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Close to Home: Farallon Islands ecosystem at risk

  • A view of Seal Cove at the Farallones National Wildlife Refuge. (ERIC RISBERG / Associated Press)

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.

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