St. Matthew Island is an uninhabited, ribbon-shaped island in the Bering Sea, with a total of about 128 square miles. It has no trees; the vegetation is lichens, mosses, grasses and low-lying shrubs. It’s one of the most remote places in the United States. The only naturally occurring mammals are a single species of vole and Arctic Foxes.
During World War II, the U.S. Coast Guard established a navigation station on St. Matthews. As a back-up food supply for the Coast Guardsmen stationed there, the Coast Guard introduced reindeer, domesticated caribou; 24 females and 5 males, in 1944. At the end of the war, the navigation station was shut down, the Coast Guard left and the reindeer remained.
In 1957, when Dr. David Klein visited the island, the population had expanded from 29 animals to 1,350. In 1963, the population had exploded to some 6,000 animals. While in 1957 the animals had been fatter and larger than the average mainland population, in 1963 the animals were under weight and there were far fewer calves.
In the harsh winter of 1963-64, the population crashed to 42 animals, 41 females and one infertile male.
The implications would seem to be obvious. In the absence of population regulation, predators in the case of reindeer, or human hunters, and with no means to migrate, a population will grow geometrically, considerably beyond what the habitat will support, and then catastrophically crash. Dr. Klein also documented the long-term alterations to the natural ecosystem of St. Matthew Island. Lichens grow very slowly.
[A lay description of these events by Ned Rozell is here. Dr. Klein’s original paper, missing most of the tables, is here. There’s even a comic version by Stuart McMillen here. Ned Rozell visited St. Matthews Island in 2012 and his report is here.]
The reindeer experience on St. Matthews Island gets cited a lot of inapposite purposes. In particular, it’s not necessarily a model for what will happen to humans on the larger island that is Planet Earth. Because humans, after all, can decide whether or not to reproduce. We’re not governed solely by instinct. But a choice implies a decision. We’re not doing so well so far.
And the current state of the planet makes this one of those situations where not deciding is itself a choice. Probably a fatal one.