Fur traders released Arctic foxes across Alaska's Aleutian Islands in the late 1800s to boost the fur trade, but the predators wiped out millions of nesting seabirds before decades-long eradication campaigns began

Picture a string of remote Alaskan islands so lush they resembled gigantic meadows floating in the Bering Sea. Now think of those very islands, decades later, stripped of their low scrubby plants, with few birds left in the sky. That transformation actually happened, and the surprising culprit was foxes.

In the study ‘Introduced Predators Transform Subarctic Islands from Grassland to Tundra,’ published in Science, biologist Donald Croll and co-authors found that introducing Arctic foxes to Alaska’s Aleutian Islands devastated local seabird colonies. It changed island ecosystems, replacing grassy areas with tundra. This is a pretty wild example if you ever wondered how one small human decision can quietly rewire nature for a century.

Why were foxes introduced to these islands in the first place
This story begins with money, not malice. Russian traders made the first recorded fox introduction in 1750, releasing arctic foxes on Attu Island, the westernmost island in the chain, according to a historical U.S. Fish and Wildlife Service report by biologist Edgar Bailey. But it was in the late 1800s that the practice turned into a full-blown industry: after the U.S. bought Alaska in 1867, the government began formally leasing Aleutian islands for commercial fox farming in 1882, and fur traders ramped up releases island by island. By the 1930s, more than 450 islands had been stocked, with demand peaking between 1915 and 1936, according to the U.S. Fish and Wildlife Service.


It was essentially an early, unregulated fur farming business. Traders put foxes on the islands because ground-nesting birds provided an easy food source. Great for the fur trade. Horrible for pretty much everything else living there.

Birds that never learned to be afraid
Here’s the part that makes this story so remarkable. Seabirds had nested on islands without land predators for thousands of years, so they had no defenses. They nested in the open, on the ground, in burrows, in the ledges of rocks. When the foxes showed up, it was not so much a hunt as it was an all-you-can-eat buffet.

Species that nest on the ground or in burrows, such as puffins, terns, and the Aleutian Canada goose, were especially hard hit. Biologists couldn't locate a single Aleutian Canada goose anywhere between 1938 and 1962, the U.S. Fish and Wildlife Service noted, until a small remnant population was discovered on one remote island that the foxes had never reached.

The twist nobody expected: dying grass
Losing millions of birds was devastating in itself, but it triggered a second, slower disaster that took years for anyone to notice.

Seabirds do more than live on these islands; they also fertilize them. Their droppings contain nutrients pulled from the ocean, which serve as free fertilizer for the naturally nutrient-poor volcanic soil. Croll and his co-authors found that islands that were still infested with foxes had breeding seabird densities about two orders of magnitude lower and guano input about 60 times smaller than islands that had always been fox-free. With fewer birds, the islands received far less natural fertilizer, and the soil could no longer support the tall grasses that once covered them.

A separate paper backs this up in more detail. Using nitrogen isotope tracking in plants and soil, ecologist John Maron and his research team, in a study published in Ecological Monographs, verified that the transfer of ocean nutrients to land was effectively severed when seabird colonies collapsed.

The paper adds that it wasn't just fewer birds on the shore: the authors found that fox-free islands had higher soil phosphorus and higher plant tissue nitrogen than fox-infested islands, though soil nitrogen itself didn't differ significantly between the two. Elevated δ15N signatures in soils and plants on fox-free islands pointed to a heavier reliance on marine-derived nutrients, while fox-infested islands relied more on internally recycled nutrients. In a four-year fertilization experiment, graminoid biomass increased 24-fold, shifting the plant community toward the lush, grass-dominated state typical of fox-free islands.

The result is a chain reaction: introduce a predator, lose the birds, lose the fertilizer, lose the grass, and end up with tundra.

A cleanup effort that took decades
After the ecological impact became clear, the U.S. Fish and Wildlife Service launched one of the longest-running restoration projects in American wildlife history. Since 1949, teams have been trapping and removing foxes, island by island, in a slow and difficult process that has continued for more than 70 years.

Results have been real. The Aleutian Canada goose population grew from a few hundred birds in the mid-1970s to about 6,300 by 1990, enough to move the subspecies from endangered to threatened, according to the U.S. Fish and Wildlife Service. The Aleutian Canada goose was officially removed from the list of endangered species in March 2001. Seabird colonies have returned to islands where foxes are now gone, and the vegetation has grown greener again.

Why does this still matter today
This is not just a quirky historical side note. It is a clear lesson in how interconnected ecosystems are. The choice to put foxes on islands for fur farming, a decision made solely to increase profits, ended up changing an entire landscape in ways no one involved could have predicted.

The Aleutian Islands are a dramatic case study for anyone concerned about biodiversity, conservation, or just how fragile natural systems can be. One tiny, seemingly harmless change silently rewired an entire ecosystem, and unravelling the damage has taken generations.