Earthquakes and volcanoes filled the former role, and their marks can still be found, but it was the gradual advance and retreat of glacial ice that carved many of the physical features of this refuge.

More than 150,000 caribou from two herds, the Nushagak Peninsula and the Mulchatna, make use of refuge lands, which they share with wolf packs, moose, brown and black bear, coyote, Canadian lynx, Arctic fox, muskrat, wolverine, red fox, marmot, beaver, marten, two species of otter, and porcupine, among other land mammals.

Seals, sea lions, walrus and whales are found at various times of year along the refuge's 600 miles (970 km) of coastline.

Refuge staff and volunteers have also documented more than 500 species of plants, demonstrating a high degree of biodiversity for a sub-arctic area.

This article incorporates public domain material from websites or documents of the United States Fish and Wildlife Service.