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Federal government tinkering with plan to poison Farallon Islands

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“This highly toxic rodenticide, it’s like dropping a nuclear bomb on this island”

The Farallon Islands from the air. Photo by Jan Roletto

The U.S. Fish and Wildlife Service wants to move forward with plans to drop 1.5 tons of rat poison on San Francisco’s Farallon Islands. However, after a Wednesday hearing with the California Coastal Commission, the federal agency has agreed to rethink the proposal.

The feds want to wipe out invasive mouse species on the uninhabited islands, which lie roughly 30 miles off the coast of SF.

“House mice are impacting the native ecosystem of the islands, including several native species and wilderness,” notes a March Fish and Wildlife report. “Eradicating invasive mice is expected to benefit native seabirds, amphibians, terrestrial invertebrates, and plants and will help restore natural ecosystem processes on the islands. Eradicating house mice would eliminate the last remaining invasive mammal species on the refuge, enhancing the recovery of this sensitive ecosystem.”

Mice and other invasive species hopped a ride to the isolated islands on ships starting in the 19th century. Dubbed “omnivorous opportunistic feeders,” the mice compete with native species for food and may prey on the eggs of rare birds that rely on the island as breeding areas.

That report concluded that “aerial broadcast of the rodent bait”—that is, dropping poison from helicopters—would wipe out the mouse population. Per documents submitted to the coastal commission:

Bait would be systematically applied to all land areas of the refuge above mean high water by a GPS-guided helicopter. Up to 12 acres of the Islands may require hand-baiting within caves and adjacent to intertidal zones, and bait stations would be placed in, under, and outside the two Island residences and four out-buildings. The project would be implemented in the November-December time period when the mouse population is declining and food stressed, and would occur no sooner than late 2020.

The poison is designed to become inert after 120 days. Architects of the plan admit that the toxins will kill animals other than mice, but argue that the impact on other populations will be minimal.

Fish and Wildlife representative Larry Simone told commission members Wednesday that similar campaigns have been waged in other areas and “nearly every one has been successful, and a lot of those were much more complicated.”

But the commission appeared highly skeptical despite these assurances.

“This highly toxic rodenticide, it’s like dropping a nuclear bomb on this island,” Commissioner Roberto Uranga said, predicting that “the effects would be much longer lasting” than promised.

“What if it fails? If you put all this poison all over this island and it fails [...] that is personally very disturbing to me,” asked Commission Chair Dayna Bochco.

“We ask that you not set a precedent that it’s okay to use poison on wildlife,” Alison Hermance, a spokesperson for the conservation group Wildcare, pleaded during public comment. She, along with other environmentalist groups, suggested that the island mouse problem could be solved through less toxic means.

In the end, Bochco declared “we haven’t been convinced” and asked that the federal agency back off from the plan and come back when more of their questions could be answered.

The Farallon Islands are a wildlife refuge maintained by the Department of Fish and Wildlife. According to the California Academy of Sciences, “The Farallones host globally significant wildlife populations, including hundreds of thousands of seabirds and thousands of seals and sea lions.”

Due to the sensitive nature of the environment, the islands are closed to the public.