Human faeces, overflowing garbage, illegal off-roading and other damaging behaviour in fragile areas were beginning to overwhelm some of the West’s iconic national parks, as a partial government shutdown left the areas open to visitors but with little staff on duty.

“It’s a free-for-all,” Dakota Snider, 24, who lives and works in Yosemite Valley, said by telephone on Monday, as Yosemite National Park officials announced closings of some minimally supervised campgrounds and public areas within the park that are overwhelmed.

“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,” Ms Snider said.

Hetch Hetchy and Mariposa Grove are now closed due to lack of restrooms and resulting impacts from human waste. People entering closed areas are being cited. https://t.co/OXlp1YQkGO

— Yosemite National Park (@YosemiteNPS) December 30, 2018

The 10th day of the partial federal government shutdown, which has forced furloughs of hundreds of thousands of federal government employees, has left many parks without most of the rangers and others who staff campgrounds and otherwise keep parks running.

Unlike shutdowns in some previous administrations, the Trump administration was leaving parks open to visitors despite the staff furloughs, said John Garder, senior budget director of the non-profit National Parks Conservation Association.

“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 artifacts,” Mr Garder said. “We’re concerned there’ll be impacts to visitors’ safety.”

“It’s really a nightmare scenario,” Mr Garder said.

A road in Yosemite National Park, California is lined with trash as the partial government shutdown left the areas open to visitors but with little staff on duty. Photo: Dakota Snider/AP

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, said Ethan Feltges, who operates a gift shop outside Joshua Tree.

Mr Feltges and other business owners around Joshua Tree had stepped into the gap as much as possible, hauling trailers into the park to empty overflowing trash bins and sweeping and stocking restrooms that were still open, Mr Feltges said.

Mr Feltges had set up a portable toilet at his store to help the visitors still streaming in and out of the park. He was spending his days standing outside his store, offering tips about the park in place of the rangers who normally would 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.”

Campgrounds in the park will be closed effective noon Wednesday, January 2nd. The park is being forced to take this action for health and safety concerns as vault toilets reach capacity. Indian Cove and Black Rock campgrounds will be open for day-use only, sunrise to sunset.

— Joshua Tree NPS (@JoshuaTreeNPS) December 31, 2018

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

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

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

-AAP