St. Matthew Island () is an uninhabited, remote island in the Bering Sea in Alaska, west-northwest of Nunivak Island. The entire island's natural scenery and wildlife is protected as it is part of the Bering Sea unit of the Alaska Maritime National Wildlife Refuge.
The island has a land area of , making it the 43rd largest island in the United States. Its most southerly point is Cape Upright which features cliff faces which exceed . Similar heights are found at Glory of Russia Cape on the north, and the highest point, above sea level, lies south from the island center.
There is a small island off its northwestern point called Hall Island. The wide sound between the two islands is called Sarichef Strait. A small rocky islet called Pinnacle Rock lies to the south of Saint Matthew Island.
The United States Coast Guard maintained a staffed LORAN station on the island during the 1940s.
Geology and climate
The climatic conditions in the entire Bering Sea Area, according to National Climatic Data Center (1986), is reported as maritime with "considerable wind and cool, humid and cloudy conditions" with mean annual temperature of and annual precipitation of on St. Matthew Island. The geological formation recorded on St. Matthew Island consists of calc-alkaline volcanic rocks of Late Cretaceous and earliest tertiary age with Pergelic Cryaquolls and Pergelic Cryoborolls soil types.
Human habitation
The first recorded attempt at settlement occurred in 1809, when a Russian group led by Demid Ilyich Kulikalov, under the guise of the Russian-American Company, established an experimental outpost.
A 2013 sailing expedition to the island showed that, in spite of the lack of human habitation, extensive areas of beach were heavily contaminated with plastic marine debris, particularly from the fishing industry.
Mammals
Presently, Arctic foxes and insular voles are the only mammals resident on the island, though polar bears occasionally visit via pack ice. Notably, St. Matthew Island represents the southern limit of the range of polar bears in the Bering Sea.
In 1944, 29 reindeer were introduced to the island by the United States Coast Guard to provide an emergency food source. The Coast Guard abandoned the island a few years later, leaving the reindeer. Subsequently, the reindeer population rose to about 6,000 by 1963 and then died off in the next two years to 42 animals. A scientific study attributed the population crash to the limited food supply in interaction with climatic factors (the winter of 1963–64 was exceptionally severe in the region). By the 1980s, the reindeer population had completely died out. Environmentalists see this as an issue of overpopulation. For example, ecologist Garrett Hardin cited the "natural experiment" of St. Matthew Island of the reindeer population explosion and collapse as a paradigmatic example of the consequences of overpopulation in his essay An Ecolate View of the Human Predicament.
Birds
Despite its high latitude, St. Matthew Island contains significant populations of endemic and migratory birds. In fact, the Department of the Interior has called the island "one of the richest seabird nesting colonies in the world", with over 5 million seabirds nesting during breeding season. Over 140 different species of birds have been identified on the island. The island, along with its small satellites Hall Island and Pinnacle Rock, contains the entire breeding range of McKay's Bunting. Additionally, a subspecies of Rock Sandpiper (Calidris ptilocnemis ptilocnemis) and a subspecies of Gray-crowned Rosy-Finch (Leucosticte tephrocotis umbrina) breed only on the island and the nearby Pribilof Islands. Both McKay's Bunting and Calidris ptilocnemis ptilocnemis, with their restricted breeding ranges, are among the rarest birds in North America, making their preservation among the top priorities for conservation groups.
Fish
There are two major lakes on the island, North Lake and Big Lake. The lakes contain a greater number of fish species (at least 5) than other nearby islands.