Native bird populations could be completely wiped out in some areas hit by this year's mega mast.
It's set to be the biggest seeding event in more than 40 years, but half-a-million hectares of forest will receive no 1080 predator control.
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"There's a huge number of rats, and there will be a huge number of stoats in our forests this year," says Peter Morton, of the Department of Conservation (DoC).
The threat to birdlife this summer is so much higher because climate change is making our native bush go through an explosion of seeding. That causes a chain reaction - the more seeds the more birds, the more birds the more rodents.
"We'll lose some of our most precious treasures in those forests," says Forest and Bird ecologist Rebecca Stirnemann.
One example is a whio nest Newshub saw. The eggs laid by a little blue duck were no match for a stoat, which stole three eggs of the endangered species in the space of 10 minutes.
With heavy seed fall expected, Fiordland all the way up to the East Cape will be hit the hardest.
But areas like Nelson Lakes National Park, the Tararua Ranges and the Tongariro Forest won't get any DoC-funded predator control.
In those regions populations of whio, kokako and kiwi could be wiped from the map.
"In years without 1080 we lost 90 percent of all our kiwi chicks, they were just decapitated by stoats, killed," says Stirnemann.
By closely watching the forests DoC has been able to estimate that the number of predators will be near saturation point.
So much so that they're expecting to see rodents in some tunnels 96 percent of the time.
The Department of Conservation believes around 1.4 million hectares of native forest is at risk of being swamped by predators this mega mast season, however, just 900,000 hectares will be covered by the current 1080 drop, leaving half-a-million hectares of native bush still at risk.
The total cost of dropping 1080 on 900,000 hectares comes to around $38 million.
Forest and Bird claim an extra $20 million is needed to cover all at-risk areas.
But Conservation Minister Eugenie Sage says the real problem is a lack of both personnel and time.
"There have been constraints in terms of the sheer number of helicopters and the weather windows, the drops need to be done when it's dry, there have been some issues with weather," says Sage.
Even if many say DoC is not going far enough, it is hoped that the effort will go some way to controlling the problem.