It was started in 1966 by an NGO led by Kerala Sasthra Sahithya Parishad (KSSP) to save the Silent Valley from being flooded by a hydroelectric project.

In 1978 Indira Gandhi, Prime Minister of India, approved the project, with the condition that the state government enact legislation ensuring the necessary safeguards.

Also that year the IUCN (International Union of conservation of nature) passed a resolution recommending protection of lion-tailed macaques in Silent Valley and Kalakkad and the controversy heated up.

Kerala Sasthra Sahithya Parishad (KSSP) effectively aroused public opinion on the requirement to save Silent Valley.

[2] Dr. Salim Ali, eminent ornithologist of the Bombay Natural History Society, visited the valley and appealed for cancellation of the hydroelectric project.

Dr. M. S. Swaminathan, a renowned agricultural scientist, and then secretary to the Department of Agriculture, called at the Silent Valley region and his suggestion was 389.52 km2 including the Silent Valley (89.52 km2), New Amarambalam (80 km2), Attappadi (120 km2) in Kerala and Kunda in Tamil Nadu (100 km2) reserve forests, should be made into a national rainforest biosphere reserve, with the aim of "preventing erosion of valuable genes from the area".

In 1982, a multidisciplinary committee with Prof. M. G. K. Menon as chairman and Madhav Gadgil, Dilip K. Biswas and others as members, was created to decide if the hydroelectric project was feasible without any significant ecological damage.