As one of the wildest and most natural places on Earth, Australia's Outback is home to few people, but a new study Wednesday argues that it needs a bigger population to escape decline.

The vast area, which spreads out from Australia's centre to cover some three-quarters of the landmass, is suffering from several threats including feral animals and invasive weeds.

But a report -- "The Modern Outback", published by the Pew Charitable Trusts -- said with Aboriginal peoples removed from or leaving the land, and fewer workers on many pastoral properties, it was bereft of people to manage these dangers.

"We often think in conservation, and protecting nature, the fundamental threat is too many people.... and that is a global truth," co-author Barry Traill told AFP.

"But that can obscure the reality in the Outback that it's a huge part of natural country which, to stay healthy, actually needs people actively managing it. And much of it now has fewer people than at any time in the last 50,000 years."

Traill said there was no accurate estimate of how many people were working to manage the Outback landscape, which stretches across state and territory borders. But less than five percent of Australia's more than 23 million people live in it.

"Much of the planet is very crowded, nature is losing out, but here we have one of the very few great natural places left on the planet, up there with the Amazon," Traill said.

"And much of it is now very empty of people and we actually need land managers back on country. It's just not about having people sitting there living there, it's about active land management working to protect the country."

The report defines Australia's Outback, a term coined by 19th century settlers to refer to "out in the back settlements", as some 5.6 million square kilometres (2.2 million square miles) of varied landscape, including red sandy deserts and tropical savannas.

"Although Australia is a relatively infertile continent, this trait is accentuated in the Outback," the Pew study said, adding that the infertility meant communities were scattered and remote, leaving environments largely intact.

But the report noted that even in isolated areas where there were no signs of humans, some native plant and animal species were in decline and others had disappeared irrevocably.

Traill acknowledged the difficulties of living in the Outback, where in some cases the nearest petrol station is eight hours' drive away, but said reforms were needed to preserve its unique native species and ensure ecosystems remained healthy.

He said the two biggest threats were introduced species -- ranging from horses and cows, to foxes and feral cats and camels -- and the loss of the indigenous Aboriginal practice of controlled fires to maintain the habitat.

He said if nothing were done, the bush would survive, but become degraded.

"It is as a whole of international significance and we need to think about it as a unified whole, not just a selection of very beautiful spots -- of Uluru, or Kakadu or the Kimberley that are somehow joined up by drabber areas of bush that we don't really care about," he said.

"If we just looked after the icons... they would degrade because they are dependent for their ecological health on the surrounding countryside. We want to maintain the fabric of all the Outback."