larger energy package, but a grassroots opposition movement formed to stop that from going forward.

In the mid-1990s, under then-President Bill Clinton, the issue was included in a budget bill, like what is happening today.

But Clinton eventually refused to sign the budget, Dunaway said.

The most recent attempt to greenlight oil and gas exploration in the ANWR came in 2005, under President George W Bush.

The situation then was exactly like today's, Dunaway said, in that the US was led by a "Republican president who no doubt would sign a budget or legislation that would open up the Arctic refuge to drilling".

Canada concerned

Canada, meanwhile, has said it "opposes opening the Arctic Refuge and the 1002 area to resource development" and has "long advocated for the permanent protection of the Arctic refuge".

Christine Constantin, spokesperson for the Canadian embassy in Washington, DC, told Al Jazeera in an emailed statement that Canada and the US also have an agreement in place to protect the porcupine caribou herds' habitat.

"Canada continues to engage the US, other partners, and Indigenous peoples on the protection of land from resource development," Constantin said.

Sousa at Greenpeace said Justin Trudeau, Canadian prime minister, should apply political pressure on the US to preserve the herd's habitat and block any oil exploration in the reserve.

"Trudeau does have a good relationship with [Donald] Trump so I'm hoping he can really press on him to make sure that that area remains protected," Sousa said.

Demientieff added: "This is one of the biggest battles that the Arctic Refuge has ever seen."