Joshua Tree, Colorado: Human waste by the side of a busy road in Yosemite. Overflowing toilets in the Grand Canyon. The Rocky Mountains inaccessible because of unploughed roads.

And in all these places, ordinary people stepping in to try to save some of America’s most revered landmarks from being overrun.

As the impasse over funding for Donald Trump’s border wall pushes the government shutdown into its third week, US national parks are bearing the brunt of the financial crunch.

The vast majority of park service staff are furloughed during one of the busiest times of the year, particularly in the western US.

Campers and hikers who might have been pleased to skip the entry fees into unstaffed parks have been welcomed by shuttered visitor centers, locked bathrooms, and garbage cans brimming over. Many have lost the reservations they had booked months or even years in advance.

At least three people have died in the parks since the shutdown began, the Washington Post reported.

Two people fell, one at the Horseshoe Bend overlook in Arizona and the second in Yosemite; another was hit by a falling tree in Great Smoky Mountains national park. It is unclear if the deaths are related to the shutdown, but experts said the staffing shortage made visits potentially more dangerous. A park service spokesman told the publication that an average of six people die each week in the parks.

Volunteers help tourists find their way at Joshua Tree.

Across the west, reporters found varying levels of crisis at three different national parks.

In the vast desert expanses of Joshua Tree, in southern California, the situation has been fraught. Unsettling news reports and cold weather have done little to drive visitors away. Just after the new year, lines of cars cruised past boarded windows where officials typically collect $30 (Dh110) per vehicle. Climbers and selfie-takers could be seen climbing rocks clumped high amid the park’s eponymous prickly trees.

“At Joshua Tree and Yosemite, impacts from human waste is a concern, which includes people relieving themselves in public places, such as behind buildings [and] on roadsides,” said Andrew Mu-oz, a park service spokesperson. He described the situation as a health hazard and said that the litter increased the risk of dangerous interactions between people and wildlife.

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Though officials were scarce, local people are coming together to fill in the gaps, determined to keep the park accessible and clean.

Megan Edge, a barista at a coffee shop next to the closed-down visitor centre, said she and other employees were handing out maps and showing out-of-towners where to go. “We live for this park and try to take care of it,” she said, adding that they had already run of out maps by midday due to the high demand for help.

Local volunteers have helped Joshua Tree stock toilet paper.

Each morning dozens of volunteers from the local not-for-profit organisation Friends of Joshua Tree have been gathering to pick up trash, stock toilet paper, and clean toilets near campsites.

“We were not prepared for this level,” said the executive director, John Lauretig, standing next to a truck loaded with toilet paper. “There are over 150 pit toilets in the park. So that’s a lot of toilet paper. The visitation over this holiday has probably been upwards of 200,000 people.”

The group has already spent more than $2,000 on toilet paper alone. “If we miss a day the toilets can get ugly quick,” he said.

Campers have been surprised by the clean conditions. Brian Dillman, who lost the New Year’s Day reservation he booked back in June for a group of 12, said he was lucky to find a new spot.

“I was expecting anarchy and chaos and filth. Instead, my experience was probably the smoothest and cleanest visit to a national part in the last few years,” he said.

Trash has piled up at Yosemite amid the shutdown. Even so, reports of pit toilets nearing capacity and off-roadingprompted officials to close Joshua Tree to campers on Wednesday. Dillman said he was glad. “It is too precious of a park to rely on the responsibility of visitors and the goodwill of community members.”

In Arizona, state officials have rallied to keep their No 1 tourist attraction open. Attracting nearly 6 million visitors per year, the Grand Canyon is responsible for generating some $650m in tourism-related revenue and 10,000 jobs in local communities.

Immediately after the shutdown began, the state provided a $64,000 “donation” to the US government that was intended to pay for one week’s worth of “essential functions”: keeping restrooms clean, removing trash, ploughing park roads. As the shutdown stretches on, Arizona is still footing the bill.

The restaurants and stores, which are privately run, were bustling over the holidays, and parking lots were full. Out on the trails it was more subdued, probably because of the below-freezing temperatures and snow over the holiday week, but rule-breakers were spotted.

“The perception is that rangers aren’t on duty,” said Helen Ranney, a hiking guide with the group Wildland Trekking. While leading clients on a hike down the popular South Kaibab trail on 27 December, Ranney encountered a woman with a dog off leash, which is against park regulations. “I told her the dog could spook mules or wildlife. She already knew this and she didn’t care,” Ranney said. Ranney also saw over-full composting toilets along the trail that were “appalling”.

Tourists take photos of a snow-covered Grand Canyon, which state officials have helped keep open.

Another major problem is lost revenues. The Grand Canyon has a maintenance backlog of $330 million for projects including restoring historic buildings and replacing essential water pipeline infrastructure. Yet currently there are no attendants to collect the $35 entrance fee.

“The [National Park Service] is already a wounded agency; it’s like a person hobbling around on crutches,” said Roger Clark, program director of the not-for-profit advocacy group Grand Canyon Trust. “And now this shutdown is just a swift kick in the knees.”

For some in Colorado, the shutdown doesn’t mean a curtailed national park visit. It means no visit at all.

Rocky Mountain National Park is one of the most visited national parks in the country, with its celebrated bighorn sheep and dozens of peaks higher than 3,600 metres. But all that is now out of reach as there is no money to plough snow from the roadways.

Theoretically anyone could hike, bike or snowshoe in (and avoid an entrance fee), but the average tourist is probably not that hardy. During the last federal shutdown, in early 2018, one popular part of the park “was all yellow snow”, said Estee Rivera, the executive director of the Rocky Mountain Conservancy. She called the image “pretty disgusting” and expected similar scenes this time around.

A few hours west, the snowy mesas of Colorado National Monument are locked behind metal gates. Rangers tried to keep the park’s narrow roadway open, but they had to close it after storms around Christmas.

People are still driving in, however, often unaware of the closure until they reach the gates. Such a thing would usually be announced on the park’s website — but there is no one to update it.