Meat eaters pollute more than vegetarians.

That’s the finding of two recently published scientific papers, both of which calculated the greenhouse gas emissions generated by people eating a range of diets – from American-style meat-based to totally planted-based vegan. Each study found meat-centric diets to be the most polluting.

“The type of food we eat matters a lot,” said Dylan Voorhees, clean energy director for the Natural Resources Council of Maine.

Voorhees said the environmental group doesn’t have a position on the issue of food and climate change, but as an individual involved in climate change work, he has come to realize animal products have a “heavy environmental footprint and climate footprint in general.”

Because of this, he and his wife eat less meat now than they did 10 years ago and avoid the most carbon-intensive meats like beef and lamb.

Just last week the National Academy of Sciences published a report showing eating beef produces five times more greenhouse gases per calorie than eating other animals or animal products, such as eggs and milk.

But when it comes to looking at what actual people are eating over time, two other studies show that meat eaters like Voorhees who reduce the amount of meat they eat reduce their contribution to greenhouse gas emissions.

For instance, a study out of the Loma Linda University School of Public Health found that switching from a meat-based diet to a semivegetarian diet (defined as eating meat a couple times a month but not every week), cut greenhouse gas emissions by 22 percent. Switching to an all-vegetarian diet cut emissions by 29 percent.

The paper, which analyzed the diets of more than 73,000 people in the United States and Canada participating in the ongoing Adventist Health Study, was published in June in the American Journal of Clinical Nutrition.

The second study, published in the July issue of the journal Climate Change, looked at the diets of more than 50,000 people in the United Kingdom and found that heavy meat eaters generated 2.5 times more greenhouse gas emissions than vegans.

The study also found that reducing meat consumption lowered greenhouse gas emissions.

WEIGHING CLIMATE IMPACT

The Loma Linda and U.K. studies illustrate that “you don’t have to go whole hog and go vegan” to reduce your carbon footprint, said Mary Ellen Camire, a distinguished food science and human nutrition professor at the University of Maine, Orono.

“You can make choices to not have meat every night and eat more fruits and vegetables,” said Camire, who is also president-elect of the Institute of Food Technologists.

But, she cautioned, if your aim is to reduce your climate impact you may not want to replace meat with vegan microwave meals or veggie burgers shipped across the country.

Processed foods take more energy to produce and distant foods take more fuel to get to our plates.

These studies reflect the inefficiencies of eating meat rather than plants.

Two summers ago, leading water researchers at the Stockholm International Water Institute released a report warning the world will face massive food shortages unless humans switch to a mostly vegetarian diet.

The scientists said we have until 2050 – a mere 36 years – to make the switch to eating no more than 5 percent of our calories from meat.

Farming livestock takes far more resources than raising plants. In the case of water, meat consumes five to 10 times more.

That’s a sobering figure when you consider that 70 percent of the world’s available water is already being used by agriculture. Then factor in world population, which is expected to add another 2 billion people by 2050, and you start to see the problem.

Not only do factory farms use a lot of water, but these confined operations often pollute the surrounding ground and surface water due to the legal use of open manure pits to deal with staggering amounts of waste.

According to the Environmental Protection Agency, an average dairy cow generates 120 pounds of manure each day. That’s the same amount of waste a group of 20 to 40 people produce in a day.

Since methane is a potent greenhouse gas, the EPA notes that cattle in the United States emit more than 5 million metric tons of methane each year, making the cattle – or more accurately the people who eat them – responsible for 20 percent of the country’s methane emissions.

Now consider what happened in 1995, when heavy rains caused an 8-acre manure pit filled with factory farm hog waste to burst. The cesspool spewed 25 million gallons of raw feces, blood and chemicals into the New River in North Carolina, killing millions of fish and contaminating thousands of acres of shellfish beds.

Factory farms – which resemble prison camps more than farms – are notorious for fostering pathogenic contamination, overusing antibiotics and filling the neighborhood with an all-encompassing stench.

“Growing meat … uses so many resources that it’s a challenge to enumerate them all,” wrote food journalist Mark Bittman in his provocative “Rethinking the Meat-Guzzler” piece published in The New York Times in 2008.

SEEING THE EFFECTS

Last May, a federal report outlined how climate change is already affecting Maine – from increased property damage because of coastal storms to growing tick populations sickening the moose herd. The Loma Linda and U.K. studies show that eating meat contributes to this changing climate.

So what can we do?

The obvious answer is to stop eating meat. Or at least eat a lot less of it.

“It would help if large numbers of people adopted a couple meatless nights a week,” Camire said.

Voorhees said one of the things keeping Americans from eating less meat is federal agricultural policy that favors factory-style, animal agriculture over fruit and vegetable farmers (not unlike how federal energy policy favors petroleum instead of solar).

The result is that meat prices are artificially low, and fruits and vegetables seem expensive in comparison.

“People need to make the right choices, that’s true,” Voorhees said. “But our policies need to make sensible choices cheaper.”

Avery Yale Kamila is a freelance food writer who lives in Portland. She can be contacted at avery.kamila@gmail.com

Twitter: AveryYaleKamila