A record seeding across the South Island’s beech forests has set off the largest predator control programme the Department of Conservation has ever run. The forests dropped what DOC describes as “trillions of seeds” over the summer, the biggest beech mast in seven years, and that glut of food is now driving a surge in rats and stoats that will fall on native birds, bats and lizards through the coming year.
It is a familiar cycle, and this year it is a big one. The response is scaled to match.
A record seeding year
Beech trees seed irregularly. Every few years, in response to a warm previous summer, most of the beeches across a region flower and seed heavily at once. Ecologists call it a mast. The seed feeds a fast build-up of mice and rats, and the rats in turn feed a build-up of stoats. When the seed runs out the following autumn, the swollen predator population turns to the next available food, which is native wildlife that nests or roosts on or near the ground.
DOC says the summer 2026 mast was the largest across the South Island beech forests in seven years. Mohua, whio, kea, kiwi, orange-fronted parakeet, rock wren and long-tailed bats are all among the species most exposed when a mast breaks, because they cannot outbreed the wave of predators that follows.
The largest programme DOC has run
On 17 June the Conservation Minister, Tama Potaka, announced a $14.1 million boost from the International Visitor Conservation and Tourism Levy to expand predator control for the mast. With that funding, DOC says the 2026/27 programme will scale up to about one million hectares, or 12 percent of all public conservation land, which it describes as its largest predator control effort ever. Operations are already under way across more than 550,000 hectares this year.
“We’re funding more predator control to protect our precious wildlife in national parks and other priority sites across the South Island,” Potaka said.
The extra money is aimed at Kahurangi, Arthur’s Pass, Mount Aspiring and Fiordland national parks, together with the Maruia, Arawhata and Landsborough valleys on the West Coast, covering more than 360,000 hectares at those sites alone. The main tool over large and rugged country is aerially applied 1080, timed to hit predators when the seed has gone and bait is most attractive to them, backed by ground trapping and bait stations at smaller sites.
The threat now is predators, not clearance
The scale of the effort points to a shift in what actually endangers New Zealand’s native forest. For most of the country’s history the story was clearance. Native forest covered about 85 percent of the land a thousand years ago and about a quarter of it today, cleared first by Polynesian fires in the eastern South Island and then by the European bush burns that opened up the North Island lowlands between the 1850s and the 1930s.
That clearance has all but stopped. Since the 1993 Forests Act ended commercial native logging on Crown land, indigenous forest cover has been close to flat, losing only about 0.02 percent a year. Three-quarters of what remains sits on public conservation land and is effectively off the table for felling. The forest is safe. What lives in it is not, and the reason is introduced predators rather than the chainsaw.
Explore the data. See how much native forest each region has lost over the past thousand years, and how little of it has gone since clearance stopped, in our interactive native forest map.
What is at stake this year
The value of a mast-year programme is measured in the birds that survive to the other side of it. In an uncontrolled mast, populations of vulnerable forest birds can be cut back sharply in a single season, and small or isolated populations can be lost outright. Well-timed control through the peak predator months lets those populations hold and, in good years, keep growing.
Recent results suggest the approach works where it is sustained. On Rakiura Stewart Island, camera monitoring after an aerial operation found no cats over a long stretch and only a handful in traps, the kind of knock-down that makes a future return of species such as kākāpō thinkable. The mast programme is the same idea at national-park scale, and this year at the largest scale the country has attempted.
Details of the 2026 operations, including which sites are treated and when, are published on the Department of Conservation’s predator control operations page, alongside the June funding announcement.
Have you seen predator control work, or its results, in a forest near you? Share what you have noticed in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂
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