Multi-millionaire Canadian film-maker James Cameron has taken aim at the meat and dairy sectors, saying in an opinion piece that people need to eat less of it in order for the world to reach any climate goals.

Cameron, writing in London's The Guardian, said people were stuck on the idea that talking about food's environmental impact "risks taking something very intimate away from us".

"In fact it's just the opposite. Reconsidering how we eat offers us hope, and empowers us with choice over what our future planet will look like.

"And we can ask our local leaders – from city mayors to school district boards to hospital management – to help, by widening our food options," he said.

"We simply need less meat and dairy and more plant-based options in our food system if we're to reach our climate goals," he said.

"Animal agriculture is choking the Earth, and the longer we turn a blind eye, the more we limit our ability to nourish ourselves, protect waterways and habitats, and pursue other uses of our precious natural resources."

Cameron said raising livestock for meat, eggs and milk generates 14.5 per cent of global greenhouse gas emissions, the second highest source of emissions and greater than all transportation combined. It also used about 70 per cent of agricultural land, and is one of the leading causes of deforestation, biodiversity loss, and water pollution.

"On top of this, eating too much meat and dairy is making us sick, greatly increasing our risk of heart disease, type 2 diabetes, several major cancers and obesity."

Cameron directed The Terminator, wrote and directed Titanic, and directed Avatar - all of them blockbusters. He owns land in Wairarapa, where he has organic farming interests.

Dairy and meat are New Zealand's first and second biggest merchandise exports, worth $11.2 billion and $5.9 billion, respectively, in 2016.

Federated Farmers' national vice president Andrew Hoggard said there was nothing new in Cameron's comments.

"It's something that we see a lot of - these claims that we can save the planet by going vegan, and quite frankly it's a bit of a jump," he said.

"It's undisputed that in the west we are probably eating too much animal protein - and there needs to be a bit more fresh fruit and vegetables in there," he said.

"But in the developing world they have the balance problem the other way. They don't have enough nutrient-dense animal protein in their diet and they need more of it," he said.

Hoggard conceded that from a carbon footprint perspective, a glass-by-glass comparison between real milk and milk from plant-based product would show the plant-based one created less carbon.

"But it also has a truckload less nutrient in it, so on a nutrient basis dairy had a better carbon footprint, so it's not that simple," he said.

"We are able to produce food at some of the lowest carbon footprints in the world, so for me that is a good selling point for dairy in New Zealand," he said.

Hoggard said Cameron's efforts would be better directed at the energy sector, which is responsible for 75 per cent of the world's carbon emissions.

Steve Carden, chief executive of Landcorp - New Zealand's biggest farmer - said some of Cameron's perspectives were valid.

"At Pamu (Landcorp's brand) we have been clear that the way people consume food is changing, and we in turn need to change the way we produce that food," he said.

Consumers are now demanding to know the environmental footprint of what they eat, as well as health and nutritional information, he said.

"We do not regard the plant-based alternatives to meat and dairy as a fad, but rather a new entrant which the traditional farming sector needs to take seriously," he said.

Landcorp last year took an industry-leading move by stopping the use of palm kernel, imported from Southeast Asia, based on its large carbon footprint.