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Close to Home: Farallon Islands ecosystem at risk

  • In this photo taken Thursday Oct. 13, 2011, California sea lions are shown at Seal Cove at the Farallones National Wildlife Refuge, Calif. This chain of small rock islands that jut sharply out of the Pacific Ocean 27 miles west of San Francisco is known as “California's Gallapagos” for its abundance of squawking seabirds, barking sea lions and great white sharks. Yet amid this menagerie lives an intruder: brown house mice brought by human vessels from another time that have now colonized here in a density unseen anywhere else in the world, researchers said. (AP Photo/Eric Risberg)

Looking westward from the Golden Gate out at the Farallon Islands, we're often reminded that we are privileged here to proudly protect our lush ocean waters within one of America's flagship national marine sanctuaries.

Amid this natural beauty, however, a new threat is emerging in which a multitude of wildlife species on these islands suddenly face an unforeseen jeopardy — the proposed aerial broadcast of 40 helicopter loads of what's known as a "supertoxic" poison, in the form of the already-controversial rodenticide called brodifacoum. The broad ecosystem dangers posed by this new generation of persistent rodenticides to "non-target" species throughout the food chain are well known to scientists and veterinary caregivers, causing these chemicals to come under increasing regulatory scrutiny by both the Environmental Protection Agency and the California Department of Pesticide Regulation.

The Department of Interior now says it wants to prevent mice that were accidentally introduced on the Farallones back in the 1800s from attracting migrating burrowing owls, which, once there, sometimes also become opportunistic predators of the recovering population of a seabird called the ashy storm petrel. Interior's stated goal is to repeatedly poison all of the mice, hoping to thereby induce the few burrowing owls found at the islands during the autumn to depart, thus hopefully enabling the ashy storm petrel population to increase in numbers (unless the owls decide to instead start eating ashy storm petrels due to the new shortage of mice).

But while there are few owls, this convoluted Interior Department scheme contains more than a few notable flaws of logic and a lot of potential for extremely dangerous unintended consequences.

This very powerful poison causes mice, and any bird or mammal that eats enough of them, to slowly bleed to death over the course of about 20 days, while any unconsumed rodenticide remains toxic on the ground for up to 120 days, depending on the weather.

Due to the persistent and nonspecific nature of the poison and the well-known tendency of seabirds to be attracted to the poison pellets as food, and also because birds of prey and seabirds can obviously be expected to eat dying and dead mice, the killing of non-target species has been a serious problem during a previous application of the same poison using the same techniques in Alaska. During the Alaska catastrophe, the same approach "accidentally" caused the unanticipated mortality of 46 eagles and nearly 400 gulls. If we repeat this here, seabirds exposed to the poison on the Farallon Islands could be observed dying unpleasant deaths along the Sonoma and Marin coastlines, or on San Francisco's Fisherman's Wharf, a grotesque but newsworthy attraction not helpful to our visitor-serving regional economy.

We should not be condoning any level of "collateral damage."

Society faces no compelling reason to rush forward with scattering poison throughout our entire national marine sanctuary ecosystem in the unconfirmed hope of perhaps getting rid of a few misplaced burrowing owls. There will almost certainly be found a more targeted way to rid the islands of mice, if we are patient until it is uncovered by an approach to sound science that generates fewer damaging side effects.

If you wish to comment on this proposal to the Department of Interior, please do so by Monday in support of the "Alternative A, no poisoning" option, by pasting this online link into your Internet browser: https://tinyurl.com/toxicislands.

<i>Richard Charter, a resident of Bodega Bay, is a senior fellow with the Ocean Foundation, helped to organize the original grassroots and local government support leading to the 1981 designation of the Gulf of the Farallones National Marine Sanctuary, and currently serves as vice-chairman of the Gulf of the Farallones National Marine Sanctuary Advisory Council.</i>


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