We love our dogs and cats. But are they bad for the environment?

NEW YORK – Our dogs and cats provide all kinds of benefits. They improve physical health, reduce stress and can fend off loneliness.

Research shows that interacting with pets can lower blood pressure. Dogs need walks and playtime, which helps people stay active. And both dogs and cats can form deep bonds with humans. Basically, they enrich people’s lives.

“There’s a whole body of literature supporting that,” said Mr Pieter De Frenne, a bioscience engineer at Ghent University in Belgium.

Yet for all the good, pets come with environmental costs. Cats and dogs eat a lot of meat, for example. They also kill wildlife.

So, how can you get all those tangible and intangible benefits and keep the environmental, um, pawprint, as low as possible? Here is what the experts have to say.

A whole lot of meat

Mr Gregory Okin, a geographer at University of California, Los Angeles, calculated in a 2017 study that the estimated 163 million cats and dogs in the United States consume a whopping quarter of the country’s animal-derived calories.

“If US dogs and cats were their own country, they would rank fifth in global meat consumption,” he said in an interview.

Pet food, Mr Okin estimated, accounts for about a quarter of agriculture-related fossil fuel emissions in the US. Globally, another study found that dry pet food was responsible for up to 2.9 per cent of carbon dioxide emissions from agriculture and 1.2 per cent of agricultural land use.

Pets fed human-grade meat have greater effects. A 20kg dog on a raw food diet has a higher food-related environmental toll than most meat-eating humans, said Dr John Harvey, a veterinarian and doctoral researcher at the University of Edinburgh in Scotland.

To reduce these effects, Mr Okin recommends pet food brands that meet dietary requirements but contain less animal-derived protein.

Pet food made from chicken is generally better than pork, and both tend to be better than beef. Dry food, on average, has a lower environmental impact than wet food.

Vegan pet foods should be approached with caution because of potential nutritional inadequacies. That is especially true for cats.

Moreover, in the US, most cats and dogs are overweight. So reducing the amount of food those animals are given would be a boon for both pet health and the environment, Dr Harvey said.

And a whole lot of something else

The nutrient-rich pet foods people feed their animals come out the other end as nutrient-rich pee and poop. “It’s basically a hyper-fertiliser,” Dr Harvey said of dog and cat waste.

High levels of nitrogen and phosphorus in pet waste have been linked to soil contamination and water pollution. In parks and other natural areas where dog walking is popular, this influx of nutrients can even lead to biodiversity loss, Mr De Frenne said.

If owners would be more responsible about cleaning up after their dogs, these effects would be lessened, said Ms Kim Maya Yavor, a doctoral candidate in sustainable engineering at Technical University Berlin.

“With urine, there’s not much to do about it, but half of this problem can be reduced by picking up your dog’s faeces and throwing it away.”

Those hunting instincts

Free-roaming pets can also disturb or kill wildlife.

“Dogs just going through an area can have dramatic impacts on biodiversity,” Dr Harvey said.

Pet predation can also have knock-on effects for other species.

“When a cat kills a mouse or vole, that animal can’t be eaten by a native predator like an owl or marten,” said Professor Arie Trouwborst, a professor of nature conservation law at Tilburg University in the Netherlands.

Many of these problems can be solved or mitigated, he added, by keeping cats indoors and leashing dogs.

The point here is not that you cannot have a companion animal or two. Being careful about pet food and pet waste, and keeping animals under your control, can help a lot.

Adopt, don’t shop

Finally, if you are considering adding a pet to your home, it is important to consider where you are sourcing that new friend.

Of the 5.8 million cats and dogs that went into US shelters and rescue centres in 2024, 607,000 were killed, according to the Shelter Animals Count, a non-profit organisation. The number of unwanted pets presents both environmental and animal welfare concerns.

Adopting a pet from a shelter or rescue group, rather than buying from a breeder, can help offset these issues. “Instead of creating a new thing, you’re taking something that’s already there,” said Dr Lena DeTar, a veterinarian at Cornell University.

And if you are specifically looking for a pet that takes a lower environmental toll, then go for something small, Dr Harvey said.

Cats and dogs also are not the only pets available, Mr Okin said. For example, rabbits and guinea pigs wind up at shelters and rescues in high numbers too. And unlike cats and dogs, they are vegetarian. NYTIMES