Alaskan island’s seashore ecosystem makes a full recovery in 11 years after removal of invasive rats

A conservation effort that removed rats from one of the islands in Alaska’s Aleutian archipelago has become a new example of how ecosystems can fully recover to their natural state in little more than a decade. 

Formerly known as Rat Island, a coordinated conservation effort conducted by Island Conservation, the US Fish and Wildlife Service, and The Nature Conservancy removed the rats on the renamed Hawadax Island with poison in 2008.

Alaska’s Aleutian Islands are home to tens of millions of seabirds, making this far-flung archipelago one of North America’s 10 birding hotspots — and the best seabird habitat in North America.

Along the western edge of the Alaskan archipelago, the land had inadvertently become populated with rodents, who were introduced to these islands following shipwrecks dating back to the 1700s and World War II occupation.

Known to be among the most damaging invasive animals, the rodents disrupted the natural ecological order and drove out native species. Rats preyed upon shore bird eggs and chicks, nearly wiping out the island’s breeding shorebird population. Without birds consuming herbivorous seashore invertebrates such as snails and limpets, the island’s intertidal plant-eaters flourished, significantly driving down the abundance of the marine kelp.

After the rat eradication effort in 2008, the seabirds returned and are again consuming the seashore invertebrates, which has allowed the recovery and rebound of the kelp community. Monitoring trips found native seabird species are benefiting in the absence of rats, including species like the Leach’s storm-petrel, a nocturnal seabird otherwise at very high risk of predation by rats because of their small size and conspicuous calling activity to attract mates. 

In 2012, the Unangan name of the island was officially restored after a campaign led by Indigenous people with deep cultural ties to this remote region. The US Board on Geographic Names made the name change official after a petition from the Aleutian Pribilof Islands Association to restore the Native name “Hawadax” to the island.

The recovery of the island was documented by a team of researchers from the University of California, who were able to compare the ecosystem after five years and, later found a fully recovered system after 11 years.

In a study published in Scientific Reports last month, Carolyn Kurle, associate professor at the University of California San Diego Division of Biological Sciences Section of Ecology, Behaviour and Evolution and lead author of the study, wrote: “We were surprised that the level of recovery unfolded so quickly – we thought it could be longer.

“Sometimes it’s hard to say that a conservation action had any sort of impact, but in this particular case we took a conservation action that was expensive and difficult, and we actually demonstrated that it worked. But we didn’t expect it to be so fast.

“When the birds returned it led to an entirely different structure in the marine community on this island.”

Around the world, introduced non-native species such as rats are a leading cause of extinctions in island communities. According to The Nature Conservancy, invasive rats have been introduced to about 90 percent of the world’s islands and are responsible for 40 percent to 60 percent of all recorded island bird and reptile extinctions.

The restoration of Hawadax Island is one example of new global efforts to eradicate invasive species in otherwise healthy island ecosystems.

Rosa Medea is Life & Soul Magazine’s Chief. She writes about lifestyle including sustainable and green living. 

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