Huge By-Kill of Brodifacoum Poison
Huge by-kill of brodifacoum poison
I don’t live in Nelson so dropping 26.5 tonnes of brodifacoum poison into the Brook Waimarama Sanctuary won’t affect me directly, but I care a lot about New Zealand wildlife. I'm the Waikato Regional Councillor for Taupo-Rotorua, and the current Chair of the Environmental and Services Performance Committee.
ACRE, a group that advises Waikato Regional Council, asked councillors to look into our use of brodifacoum during our last Long Term Plan. They were concerned about the bio-accumulation and persistence of brodifacoum in wildlife, and the implications for our food chain. Our EPC Chair at the time, Clyde Graf, agreed to a review.
We invited Penny Fisher, a scientist at Landcare Research to give us readings about brodifacoum and other second-generation anticoagulant rodenticide residues in wildlife. She did a teleconference with our committee; We gathered information from other councils and government agencies and we looked at what’s happening overseas.
A lot of the New Zealand data about brodifacoum by-kill concerned me:
The entire western weka population was exterminated in a brodifacoum drop on Tawhitinui Island (1984); Nearly 60% of the Tawharanui Regional Park dotterel population died through eating brodifacoum baits and poisoned sand-hoppers (2004); Brodifacoum residues continued to be found in wildlife more than 24 months after the brodifacoum poison drop in and around the Rotoiti Nature Recovery Project in Nelson (2005); The Rangitoto and Motutapu Island eradication by-kill included dolphins, penguins, fish, numerous dogs and birds. Vast numbers of dead mussels washed up on Waiheke Island up to five months after the poison drop. Hundreds of dead birds also washed up on Coromandel Peninsula beaches in the months following (2009); More than 10,000 seagulls were killed in Shakespear Regional Park (2011);
Blue cod, mussels, limpets and birds had brodifacoum residues in them after the Ulva Island drop, prompting restrictions on harvesting. Dead robin nestlings on the island were found to have brodifacoum residues, indicating that poisoned invertebrates had been fed to the young birds. Nearly 90% of the weka population was also killed (2011); Brodifacoum and other anticoagulant residues were found in freshwater fish, eels and sediment in Southland (2012); After Great Mercury Island was poisoned, 16 dead seals and a multitude of birds and fish washed up dead on Coromandel beaches (2014); A Landcare Research study of road-killed harrier hawks revealed 78% of those tested had at least one anticoagulant rodenticide in them. Some had as many as four different types. Brodifacoum was common.
It’s dangerous stuff, no doubt.
I asked Auckland Council for the results of their monitoring of feral pigs on islands in the Hauraki Gulf. The reply stated that 13 out of 14 pigs tested positive for brodifacoum residues. Brodifacoum has now been confirmed in fish, shellfish, pigs, bats, deer, eels and birds across New Zealand, which is a concern for those who hunt and fish. There’s also concern for those who commercially harvest wildlife. MPI notified a restricted procurement area for feral pigs in Marlborough due to high levels of brodifacoum residues in pig livers in 2004.
Why would we use brodifacoum when our own scientists have expressed concern about residues persisting in the environment?
Penny Fisher said in 2013 in her Overview/Summary – Environmental Residues of Anticoagulants Used for Pest Control, 10 June 2013.
“There is increasing evidence that uses of anticoagulants for both household rodent control and field pest management are resulting in widespread contamination of both terrestrial and aquatic wildlife. The latter is presumably through carcasses of poisoned animals entering waterways ….”
According to MPI, brodifacoum is the most inhumane toxin we’ve got, causing pain and suffering for days to weeks before an animal succumbs to internal haemorrhaging. Apart from the lethal effects, brodifacoum also causes sub-lethal reproductive and developmental damage. Would you choose to use brodifacoum if you knew it was also going to harm and kill the native species you’re trying to protect?
Personally, I'd prefer to find another method of pest control that’s acceptable to the Nelson community. There are plenty of alternatives.
Kathy White is the Waikato Regional Councillor for Taupo-Rotorua and the current Chair of the Environmental and Services Performance Committee. This is her personal view.