Arctic foxes turned Alaskan grasslands into tundra, study finds

A study in the journal Science reports that Arctic foxes introduced to more than 400 Alaskan islands for fur have transformed grasslands into maritime tundra by disrupting nutrient flow from seabird guano. The foxes preyed on seabirds, causing breeding densities to fall nearly 100 times on infested islands. Annual guano input dropped from 361.9 grams per square metre on fox-free islands to 5.7 grams on fox-infested ones.

Researchers from the study compared nine fox-infested and nine fox-free islands in the Aleutian archipelago. They found soil phosphorus was three times higher and grass biomass nearly three times higher on fox-free islands. A fertilisation experiment on a large infested island showed grass biomass increased 24-fold over three years, confirming that nutrient loss drove the shift from grasslands to tundra dominated by shrubs and forbs.

The US Fish and Wildlife Service has removed Arctic foxes from most islands in the Alaska Maritime National Wildlife Refuge as part of restoration efforts.