The U.S. Fish and Wildlife Service has agreed to withdraw a controversial proposal to exterminate tens of thousands of invasive mice on the Farallon Islands, 27 miles off the coast of San Francisco.
The agency's decision came after a California Coastal Commission hearing on Wednesday, during which commissioners and members of the public voiced concerns about the plan, which involves bombarding the environmentally sensitive national marine sanctuary with 1.5 tons of rat poison.
The commission was hearing public comment on the extermination plan, which has drawn criticism from local conservation groups, as it sought to determine whether the plan complies with California's coastal management rules.
The U.S. Fish and Wildlife Service said in a report presented to the commission in March that a massive house mice population is threatening the whole ecosystem on the rugged islands, which are also a National Wildlife Refuge.
The archipelago is home to the largest seabird breeding colony in the contiguous United States, with approximately 300,000 to 350,000 birds of 13 species, including rare ashy storm petrels. The islands are also used by marine mammal species for resting and breeding, and by migratory birds.
Watch a KQED Science video about the Farallon Islands, produced in 2009:
Federal wildlife officials proposed using helicopters to dump 2,900 pounds of cereal grain pellets laced with brodifacoum, an anticoagulant that causes rodents to bleed to death, which is banned in California.
Officials had acknowledged the plan would kill some seagulls and other species, but argued that the benefits of eliminating the invasive species would heal the whole ecosystem.
"The only way to protect these species and allow the ecosystem to recover is 100% eradication of the mice," said Pete Warzibok, a biologist who has worked on the Farallon Islands for more than 20 years. "Anything else is simply a stopgap measure that will not adequately address the problem."
Critics argued the poison will not only kill the mice — first introduced by ships that stopped in the islands 200 years ago — but also wildlife on the island and scavengers that would feed on the carcasses of the poisoned animals.
"These poisons are deadly, they persist in the environment for hundreds of days and they do kill animals," said Alison Hermance, the spokeswoman for the conservation group WildCare.
"The situation on the Farallon Islands has existed for decades. It does not need to be solved overnight with a massive poison drop," she said.
The commission had no power to veto the plan, but before federal officials could have proceeded, the plan would have required approval from various state and federal agencies.
After a nearly two-hour hearing, commissioners said they still have questions on the impact to seabirds and other species.
"We haven't been convinced that this is the best and only way to go," Commission Chair Dayna Bochco said.
The commissioners asked federal officials to withdraw the proposal and resubmit it after their questions have been answered.
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.
This post includes reporting by The Associated Press and KQED's Chloe Veltman.
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