Proposed Stewart Island 1080 Drop An Ecological Disaster?

A planned aerial 1080 drop for next year to rid Stewart Island (Rakiura) of Norway rats and other pest species is running into growing opposition.

Among the opposition or doubters that includes not only local residents but conservationists, there are even some scientists and surprisingly even the Department of Conservation.

DoC scientists Phil Bell and Al Bradley in a scoping report were sceptical and said “we do not consider that it is technically feasible to eradicate rats, cats, and possums from Stewart Island at this time".

However Zero Invasive Predators (ZIP) has been engaged to lead the planning and delivery of the Predator Free Rakiura project.

In conjunction with 1080 poison, ground-based tools, such as traps and bait stations, will also be used in and around people’s residences, including around Oban township.

Te Puka Rakiura Trust (TPRT) and the Department of Conservation are working closely with ZIP as the project transitions to the new operating model.

“Zero Invasive Predators (ZIP) is a non-profit organisation founded by DOC and the NEXT Foundation,” says ZIP’s blurb.

But people are increasingly not convinced.

Dairy farmers Mary and Lindsay Molloy of Harihari on the West Coast have a holiday home at Stewart Island where they regularly and often stay.

“I am gutted at the stupidity of those who poison to satisfy their hideous extermination policies,” she said.

Mary who has first hand experience also of ZIP’s poisoning on the West Coast of the Perth-Whataroa-Okarito-Franz Josef wilderness said the organisation has falsely claimed to have poisoned predators there. Based on ZIP’s failure at Whataroa she is adamant that she will resist attempts to enter their Stewart Island property.

“I for one will evict ZIP or DoC people who get near our Stewart Island house,” she says.

Blanket Poisoning

Scientist Dr. Jo Pollard is critical of DoC’s recent aerial poisoning of nearby Ulva island with brodifacoum toxin and said she had no faith in the proposed blanket poisoning of Stewart Island.

DoC’s actions are negligent since previous DOC poisoning drops on Ulva Island had devastating effects with several native bird species being killed in considerable numbers. She described as “totally irresponsible” ZIP’s and DoC’s attitude to investigating by-kill.

“That was clear in November 2021 when ZIP poisoned over 550 native black-backed gulls (Larus dominicanus), whose bodies appeared on the beaches of a south Westland river in the Perth valley area after a 1080 drop,’ said Dr Pollard.

In a reply to an OIA request, DoC defended ZIP, saying “they had not known there were so many gulls in the area.” Then more of the gulls were killed by ZIP’s poisoning in May 2022.

“The fact that many more species were likely being poisoned off in large numbers, but less obviously, was not acknowledged by either ZIP or DoC,” said Dr. Pollard. “Unbelievably, monitoring of any other creatures’ survival or recovery was only ‘incidental and anecdotal’ when ZIP researchers aerially poisoned with 1080 baits twice at extra high density, a few months apart, in “research” attempting to get rid of all rats, stoats and possums.”

The toxin 1080 was first patented in the 1920s as an insecticide. Insects are vital to pollination and as food for insectivorous birds on Stewart Island such as fantails, grey warbler, bush-wren, robins, rifleman, tomtits and others while other invertebrates such as earth worms are the food for the island’s brown kiwi.

Rat Explosion

Landcare Research studies also show that the rats that survive 1080 drops (usually plus or minus 15%), with abundant food available, accelerate breeding and within 18 months have regained or well overshot pre-poison levels. “Rats are invasive, fast breeding, opportunistic feeders – and after 1080, survivors and immigrants multiply exponentially. Not only are many native animals killed in the poisoning, within months the rat plague causes further ecological disruption and damage” she said.

Trying to control nature with poisons has not gone well for DoC in its other “island eradications” of mammals. On the Antipodes Islands, the monitored species of native birds were severely culled in aerial poisoning, which was followed by an apparent takeover by introduced hedge sparrows. On Fiordland islands, where predators (Norway rats and stoats) were removed, South Island robins (Petroica australis) have flourished and ousted other species.Laurie Collins, a retired Forest Service officer who as a trainee was involved in the first 1080 trials in Wakatipu’s Greenstone valley in the late 1950s, suspects ZIP’s plan is a disguised attempt to poison the whitetail deer, a herd unique to the island. Yet ZIP says in publicity “deer are not a target species for Predator Free Rakiura.”

Deer Kill

But Laurie Collins is not convinced.

“The fact is deer do get poisoned by aerial 1080 drops,” says Laurie Collins. “And ZIP and DoC must know that plus in zealously following their anti-introduced animal ideology, they’ll kills countless native birds and insects,” he says. “It’s grossly irresponsible, more so as they’re funded by public’s tax money.”

Predator Free Rakiura is planning to use a 10,000ha trial block at the southern end of Stewart island (Rakiura) in Autumn 2025, to asses what is needed to then extend the operation to remove possums, feral cats and hedgehogs across the remainder of the island.

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