Congress and the Carter administration doubled the size of the refuge, to 18 million acres, in 1980 under the Alaska National Interest Lands Conservation Act, renaming the area as the Arctic National Wildlife Refuge. (With an addition, it is now 19.6 million acres.) Native people retained their hunting rights, and licensed trophy hunters were permitted to kill Dall sheep and caribou.

The refuge also includes the 1.5 million acre “1002 area” adjoining the Arctic Ocean. This swath of coastal plain is thought to be rich in oil and gas, and even though vast portions of the Arctic slope and coastal waters of northern Alaska are open for oil leasing and drilling, the Trump administration, and oil interests and their allies in Congress want to invade and squander this pristine area, which takes up less than 5 percent of the coastal plain.

This part of the Arctic slope extending northward from the Brooks Range to the Arctic Ocean is a critical site for polar bears to make their dens and give birth. It is also the calving ground of America’s largest caribou herd, which migrates widely through the region. The Gwich’in Indians of Arctic Village in the Brooks Range and the Inupiat of Kaktovik on the coastal plain depend on the animal for food and clothing.

The Gwich’in call the calving area that oil companies hope to develop “the sacred place where life begins.” As Trimble Gilbert, chief of Arctic Village, said: “We hurt because we see the land being destroyed,” and added that “we believe we have something to teach the world about living a simple life, about sharing, about protecting the land.”

On the 50th anniversary of the Murie expedition in 2006, the explorer and author Jonathan Waterman organized a return trip to the Arctic refuge. We joined the team, along with graduate students Forrest McCarthy and Betsy Young.

It was exhilarating for Dr. Schaller to return after 50 years and still find no roads, no buildings, no garbage. On the Sheenjek River, even an eagle nest he had seen on a cliff in 1956 was still there. Arctic loons still called near our camp on Last Lake, and caribou continued to meander across the coastal plain as we floated first the Canning and then the Hula Hula Rivers.