WELLINGTON, New Zealand (AFP) — Farmers quit their fields and hit the streets of New Zealand's cities Thursday in countrywide protests against plans to tax greenhouse emissions from farm animals.

Convoys of tractors, 4x4s and farmyard vehicles disrupted traffic in Wellington, Auckland and other major hubs, as protestors demanded the center-left government ditch plans for an animal "burp and fart" tax.

Earlier this month, Prime Minister Jacinda Ardern touted a "world first" levy on emissions of methane and nitrous oxide produced by the nation's six million cows and 26 million sheep as a step to tackling climate change.

Thousands of farmers gathered Thursday brandishing signs saying the policy "stinks" and warning that the tax would make food more costly, while putting their livelihoods at risk.

"Most farmers have had enough," one Wellington protestor who gave his name only as Chris said. "It's getting hard to carry on farming and this government isn't really supporting us — it's a tough gig at the moment."

Animals produce methane and nitrous oxide as a byproduct of munching on grass and feed.

Methane is much less abundant than carbon dioxide and does not linger as long in the atmosphere, but is a much more potent warming agent.

Scientists believe methane is responsible for roughly 30 percent of the global rise in temperatures despite being a fraction of the greenhouse gas mix.

Ardern has argued the tax is needed to reach climate targets and could even benefit farmers if they can charge more for climate-friendly meat.

She also signalled a possible willingness to compromise.

"We are out talking to our farmers and food producers as to the best possible design," she told reporters in Auckland.