Where: Northern Alaska, United States

What's at stake: Critical sanctuary for Arctic wildlife

Threatened by: Oil drilling

Animals include: Polar bear, beluga whale, bowhead whale, Arctic wolf, caribou, yellow-billed loon, tundra swan, Pacific brant

• Established in 1960, the Arctic National Wildlife Refuge is the second largest and most northerly of the United States' 500 wildlife refuges. Spanning 19 million acres -- an area roughly the size of South Carolina -- it includes 18 major rivers flowing through a range of Arctic landscapes, from spruce-covered valleys to Arctic tundra. The Arctic coastal plain of the refuge is the birthing ground for the Porcupine Caribou herd and for polar bears.
• Nestled between the high glaciers of the Brooks Range and the lagoons and ice floes of the Beaufort Sea, the refuge's wind-swept coastal plain is often likened to Africa's Serengeti because of its abundant wildlife. This 1.5-million-acre expanse -- considered by scientists the biological heart of the refuge -- is the also the land most sought after for drilling by oil companies.
• The refuge is one of the few ecosystems that's home to all three North American bear species. Polar bears and grizzlies roam the coastal plain; black bears inhabit the broad valleys south of the Brooks Range.
• At least five species of marine mammals live in or near the Beaufort Sea along the coastal plain's northern edge. These include spotted seals, ringed seals, bearded seals, beluga whales and endangered bowhead whales.
• The Western Arctic Reserve provides crucial nesting habitat for the Steller's eider, one of several species named for Georg Wilhelm Steller, a German naturalist who accompanied Vitus Bering on his pioneering voyage from Russia to Alaska in 1741. Now threatened, this black-and-white duck was once common in parts of western and northern Alaska.
• Roughly half of Alaska's Arctic peregrine falcons nest in the river systems and highlands of the Western Arctic Reserve's interior coastal plain.
• Researchers have discovered the fossils of 13 different dinosaur species along the Colville River, which flows through the Western Arctic Reserve along the northern slope of the Brooks Range before joining the Arctic Ocean. They also have found mammoths with their soft tissue still intact.
• The Utukok Uplands, which span some 4 million acres in the southwest corner of the Western Arctic Reserve, provide critical calving grounds for the vast Western Arctic caribou herd. Numbering roughly 430,000 animals, the herd sustains some three dozen Alaskan Native villages.
• Due to the extreme cold, short growing season and nutrient-poor soils, Arctic vegetation is extremely fragile. Plant communities scarred by bulldozer tracks, oil spills and other human activities can take decades to recover.