Planet Earth has lost one tenth of its area of wilderness since 1993, equivalent to half of Australia in size, according to a new study.

Key points: 3.3 million square kilometres of wilderness has been lost since 1993

3.3 million square kilometres of wilderness has been lost since 1993 Wilderness supplies fresh water, food, medicine and reduces extreme weather

Wilderness supplies fresh water, food, medicine and reduces extreme weather A global agreement on protection of wilderness is required, researchers say

The loss, mainly in the Amazon and Central Africa, highlights the need for global agreements to protect remaining areas unaffected by human activities, researchers said.

"An area half the size of Australia has disappeared in just two decades. That's a catastrophic loss of wilderness," said Associate Professor James Watson, an ecologist from the University of Queensland and the Wildlife Conservation Society.

Dr Watson and colleagues report their findings in today's issue of Current Biology.

The researchers define wilderness as an area free from significant human disturbance such as urbanisation, agriculture, mining and logging.

They compared the global footprint of humans as it was in 1993 with that as it was in 2016.

Their analysis showed that while more than 20 per cent of the world's land area remained as wilderness — with the majority being located in North America, North Asia, North Africa, and Australia — there has been a 10 per cent loss of total wilderness area across the world.

"We found that over 3 million square kilometres of wilderness has been lost globally," Dr Watson said.

They found that most loss had occurred in Amazonia, which has lost 30 per cent of intact landscapes, and central Africa, where 14 per cent of the forests have been lost.

A relatively small proportion of Australian wilderness has been lost.

Dr Watson said this was the first assessment of global wilderness decline.

Central Africa is one hot spot for loss of wilderness. ( Supplied: Liana Joseph )

The importance of wilderness

Wilderness, which is often home to Indigenous communities, is a "stronghold for biodiversity and ecosystem services", Dr Watson said.

Food, medicines, fibre and water all come from the intact system and when you degrade it there's plenty of evidence to show that you don't get those ecosystem services."

Dr Watson said wilderness areas support species with a high degree of genetic variation, helping them to be resilient to environmental change.

"They have the ability to buffer and adapt to change."

Wilderness also helps regulate local climate — reducing extreme climatic events, he said.

He said there was no evidence that lost wilderness areas could be restored to their previous state.

"Once you lose them, you lose them ... and that's a tragedy because humans are putting their fingerprints everywhere and we're losing that reference point for nature."

Wilderness needs to be recognised as valuable in its own right - not just for the species that live there, researchers say. ( Supplied: Liana Joseph )

Call for global protection

Dr Watson said that the total area of wilderness was decreasing despite efforts to increase protected areas, partly because of a focus on preventing species from going extinct while ignoring the value of wilderness.

He pointed to wilderness areas such as the savannas of Northern Australia and the Great Western Woodland in Western Australia, which were both largely intact but "slowly eroding".

"Those areas should be recognised as valuable in their own right — not just for the threatened species that live in it," Dr Watson said. "They are both important."

He said wilderness protection should include creating conservation corridors between large protected areas, and enabling Indigenous communities to be involved in conservation.

"All nations need to start conserving their wilderness areas, and we've got to have a global agreement that these things are declining rapidly," he said.