BRUSSELS — Delegates arriving at the gates of the climate conference in Copenhagen last month were met by women in furry animal suits holding placards showing pictures of lambs, cows and pigs and warning, “Don’t Eat Me.”
As they lined up for hours in freezing conditions, many of the delegates seemed grateful for the neatly wrapped snacks — meat-free sandwiches — that the women were handing out free.
Followers of Ching Hai say that one of her principal goals is to fight environmental disasters, and her representatives in Copenhagen appeared eager to spread the message that methane, which is belched in large quantities by cows and other livestock raised for the meat and dairy industries, is among the most potent planet-warming gases.
But the virtues of vegetarianism as part of the battle to curb climate change are far from being an issue just for the spiritually inclined.
Long before the summit meeting in Copenhagen, rising demand for meat and dairy products, particularly among the burgeoning middle classes in countries like China and India with fast-developing economies, meant that links between climate change and food policy were becoming an important element in the debate over what to do about the rising levels of greenhouse gases.
The issue appeared to have gained traction in the weeks leading up to the Copenhagen conference, with prominent figures from the worlds of science and entertainment stepping into the fray.
Speaking at the European Parliament in early December, Paul McCartney, a former member of the Beatles, said there was an urgent need to do something about meat production, not only because of its effects on the climate but also because of related issues like deforestation and ensuring secure supplies of water.
Mr. McCartney, who has long advocated vegetarianism, urged European legislators to support policies like encouraging citizens to refrain from eating meat for one day a week, something that he said could become as commonplace as recycling or cars that run on hybrid technology.
Civil servants in the Belgian city of Ghent and schoolchildren in Baltimore already observe a meat-free day each week, he said.
Mr. McCartney was joined at the parliament by Rajendra Pachauri, the chairman of the 2007 Nobel Peace Prize-winning Intergovernmental Panel on Climate Change, which is the main United Nations body studying the climate.
Public awareness of the problems linked to meat is low, and the authorities might have to consider levying a surcharge on beef to discourage consumption, Mr. Pachauri said in comments reported by Agence France-Presse.
Meat farmers immediately branded the comments as an assault on the industry, and criticism came from as far away as New Zealand.
“Cutting out meat one day a week might seem a simple solution, but there is little evidence to show any benefit,” Rod Slater, the chief executive of Beef and Lamb New Zealand, told the country’s press association.
“Suggesting meat’s not green is an emotive slur on an industry which continues investment in ongoing research, striving for further improvements,” added Mr. Slater, who said people living in New Zealand obtained daily nutritional necessities, and most of their protein, zinc and vitamin B12, from beef and lamb.
In fact, like a number of other areas of research in climate science, the greenhouse gas intensity of meat production is contested.
When a study in the November-December issue of the magazine World Watch claimed more than half of human-produced, planet-warming gases were caused by meat industries, a research group for the livestock industry countered that a study by the United Nations Food and Agriculture Organization already had shown that the relevant figure was closer to 18 percent.
The study published in World Watch failed “to enlarge on any counterfactuals, such as what a world without domesticated livestock would look like,” Carlos Seré, the director general of the International Livestock Research Institute in Nairobi, wrote to Green Inc. in November.
“Would, for example, wild herbivores and termite mounds take over many of these environments, and end up producing as much greenhouse gases as domestic ruminants?” Mr. Seré asked. “We frankly don’t, and can’t, know that yet.”
Certainly the issue may be more nuanced than some commentators have suggested.
For example, cattle fed on grass may have much lower carbon footprints than those fed in feedlots because animals in pasture lands require fewer fossil fuel-based inputs like fertilizers and because they help the soil sequester carbon.
Renewed efforts are under way to get to the bottom of the matter.
Early this month, the Paris-based World Organization for Animal Health said it would study the effect of meat output on climate change in light of requests from its member countries.
“It’s a question that needs to be studied with a lot of distance,” Bernard Vallat, the organization’s director-general, told a news conference, according to Reuters. “We want to make a modest and independent contribution,” he said.
Mr. Vallet said that one of the thorniest issues was how to involve agriculture in efforts to reduce gases while maintaining food security.
Mr. Seré, of the livestock research institute, acknowledged the need to develop a form of livestock production between factory and family farming that would ease poverty without depleting natural resources or hurting the climate.
He said environmental campaigners should keep in mind that the “biggest concern of many experts regarding livestock in developing countries is not their impact on climate change but rather the impact of climate change on livestock production.”
The “hotter and more extreme tropical environments being predicted threaten not only up to a billion livelihoods based on livestock but also supplies of milk, meat and eggs among hungry communities that need these nourishing foods most,” he said.