They are predicting that up to 3,000 languages will become extinct over the next 100 years - and that more than 2,000 others will become severely endangered and threatened with extinction in the following century.
According to the world's first comprehensive language atlas, published in London this month, almost one-third of the world's languages are now each spoken by fewer than 1,000 people.
In Australia, 135 out of 200 surviving Aboriginal languages are each spoken by less than 10 people and are rapidly approaching extinction. In Papua New Guinea there are 155 languages with fewer than 300 speakers, and in South America there are 70 languages with fewer than 300 speakers.
In Europe, excluding the former Soviet Union, the atlas reveals that there are a dozen languages with fewer than 15,000 speakers, including Sorbian (4,000), East Frisian (under 11,000), North Frisian (under 10,000), all in Germany; four separate Lapp languages in northern Scandinavia (total 50,000); and the tiny Hellenic language Tsokanian in southern Greece (just 300 speakers).
Linguistically the world probably reached its peak, in terms of diversity, about 15,000 years ago when there were probably somewhere between 10,000 and 15,000 different languages, with each language being spoken on average by around 600 people, in a world whose total population was around 0.002 per cent of its current total.
The decline in language diversity probably started around 10,000 years ago with the beginning of settled life. However, by around 500 years ago, there were at least 7,000 languages in the world, but pressure exerted by European imperial expansion - especially in Australia and the Americas - over recent centuries has reduced the world's language stock by almost 15 per cent to 6,000.
In the past, most individual languages have each probably lasted for between 300 and 1,000 years before mutating into something new. It is, therefore, likely that there have been at least 500,000 languages in the world since humans started talking to each other more than 100,000 years ago.
Now accelerated language extinction means that large numbers of languages are no longer mutating into related successor tongues, but are being increasingly displaced by the languages of economically and politically more powerful cultures.
A 50 per cent cut in the world's surviving 6,000 languages is expected in the next 100 years, with the majority of the rest disappearing the following century, leaving the world with just 600 languages - around 10 per cent of the current figure.
A leading authority on endangered languages, Professor Michael Krauss of the University of Alaska at Fairbanks, has broken down the world's languages into those which are no longer learnt by children and are therefore on the verge of extinction; those which are still learnt by children, yet have very few speakers and are therefore merely endangered; and those which are relatively safe. He calculates that one-third of all the native languages of the Americas are no longer learnt by children and will become extinct when the last adult speakers die. In Alaska only 2 of the 20 native languages are still learnt by children.
For North America as a whole the figure is 38 languages out of 187 and in South America 27 per cent of the 400 native languages are not now being passed on to new generations. In Australia, 90 per cent of Aboriginal tongues are facing rapid extinction because most Aboriginal children are not learning their parents' languages. Worldwide, Professor Krauss has calculated that only between 300 and 600 of the world's languages could be described as 'safe'.
It is not just the languages themselves that are disappearing. Entire literary traditions, both oral and written; unique systems of grammar and vocabulary reflecting equally unique systems of thought and lifestyle; language as the cornerstone of thousands of human cultures: all will vanish, leaving the world immeasurably poorer in cultural terms.
Empire building and genocide were the main causes of language extinction over the past 500 years. However, it is the onward march of television, the growth of vast cities in the Third World, the destruction of natural habitats, and the intolerance of nationalism that are now threatening to wipe out 90 per cent of the world's surviving languages.
What has been lost linguistically over the past 500 years is catalogued remorsely in the language atlas. Of the 135 maps, 29 covering North, Central and South America and Australia record what languages were spoken when Europeans first arrived, contrasted with which languages are now spoken. The atlas reveals that hundreds of American languages and up to 300 Australian ones have been wiped out.
The work - the first atlas of its type ever produced - has been researched and compiled over eight years by a team of 27 academics from universities in Britain, Continental Europe, North America, Australia and Africa.
'The scale of the tragedy is immense. The outlook is indeed bleak for most of the world's languages, with up to 2,000 languages disappearing in the next 50 years and at least 3,000 more threatened with oblivion after that,' says Christopher Moseley, editor of the atlas and a linguist working for the BBC World Service monitoring centre at Caversham, Berkshire.
'Atlas of the World's Languages' edited by Christopher Moseley and R E Asher, published by Routledge (London and New York) at pounds 395.Reuse content