Giving up meat and dairy is the single most effective way a person can reduce their environmental impact, new research has found.

The meta-analysis, published in the journal Science, analyzed data from 750 studies, encompassing 40,000 farms in 119 countries.

The researchers found that while meat and dairy products provide 18 per cent of all calories and 37 per cent of all protein, its production uses 83 per cent of farmland and produces 60 per cent of the agriculture industry's greenhouse gas emissions.

"Meat production involves the production of feed and that often results in the deforestation, particularly of tropical rain forests," lead author Joseph Poore, an environmental researcher from Oxford University, told As It Happens host Carol Off.

"Then you've got all the emissions from transporting that feed. And then we have emissions on the farm. And you even have more emissions when you go through processing, packaging and retail."

Demand for meat products is on the rise globally. (Tiziana Fabi/AFP/Getty Images)

The researchers looked 40 products that represent 90 per cent of human protein and calorie consumption, and assessed their farm-to-table impact on land use, climate change emissions, freshwater use, water pollution and air pollution.

Some farms were significantly better at mitigating their environmental impacts.

"For me the biggest discovery is the variation," Poore said.

"One example might be rice. A high-impact farm creates 500 per cent more greenhouse gas emissions per serving than a low-impact farm."

Demand on the rise

But even meat and dairy from most environmentally sustainable farms has a higher impact than non-animal alternatives, Poore said.

"Even if we go and buy the lowest-environmental impact milk available in the shops, it's still going to have higher impacts for even the worst soy milk you can purchase," he said.

"And we find the same for animal products ... they consistently have higher emissions and typically higher land use than vegetable equivalents."

While some companies are better than others, the study found non-animal alternatives almost always have a lower environmental impact. ( Denis Contreras/Getty Images for SOBEWFF)

And as global wealth rises, so does demand for meat and dairy.

Poore said it will take one trillion litres of milk and 500 billion kilograms of meat per year to meet demand by 2050, driven by growth in Africa and Asia.

"These are just vast, vast numbers, and it's the catching up of the developing world to the industrialized world's meat-eating and dairy consumption habits," he said.

"Obviously, as you scale that up across all of these different indicators, it's hard to see any scenario that looks positive."

Should everyone go vegan?

Poore said the study lays out several ways to tackle this problem — such as improved farm technology, more sustainable farming practices, and better information for consumers.

But the single most effective game plan, he said, would be if everyone became a vegan like him.

The study recommends more transparency for consumers and more sustainable practices for farmers. (Patrick Hertzog/AFP/Getty Images)

In that scenario, he said, food land use would be reduced by 3.1 billion hectares — or 76 per cent.

"Personally and from the evidence that we've assimilated, I think it's pretty clear that doing that would just have transformative impacts on the planet," he said.

Written by Sheena Goodyear. Interview produced by Julian Uzielli.