The world's wilderness has reduced by a tenth in the past two decades, according to a study by World Conservation Society scientists.

The research findings published in the journal Current Biology noted the wild areas that vanished are mostly in South America and Africa, and only about 20 per cent of the world's land area is sorted as wilderness currently, Xinhua news agency reported on Monday.

The concept of wild areas or wilderness means landscapes free of human disturbances such as housing, development and industry, according to the scientists.

The findings are based on a map of worldwide wilderness now compared with the condition in the early 1990s. 

The distribution of different colours in the map shows that around 3.3 million sq.km of wild areas has reduced during the period of time.

"International policy mechanisms must recognize the actions needed to maintain wilderness areas before it is too late," said professor James Watson of the University of Queensland, Australia, and the US Wildlife Conservation Society in New York.