DENVER — Mounting piles of human waste and trash have prompted a coalition of retired National Park Service leaders to press the Trump Administration to shutter every national park during the ongoing federal shutdown.

Although federal funding has stopped until at least next week, many national parks are operating under a "soft" closure. That means they're largely unstaffed and unpatrolled while visitors continue entering.

The situation has led to piles of trash accumulating in some parks, locked and stinking toilets in others, and concerns that unsupervised users are destroying the resources and landscapes the parks are supposed to protect.

“It’s really an awful situation to be in, but our primary job is to protect park resources and the safety of the public," said Phil Francis, the chairman of the Coalition to Protect America’s National Parks. "I hate it. I always advocated for keeping the parks open and finding a solution, but when you’re unable to protect the park resources and protect the visitors, it changes how you have to look at it.”

The coalition, along with the Trust for Public Land, is asking the president to shutter every park until funding returns. There are more than 400 national parks, monuments, battlefields and other sites around the country. Some are small, like the John Fitzgerald Kennedy National Historic Site in Brookline, Massachusetts, and can be easily closed to access.

But others, like the Great Smoky Mountains National Park, have no entrance stations and would have to be barricaded by staff, said Francis, who was a deputy superintendent there for nearly 10 years.

"I do not make this request lightly — closing the national parks will disrupt many lives. But leaving them open without the staffing and resources they need imperils the health and safety of visitors and the long-term integrity of the parks," Diane Regas, the TPL's president and CEO, said in a statement.

Francis said volunteer efforts to clean up trash are welcome, but only park workers have the knowledge necessary to operate wastewater treatment systems, manage wildlife and prevent looting of artifacts or plants like ginseng.

Some states, including Arizona and Utah, are using state money to keep some parks open, including the Grand Canyon, Zion, Arches and Bryce Canyon. Arizona is kicking in about $64,000 a week to maintain essential services at the Grand Canyon, although no one is staffing the entrance booths.

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At California's Yosemite National Park, privately run hotels and lodges within park boundaries remain open and reservations are being honored. But volunteers are picking up trash and removing diapers and human waste, a trying task made worse by freezing temperatures.

“I thought they were kidding when they said there was feces everywhere, but there is,” said volunteer Anthony Martinez, 42, as he poked at a tissue paper frozen to some grass. "That’s going to stay there until spring,” he said with a sigh.

Without the watchful eye of rangers and park stewards, Yosemite visitors have been leaving garbage at vista points, bringing dogs into pet-restricted areas, driving vehicles over curbs and even defecating on the ground near padlocked restrooms. It's a scene that's being repeated across the country as tourists refuse to let the closures ruin their vacation plans.

During the last government shutdown, Oct. 1-17, 2013, the Obama administration sparked widespread outrage when it closed park entrances and put up barriers around national monuments, and briefly turned away veterans trying to visit the World War II Memorial in Washington, D.C.

By keeping many of the parks open now, the Trump administration has been able to avoid the same kind of outright anger faced by the Obama administration.

Jeff Jarvis, who ran the park service during the 2013 government shutdown, said he took a lot of political heat then. But he still believes it was the right decision.

He said it would also be the right decision now. Jarvis served under President Barack Obama from 2009-2017, and spent five hours testifying before the Republican-led Congress after his shutdown decision.

“I think this is purely politically driven,” Jarvis said of the soft closures instituted by the Trump administration. “They did it to avoid the public backlash but we’re already starting to see public outcry about what’s happening in the parks.”

Trump told Democrats on Friday he is prepared to allow the government shutdown to go on months or even years if that's what it takes to get a border wall, the primary source of conflict for the government shutdown.

Outside Washington, however, frustration among tourists is mounting, especially in parks where garbage cans are taped shut and toilets locked.

"Having the park closed, that kind of hurts," said Efrain Turrubiartez, 45, who was visiting Rocky Mountain National Park this week with his family from Waco, Texas.

Francis said he understands the desire to keep public land accessible to the public. But when it comes down to a decision between allowing access and protecting the park resources, there's no more room for debate: “I think it’s to the point now were where it has to be done."

Contributing: Sam Gross, Reno Gazette Journal