In 1959, two New Brunswick men released a dozen snowshoe hares on Hay Island, a small island in the Bay of Fundy, to provide a source of income and a bit of amusement during the long days of winter when they weren’t fishing. They figured they could sell the trapped hares for $3 a head to hunting clubs on the mainland.

Introducing a species into a ecosystem, particularly on an isolated island, can have disastrous effects. The hares multiplied and spread to nearby Kent Island, the location of the Bowdoin Biological Field Station. There the animals devoured tree seedlings and saplings, destroying the island’s forests of red and white spruce, balsam fir, tamarack, heart-leafed and yellow birch, mountain maple and mountain ash. “The islands’s forests were becoming transformed into open tangles,” describes Nat Wheelwright, the Anne T. and Robert M. Bass Professor of Natural Sciences at Bowdoin.

The loss of trees threatened several forest-breeding birds, including the island’s population of Leach’s storm petrels, which has been continuously monitored by scientists and students since 1954.

In a new article published in The Ecological Society of America’s journal, Frontiers in Ecology and the Environment, Wheelwright tells the story about how the hares decimated the islands’ woods and how they were finally eradicated. He was director of the Bowdoin Scientific Station from 1987 to 2004.

“Something had to be done to control the snowshoe hares,” Wheelwright writes. “Authorities on pest control recommended poisons, viruses, antifeedants, falconers, traps, lynx, dogs and professional hunters.” He dismissed viruses and poisons because they can jeopardize other species. And introducing outside predators, such as lynx or dogs, would threaten the seabird colony.

In 1998, Wheelwright launched a hunting and trapping program with permission from New Brunswick’s government. But just two years later, the population rebounded to its former size. Again he tried in 2002, but again, the hares rebounded. “In desperation,” Wheelwright said, he consulted the head of New Zealand’s office of vertebrate control, which is famous for eliminating problem species from islands worldwide. She told Wheelwright that getting rid of the hares from a small island like Kent was “trivial,” and accused him of not trying hard enough.

So Wheelwright said they tried harder, and finally in 2007, successfully trapped the last hare. “The response of the plant community to the elimination of an introduced keystone herbivore was immediate and dramatic,” he writes. Many young trees now blanket the island’s forest floor, and more young trees are bolting skyward. “Boreal forests that have long provided nesting habitat for birds and other animals are now able to recover and flourish,” he says.