An Alien's Long Reach
A study of the Aleutian Islands shows how the effects of introduced species can spread in unpredictable ways
WHEN FUR TRADERS introduced foxes onto some Aleutian Islands in the 1700s, the predators quickly wiped out huge colonies of ground-nesting seabirds--and ultimately transformed entire ecosystems.
In a survey of dozens of islands, researchers found that on those colonized by foxes, scrubby tundra has replaced the lush grasslands that still carpet fox-free islands. Based on soil nutrient tests, they conclude that native vegetation relies on fertilization by seabird droppings. The study, published in Science, "shows how the effects of introduced species can spread in unpredictable ways," says lead author Donald Croll, a University of California–Santa Cruz ecologist.