By SIMON COLLINS
Auckland water supply company Watercare will seek details this week of a plan to drop 1080 poison over a world-renowned wetland just upstream from an intake for the city's water.
Farmers around the 7100ha Whangamarino Wetland, near Meremere, have been told to keep their dogs tied up for five weeks because the poison will kill them if they scavenge any of the expected thousands of possum carcasses.
A possum plague has hit the area and threatens to spread tuberculosis in the country's dairying heartland.
Meremere farmer Peter Buckley said a neighbour recently shot 327 possums on his farm in one night.
However, Meremere sharemilker Cyril Mexted, who was notified of the $140,000 plan by Environment Waikato contractors Epro last week, vowed to do everything he could to stop the 1080 drop.
"What if the cows get it? Ninety-five per cent of my farm boundaries are on the swamp," he said.
"There are enough deer in there for cullers to go through once a year and try to keep them under control. What about all the wildlife they are going to destroy?
"We are meant to be a clean, green country and yet here we are pouring poison into the river."
Whangamarino, listed in 1989 as a wetland of international significance, has more than 20,000 waterbirds, including a quarter of the country's Australasian bitterns.
It drains into the Waikato River just upstream of the Tuakau intake which supplies about 10 per cent of Auckland's water.
Watercare spokesman Owen Gill said the water company would seek details of the poisoning plan when it meets Environment Waikato to discuss other issues this week.
"These drops are not unknown in water catchments in the Hunuas and the Waitakeres under the auspices of the Auckland Regional Council," he said.
"We routinely test anyway for pesticides, including 1080. Given the fact that there is going to be a drop up in the catchment, we'll get an agreement with Environment Waikato and, if necessary, we'll step up the testing."
Epro managing director Roger Lorigan said a helicopter would drop the poison on about 2000ha of the wetland late next month.The satellite-based Global Positioning System (GPS) would pinpoint clumps of trees likely to be favoured by the possums.
"Most of the high ground will relate to where willows are growing. They have a big stump at the base of them andthose are the areas we are trying to treat," he said.
There were "definitely a few thousand" possums in the swamp.
He expected the 1080 would kill 90 to 95 per cent of them within three nights.
"Out of a population, you'll kill 80 per cent of what you're going to kill on the first night, 10 per cent the next night and 10 per cent the next night," he said.
"When we do the poisoning we'll have staff walk the whole perimeter - all the farm edges - to make sure there are no stray drops."
Possums would be left where they died. Their carcasses would have rotted before the duck-shooting season in May.
Mr Buckley, who is vice-president of Waikato Federated Farmers, said farmers were concerned about the danger of poisoned carcasses for dogs.
"But there is a big problem here and I think something has to be done about it. If our overseas markets look at it and say we have TB in our herds and we can't send our produce overseas, we'll have a major problem," he said.
"Probably it's worth keeping our dogs tied up for five weeks to deal with it."
Waikato Medical Officer of Health Dr Dell Hood said a condition of the operation would be that the 1080 did not get into water.
"It's not particularly toxic in water, it degrades quite quickly," she said. "But the principle of dropping these things into water, where it is not going to kill the possums anyway, is unacceptable.
"Certainly we would close drinking water supplies if the level was considered to be unsafe."
Green Party co-leader Jeanette Fitzsimons, who campaigned against using Waikato River water for Auckland, said that "from a scientific perspective, the dilution factor in the Waikato River is going to be massive".
But, the Greens opposed aerial drops of 1080 in places where poisoned bait stations could be laid more carefully by hand, she said.
Since the Whangamarino Wetland was flat, bait stations "could have done it".
Herald feature: Environment
By SIMON COLLINS