Noam Chomsky aside, Mark Okrand is probably the world's only celebrity linguist. Okrand, whose dissertation focused on Native American languages, was hired by Paramount Pictures in the early 1980s to devise a language for the Klingons for the second film in the Star Trek franchise, The Wrath of Khan. As is the way with most things Star Trek, Klingon - tlhIngan Hol - escaped the confines of the big screen and is now said to have a vocabulary of around 3000 words, some of which appear in Okrand's Klingon Dictionary (1992). A pronunciation guide and phrasebook are included with the dictionary, containing translations of such handy phrases as "Activate the transport beam," and the ever popular "Surrender or die!"

Novice speakers can develop their skills with instructional CDs with titles like Conversational Klingon and Power Klingon, both of which are available from Amazon. Those with a more literary bent can purchase translations of Hamlet, Much Ado About Nothing and Gilgamesh. And a font set for the Klingon alphabet can be downloaded from the web-based Klingon Language Institute, licensed by Paramount Pictures as "An Authorized User of Klingon". The institute even has a journal, Qo'noS QonoS (The Kronos Chronicle), which publishes articles in, yes, Klingon.

In 2003, CNN reported that a hospital in Portland, Oregon was seeking a Klingon-speaking interpreter. "We've had mental-health patients where this was all they would speak," a representative said. Reliable figures on the number of Klingon speakers are, unsurprisingly, difficult to come by, although one estimate suggests that there are around a thousand on the planet. A recent academic study featuring interviews with 19 advanced Klingon users places the number of fluent speakers much lower: perhaps between ten and 30 people. But even if this is accurate, Klingon, with its readily available dictionaries and guides, is in fairly rude health. According to UNESCO's Atlas of the World's Languages in Danger of Disappearing (2001), there are around 6000 languages in the world. Of these, half or more are deemed to be "endangered, seriously endangered or dying".

Throughout history languages have come and gone. In the past, though, dead languages tended to be replaced by new ones, so that the overall number remained relatively stable. The past 200 years has seen the rate of language death accelerate to the point where some experts estimate that in the next century 5400 - 90% - of the world's languages will disappear. David Crystal, an eminent British linguist, calculates that on average one will die every two weeks. There were around 250 Aboriginal languages spoken in Australia before 1788; recent estimates published by the Department of the Environment and Water Resources suggest that half of those are now extinct and most others are in danger of extinction or are in decline.

That's not to say that they are all going quietly. Adnyamathanha, the language of the Flinders Ranges, has only around 20 fluent speakers but its prospects are looking up, thanks to a team of dedicated teachers, linguists and volunteers who run weekly classes for 35-40 people. The language is being recorded, photocopies of an unpublished dictionary are in circulation and a teachers' manual is being put together; a blog is also in the works. The Adnyamathanha teacher Uncle Buck McKenzie says that teaching the language should be no different from teaching Italian, Vietnamese or Greek in schools. "After all, it is the real Australian language and we need to preserve it and respect it as the oldest living language on earth," he says.

Documenting and recording any language is a massive task; bringing one back to the point where it is spoken in everyday settings is almost impossible. Should we even try? Walter Benn Michaels, the author of The Trouble with Diversity, argues that concern about the fate of languages is a sop which distracts from more pressing matters, like employment and health care. "Everybody always has a language to speak and whatever language it is, it's just as good as every other," he says, pointing out that pushing people towards a dying tongue may even consign them to low-paid jobs.

Matters are rarely so simple. Languages are storehouses of knowledge, records of our natural and social worlds. They are intimately connected with, for example, a people's health and wellbeing. In the early 1990s the anthropologist Luisa Maffi visited a group of indigenous people in South America. They were receiving care from the Mexican health service for the kinds of common ailments - coughs, colds and the like - they would once have addressed themselves. When asked how they had treated these complaints in the past, the local people replied that they'd used plant medicines, though in many cases they had trouble recalling which plants were appropriate for what symptoms and could barely summon the words to describe them. In time, these people will probably become wholly dependent on outsiders for their medical care.

Closer to home, Aboriginal languages may contain knowledge that helps us in tackling climate change. In 2002 the Australian Bureau of Meteorology launched a website to collect and disseminate Aboriginal weather knowledge, which is based on detailed observation of the relationships between meteorological events and changes in plant and animal species. For the most part, this information is passed orally from one generation to the next. In north-east Tasmania, for example, the local Aboriginal people developed a climate calendar with three seasons; the Arrernte people of the Central Australian desert identified five.

Mapping what remains of this diverse knowledge enriches our understanding of how the continent's climate looked in the past, and what changes in the present and future might mean. In this way, keeping the world's indigenous languages alive offers us the ability to do something more than jaqtaHvIS Daq ghoSpu'bogh pagh ghoSqangbej - which, translated from the Klingon, means "to boldly go where no one has gone before."