The Department of Conservation (DOC) is planning to ramp up its predator control in South Island beech forests - including the use of the controversial 1080 poison - ahead of potentially the biggest masting (seeding) in the last 7-years.

Beech forests naturally mast or seed every two to six years, providing a short-term windfall of free food - and a population spike - to introduced rats and stoats.

However when optimal climatic conditions trigger a beech 'mega mast', predator numbers can explode, putting additional pressure on Aotearoa's native birds and other fauna once the beech seed has been consumed.

DOC’s National Predator Control Programme Manager, Peter Morton, said the mega mast seeding would most likely be in western areas from Kahurangi at the top of the South Island to Fiordland.

“We are planning a bigger predator control programme than usual over the next two years to protect our most vulnerable native species like mohua, rock wren and pekapeka from beech-seed fuelled plagues of rats and stoats.

“Operations will be focused on the best surviving populations of endangered wildlife in Kahurangi, Mt Aspiring, Arthur’s Pass and Fiordland national parks.

Mohua/Yellowhead. Photo: DOC

“We know if we do nothing, native species will be decimated."

"Some of our last surviving mohua populations are hanging on by a thread and there’s a risk with a surge in predators we could lose them,” Morton said.

Morton said DOC's monitoring had shown that carefully timed aerial 1080 operations prevented large spikes in predator numbers, enabling birds and bats to survive and breed successfully.

“Controlling predators is one of the most important actions we can take to protect nature."

"People can do their bit of ‘naturing’ by setting traps in their backyards, joining a local trapping group or donating, as we work towards New Zealand’s Predator Free 2050 goal,” Morton said.

Beech mast response operations will be focussed in two rounds – later this year before seed falls in autumn and from late 2026, once seed has been eaten or germinated.

Rock Wren. Photo: Digby Shaw/DOC

This avoids times when beech seed carpets the forest floor and rodents are less likely to eat toxic bait.

Monitoring through a smaller beech mast in 2023 showed this timing led to the most effective control of predators and best outcomes for native wildlife.

Planning is underway for 15 predator control operations over 650,000 ha at priority South Island sites from spring to early summer in 2025.

This is in addition to DOC’s regular programme over another 150,000 ha. DOC is consulting with iwi and hapū, stakeholders and local communities about all proposed operations.

The predator control programme for the second part of the beech mast response in 2026 and early 2027 will be determined by rat and stoat monitoring results from the sites DOC is protecting.

If rodent numbers do not reach anticipated damaging levels in some areas, the programme will be scaled back.

DOC has received $6.5 million from the International Visitor Conservation and Tourism Levy for its expanded programme to tackle invasive predators, Morton said.

DOC uses climate modelling to predict beech masts a year in advance, and satellite imagery to monitor beech forest flowering across New Zealand.

Profuse red flowering of beech trees this summer will be the first sign that the beech mast has started, he said.