The extensive study, conducted throughout the country over four years and released this week, has found 230 languages have "elapsed" while another 870 have survived the test of time in richly diverse but rapidly modernising India, home to a vast number of indigenous or tribal peoples.
Ganesh Devy, who spearheaded the survey, said 480 tribal languages are among those still spoken in India, where Hindi and English are strengthening their grip in an increasingly mobile and interconnected world.
"I am concerned and alarmed that a very large number of languages have been rapidly declining in India," Devy, an author and founder of the non-profit Bhasha Trust, which seeks to preserve languages, told AFP.
Devy's team of 3,000 volunteers fanned out across India, visiting communities in the most remote parts of the country of 1.2 billion people, to study and document living languages spoken and written today.
The team scrutinised evidence of the existence of a language such as a community's use of folk songs and stories in their mother tongue as well as terms used for their geographical surroundings.
The team compared their findings with the results of a government census conducted in 1961 which stated that some 1,100 languages existed throughout the country.
The first five of some 50 detailed volumes of the team's People's Linguistic Survey of India will be released in New Delhi on Thursday.
Devy said languages of coastal communities seemed to have eroded the most over the years as traditional fishermen, whose livelihoods have declined, move inland in search of employment in cities.
"For coastal communities, hit adversely by changing sea-farming technology, a wonderfully abundant terminology for fish and waves is of no use in inland areas," he said.
Tongues are also dying out among nomadic tribes, branded criminals by many in the past and considered at the bottom of India's caste system. Many attempt to conceal their identity, including by not speaking their traditional dialects, to "escape harassment", Devy told AFP.
Some, who abandon their nomadic lifestyle for cities and towns, are "likely to move away from their social practices, culture and language" for fear of rejection from mainstream society, he said.
The survey found kinship terms are shrinking in most languages, reflecting erosion of strong family ties, along with terms for forms of prayer, Devy wrote in The Hindu newspaper on Tuesday.
"Weakening ecological bonds are reflected in people's inability to name surrounding trees or birds (in their traditional language)," he added.
However there are exceptions among non-nomadic tribes, especially those enjoying inclusive economic growth in their homelands, Devy said. He pointed to the eastern state of Jharkhand, where 30 percent of the population belongs to tribes whose heritage remains strong.
About 190 tribal groups are spread throughout India, from the remote Andaman and Nicobar Islands, to the Himalayas, and northeastern regions bordering Bhutan and China, with a combined population of about 60 million.
The strong presence of indigenous groups means India continues to enjoy a relatively rich diversity of languages despite economic development as well as British colonisation.
"It is only in India that despite the colonial experience of over two centuries, more than 800 languages have survived.
"The high rate of language loss in India needs therefore to be seen together with the high rate of language survival," Devy said.
India's constitution lists 22 official languages, with Hindi as the main official language and English - the preferred language for business and academics - given associate status.
An educated and English-speaking population has been one of the key factors behind the outsourcing boom to India, which has seen Western companies set up IT back-up or call centres across the country.