Human faeces, overflowing garbage and illegal off-road driving in fragile areas were beginning to overwhelm some of the iconic national parks in the US, where a partial government shutdown left areas open to visitors but few staff on duty.

Key points: Concerns natural resources and cultural and historic artefacts could be damaged

Concerns natural resources and cultural and historic artefacts could be damaged Yosemite resident said he had never seen so much rubbish, human waste and disregard for rules in the area

Yosemite resident said he had never seen so much rubbish, human waste and disregard for rules in the area Parks across the US are closing camping areas, toilets and bins while business operators try to provide services

On the 10th day of the partial federal government shutdown many parks were without most of the rangers and others who staff campgrounds and otherwise keep facilities running.

Campers at Joshua Tree National Park in Southern California's deserts were reporting squabbles as different families laid claims to sites, with no rangers on hand to adjudicate, according to local gift shop owner Ethan Feltges.

Instead, Mr Feltges said he and other business owners had stepped into the gap as much as possible.

They have been emptying overflowing bins and sweeping and stocking restrooms that remained open.

Outside his Coyote Corner gift shop, Mr Feltges had set up a portable toilet for the visitors still streaming in and out of the park.

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He was spending his days standing outside his store, offering tips about the park in place of the rangers who would normally be present.

"The whole community has come together," Mr Feltges said.

"Everyone loves the park. And there's a lot of businesses that actually need the park."

Some visitors have strung Christmas lights in the twisting Joshua trees, many of which are hundreds of years old.

Most visitors were being respectful of the desert wilderness and park facilities, Joshua Tree's superintendent David Smith said.

But some are seizing on the shortage of park staffers to drive off road illegally and otherwise damage the park, as well as relieving themselves in the open.

Joshua Tree is expected to begin closing some campgrounds for all but day use.

'More trash and human waste and disregard'

Yosemite National Park officials closed some minimally supervised campgrounds and public areas within the park that were overwhelmed on Monday.

Under the shutdown plan, authorities have to close any area where garbage or other problems become threats to the health and safety of humans or wildlife.

But that's not stopping visitors from coming.

Yosemite Valley resident Dakota Snider said crowds were driving into the park to take advantage of free admission.

"It's so heartbreaking. There is more trash and human waste and disregard for the rules than I've seen in my four years living here," Mr Snider said.

"It's a free-for-all."

Tourists are still coming and are discarding rubbish on the road in Yosemite National Park. ( AP: Dakota Snider )

They had unleashed their dogs and let then run freely in an area rich with bears and other wildlife, and were scattering bags of garbage along the roads, Mr Snider said.

"You're looking at Yosemite Falls and in front of you is plastic bottles and trash bags."

A Yosemite resident said the littering was the worst he had seen in his time living near the park. ( AP: Dakota Snider )

Unlike shutdowns in some previous administrations, the Trump administration was leaving parks open to visitors despite the lack of staff.

"We're afraid that we're going to start seeing significant damage to the natural resources in parks and potentially to historic and other cultural artefacts," John Garder, senior budget director of the National Parks Conservation Association, said.

"We're concerned there'll be impacts to visitors' safety.

"It's really a nightmare scenario."

Officials at Rocky Mountain National Park in Colorado said they were closing restrooms and locking up trash bins in many locations.

In Yellowstone National Park private tour companies have picked up some of the maintenance normally done by federal workers.

ABC/AP