The world's roughly 7000 known languages are disappearing faster than species, with a different tongue dying approximately every 2 weeks. Now, by borrowing methods used in ecology to track endangered species, researchers have identified the primary threat to linguistic diversity: economic development. Though such growth has been shown to wipe out language in the past on a case-by-case basis, this is the first study to demonstrate that it is a global phenomenon, researchers say.

Many people know about the threatened polar bear and extinct passenger pigeon, but few have heard of endangered and extinct languages such as Eyak in Alaska, whose last speaker died in 2008, or Ubykh in Turkey, whose last fluent speaker died in 1992, says Tatsuya Amano, a zoologist at the University of Cambridge in the United Kingdom and lead author of the new study. It’s well known that economic growth or the desire to achieve it can drive language loss, he notes—dominant languages such as Mandarin Chinese and English are often required for upward mobility in education and business, and economic assistance often encourages recipients to speak dominant languages. Whereas specific case studies demonstrate such forces at work, such as the transition from Cornish to English in the United Kingdom and from Horom to English in Nigeria, this is the first study to examine losses worldwide and rank economic growth alongside other possible influences, he says.

Data on the number and location of surviving fluent speakers of endangered languages are scant, but Amano and colleagues used the most complete source available—an online repository called Ethnologue—for their analysis, he says. From the database, the group was able to calculate the geographical range, number of speakers, and rate of speaker decline for languages worldwide and map that data within square grid cells roughly 190 km across, spanning the entire globe. Although they were able to obtain information about the range and number of speakers for more than 90% of the world’s estimated 6909 languages, they could only glean details about the rate of decline or growth for 9%, or 649, of those languages, Amano notes.

Next, they looked for correlations between language loss and factors such as a country's gross domestic product and levels of globalization as calculated by an internationally recognized index. In addition, they examined environmental factors such as altitude, which might contribute to language loss by affecting how easily communities can communicate and travel.

Of all the variables tested, economic growth was most strongly linked to language loss, Amano says. Two types of language loss hotspots emerged from the study, published online today in the Proceedings of the Royal Society B. One was in economically well developed regions such as northwestern North America and northern Australia; a second was in economically developing regions such as the tropics and the Himalayas. Certain aspects of geography seemed to act as a buffer or threat, Amano says. For example, recent declines appear to occur faster in temperate climates than in the tropics or mountainous regions—perhaps because it is easier to travel in and out of temperate regions, Amano says. More research is necessary to determine precisely what it is about economic development that kills languages, he adds. Figuring out how growth interacts with other factors such as landscape is the next step, he says.

"This is the first really solid statistical study I've seen which shows principles about language decline that we've know about, but hadn't been able to put together in a sound way," says Leanne Hinton, a linguist at the University of California, Berkeley. Economics is far from the whole story, however, she says. In the United States, for example, current attitudes toward endangered tongues stem in large part from historical policies that forced young American Indians to eschew their native tongues in order to learn English, she says. Generations of disease, murder, and genocide—both historic and present, in some regions—have also played an important role and were not included in the new study's analysis, she says.

Although the study is silent on the subject of interventions to help preserve endangered languages, there is a range of revitalization efforts that can serve as examples, such as the incorporation of the Hawaiian language into school curricula and daily government operations, she says.