A world-first study warns 1,500 endangered languages could no longer be spoken by the end of this century.
The study, led by The Australian National University (ANU), identified predictors that put endangered languages at high risk.
Co-author Professor Lindell Bromham said that of the world's 7,000 recognised languages, around half were currently endangered.
"We found that without immediate intervention, language loss could triple in the next 40 years. And by the end of this century, 1,500 languages could cease to be spoken."
Published in Nature Ecology and Evolution, the study charts the widest range of factors ever putting endangered languages under pressure.
One finding is that more years of schooling increased the level of language endangerment. The researchers say it shows we need to build curricula that support bilingual education, fostering both Indigenous language proficiency as well as use of regionally-dominant languages.
"Across the 51 factors or predictors we investigated, we also found some really unexpected and surprising pressure points. This included road density," Professor Bromham said.
"Contact with other local languages is not the problem. In fact, languages in contact with many other Indigenous languages tend to be less endangered.
"But we found that the more roads there are, connecting country to city, and villages to towns, the higher the risk of languages being endangered. It's as if roads are helping dominant languages 'steamroll' smaller languages."
The researchers say the findings also have important lessons for preserving many of the endangered languages spoken by Australia's First Nations peoples.
"Australia has the dubious distinction of having one of the highest rates of language loss worldwide," Professor Felicity Meakins, from the University of Queensland and one of the study's co-authors, said.
"Prior to colonisation, more than 250 First Nations languages were spoken, and multilingualism was the norm. Now, only 40 languages are still spoken and just 12 are being learnt by children.
"First Nations languages need funding and support. Australia only spends $20.89 annually per capita of the Indigenous population on languages, which is abysmal compared with Canada's $69.30 and New Zealand's $296.44."
Professor Bromham said that as the world enters the UNESCO Decade of Indigenous Languages in 2022, the study's findings were a vital reminder that more action was urgently needed to preserve at-risk languages.
"When a language is lost, or is 'Sleeping' as we say for languages that are no longer spoken, we lose so much of our human cultural diversity. Every language is brilliant in its own way.
"Many of the languages predicted to be lost this century still have fluent speakers, so there is still the chance to invest in supporting communities to revitalise Indigenous languages and keep them strong for future generations."