Picture this: You're hiking through the tall red pines at the Hartley Nature Center in Duluth. The birds are singing in the trees, it's a beautiful spring day, the only thing that's missing is the opening bars of Edvard Grieg. And then — squish ...

Someone didn't pick up after their dog.

"Everyone's had the moment where you accidentally stepped in dog poop, and you take a stick or something and you're trying to get it out of the tread of your shoe, it's foul and disgusting and it smells..." Tom O'Rourke trails off. He's the executive director of the Hartley Nature Center. And he knows this moment all too well.

Spring is an especially bad time for that unexpected squish, he said — and this year was exacerbated by an interminable winter that dumped a huge amount of snow.

When all that snow melted, it revealed frozen piles of excrement that dog owners failed to pick up — all winter long. And then those piles melted — slowly — in the spring thaw.

O'Rourke has a name for this time of year: "We call it poopsicle season."

Hartley is one of the many Duluth parks and green spaces that have this problem every spring.

So a few months ago, the city took action. The parks department has launched a campaign to remind residents — with signs and postcards and on social media — to do the responsible thing and pick up after their pets.

A Poop Fairy sign in Congdon Park, along Tischer Creek in Duluth. Dan Kraker | MPR News

The message is simple: "There's no such thing as the Poop Fairy!"

It's actually part of a campaign that's popped up all over the country in the past few years, from New Mexico to South Carolina to Colorado. But in Duluth, it all started with Dave Grandmaison.

Grandmaison spends a lot of time at Hartley Park, all year round. He snowshoes and mountain bikes on trails that wind through the forest. And, like O'Rourke, he experienced the messy problem this spring firsthand.

"At first it was just a little bit of an annoyance," Grandmaison said. "But it got to the point where it was very difficult to dodge the piles."

And for Grandmaison, it was also a business problem. He doesn't just use Hartley Park's trails for his own recreation. He leads tourists on hikes and bike rides here with his company, The Duluth Experience.

"It got to the point where I could no longer bring my guests out to Hartley, because I was embarrassed," he said.

So, earlier this spring, he contacted O'Rourke and the city to see what they could do about the smelly problem.

Dave Grandmaison, left, and Tom O'Rourke, director of the Hartley Nature Center, pose in front of a Poop Fairy sign in Duluth's Hartley Park on Tuesday. The two were instrumental in making the city's new Poop Fairy awareness campaign happen. Dan Kraker | MPR News

"It was something I felt compelled to make a stink about," he said.

Pun absolutely intended.

"And it wasn't just Hartley," he said, "but Hartley was kind of the epicenter of the poop-idemic."

It was around that time, as O'Rourke was working on a fix, when someone sent him a picture of a sign in Santa Cruz, Calif. On it, a fairy is using a scooper to pick up after a dog. "There is no Poop Fairy," it says. "Please clean up after your dog."

O'Rourke passed it on to the city. And Duluth Parks & Recreation's whimsical campaign — with its own bag-toting fairy — was born.

"We wanted to do something that was fun," said the department's volunteer coordinator, Cheryl Skafte. "I think that message resonates with people."

The city launched its do-the-right-thing social media campaign in March. It's handing out large postcards around town, and has posted signs at popular trailheads.

Something the city is not doing — at least, not yet — is adding more garbage cans to its parks and trails. Skafte said there are about 100 cans now, but noted that it's not exactly possible to put a can near every spot a dog might need to take a break.

Cheryl Skafte is a volunteer coordinator with Duluth Parks & Recreation, in Congdon Park. Dan Kraker | MPR News

"One of the things we want to really instill in people across the community is [that] sometimes you have to pack out what you pack in, and your dog's poop is one of those things," she said. "There's not going to be a garbage can everywhere your dog goes to the bathroom."

Duluth is a dog-friendly town. Skafte said there are about 20,000 dogs in the city, about one for every four people. And those dogs, she estimates, generate about 4 million pounds of droppings every year. Sometimes their owners just don't pick it up.

"Every spring, we get complaints about it," Skafte said. "We've come up with some interesting names for it. Like: The Great Poop Melt. Poop-pocalypse was one of them, too, that we came up with. I actually never thought I would say 'poop' so much at work."

But the reason they talk about it so much is because it can be a serious public health and environmental concern.

"It's something that's not just uncomfortable for our users, and unattractive, but it's also unhealthy for our ecosystem," Skafte said.

When it rains — or when the snow melts — all of that mess gets washed down stormwater drains and into the streams that rush down the hill through the city. The extra nutrients in that waste cause algae growth in the water, and deplete the oxygen that fish need to survive. And it contains harmful parasites and bacteria, like E. coli.

And that's when it becomes a public health concern, said Tom Estabrooks, who works in the Minnesota Pollution Control Agency's Duluth office.

"Humans boating, wading, fishing, kayaking — things like that: You're exposed to those conditions, and ingesting that water can make you sick," he said.

In many cities dog waste is a major source of the bacteria found in urban waterways. In New Mexico, the city of Albuquerque found that dogs were the source of about 20 percent of E. coli contamination found in the Rio Grande River.

After Bernalillo County launched a Poop Fairy campaign in 2014, E. coli levels dropped significantly.

Caroline Scruggs, a professor at the University of New Mexico, wondered whether that drop was a coincidence. She assigned a student study the effectiveness of the campaign. And while the results are preliminary, she said it appears the campaign deserves credit for changing dog owners' behavior.

The county "did everything right," she said. "They used humor. They kept it short and sweet with an easy-to-remember slogan. That's the kind of thing people can pick up really quickly. They remember it."

Last year, the MPCA found elevated E. coli levels in several Duluth streams, including Keene Creek, where in 2006 the city opened a popular dog park.

It's too early to say whether dogs — or, rather, their scofflaw owners — are to blame for the elevated E. coli on Keene Creek and other waterways in Duluth.

Keene Creek in western Duluth has tested positive for elevated levels of E. coli. The city is now trying to determine whether dog waste, possibly from the nearby Keene Creek dog park, is to blame. Dan Kraker | MPR News

"There's a potential that they could be a source, especially in some urban parks that are very popular," Estabrook said. "Most of the trails are very near the streams and things like that. Dog poop doesn't have far to go to make it into the water."

The city is doing DNA analysis to pinpoint exactly where the bacteria is coming from, and to determine if there's any connection between the dog park and the high levels of E. coli in the water nearby.

Adriana Swartz and her husband bring their golden retriever, Kevin, to the Keene Creek dog park almost daily. "We try to, for every one poop, to at least get another poop," Swartz said. "Last time I came I got eight poops. I was very proud of that number. Eight orphan poops, plus my dog's own, so I guess that's nine."

Adriana Swartz and her golden retriever, Kevin, visit the Keene Creek dog park in Duluth nearly every day. On Tuesday, Swartz said she's frequently picking up after not only her own dog, but others. Dan Kraker | MPR News

At this park, at least, Swartz is something of that mythical fairy Duluth's new signs debunk. But picking up after your own pet is a more reliable strategy, city officials say.

"Aldo Leopold, the conservationist, said [that] ethics is doing the right thing even if no one is looking," Tom O'Rourke, the Hartley Nature Center director, said.

"That's what we need to see in Hartley. It's really easy to watch your dog go to the bathroom and walk away from it, but do the right thing."

It's still too early to tell what kind of an impact the new campaign is having in Duluth. People say they'll have a better gauge next spring — during poopsicle season.