The Silent Valley, situated in South Western Ghats, is one among the world's ten "Hottest Biodiversity Hot Spots" and is believed to be the sole surviving bit of virgin tropical rain forests in this country. Located about 80 km north east of Palakkad, Kerala, India It was declared a National Park on 14'" November 1984 and now it forms part of the core of Nilgiris Biosphere Reserve.
The evolutionary age of Silent Valley, the evergreen rain forests, is believed to be more than 50 million years. This is a cliff forest cut off on all sides by steep ridges and escarpments. The topographic isolation of Silent Valley has prevented human habitation, allowing the forest to remain untouched and to emerge as an ecological oasis, preserving the flora and fauna. It is not clear who named it the "Silent Valley". It is believed that the name owes its origin to the relative absence of the cicadas which normally provide a distinctive sound in the forest environment.
The flora of the Valley includes about 1000 species of flowering plants, 107 species of orchids, 100 species of ferns and fern allies, 200 liverworts, 75 lichens and about 200 algae.
This valley is home, to 23 mammalian species including three endangered ones: the tiger, the lion tailed macaque and the Nilgiri langur. Other than the elephant, lion tailed macaque, Nilgiri langur, common langur, Nilgiri tahr, tiger, leopard, sloth bear, Gaur, wild dog, etc., The Silent Valley is home to birds, reptiles, amphibians, fishes and insects.
The Silent Valley Hydroelectric Project (SVHP) was established during 1977-80, which was submerged 830 hectares of forest. The struggle that followed to preserve the forest was perhaps one of the most successful stories of protection of the environment, capturing the imagination of writers, artists, scientists, politicians, nongovernmental organisations, media and the public alike.