Born amidst controversy, Silent Valley National Park has come to symbolise both the extraordinary biological diversity of the southern Western Ghats evergreen forests as well as the ongoing struggle to conserve them. It's origin in the famous campaign in 1973 by a wide constituency of people, that resulted in the stoppage of a hydroelectric dam project across the Kunthipuzha valley (MoEF 2006), is a well documented part in the history of India's conservation movement. The proposed dam would have resulted in the flooding of 8.3 sq km of intact rainforest and threatened the endangered lion-tailed macaque (Macaca silenus). In 1976 the Kerala State Electricity Board announced a plan to begin dam construction and the issue was brought to public attention. In 1984 the then Prime Minister of India abandoned the project and declared Silent Valley as a national park. In 1986 Silent Valley National Park was designated as the core area of the Nilgiri Biosphere Reserve as part of the sustained effort to preserve its forests.

Silent Valley is located in Kerala's Palakkad district between the latitudes of 11o3'47.88"N and 11o12'26.64"N and the longitudes of 76o23'4.2"E and 76o29'7.8"E. It covers 89.52 sq km and lies adjacent to Tamil Nadu's Mukurthi National Park and is also contiguous with the proposed Karimpuzha National Park (225 sq km) to the west. It is flanked to the north and east by the high ridges of the Nilgiri mountains, and to the south and west by a low, irregular ridgeline. The altitude within the park varies from 520-2,383 m and the mean annual rainfall is about 3,500 mm (Islam and Rahmani 2004, Krishnaswamy et al. in prep). Most streams and rivulets flowing through the park drain into the Kunthipuzha, which flows southwards through the park, for about 15 km (MoEF 2006).

The main vegetation types found in this protected area are-medium elevation evergreen forests (Cullenia exarillata-Mesua ferrea-Palaquium ellipticum type), high elevation evergreen forests (Schefflera spp.-Meliosma arnottiana-Gordonia obtusa type and Litsea spp.-Syzygium spp.- Microtropis spp. type) (Franceschi et al 2002). Seven different associations are recognised in Silent Valley's rainforests-Palaquium ellipticum-Cullenia exarillata, Palaquium ellipticum-Mesua ferrea, Palaquium ellipticum-Poeciloneuron indicum, Mesua-Calophyllum elatum, Mesua-Cullenia, Ochlandra-Calophyllum and Ochlandra-Poeciloneuron (MoEF 2006). The angiosperm flora comprises 966 species belonging to 134 families and 559 genera. Dicotyledons total 701 species distributed among 113 families and 420 genera, and monocotyledons consist of 265 species within 21 families and 139 genera. Families best represented are the Orchidaceae, Poaceae, Fabaceae, Rubiaceae and Asteraceae (MoEF 2006).

Silent Valley has been recognised as an Important Bird Area owing to the presence of one 'Endangered' species, the Nilgiri laughing-thrush (Garrulax cachinnans), and three 'Vulnerable' species, the Nilgiri wood-pigeon (Columba elphinstonii), white-bellied shortwing (Brachypteryx major) and broad-tailed grass-warbler (Schoenicola platyura). It also has 13 of the 16 bird species that are endemic to the Western Ghats and nine of the 15 species whose distributions are largely or wholly confined to the Indian Peninsula Tropical Moist Forest biome (Islam and Rahmani 2004). A total of 200 species have been recorded from this area. Some of the interesting species found here include-the black-and-orange flycatcher (Ficedula nigrorufa), the Nilgiri flycatcher (Eumyias albicaudata), the Malabar grey hornbill (Ocyceros griseus), white-bellied blue flycatcher (Cyornis pallipes), Ceylon frogmouth (Batrachostomus moniliger) and Malabar pied hornbill (Anthracoceros coronatus). The park is also an important wintering site for long distance migrants such as the Tickell's leaf warbler (Phylloscopus affinis), large-billed leaf warbler (P. magnirostris), blue-headed rock thrush (Monticola cinclorhynchus) and rufous-tailed flycatcher (Muscicapa ruficauda) (Islam and Rahmani 2004).

About 26 species of mammals, excluding bats, rodents and insectivores, have been recorded from here (Balakrishnan 1984). Several red-listed Western Ghats endemics such as the Nilgiri langur (Trachypithecus johnii), lion-tailed macaque (Macaca silenus), Jerdon's palm civet (Paradoxurus jerdoni), Nilgiri marten (Martes gwatkinsi) and Nilgiri tahr (Hemitragus hylocrius) occur in these forests. Threatened wide-ranging large mammals such as the tiger (Panthera tigris), wild dog (Cuon alpinus), Asian elephant (Elephas maximus) and gaur (Bos gaurus) are also found here.

Ninety-two species of fish including two new species have been recorded from the area. Of these, 37 species are endemic to Western Ghats and nine strictly endemic to Kerala (Easa and Shaji 1997). Lepidopteran fauna comprise about 100 species of butterflies in nine families, and about 400 of moths, including 13 endemic to South India (Mathew 1990, Islam and Rahmani 2004). Thirty-three species of crickets and grasshoppers have been recorded, of which one was new, and 128 species of beetles including 10 new species have been recorded (ZSI 1986).

Settlements of ethnic tribes such as the Cholanayakans, Paniyans and Eranadans are found in New Amarambalam and Kalikavu areas. Of these, the Cholanayakans are considered as being heavily dependent on the forests for their livelihood (MoEF 2006). The Mudugar and Irula tribal people are indigenous to the area and live in the adjacent valley of Attappady reserve forest. Also, the Kurumbar people occupy the highest range outside the park bordering the Nilgiris1.

Apart from smaller scale threats such as forest fires, livestock grazing and illegal ganja cultivation, the park remains almost completely free from large-scale disturbances. There is, however, a remaining threat from the proposed Pathrakkadavu Hydroelectric Project on the Kuntipuzha just outside Silent Valley National Park (MoEF 2006).

References

Balakrishnan, M. 1984. The larger mammals and their endangered habitats in the Silent Valley forests of south India. Biological Conservation. 29: 277-286.

Easa, P. S. and Shaji, C. P. 1997. Freshwater fish diversity in Kerala part of the Nilgiri Biosphere Reserve. Current Science. 73:180-182.

Franceschi, D., Ramesh, B.R. and Pascal, J.P. 2002. Forest map of South India: Coimbatore-Thrissur. French Institute, Pondicherry, India.

Islam, M. Z. and Rahmani, A. R. 2004. Important bird areas in India: priority sites for conservation. Indian Bird Conservation Network: Bombay Natural History Society and Birdlife International, UK.

Krishnaswamy, J., Mehta, V., Kiran MC. Interpolation of annual rainfall data of Western Ghats using ordinary kriging.(in prep.)

Mathew, G. 1990. Studies on the lepidopteran fauna of Silent Valley. In: Ecological studies and long-term monitoring of biological processes in Silent Valley National Park. Kerala Forest Research Institute Research Report. Pp. 13-53.

MoEF. 2006. India's Tentative List of Natural Heritage Properties to be inscribed on the UNESCO World Heritage List. UNESCO, Paris, France.

ZSI. 1986. 'Silent Valley'. Records of the Zoological Survey of India 84 (Silent Valley Special Issue): 1-4. Zoological Survey of India, India.

1 http://en.wikipedia.org/wiki/Silent_Valley_National_Park .Accessed on 6 December 2007