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© Rob Dobi for the Star Tribune
New Zealand farmers have five years to reduce their carbon emissions before the government introduces financial penalties, prime minister Jacinda Ardern has announced.

Ardern's Labour coalition government has committed to making New Zealand carbon net-zero by 2050, with the PM likening the climate change battle to the previous generations' struggle against the rise of nuclear power.

If emissions are not adequately reduced, farmers could face additional taxes as early as 2022.

There has been long-simmering hostility between the Labour government and farmers, especially in the dairy sector, with many saying the government's sweeping plans to force them to be more environmentally sustainable are not economically viable and would cause some to walk off their properties.

The climate emissions reform plan and cleaning up the waterways has caused stress for many, farmers say.

But Ardern says she has listened to farmers and is willing to give them time to reform on a property-by-property basis. "For too long politicians have passed the buck and caused uncertainty for everyone while the need for climate action was clear," Ardern said.

"This plan provides the primary sector with certainty and puts us shoulder-to-shoulder on a path to reduce emissions, with ongoing support to help with the plan such as the $229m sustainable land use investment."

"This will reduce emissions by giving farmers the autonomy to plan to do so, and reward those who do," she said.

In the run-up to the 2017 general election, Ardern said farmers would be included in the emissions trading scheme (ETS) - a commitment she softened on Thursday, with critics accusing her of caving in to pressure from the powerful industry.

The government has said if the primary sector takes enough proactive action to reduce emissions it would not be brought into the ETS. However there is a backstop. If the sector fails to innovate and manage emissions, it could be brought into the ETS as early as 2022.

In a joint statement signed by the major industry leaders including DairyNZ, Federated Farmers and Beef and Lamb New Zealand, the sector welcomed the collaborative approach, and said it was "pleased" agriculture would not have its emissions taxed.

"Achieving this programme of work will not be cheap, and it will not be easy ... we welcome this pragmatic and sensible decision by the government to work in partnership with industry to achieve tangible on-farm change and hope that it might provide a blueprint for the way we work together to solve environmental challenges in the future."

The five-year action plan will include government incentives for early adopters, improved tools for estimating and benchmarking farm emissions, integrated farm plans that include a climate module, and recognition of on-farm climate mitigation efforts such as small plantings, riparian areas and natural cover.

The opposition National party's spokesman on climate change, Scott Simpson, said the ETS tax was hanging over farmers' heads if they didn't adapt quickly enough.

Forcing farmers out of business would also raise global emissions, Simpson said, because New Zealand would be forced to import more food.

"National has a clear criteria that would need to be met before we're comfortable with agriculture entering the ETS or a similar pricing mechanism. There needs to be science-based mitigation options available for farmers that don't lead to herd culling and decreased food production," Simpson said.

"New Zealand would have the only farmers in the world to be a part of an ETS. It's important we are not put at a disadvantage to our international competitors or we risk losing our valuable market share to a less sustainable producer."

As well as government grants totalling more than NZ$200m, industry bodies said they would also commit at least NZ$25m a year to boost emissions-reduction efforts around the country.