Even responsible pet owners do it all the time.

They’ll take their dog for a walk in the woods and won’t bother picking up his feces, an oversight they’d never consider on a walk around the neighborhood.

Maybe they think, “Hey, it’s the woods, nobody’s going to step in it.” Or, “Hey, it’ll decompose and help fertilize the ground.” Or, “Hey, bears go in the woods and nobody picks up their poop. What’s the difference?”

The difference is their diet.

Bears don’t eat commercial dog food (unless they’ve stumbled upon a campsite where campers with a dog failed to secure their food stuffs). Dogs do, and if they poop in the woods and owners don’t pick up after them, it has a huge environmental impact.

To measure that impact, the Leave No Trace Center for Outdoor Ethics, a national organization that protects the outdoors by teaching people to enjoy it responsibly, tracked what they called “canine defecation events” on Open Space and Mountain Parks (OSMP) land in Boulder, Colorado, last summer. The OSMP includes 45,000 acres of wildlife habitat, unique geological features, and greenways.

OSMP sees 5.3 million visitors each year and many of them bring their dogs. Not surprising, considering that 90% of OSMP’s 150 miles of hiking trails are open to dogs.

According to the study, only about 73% of dog owners picked up their pets’ waste. That means an estimated 60,000 pounds of dog poop gets left behind each year.

Here’s where the difference in diet comes in.

Like all wildlife, bears forage for food in their home environment. That means they’re consuming resources and nutrients from the same ecosystem they’re a part of. And after they’ve digested and absorbed that food, they return those same resources and nutrients to the ecosystem via their scat. The system is basically a closed loop, with no net gain or loss in nutrients or resources.

Not so with dogs, who are unlikely to be eating a diet rich in native plants from the ecosystem they leave their waste in.

Most dogs eat pet food rich in nutrients designed to provide them with a complete and healthy diet. And those pet foods lead to excess nutrients like nitrogen and phosphorus in the environment when dog poop isn’t picked up. A buildup of those nutrients can create unstable conditions in many ecosystems.

Those unstable conditions can lead to algae blooms in rivers, lakes, and streams, which creates an inviting habitat for invasive weeds that slowly kill off the local plant and fish life.

Now, consider that dogs produce more than 20 billion pounds of poop in the United States each year. Given that, nationally, 40% of dog owners don’t pick up after their pets, that leaves a lot of dog poop lying around.  

Another problem: all that dog poop is full of bacteria, and potentially parasites. Just one gram of dog poop can contain up to 23 million fecal coliform bacteria—all just lying there on the ground.

Until it gets into the air.

A recent study of air samples in Cleveland, Ohio, and Detroit, Michigan, found that 10%–50% of the bacteria in the air came from dog poop.

That’s one more reason for people to pick up after their pets no matter where they go.

Because dog poop really gets around.

Photo credit: © iStock/s-eyerkaufer