But even seemingly untouched corners of the Earth like the Farallon Islands bear human fingerprints. (Courtesy photo)

But even seemingly untouched corners of the Earth like the Farallon Islands bear human fingerprints. (Courtesy photo)

It’s time to reconsider risky plan to eradicate rodents on the Farallones

About 30 miles west of the Golden Gate Bridge lie a small group islands known as the Farallones.


About 30 miles west of the Golden Gate Bridge lie a small group islands known as the Farallones. Squawking, flapping seabirds, rare plants and barking sea lions and seals fill the shorelines and rocky peaks of these islands. Great white sharks, whales and dolphins swim in the nationally significant marine waters below.

For those lucky enough to get a glimpse of the national refuge and marine sanctuary — to which access is restricted — it can feel like a peek back in time to the San Francisco Bay Area before European colonization.

“The Farallones are one of the most amazing places on the planet,” David McGuire, director and founder of the nonprofit Shark Stewards, told me. “It’s wind and wave swept. It feels raw and magical.”

But even seemingly untouched corners of the Earth bear human fingerprints. In the 19th century, European colonists used the Farallon Islands to hunt birds and marine mammals and gather eggs. During the two world wars, the military operated a post on the site, and the U.S. Light Service and U.S. Coast Guard manned a light station there until 1972. These activities resulted in the near to complete extirpation of some species and introduced invasive plants, rabbits and house mice to the landscape.

To restore the ecosystem, the U.S. Fish and Wildlife Service recommended using a rodent poison called brodifacoum to eradicate mice. The preferred method is identified in documents released last month after the agency spent over a decade analyzing different approaches.

It’s a disappointing result. The rodenticide puts many species at risk through direct and indirect exposure. But doing nothing to address mice isn’t an option. The invasive species is threatening wildlife that has called the Farallones home for millennia.

The abundance of mice has attracted burrowing owls to stay on the islands during their fall migration. Unfortunately, when the mice population drops at the start of the rainy season, owls turn to other food sources. The ashy storm petrel, a California seabird considered endangered, is their favored alternative.

As the federal agency tasked with protecting the Farallones, Fish and Wildlife Service officials have a responsibility to address the problem. Other efforts on islands in California and New Zealand have successfully eradicated rodents using brodifacoum. The agency believes dropping pellets from a helicopter will yield the same result on the Farallones.

“Mice are out there in plague-like numbers,” Doug Cordell, spokesperson for the Fish and Wildlife Service, told me. “You have to get rid of every single one or else they’ll bounce back.”

But exposure to the highly potent brodifacoum isn’t limited to mice. Non-target species, such as burrowing owls, other birds and marine mammals, are also at risk. They may eat the rodenticide, or experience exposure by eating an animal that ate the poison. In a letter to the federal agency in 2014, City officials expressed concern about dead gulls washing up on City beaches and Fisherman’s Wharf.

“The Farallones are within the City and County of San Francisco, and this proposed project raises many troubling ethical and environmental questions,” wrote Deborah Raphael, director of the San Francisco Department of Environment. “We feel strongly this project should not move forward with the currently favored option of using brodifacoum.”

There is still time for the Service to reverse course. While the federal agency could approve the approach as early as this month, Cordell doesn’t anticipate a decision until later this year and plans may change.

But doing nothing to address the serious mouse problem shouldn’t be an option. We can’t sit back and let a species vanish into extinction; especially, while the planet is experiencing significant biodiversity loss. We must push for alternate methods proven to protect habitat and wildlife without poison. Until then, it feels like we’re stuck.

“For storm petrels to survive, we need to do something and do something soon,” Pete Warzybok, Farallon Program Leader with the nonprofit Point Blue Conservation Science, told me. “Right now, the rodenticide is the only proven method and the most likely to succeed. But it doesn’t mean rodenticide is always the right solution.”

Concerned readers are invited to review the Service’s documents on the South Farallon Islands Mouse Eradication Project available at the San Francisco Public Library-Main Branch or online. Readers can also voice their support for pending California legislation, AB 1788, that would restrict and ban the use of rodenticides.

Robyn Purchia is an environmental attorney, environmental blogger and environmental activist who hikes, gardens and tree hugs in her spare time. She is a guest opinion columnist and her point of view is not necessarily that of The Examiner. Check her out at robynpurchia.com


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