The Department of Conservation will increase its 1080 coverage sevenfold this spring to fight an oncoming plague of rats, mice and stoats.
Doc's top scientist Dr Graeme Elliott said the plague was a result of a ''beech mast'' year, in which beech trees drop seeds that provide an abundance of food for pests.
''Every time you have a beech mast, you get a plague of mice and stoats the following summer.''
Dr Elliott said usually beech masts occurred only in a few forests each year, but this year they had occurred across the country. ''What we're having is a mega-mast year.''
The volume of 1080 poison used in each location would not increase, but it was important to reach as much seeding beech forest as possible.
''We've typically done about 100,000ha a year. This is going to be about 700,000ha in one year.''
The increased cost of this year's pest-killing poison drop would be absorbed into Doc's budget, with some ''stretching and bending'' to accommodate it, he said.
''Once in every five to 10 years, you'll want to spend three years' worth of budget in one year,'' Dr Elliott said.
''But you can return to normal levels after that.''
Bird populations in the Catlins would be under great risk if 1080 was not dropped, Dr Elliott said.
''The Catlins is a real stronghold for mohua, but if we don't do anything, the mohua population will undoubtedly take a big hit,'' he said.
''There will be a drop of 30%-50% of the abundance of birds in that forest, if we don't do something.''
Although a small number of birds might die from 1080 poisoning, a greater number would be saved from predators because of its use.
''If we do a good job, we should expect to see recoveries in a whole lot of birds,'' he said.
''Things like kaka, they used to be incredibly abundant birds.
''Instead of our forests being deserts, they can be back to the kind of levels we had 100 years ago, before this decimation began.
''We'd be swatting parakeets away like sandflies,'' he said.
1080 drops
Planned from August onwards for 18 native beech forests in the following areas. -
Maruia, West Matukituki, Abbey Rocks, Landsborough, Haast Range, Makarora, Hollyford, Dart-Caples, Clinton-Arthur-Cleddau, Kahurangi, Makarora, Eglinton, Kepler, Dusky, Waitutu, Mt Stanley, Waikaia, Catlins.
- Robert Steven
