MIAMI • Areas of the world that are untouched by humans are disappearing, with some 10 per cent of the planet's wilderness gone since the 1990s, researchers have said.

The study published in the journal Current Biology on Thursday raises concern about these vital areas that form the foundation for ecosystems, particularly in the places that have lost the most, the Amazon and Central Africa. "We can't restore or offset our wilderness. Once it is gone, it is gone," lead study author James Watson said.

For the study, researchers defined "wilderness" as "biologically and ecologically intact landscapes free of any significant human disturbance".

They made a map of such areas at present, and compared it to a map made using the same methods in the early 1990s. The result showed that about 20 per cent of the world's land area is currently wilderness, or about 30.1 million sq km.

Most of that wilderness is in Australia, North America, North Asia and North Africa.

Comparing the old map to the new one showed that an estimated 3.3 million sq km - almost 10 per cent of the wilderness area - has been lost in the past two decades. The amount lost is equal to twice the land mass of Alaska, or about half the entire Amazon.

"If we don't act soon, there will only be tiny remnants of wilderness around the planet, and this is a disaster for conservation, for climate change, and for some of the most vulnerable human communities on the planet," said Dr Watson.

AGENCE FRANCE-PRESSE