INDIA, October 1, 2021 (BBC): Between 1961 and 1971, thousands of languages vanished from Indian census data. One man decided to track them down, before they were lost forever. It was 2010 and Ganesh N. Devy was concerned about the lack of comprehensive data on the languages of India. “The 1961 [Indian] census recognized 1,652 mother tongues,” says Devy, “but the 1971 census listed only 109. The discrepancy in numbers frustrated me a lot.” India is one of the most linguistically diverse countries in the world. K. David Harrison, a linguist from Swarthmore College in Pennsylvania, has labelled the country a “language hotspot.” This, according to Harrison, is a place with a high level of linguistic diversity and endangerment, as well as a low level of documentation.

As a professor of English at Maharaja Sayajirao University of Baroda in Gujarat, Devy has always had an interest in languages. Devy felt that it would take a long, arduous process to document every language in India, so launched the People’s Linguistic Survey of India (PLSI) in 2010, for which he put together a team of 3,000 volunteers from all over the country. Most of these volunteers weren’t researchers, but writers, school teachers, and other non-professional-linguists who possessed an intimacy with their mother tongue that was invaluable to Devy. In a survey conducted during 2010-2013, Devy and his team recorded 780 languages and 68 scripts across the country. Since 2013, the PLSI has published 68 volumes, featuring detailed profiles of each language that Devy came across. The remaining 27 volumes will be published by 2025.

This lengthy and interesting article can be read at “source”.
https://www.bbc.com/future/article/20211014-the-man-who-found-indias-hidden-languages