It serves as a magnet for a wide diversity of wildlife species and is strategically located along migration corridors serving both the Pacific and Central Flyways. The refuge has been identified as one of 500 Globally Important Bird Areas by the American Bird Conservancy.

The National Park Service designated the South Marsh a National Natural Landmark because of the biological diversity and pristine condition of the habitat. The refuge is one of the most important waterfowl nesting areas in the Great Basin and intermountain West.

The South Marsh supports the largest population of nesting canvasback ducks west of the Mississippi River (outside Alaska), and holds the highest concentration of nesting canvasbacks in North America. Due to habitat loss elsewhere in the Great Basin, the refuge has become increasingly important to resident wildlife, including mule deer, pronghorn antelope, and sage grouse. The refuge fishery is popular with local anglers.