Forests in the Fiordland and Mt Aspiring national parks, Catlins Conservation Park, Waikaia Forest Conservation Area and Haast River Conservation Area are to benefit from an increased pest control programme announced by Conservation Minister Nick Smith this week.
The programme was in response to the predicted one-in-10-to-15-year beech mast - a year of exceptional flowering and seeding - which will trigger a plague of rats and stoats which are a major threat to New Zealand's native species.
Southern forests are home to many native species, including mohua, kaka, robin, short and long-tailed bats, rock wren, kiwi, kakariki and kea.
About $21 million had been allocated to the programme over the next five years, but the cost of this year's planned beech mast response was about $11 million.
How much of that would be spent in Otago-Southland would not be known until the extent of the beech mast and predator response was understood.
''Until we know the scale of the beech mast and increases in rodent levels in particular areas we won't know where the pest control response is actually needed,'' a Doc spokeswoman said.
Doc staff would be measuring the amount of beech seed produced over the summer and seed fall in autumn to gauge the scale of the beech mast and would also be monitoring pest numbers.
Dr Smith said the programme was being funded through savings from last year's restructuring, partnership funding, efficiency gains from improved pest control technologies and economies of scale.
The Doc spokeswoman said some low-priority work might be deferred to enable urgent pest control work to be funded.
However, the work was in the early planning stages and Doc would not know exactly how resources would be reallocated until pest control operations were confirmed.
Landcare Research managing invasive weeds, pests and diseases leader Dr Andrea Byrom said there was no doubt pest numbers would explode this year in response to the expected ''phenomenal'' mast year.
''With the pest control plan outlined for the 35 sites around the country, these species will have a chance.''
In the long term, Doc's proposed plan will prevent localised or even national extinctions of taonga species such as mohua in high-priority areas.
''The planned drops will be enough to 'hold the line' and get a 'pulse' of breeding and recruitment through the coming year for native species in the targeted areas.''
