Owning a furry friend can take a big bite out of your household budget, but what about your pet’s cost to planet earth?

A new study says dogs and cats take a toll on the environment each year that’s roughly equivalent to a year’s worth of driving by 13.6 million cars, a researcher at the University of California at Los Angeles found. The study was published Wednesday in the journal PLOS ONE.

UCLA geography professor Gary Okin found that the country’s 163 million cats and dogs are “responsible for 25% to 30% of the environmental impact of meat consumption in the United States,” the university announced. That adds up to some 64 million tons of carbon dioxide a year. Okin compared how much meat humans eat versus pets, then analyzed the environmental impact of each.

People spend small fortunes to bury pets at this cemetery

If America’s pets were their own country, their meat consumption would rank fifth in the world behind only Russia, Brazil, the United States and China, Okin concluded. They’re also responsible for generating 5.1 million pounds of feces per year, which is roughly equivalent to the amount of garbage produced by all the humans in Massachusetts, the study found.

Read more: These millennials are buying houses because they want their pets to have more space

Meat production creates a range of environmental impacts, including greenhouse gases that fuel climate change. Its environmental impact is one reason some consumers have turned away from meat in favor of more plant-based diets.

But turning your back on your pet would not be so easy, even for the most eco-conscious. Pets provide well-documented social and emotional support to their owners. Owning a pet has been linked to getting more exercise, having better self-esteem, and cultivating healthier relationships.

Some owners feed their pets vegetarian diets, and some research has found these diets can be healthy as long as they contain enough protein and Vitamin D.

“I like dogs and cats, and I’m definitely not recommending that people get rid of their pets or put them on a vegetarian diet, which would be unhealthy,” Okin said in a statement. “But I do think we should consider all the impacts that pets have so we can have an honest conversation about them. Pets have many benefits, but also a huge environmental impact.”