Fur traders introduced Arctic foxes across Alaska's Aleutian Islands to produce pelts; by killing seabirds, the foxes helped turn lush grasslands into tundra

• The foxes reduced seabird populations, which meant less nutrient-rich guano reached the islands.
• Arctic foxes introduced to more than 400 Alaskan islands for fur changed far more than the local wildlife.
• According to a study published in journal Science, by preying on seabirds, they disrupted the flow of nutrients from the ocean to land and helped turn some of the Aleutian Islands from grasslands into maritime tundra.