Livestock farming accounts more than half of all agricultural greenhouse emissions, according to a new report.
Previous estimates put the figure closer to 20%, but this latest study is the first to incorporate the impact of land use changes overseas.
Taking changes overseas into account increases the estimate of emissions attributed to UK food consumption from 152MtCO2 to 253MtCO2.
Land use change, mainly deforestation to create agricultural land, is cited a major source of climate changing emissions.
All stages of the UK food chain give rise to emissions, the report says.
It includes production and initial processing (34%); manufacturing, distribution, retail and cooking (26%) and agriculturally-induced land use change (40%).
Livestock farming contributes to 57% of agricultural greenhouse gas emissions.
The report – How Low Can We Go: an assessment of greenhouse gas emissions from the UK food system and the scope for reduction by 2050 – states if the food industry is to play its part in keeping temperature rises below two degrees, emissions need to be cut by at least 70% by 2050.
The report concludes that no one solution alone can reduce emissions to this extent.
And it calls on the government and industry decision-makers to recognise that a focus on technology alone is not enough – food consumption must change too.
Mark Driscoll, head of WWF-UK’s One Planet Food programme said the target to cut emissions was a daunting task, but not an impossible one.
“We must stop chewing over some of the issues and start making change happen – both in terms of technology and behaviour.”
Recommendations include increasing production efficiency, including improved crop yields and changes to animal feeds to reduce methane emissions.
Dietary changes would also ease land pressures, in terms of reducing the amount of land needed to produce food, the report says.
But the recommendations were criticised by the UK dairy industry.
Milk producers were reducing emissions every day, said Jim Begg, director general of the industry body Dairy UK.
“The conclusion that dairy farmers should be encouraged to invest in slashing their output as the world’s population grows is unrealistic.
“And it is not sensible to advocate that consumers switch to a vegetarian diet, topped up with vitamin supplements.
“It is high time that environmental pressure groups recognised that dairy foods are in fact very efficient sources of nutrition.”
Dairy producers had reduced methane emissions by 14% since 1990, said Mr Begg.
Milk processors had reduced energy use per kilogram of product by 11% over the past nine years, he added.
And the industry forecast that half of the 130,000t of plastic used annually to make milk bottles would come from recycled sources by 2020.
“Processors, retailers and dairy farmers are quietly making progress towards targets that will see a major reduction in emissions,” said Mr Begg.