WASHINGTON - When every known speaker of the language Amurdag gets together, there's still no one to talk to.

Native Australian Charlie Mungulda is the only person alive known to speak that language, one of thousands around the world on the brink of extinction.

From rural Australia to Siberia to Oklahoma, languages that embody the history and traditions of people are dying, researchers said Tuesday.

While there are an estimated 7,000 languages spoken around the world today, one of them dies out about every two weeks, according to linguistic experts struggling to save at least some of them.

Five hotspots where languages are most endangered were listed Tuesday in a briefing by the Living Tongues Institute for Endangered Languages and the National Geographic Society.

In addition to northern Australia, eastern Siberia and Oklahoma and the U.S. Southwest, many native languages are endangered in South America - Ecuador, Colombia, Peru, Brazil and Bolivia - as well as the area including British Columbia, and the states of Washington and Oregon.

Losing languages means losing knowledge, says K. David Harrison, an assistant professor of linguistics at Swarthmore College.

"When we lose a language, we lose centuries of human thinking about time, seasons, sea creatures, reindeer, edible flowers, mathematics, landscapes, myths, music, the unknown and the everyday."

As many as half of the current languages have never been written down, he estimated.

That means, if the last speaker of many of these vanished tomorrow, the language would be lost because there is no dictionary, no literature, no text of any kind, he said.

Harrison is associate director of the Living Tongues Institute based in Salem, Ore. He and institute director Gregory D.S. Anderson analyzed the top regions for disappearing languages.

Anderson said languages become endangered when a community decides that its language is an impediment. The children may be first to do this, he explained, realizing that other more widely spoken languages are more useful.

The key to getting a language revitalized, he said, is getting a new generation of speakers. He said the institute worked with local communities and tries to help by developing teaching materials and by recording the endangered language.

Harrison said that the 83 most widely spoken languages account for about 80 percent of the world's population while the 3,500 smallest languages account for just 0.2 percent of the world's people. Languages are more endangered than plant and animal species, he said.

The research is funded by the Australian government, U.S. National Science Foundation, National Geographic Society and grants from foundations.