Beech forests from Fiordland to Tasman have flowered this spring and early summer, confirming the predicted major South Island beech mast is occurring. Beech seeds will form on the trees and drop in autumn and are predicted to number in the trillions.
Department of Conservation national predator control programme manager Peter Morton said the seeds provided a bounty of food for rodents, fuelling their population growth, which in turn feeds stoats, leading to a spike in predators the following summer.
Doc has completed 11 out of 15 planned aerial 1080 predator control operations over the past three months. These cover 460,000 hectares out of the planned 650,000ha programme.
Mr Morton said the operations focused on protecting the best-surviving populations of endangered wildlife in Kahurangi, Mount Aspiring, Arthur’s Pass and Fiordland National Parks, and West Coast conservation areas.
The operations will safeguard vulnerable native wildlife — such as mohua/yellowhead, rock wren, kea and bats — at high risk from introduced predators.
Wet and windy weather in early spring caused delays to some operations but Doc caught up when weather improved in the past two months. The remaining four operations will take place next month when conditions allow.
Mr Morton said the operations were being carried out prior to the seed fall to avoid the time when beech seed carpeted the forest floor and rodents were less likely to eat toxic bait.
Doc monitored rodent and stoat numbers before and after operations, he said. Results were still coming in but so far were looking good.
Doc also monitored native species at some sites to check how they were responding to management efforts, but this data would not be in until after summer. However, past monitoring and research showed predator control helped more native birds, bats and other native species to survive, breeding success went up and populations could increase, he said.
Beech mast response operations would move to a second round late next year once the seed had been eaten or had germinated.
This avoided times when beech seed carpeted the forest floor and rodents were 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, he said.
The predator control programme for the second part of the beech mast response next year and early 2027 would be determined by rat and stoat monitoring results from the sites Doc was protecting. If rodent numbers did not reach anticipated damaging levels in some areas, the programme would be scaled back.
Doc received $6.5 million from the international visitor conservation and tourism levy for its expanded programme to tackle invasive predators.
Climate modelling is used to predict beech masts a year in advance, and satellite imagery to monitor beech forest flowering across New Zealand.
The last big mast was in 2019, when beech forests and tussock grasslands across New Zealand seeded in a "mega mast".
