Around 1,500 endangered and rare languages are at a high risk of being lost in the next century, according to a study of thousands of spoken languages. The study, published on Thursday in Nature Ecology and Evolution, evaluated 6,511 spoken languages in 51 different categories pertaining to language maintenance — like population of speakers, documentation, legal recognition and environmental features. The study found that around half of the world's 7,000 documented languages are endangered. It also found that greater road density was associated with higher risk of endangerment. "It's as if roads are helping dominant languages 'steam roll' over other smaller languages," co-author and professor at the Australian National University Lindell Bromham said in a press release. Greater endangerment was also associated with higher average years of schooling, suggesting that formal education contributes to loss of language diversity. "Mainstream education in a dominant language can lead to loss of competence in minority languages. We urgently need to invest in bilingual education and develop programs that allow communities to bring their heritage language into schools, to make sure the language stays strong and is passed on to future generations," Bromhall told CBS News. The scientists said that the findings have special meaning in Australia, where the research was conducted. "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 in the press release. "Prior to colonization, 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." The study found that unless there is intervention, the world could lose at least one language per month, with language loss tripling in the next 40 years. The authors recommended "urgent investment" in community-based programs like bilingual education programs and language documentation. Mass language loss has been predicted for decades — with linguists estimating 3,400 to 6,120 languages could become extinct by 2100. And some of the recommendations that experts made 20 years ago are still the same: governments should remove bans on languages and adults should encourage children to speak other languages — including their Indigenous language. "Each language is a tribute to the creativity and inventiveness of human minds, a beautiful and fascinating solution to complex communication challenges," Bromham told CBS News. "Most importantly, for many people, language symbolizes cultural identity and belonging. Many groups mourn the decline of unique languages and yearn for competency in languages no longer spoken."