Ecological overshoot

"Ecologists are intimately familiar with the overshoot-and-collapse phenomenon. One of their favorite examples began in 1944, when the Coast Guard introduced 29 reindeer on remote St. Matthew Island in the Bering Sea to serve as the backup food source for the 19 men operating a station there. After World War II ended a year later, the base was closed and the men left the island. When U.S. Fish and Wildlife Service biologist David Kline visited St. Matthew in 1957, he discovered a thriving population of 1,350 reindeer feeding on the thick mat of lichen that covered the 332-square-kilometer (128-square-mile) island. In the absence of any predators, the population was exploding. By 1963, it had reached 6,000. He returned to St. Matthew in 1966 and discovered an island strewn with reindeer skeletons and not much lichen. Only 42 of the reindeer survived: 41 females and 1 not entirely healthy male. There were no fawns. By 1980 or so, the remaining reindeer had died off."

From Lester R. Brown's Plan B 2.0: Rescuing a Planet Under Stress and a Civilization in Trouble