WASHINGTON: United Nations specialists are now looking again at the contribution of meat production to climate change, after a leading air quality expert claimed that an earlier UN report exaggerated the link.
The new study, due to be completed by the end of this year, will allow for comparisons between diets that include meat and vegetarian ones.
University of California, Davis air quality expert Frank Mitloehner on Monday questioned the 2006 UN report, Livestock's Long Shadow, that said livestock cause more greenhouse gases - 18 per cent of all emissions - than all global transportation combined.
He argued that consuming less meat and milk is not effective in reducing greenhouse gas production, reported the Agence France-Presse (AFP).
'Smarter animal farming, not less farming, will equal less heat,' he said.
'Producing less meat and milk will only mean more hunger in poor countries.'
The 18 per cent figure in the UN report has been widely cited by climate change proponents - including key figures like the UN-affiliated Intergovernmental Panel on Climate Change's chairman Rajendra Pachauri and British economist Nicholas Stern - as the reason why people should try changing their diets.
The notion that eating less meat will help to combat climate change has spawned campaigns for 'meatless Mondays' and a European campaign launched late last year called 'Less Meat = Less Heat', backed by former Beatle and well-known vegetarian Paul McCartney, said AFP.
'McCartney and others seem to be well-intentioned but not well-schooled in the complex relationships among human activities, animal digestion, food production and atmospheric chemistry,' said Dr Mitloehner.
He said the UN report, published by the UN Food and Agriculture Organisation (FAO), did not compare like with like when it analysed the role of livestock versus fossil fuel emissions in spurring global warming.
While it arrived at the emissions figure for livestock rearing by considering all gas emissions from land clearance to transporting livestock, that of transport only included the burning of fossil fuels.
Rather than focusing on producing and eating less meat, Dr Mitloehner said, developed countries 'should focus on cutting our use of oil and coal for electricity, heating and vehicle fuels'.
In the United States, transportation creates an estimated 26 per cent of all greenhouse gas emissions, whereas raising cattle and pigs for food accounts for only about 3 per cent, he said.
One of the authors of the 2006 report, FAO livestock policy officer Pierre Gerber, told BBC News that he accepted Dr Mitloehner's criticism.
'I must say honestly that he has a point - we factored in everything for meat emissions, and we didn't do the same thing with transport,' he said.
Mr Gerber said the FAO is now working on a much more comprehensive analysis of emissions from food production, which will allow for comparisons between diets.