Mr. Green digs around for the answer
Q: Has any individual or institution investigated the potentially disruptive impacts of the United States close to 90 million registered dogs on our environment and wildlife?
—Wolf in Tahoe City, California
A: Surprisingly little research has been done on canine environmental impacts, maybe because of a certain bias toward “mans best friend.” However, a recent study indicates that dogs and cats combined are responsible for around 1.5 percent of U.S. emissions of methane and nitrous oxide. Their diet alone accounts for up to 30 percent of the environmental impact from all animal production, in terms of the use of land, water, fossil fuel, phosphates, and biocides.
Several researchers contend that dogs rank third in their ability to disturb other species, outdone only by cats and rodents. (One study revealed that even dogs piously walked on a leash scared away 40 percent of the birds as they went through an area.) Dogs have driven 11 species into extinction, and they threaten another 188, according to a 2017 study published in Biological Conservation.
The good news for dogs and cats is that there are now fewer being euthanized at U.S. shelters, down from 2.6 million in 2011 to 1.5 million annually, according to the American Society for the Prevention of Cruelty to Animals. This big reduction has been made possible by an increase in the number of adopted animals and stray animals returned to their owners.
We still need better control of pet dogs and stronger efforts to contain feral populations. However, given our longtime affection for the critters—one estimate puts our relationship with dogs back an astounding 30,000 years—its understandable that we are a bit reluctant to take action.
Using the IUCN Red List of Threatened Species, we counted how many species are negatively affected by dogs, assessed the prevalence of different types of impacts, and identified regions with the greatest number of affected species.
Dogs not only interact with wildlife, but can also attack and spread disease to humans, livestock and other domestic animals. As such, managing the problem requires looking at ecological, cultural and social perspectives.
Predation was the most commonly reported impact of dogs on wildlife. The typically omnivorous diet of dogs means they have strong potential to affect a diversity of species. For instance, dogs killed at least 19 endangered Kagu (a ground-dwelling bird) in New Caledonia in 14 weeks. Threatened species with small population sizes are particularly vulnerable to such intense bouts of predation.
For example, in Australia, the closely related dingo (Canis dingo) can suppress populations of introduced predators such as red foxes (Vulpes vulpes), and in doing so can benefit smaller native prey. It is possible that domestic dogs could perform similar ecological roles in some situations.
Despite their widespread and sometimes severe impacts on biodiversity, dogs can also benefit some species and ecosystems.
Working dogs have many roles, and that includes using their powerful sense of smell to help with wildlife conservation. Find out how they do it.
From guide dogs to therapy dogs to police dogs…working canines abound. But did you know that dogs — or more specifically, their amazing olfactory powers — are also being used to help with wildlife conservation and other environmental issues? Let’s visit with a few of these “conservation dogs” and see how they’re making a difference with helping the planet.
The Science of DOGS
A UCLA study has found that dogs and cats are responsible for 25 to 30 percent of the environmental impact of meat consumption in the United States.
With many Americans choosing to eat less meat in recent years, often to help reduce the environmental effect of meat production, UCLA geography professor Gregory Okin began to wonder how much feeding pets contributes to issues like climate change.
All that meat has important consequences. Okin calculated that meat-eating by dogs and cats creates the equivalent of about 64 million tons of carbon dioxide a year, which has about the same climate impact as a year’s worth of driving from 13.6 million cars.
“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. “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.”
In a paper published today in the journal PLOS One, Okin says he found that cats and dogs are responsible for 25 to 30 percent of the environmental impact of meat consumption in the United States. If Americans’ 163 million Fidos and Felixes comprised a separate country, their fluffy nation would rank fifth in global meat consumption, Okin calculated, behind only Russia, Brazil, the United States and China. And it all has to go somewhere — America’s pets produce about 5.1 million tons of feces in a year, as much as 90 million Americans. If all that were thrown in the trash, it would rival the total trash production of Massachusetts — from the humans, at least.
Compared to a plant-based diet, meat requires more energy, land and water to produce, and has greater environmental consequences in terms of erosion, pesticides and waste, Okin noted. Previous studies have found that the American diet produces the equivalent of 260 million tons of carbon dioxide from livestock production. By calculating and comparing how much meat 163 million cats and dogs eat compared to 321 million Americans, Okin determined how many tons of greenhouse gases are tied to pet food.
His calculations start with publicly available information, like the number of dogs and cats in the country and the ingredients in market-leading pet foods, leading to complicated equations like the mathematical menagerie below, and producing estimates that create a starting point for conversation.
He found that the nation’s dogs and cats eat about 19 percent as many calories as the nation’s people, on par with all the calories consumed by the population of France in a year. Because dog and cat food tends to have more meat than the average human diet, this means that dogs and cats consume about 25 percent of the total calories derived from animals in the United States.
Okin, a member of UCLA’s Institute of the Environment and Sustainability, usually researches dust bowls, desert landscape dynamics and wind erosion, and how those things can impact individual ecosystems and the global climate. Pinning down the environmental impact of canine companions and feline friends was more of an — ahem — pet project that occurred to him while he was thinking about the growing trend of raising backyard chickens.
“I was thinking about how cool it is that chickens are vegetarian and make protein for us to eat, whereas many other pets eat a lot of protein from meat,” he said. “And that got me thinking — how much meat do our pets eat?”
Okin recognizes that some of the products in pet food aren’t something people should or would eat. But some of it is. In his research, he confirmed his hunch that premium pet foods usually contain more animal products than other brands, and that premium pet food purchases are increasing. As growing numbers of people consider pets less as animals and more as family members, Okin said, pampering has increased and the options for pet food with high-quality meat has kept pace. This means pets are increasingly eating cuts of meat suitable for humans.
“A dog doesn’t need to eat steak,” Okin said. “A dog can eat things a human sincerely can’t. So what if we could turn some of that pet food into people chow?”
A commitment to snout-to-tail consumption, where as much rendered product as possible is produced for human use, could significantly reduce national meat consumption. Okin estimates that if even a quarter of the meat in pet food could be consumed by humans, it would equal the amount of meat consumed by 26 million Americans, nearly the population of Texas. Okin noted that ideas about what is edible vary dramatically by culture. He also pointed to a controversy in 2012 about “pink slime,” also called lean finely textured beef.
“It’s perfectly edible and completely safe, but it’s unappetizing, so people don’t want it in their food,” Okin said. “But frankly, it’s a good, inexpensive protein source.”
As eating less meat expands from vegetarian to environmental circles as a way to reduce one’s carbon footprint, considering what to feed pets is a natural next step, Okin said. It’s not just an issue in the United States, he noted. In places like China, Brazil and other emerging countries, as the population becomes more affluent, they’re eating more meat and they’re getting more pets.
“I’m not a vegetarian, but eating meat does come at a cost,” he continued. “Those of us in favor of eating or serving meat need to be able to have an informed conversation about our choices, and that includes the choices we make for our pets.”
He doesn’t see a simple solution. Pets provide friendship and other social, health and emotional benefits that can’t be discounted, Okin said. People concerned about meat intake could consider vegetarian pets, like birds or hamsters, he suggested. The pet food industry, he noted, is also beginning to take steps toward sustainability, and could work to reduce overfeeding and consider alternative sources of protein. But it’s a complicated issue, and where pets are concerned, Okin knows it’s important to have a sense of humor about it.
“Maybe we could all have little ponies,” he said, half-jokingly. “We’d all get more exercise taking them for walks, and they would also mow the lawn.”