Turns out that chow you're feeding Fido and Felix produces a pretty big carbon pawprint. In a study released Wednesday, a geography professor at UCLA calculated that the meat-based food Americans' dogs and cats eat -- and the waste those pets produce -- generate the equivalent of about 64 million tons of carbon dioxide a year.
That's as much as about 13.6 million cars driving for a year, says professor Gregory Okin in a paper published in the journal PLOS One.
Put another way: Dogs and cats are responsible for 25 to 30 percent of the environmental impact of meat consumption in the United States.
Livestock emit methane, which is the source of about 10 percent of all greenhouse gases. Previous studies have found that Americans' meat-heavy diet results in the release of 260 million tons of carbon dioxide -- the leading greenhouse gas -- through livestock production. Okin used similar estimates to calculate how much meat the nation's 163 million cats and dogs eat and its carbon equivalent.
Okin said he isn't suggesting Americans put their pets on a vegetarian diet, "which would be unhealthy." However, Okin -- who is allergic to dogs and cats but keeps two fish as pets -- said he wants pet owners to consider the climate impacts of pet ownership, particularly as many Americans switch their dogs and cats to high-protein premium foods.
"This was not a study to make anybody feel guilty," Okin said in an interview Wednesday. "I'm not saying people should go out and kill their animals or feed them something that isn't appropriate....It was a study just to figure out how big these numbers are, and the numbers are surprisingly large."
Frank Mitloehner, an animal science professor at UC Davis who specializes in livestock emissions, said the study shows that pets "clearly have an environmental footprint, and it is not a small one."
But he said almost all of the meat pets consume in their food comes from rendered livestock byproducts. Those are the nasty bits that meat processors would otherwise toss because people won't eat them.
"If this material wouldn't go into pet food than what would be the alternative use?" he said. "It would most likely be wasted."
Jennifer Fearing, a Sacramento lobbyist for the Humane Society of the United States, said the study shows that "everybody who's eating meat is contributing to global warming."
Fearing said her own dog, a shepherd mix, is doing well on a vegan diet, as did her previous dog, who died last year at age 15.
"He thrived on it," she said. "He was a remarkably healthy dog." She cited studies, including a 2009 report in the British Journal of Nutrition, showing dogs can do well on a meat-free diet.
However, many veterinarians warn against feeding dogs and cats a purely plant-based diet. Cats are especially prone to heart and eye problems if they don't get enough of a particular amino acid called taurine found in meat.
A 2015 study by the Journal of the American Veterinary Medical Association tested 24 types of dry and canned vegetarian pet foods and found that most weren't compliant with minimum labeling standards set by the pet-food industry. At least six of the foods tested were lacking in certain amino acids critical to pet health.
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