A big swath of inland Wanganui forest will soon get pest control for the first time in 10 years, as part of the "battle for our birds".
The battle has been mainly to combat the plague of rats and stoats building up in South Island beech forests after a year when beech trees have produced profuse amounts of seed. When that runs out, predators such as rats and stoats usually turn on protected native wildlife, including birds, frogs, insects and lizards.
Conservation Minister Nick Smith has said predator numbers could reach "biblical proportions" this year. There are already five times as many rats as usual and that number could double.
Stoat numbers increase while there are plenty of rats around, and stoats pose an even greater risk to native birds.
Most of the effort and the $9 million-$12 million national cost of the battle will involve the South Island.
But Conservation Department (DoC) staff also made a case for some predator control in the Waitotara Conservation Area. It will be done in conjunction with regular pest-control work in the Whanganui National Park under the Kia Wharite initiative. The Whangamomona Conservation Area also gets a share.
The cost across all three areas will be $467,000, an average of $9 a hectare, DoC Whanganui partnerships manager Jasmine Hessell said.
The areas are remote and rugged and the 1080 poison baits will be applied mainly from the air. Application will probably happen in late August and will need a period of fine weather.
One piece of land - 23,000ha in the Waitotara Conservation Area - will be getting its first pest control since 2004. Pest numbers there are expected to be high.
Waitotara is in the Nga Rauru rohe (tribal area) where iwi have been concerned about degradation of the forest, kaiwhakahaere (CEO) Anne-Marie Broughton said. "The canopy is dying ... It's being decimated by pests."
The tribe discussed the pest-control effort. Members accepted the use of 1080 poison, but would have preferred another method. "... it's the best tool in the box, given the geography of our land."
DoC staff are pleased to have additional resourcing to treat the Waitotara Conservation Area.
Possum, rat and stoat numbers are likely to be lower in Whanganui National Park, where pest control is done every three years as part of the Kia Wharite project. But monitoring in the Matemateaonga area has found large numbers of rats, and the pest control will take in 28,000ha of that.
The Whanganui/Waitotara area does not have high numbers of beech trees, so pest numbers there are not a result of the extra beech seed. Ms Hessell said the pest operation there was to protect important species, such as North Island brown kiwi and whio (blue duck). Without control, only 10 per cent of kiwi survived to breeding age. Monitoring showed 70 per cent lived if predators were controlled.
There will be a drop of non-toxic baits across the remote forest two weeks before the poison baits are dropped. Baits with poison will be 2cm-long and dyed green. The baits for possums will be 12g. Baits for rats will be half that weight.
Poison baits will not be dropped near huts or water, and rangers will be on the ground to pick baits off tracks. Warning signs will be put up, and only one or two kilos of bait will be applied per hectare.