Coastal jewel faces poison blitz

By EUGENE BINGHAM

On the sandy stretch of Tawharanui Peninsula north of Auckland, with its vista up the east coast and out to the deep blue Pacific, there are few clues about the environmental skirmish brewing on two fronts.

If it wasn't for the new fence at the entrance to the regional park and popular beach, which attracts about 90,000 people every year, visitors this week would hardly have been aware of the plans which some believe will have implications for public spaces throughout the country.

The Auckland Regional Council intends turning Tawharanui Regional Park, east of Warkworth, into a sanctuary for native birds and animals - it even hopes to one day introduce the region's first mainland population of kiwi.

As part of its plans the council has declared war on pests and wants to pound them with poison baits dropped by helicopter.

But the aerial bombardment proposal has drawn fire from an environmental watchdog group concerned that the poison, brodifacoum, will kill more than its intended targets and pose a risk to people. The group has also questioned why restrictions on the aerial use of brodifacoum on the mainland should be lifted to allow the operation to go ahead and was worried about the precedent it sets.

"I don't doubt that people are aiming at a good environmental outcome but we don't consider its appropriate to do a saturation poisoning with such a broad-spectrum toxin," said Friends of the Earth co-director, Bob Tait.

Next week, the ARC will argue its case before three independent commissioners who will have to decide whether to grant the council resource consent to take to the skies. Friends of the Earth has opposed it.

Tawharanui, the largest peninsula in publichands, covers more than 500ha. As well as a surf beach which looks out to several islands including Little Barrier, it boasts stands of native trees, bush, wetlands, and pasture used to farm sheep and a Hereford breeding herd.

The ARC's director of heritage, Graeme Murdoch, said the idea to develop the park had been nurtured over the past six years with the help of local Maori and a group called the Tawharanui Open Sanctuary Society.

The society raised money, including about two-thirds of the $660,000 cost of the 2.5km predator-proof fence which now stretches across the peninsula.

Mr Murdoch said for the sanctuary to develop and for there to be any hope of seeing native plants, animals and birds thriving, pests including rats, mice, feral cats, possums, stoats and ferrets must be eradicated.

The council decided that aerial drops of brodifacoum was the best way to do this. If the consent is approved, the council wants to start in August, a year earlier than previously planned.

"There are some risks and there will be some losses but they are way, way outweighed by the benefits," said Mr Murdoch.

As precautions, the park will be closed to the public for about 60 days after the operation, and stock will be moved off for 112 days.

Once the park is re-opened, there will still be free access to the public, but signs at the entrance will warn visitors to be careful they are not carrying pests into the sanctuary. Campers will have gear inspected.

In papers submitted for next week's hearing, the council says it has chosen brodifacoum because it is a proven killer of rodents and rabbits, and believes it will act as a secondary poison to kill other pests such as ferrets and cats.

The New Zealand Food Standards Authority also has to approve the use of the poison because it is currently restricted to islands where stock do not have access.

"The reason for this restriction is the possibility of the persistence of brodifacoum in tissues, particularly kidney and liver, of animals with the potential to enter the food chain," said Debbie Morris, director of the authority's agricultural compounds and veterinary medicines group.

She said the authority was considering the issue under a code of practice designed to manage the potential for residues in livestock.

Mr Tait said Friends of the Earth was worried that if brodifacoum was allowed at Tawharanui, it would be used elsewhere.

The group was concerned about the effects on native birds, and livestock, and did not believe it was clear that the secondary poisoning would work because cats in particular had been known to become wary.

"They are looking at brodifacoum as a magic bullet," he said. "And when you are dealing with huge quantities of a very persistent and broad spectrum poison, we don't think they can be confident about it having no effects beyond minor ones."

Another Friends of the Earth co-director, Paul Stanley, said fernbirds in particular would be at risk. He believed the ARC should use ground-baiting and trapping instead.

But Hamish Alexander, chairman of the Tawharanui Open Sanctuary Society, said he could not understand Friends of the Earth's stance.

"It comes down to how puritanical they want to take things," said Mr Alexander. In the meantime, by opposing the ARC's application, the group was holding up the development an Auckland jewel.

The poison

What is it?

Brodifacoum is considered to be highly toxic and effective at small doses to rodents.

How does it work?

It is absorbed through the gut and leads to fatal haemorrhaging.

Risks to other wildlife?

The main risk is through secondary poisoning when animals feed on the carcasses of poisoned rodents.

Is it risky for humans?

The World Health Organisation says brodifacoum may be absorbed through the gastrointestinal tract or the skin. It says more than 500g would need to be consumed by an adult to cause toxic effects, but warns that children should not be exposed to it. However, The Department of Conservation told the Herald a 15mg dose would be lethal.

Where else has it been used?

For pest eradication on several offshore islands, including Little Barrier and Raoul. On Raoul, there has been no sign of rats since the aerial drop, and 90 per cent of feral cats have been eradicated.