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California Coastal Commission approves poison drop on mouse-infested island

Some 60,000 house mice occupy Farallon Islands off the coast of San Francisco, an infestation that has disturbed the ecosystem of the wildlife refuge.

(CN) — Eradicating 60,000 house mice that have infested a wildlife refuge off the coast of San Francisco will take a modern-day Noah’s ark effort, with sensitive burrowing owls, falcons and arboreal salamanders to be moved off the South Farallon Islands so poison can be airdropped on mice who’ve disrupted the natural ecosystem.

The California Coastal Commission approved the complicated, controversial plan 5-3 during an hourslong hearing Thursday night, with vice chair Dr. Caryl Hart and commissioners Roberto Uranga and Carole Groom voting against the plan.

The agency, which approves and regulates land use plans in the coastal zone, heard from U.S. Fish and Wildlife Service about why it should be allowed to move forward with airdropping nearly 3,000 pounds of bait pellets treated with the rodenticide brodifacoum across dry-land portions of the Farallon Islands.

The split vote reflected the spirited debate between environmentalists and scientists on how best to eradicate the mice.

When expressing her support for the plan, commission chair Donne Brownsey noted less invasive, nontoxic alternatives to eliminate the mice were "theoretical" and based on "hope" rather than science which showed deploying rodenticide was the best option for permanently eradicating the pests.

"I hate pesticides, I hate manmade chemicals and the legacy they have just wrought on our environment, on our ecosystems, on our animals and plants and on people. It is painful — here we are in 2021 and this is still the only viable option for eradication," Brownsey said.

Brownsey and some of the other commissioners were able to tour the island, which she called "one of the most transformative nature experiences of my life."

She added: "I do know the potential impacts of this could be we could somehow harm portions of that pristine environment, but it has already been harmed. Human beings created this problem; now I think we have a responsibility to make an incredibly tough decision to fix it."

Thursday’s hearing follows a prior hearing on the matter in 2019, when Fish and Wildlife withdrew its pending application after commissioners expressed concern about potential impacts the poison could have on nontargeted species who inadvertently eat it.

The plan presented Thursday was not all that different from the earlier iteration.

It includes additional information on why Fish and Wildlife Service believes the plan is consistent with the California Coastal Management Plan enforced by the Coastal Commission, including summaries of alternative and nontoxic methods for mouse eradication that were ultimately rejected due to not being effective enough.

Any potential impacts on other island species are expected to be negligible, according to presentations given to the Coastal Commission, as certain tried-and-true methods including hazing of western gulls to prevent them from returning to the islands during the bait application would be employed.

Targeted applications of brodifacoum to eradicate pests has been successful for other island ecosystems, including the formerly named “Rat Island” within the Alaska Maritime National Wildlife Reserve. There, Norway rats were successfully removed in 2008 and bird populations rebounded.

Commission staff recommended approval of the plan contingent on three conditions including the implementation of an independent monitor of bait application and gull hazing efforts; revisions to the Bait Spill Contingency Plan to address moderate and worst-case scenario bait spills, including into the Pacific Ocean; and providing the plan revisions to Coastal Commission executive director Jack Ainsworth to ensure the plan does not result in adverse impacts to environmental sensitive habitat areas, marine resources and water quality.

When voting on the plan Thursday, commissioners added a requirement for a water quality plan. Fish and Wildlife will also come back to the full commission for an informational hearing when the conditions have been fully incorporated.

Supporters of the plan included Senator Dianne Feinstein, the Marin Audubon Society, Marin Conservation League, National Wildlife Refuge Association and International Bird Rescue.

According to a letter of support by the Marin Audubon Society, previous efforts by the U.S. Fish and Wildlife Service to remove feral cats and European rabbits introduced on the Farallon Islands by lighthouse keepers were successful and resulted in the “exponential increase” of tufted puffins and rhinoceros auklet.

“While MAS is opposed to the commercial and private chronic use of rodenticide on the mainland, we recognize that this one-time and controlled use for conservation purposes is acceptable in this instance and in keeping with integrated pest management principles,” the group's president Barbara Salzman and director Roger Harris wrote.

But other environmental advocates didn’t think those proposed conditions were enough to prevent potentially lethal consequences for sensitive species that live on the islands and might be harmed by the poison.

The nonprofit Beyond Pesticides noted in its letter in opposition to the plan that brodifacoum applied in an aerial drop on Palmyra Island off the coast of Hawaii had been found in soil and water, with documented mortality of nontarget organisms.

“As much as we would like to restore native ecosystems, the application of a poison is a toxic, simplified solution to a complex problem that requires the wisdom of nature herself, as species evolve and adapt to new conditions,” Beyond Pesticides director Terry Shistar wrote, asking for a supplemental environmental impact statement to be conducted.

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