Minister of Conservation Eugenie Sage has announced there will be $81.3m spent on pest control over the next four years.

Pests are the big losers in this year's Budget as the Government declares war on possums, rats and stoats.

An extra $81.3 million will be spent on predator control across the country over the next four years, Conservation Minister Eugenie Sage announced in Wellington on Saturday morning.

The extra funding would let the Department of Conservation [DOC] cover 1.8m hectares, nearly double the current area and the size of Northland and Auckland combined. The investment was needed to protect wildlife like the endangered kiwi, Sage said.

BRADEN FASTIER/STUFF Stoats are one of the three pests targeted by the Department of Conservation.

"We have a biodiversity crisis, where 82 per cent of native birds are threatened with, or at risk of, extinction."

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The pre-Budget announcement was only the start of the Government's investment in nature, she said.

123RF.COM Rats are endangering native birds, the Department of Conservation says.

Previously, DOC was funded to undertake possum trapping over 1m hectares and the new funding meant it would be able to tackle the largest area ever covered.

"For the first time, predator control funding will be locked in. Budget 2018 means DOC won't have to divert funding from other priorities or scramble to get one-off allocations from Government to do this essential work."

The department's pest control improved forest health and the breeding success of threatened species like kākā, kea, rock wren, whio/blue duck and bats.

"When 4000 of our native plants and animals are threatened or at risk of extinction, every single conservation dollar counts."

The announcement comes as DOC continues to work towards Predator Free 2050, a goal of ridding the country of pests.

The department's website says it currently spends $70m annually on eradicating rats, stoats and possums.

National's Conservation spokesperson Sarah Dowie criticised the announcement.

"The $81.3 million increase over four years is a 4.6 per cent increase and barely more than inflation - and it's less than what National put up. National's 2017 Budget committed more than $107 million to DOC – the largest funding injection in its history.