29
Nov
Aerial Drop of Rodenticides on Farallon Islands in California Threatens Ecosystem, Comments Due
(Beyond Pesticides, November 29, 2021) The U.S. Fish and Wildlife Service (FWS) is reviving its proposal to aerially apply (by helicopter) the toxic rodenticide brodifacoum to kill house mice on the Farallon Islands National Wildlife Refuge off the Northern California coast. Globally significant wildlife populations inhabit the Farallones, including hundreds of thousands of seabirds and thousands of seals and sea lions. According to FWS, these include: thirteen species seabird species that nest on the islands including Leach’s Storm-petrel, Ashy Storm-petrel, Fork-tailed Storm-petrel, Double-crested Cormorant, Brandt’s Cormorant, Pelagic Cormorant, Black Oystercatcher, Western Gull, Common Murre, Pigeon Guillemot, Cassin’s Auklet, Rhinocerous Auklet, and Tufted Puffin; pinnipeds including Northern fur seals, Steller sea lions, California sea lions, harbor seals, and northern elephant seals that breed or haul-out onto Farallon Refuge; and endemic species including white sharks, hoary bats, and arboreal salamanders.
Brodifacoum is a “second generation anticoagulant rodenticide” (SGAR) that is highly toxic to birds, mammals, and fish. It also poses a secondary poisoning risk to predators. The California Department of Pesticide Regulation quotes the FWS: “Secondary exposure to SGARs is particularly problematic due to the high toxicity of the compounds and their long persistence in body tissues. For example, brodifacoum, a common SGAR, is persistent in tissue, bioaccumulates, and appears to impair reproduction… Even in cases where the proximate cause of death has been identified as automobile strike, predation, or disease, toxicologists and pathologists have attained sufficient toxicological evidence to conclude that rodenticide-induced blood loss increased animal vulnerability to the proximate cause of death.” The threat of secondary poisoning has led the state of California to ban the use of brodifacoum for almost all uses. Although this particular use is an exception, the risks of the use are extremely high.
Aerial application of brodifacoum places at risk the mammalian and avian wildlife on the Farallon Islands, as well as marine life that may be exposed when the poison washes or settles into the ocean. There is no way to limit the impact to the targeted house mouse. A 2015 study conducted after aerial drop of rodenticides on Palmyra Island off the coast of Hawaii reported: “We documented brodifacoum [rodenticide] residues in soil, water, and biota, and documented mortality of nontarget organisms. Some bait (14–19% of the target application rate) entered the marine environment to distances 7 m from the shore. After the application commenced, carcasses of 84 animals representing 15 species of birds, fish, reptiles and invertebrates were collected opportunistically as potential nontarget mortalities. In addition, fish, reptiles, and invertebrates were systematically collected for residue analysis. Brodifacoum residues were detected in most (84.3%) of the animal samples analyzed. Although detection of residues in samples was anticipated, the extent and concentrations in many parts of the food web were greater than expected.”
Home to rare, endemic seabirds such as the ashy storm-petrel, the Farallon Islands certainly have a serious mouse problem – 59,000 rodents occupy the rocky islands. Mice compete with native species for resources and attract an average of six burrowing owls a year. Owls prey upon ashy storm-petrels when mouse populations drop during the winter, killing hundreds of petrels annually. The global population of the ashy storm-petrel is small (10,000 – 20,000), but it is not considered an endangered species.
As important as native ecosystems are, the application of a poison is a toxic, simplified solution to a complex problem that requires the wisdom of nature herself, as species evolve and adapt to new conditions. The SEIS should investigate the possibility of controlling the mice through controlled intensified predation by providing nesting boxes for barn owls and/or kestrels.
Tell the California Coastal Commission to deny the proposed aerial dispersal of the highly toxic rodenticide brodifacoum on the Farallon Islands.
Letter to California Coastal Commission:
I request that you deny the proposal to aerially apply (by helicopter) the toxic rodenticide brodifacoum to kill house mice on the Farallon Islands National Wildlife Refuge. Globally significant wildlife populations inhabit the Farallones, including hundreds of thousands of seabirds and thousands of seals and sea lions. These include: thirteen species seabird species that nest on the islands; pinnipeds including Northern fur seals, Steller sea lions, California sea lions, harbor seals, and northern elephant seals; and endemic species including white sharks, hoary bats, and arboreal salamanders.
Brodifacoum is a “second generation anticoagulant rodenticide” (SGAR) that is highly toxic to birds, mammals, and fish. It also poses a secondary poisoning risk to predators. The California Department of Pesticide Regulation quotes the FWS: “Secondary exposure to SGARs is particularly problematic due to the high toxicity of the compounds and their long persistence in body tissues. For example, brodifacoum, a common SGAR, is persistent in tissue, bioaccumulates, and appears to impair reproduction… Even in cases where the proximate cause of death has been identified as automobile strike, predation, or disease, toxicologists and pathologists have attained sufficient toxicological evidence to conclude that rodenticide-induced blood loss increased animal vulnerability to the proximate cause of death.” The threat of secondary poisoning has led the state of California to ban the use of brodifacoum for almost all uses. Although this particular use is an exception, the risks of the use are extremely high.
Aerial application of brodifacoum places at risk the mammalian and avian wildlife on the Farallon Islands, as well as marine life that may be exposed when the poison washes or settles into the ocean. There is no way to limit the impact to the targeted house mouse. A 2015 study conducted after aerial drop of rodenticides on Palmyra Island off the coast of Hawaii reported: “We documented brodifacoum [rodenticide] residues in soil, water, and biota, and documented mortality of nontarget organisms. Some bait (14–19% of the target application rate) entered the marine environment to distances 7 m from the shore. After the application commenced, carcasses of 84 animals representing 15 species of birds, fish, reptiles and invertebrates were collected opportunistically as potential nontarget mortalities. In addition, fish, reptiles, and invertebrates were systematically collected for residue analysis. Brodifacoum residues were detected in most (84.3%) of the animal samples analyzed. Although detection of residues in samples was anticipated, the extent and concentrations in many parts of the food web were greater than expected.”
Home to rare, endemic seabirds such as the ashy storm-petrel, the Farallon Islands certainly have a serious mouse problem – 59,000 rodents occupy the rocky islands. Mice compete with native species for resources and attract an average of six burrowing owls a year. Owls prey upon ashy storm-petrels when mouse populations drop during the winter, killing hundreds of petrels annually. The global population of the ashy storm-petrel is small (10,000 – 20,000), but it is not considered an endangered species.
As important as native ecosystems are, the application of a poison is a toxic, simplified solution to a complex problem that requires the wisdom of nature herself, as species evolve and adapt to new conditions.
Please deny a finding of consistency of the proposed aerial dispersal of the highly toxic rodenticide brodifacoum on the Farallon Islands and require that a Supplemental Environmental Impact Statement (SEIS) be conducted by an independent body examining alternatives, including the no action alternative and nontoxic integrated control methods. The SEIS should investigate the possibility of controlling the mice through controlled intensified predation by providing nesting boxes for barn owls and/or kestrels.
Thank you for considering this request.
Thank you for this information. It will be a tragedy in so many ways if this poison drop takes place. Many of us appreciate your broadcasting this to your broad audiences.
November 29th, 2021 at 8:55 pmConsider an alternative. Otherwise all life will perish on the island.
November 30th, 2021 at 1:15 am