The University of California, Los Angeles (UCLA) has recently explored new frontiers in environmental research. In this case, they made the first attempt to quantify the environmental impacts of food consumption by companion dogs and cats. By their estimates, there are more than 163 million dogs and cats in the U.S. As conventional companion animal diets are largely based on animal products, the researchers suspected the food of companion animals (typically comprising 31–34% of animal-derived ingredients) to have a significant environmental footprint. The study includes a first-of-its-kind evaluation of the animal-derived energy in pet food. The researchers also considered the environmental impacts from the animal products fed to them and the faeces production from the companion animals.

It is becoming well known that meat-based diets require more energy, land, and water than plant-based diets do. And meat-based diets also have greater environmental consequences in terms of erosion, pesticides, and waste than plant-based diets do. Researchers widely accept 4.7 as the feed conversion ratio for meat on an energy basis. It is the average of the loss-adjusted values for cow meat, lamb meat, pig meat, and chicken meat, weighted by their relative abundance in American diets. The study notes that as more than 60% of U.S. households have companion animals, it is crucial to take this consumption into account when making calculations of the environmental impacts of overall dietary choices. In fact, the number of people with dog or cat companions is increasing globally. Should nothing change, the ever-increasing number of omnivorous companion animals—combined with the increasing trend of “pet humanization” (when people opt for higher quality meat in companion animal feed)—are bound to increase the demand for animal products worldwide.

The study comes with some assumptions and limitations. For example, dry pet food typically has lower animal content than that of wet food. So, the use of dry food for these calculations provides a conservative estimate. Also, there is no way of knowing the exact proportions of ingredients in commercial pet foods. This is due to trade secrets. And so the author resorted to calculating a minimum overall estimate of animal-derived energy in dog and cat food by weighting the first five ingredients equally. Finally, the study was limited to meat consumption. Hence the term animal-derived products should be understood as meat derivatives.

The findings are worrying indeed. In terms of the use of land, water, fossil fuel, phosphate, and biocides, U.S. dogs’ and cats’ diets constitute 25–30% of the environmental impacts from animal production. Let’s put this into perspective. The study proposes that—based on the calculated average animal-derived products in U.S. citizen diets (19%)—the equivalent plant-derived energy in U.S. dogs’ and cats’ diets could support 39 million people if companion animal diets were to contain less meat. Also, the equivalent plant-derived energy could support 553 million people should people in the U.S. ditch meat themselves. The combination of these two figures is equivalent to 8% of the global population.

The environmental impacts of omnivorous companion animals are not limited to demand and consumption—let’s not forget production. In total, researchers estimate that U.S. dogs and cats produce 5.1 megatons of faeces each year. This is around 30% of that produced by humans. This is easier to imagine as a visualization: if U.S. dog and cat guardians would dispose of all their companion animals’ faeces as garbage, the faeces would equate to the total garbage produced by 6.6 million U.S. citizens. This figure is roughly the population of Massachusetts. We have not even mentioned the production of methane and nitrous oxide that is related to companion animals’ animal-derived diets. Up to 64 million tons of the equivalent CO₂ greenhouse gases are associated with dogs and cats. But, due to the nature of the meats used in commercial pet feed, this figure may be lower.

The study notes that people often argue that meat fed to cats and dogs should not count as consumption beyond that of humans. This is because dogs and cats eat meat that humans will not consume. And people view this meat as merely a by-product of production for human use. These arguments assume such meat would otherwise go to waste. And they rely on the assumption that we could not make these by-products suitable for human consumption. This is despite reports of impoverished U.S. citizens eating pet food as a necessary supplement to their diet on a long-term basis. In fact, it is not only what we feed our companion animals, but also how we feed them that is important in assessing companion animals’ environmental impacts. For example, obesity is a major problem among domestic animals these days.

The study proposes that future guardians of companion animals transition to companion animals that eat less meat. This is because they would have less environmental impact. The author also suggests that current companion animals receive only nutritionally appropriate amounts. But, the study warns that without a large-scale reduction in companion animal numbers worldwide, or changes to the food system that would drastically reduce the per-capita animal product consumption, the environmental and energetic impacts of these animals will remain significant.

Animal advocates will surely be thrilled to learn of this study that finally addresses the environmental impacts of companion animal diets. It serves as a good reference for raising awareness on the topic and for encouraging people to adopt balanced plant-based diets for their omnivorous companions.