Climate Commissioner Rod Carr has told farmers to clean up their practices or risk international punishment.
Dr Carr told hundreds of people - including farmers - at an agricultural climate change conference in Wellington today that for the agricultural sector there would be no way to wriggle out of slashing emissions.
He said in the past there had been a mindset in the agricultural sector that it should get exemptions because it was such an export powerhouse, but New Zealand's trading partners were increasingly making decisions based on the climate impact of products.
He said foreign regulators would not take kindly to exporters not pulling their weight, and this, combined with changing international consumers preferences, posed a much greater threat to business than local regulations.
"The world will hold countries to account," he said.
"So the challenge for New Zealand ... is what club do we want to be in?
"Because there's no doubt there will be rogue nations but is that the company we want to keep?"
Carr said agriculture made up about half of New Zealand's emissions, and this needed to be reduced to meet climate obligations.
He said international customers would go elsewhere, costing the economy billions of dollars in the coming years.
"New Zealand will transfer real wealth to the other nations who have done more, sooner.
"And, in a way, that's an accountability regime. You will be transferring wealth in your lifetime for our failure to do as much as we can domestically."
He said New Zealanders per capita produced about 16 tonnes of emissions a year, compared to just four tonnes in India and China - and China was the world's manufacturer.
"So if you're an outsider looking at New Zealand you go 'wow, not only do you emit a lot today, but you've really done quite a bit in the past, from which you've profited in the past'."
He said often those in New Zealand's agricultural sector argued that they were the most efficient farmers in the world.
"The most efficient what?" Carr said.
"The most efficient producer of ruminant pastoral meat and milk the way [New Zealand does] it.
"Well that's good, we defined a class and when we were the best in it. The Americans usually win the prize for that approach to the 'best of'."
North Canterbury farmer John Sexton said the changes the commission suggested - dropping methane by 10 percent by 2030 - did not make financial sense for many farmers, so it would not happen.
"They all talk about sustainability.
"But unless it's financially sustainable, it won't happen and we won't have exports.
"It's as simple as that."
He thought many farmers would be forced out of business.
"It's just not worth it. The days of the one-man family farm are over.
"It's just getting too complicated and too expensive to go through all the bureaucracy that's going with it."
Vern Brasell part-owns a 900-head dairy farm in Wairarapa.
He said many farmers were more sceptical about climate issues and the changes they might need to make five years ago, but the attitude was changing.
The Canterbury floods, and droughts elsewhere showed farmers needed to face up to reality, he said.
"I once knew when winter, summer, and spring [were]. They turn up at all sorts of times [now].
"People who can adjust to the reality that are in will do better than those who just think 'well, it worked in the past'."
Nicky Hyslop owns a sheep and beef farm in south Canterbury just out of Timaru.
She said there was still a lot of work to do to convince all farmers of the changes needed, and the younger generation would lead the way.
"They'll drag some of us who are a little bit more, you know, fearful or guarded in terms of what what lies ahead - they'll drag us with them."
The final Climate Change Commission report will be released on Wednesday next week.