Half the world's 6,000 languages are under threat of extinction, a new edition of the 'Atlas of the World's Languages in Danger of Disappearing' warned Thursday to mark International Mother Language Day. The death of languages also spells the end of the culture which gave rise to them, making them "a living heritage we should cherish," said Koichiro Matsuura, director-general of the United Nations (news - web sites) Educational, Scientific and Cultural Organization (UNESCO (news - web sites)), commemorating the special day his agency established three years ago. UNESCO plans to set up a monitoring system that will warn when an endangered language--classed as those no longer spoken by at least 30 percent of a community's children--is threatened with extinction. The agency is urging countries to protect languages as natural and cultural treasures.