Kerala has three biogeographic entities viz. the coast, the coastal plain and the Western Ghats. Due to demographic pressures, the majority of terrestrial wilderness now is confined to the Western Ghats of Kerala. The biological resources of the forests of Kerala constitute a national heritage par excellence.
It is widely recognised that the creation of a representative net work of Protected Areas is one way of securing biodiversity and associated natural habitats for posterity. Over the years, countries all over the world have increased the extent of Protected Area net work. In order to preserve the varied landscapes and associated biological diversity in Kerala, the Government of Kerala have notified two National Parks and 12 Wildlife Sanctuaries extending over an area of 2324.72 km2 which works out to 5.98 percent of the state's geographical area and 22.49 percent of the forest area. The declaration of Silent Valley as National Park in 1984 by the Government of Kerala has resulted in a radical change in the management strategies in order to ensure the long term survival of the biological wealth of the area.
CHARACTERISTICS OF THE AREA
Silent Valley National Park is situated at the south-eastern corner of the Nilgiri hills of the Western Ghats and is located between 11 ° 00' and 11 ° 15' N latitude and 76° 15' and 76° 35' E longitude. The total extent of Silent Valley National Park is 8952 hectares (89.5 km2) with about 20 percent of the area falling under grassland and the rest under woodland. The entire area is roughly a rectangular plateau closed on all sides by the high mountains of the Western Ghats, thus shielding the vegetation of the plateau from extremes of climate, which in turn creates a special micro climate in the plateau. The northern and western boundaries of the plateau are constituted by the forests of Mukkurthy tahr sanctuary in Tamil Nadu and Nilambur South Division in Kerala. The forests of Mannarkkad Division constitute the eastern and southern boundaries. Biogeographically, as part of the southern Western Ghats, the Silent Valley National Park is placed in Indomalayan biogeographic zone (5b- Western Ghats). This zone is characterised by tropical climate and a high degree of endemism.
Both the south-west and north-east monsoons bring plenty of rain to this area. The recorded mean annual rainfall is 4,400 millimetre. The northern portions of Silent Valley receive the highest rainfall in the region i.e. 7500 millimetre annually, whereas the foothills receive the lowest rainfall i.e. 2717 millimetre annually. The mean annual temperature is 20.2° C with April and May being the hottest months of the year. The hilly areas are relatively cooler but experience greater diurnal variation in temperature. From June to December the relative humidity is often high and is around 95 percent.
The landscape of the Park is highly undulating with high and continuous ridges along its north-eastern boundary. Along its entire length the plateau slopes towards the bed of river Kunthi. Meandering in a north-south direction, the river Kunthi is formed by the confluence of three tributaries and divides the National Park into two parts. It originates at an elevation of about 2,400 metres in the outer ridge of the Nilgiris, descends rapidly to 1150 metres on the northern edge of the plateau and then flows gently in a southward course for about 15 kilometres before cascading down to the Mannarkkad plains. The bed level of the river Kunthi is relatively flat in the southern part of the Park. As one moves northwards the landscape becomes undulating and steep at higher reaches. The mountainous land and rivers in Silent Valley produce riparian and non riparian systems at mid-elevation with high rainfall. These systems act as repositories of diverse biological wealth.
BIOLOGICAL SIGNIFICANCE
In a biogeographical sense, the Silent Valley National Park represents an 'Ecological Island' in which the conditions that prevailed before anthropogenic activities in the humid tropical forest of Peninsular India still exists. This particular state of these forests was due to the physical barrier caused by the presence of the surrounding high Western Ghat hills which in turn had induced 'isolation', an important factor in the biogeographical evolution. The biogeographic isolation manifests itself in the presence of a large number of endemics in the area. Besides being an important life support system, the forests of Silent Valley National Park constitute the store house of a large number of valuable plants and animals. Yet a greater value of Silent Valley lies in its unknown flora and fauna and the immense possibilities of research in future.
The forests of Silent Valley National Park are typical wet-evergreen. However, due to the hilly and undulating terrain and micro climatic variations, there are changes in species composition and association.
Most of the slopes and valleys of the National Park are covered with dense tropical wet-evergreen forests. Grasslands are limited to the narrow sector, west of Kunthipuzha and on the higher slopes in the eastern sector. A number of rare, vulnerable, endangered species of plants are also found in the Park. Scientists have also recorded many new plant species which have enriched our knowledge base.
Singh et al. (1984), found that the predominant vegetation of Silent Valley consists of tropical evergreen and riparian forests. Except for the riverine zones and high altitude grassland shola forest combination, these forests exhibit characteristics of evergreen forests, which include multilayered forest structure, copious growth of fine feeder roots, slender and clear boles of trees with thin barks and the presence of lianas and woody species.
The study by Singh et al. (1984) indicated that the basal area values of trees in the National Park were much higher than those obtained from many tropical forests (102.7 m2 fha. compared with 35-73.6 m2 fha. elsewhere). In just 0.4 hectare of sampled area 118 vascular plants belonging to 84 species were recorded. Alpha diversity index was calculated to be higher than that of many other tropical forests. Another interesting feature of species diversity is the dominance of mixed species in the vegetation indicating favourable growth conditions. The study concluded that the evergreen forests of Silent Valley exhibit a relatively high degree of species richness, remarkably thin barks, high total basal area and, therefore, are indicative of their pristine quality.
Corresponding to the diverse vegetational elements, high species richness including a number of endemic and threatened species characterises the fauna of Silent Valley. The major large mammals occurring in the Park are Lion tailed macaque (Macaca silenus), Nilgiri langur (Presby tis johnii), Tiger (Panthera tigris), Elephant (Elephas maximus), Gaur (Bas gaurus), Nilgiri tahr (Hemitragus hylocrius) and Sloth bear (Melursus ursinus). Twenty five species of large and medium sized mammals have been recorded from the National Park (Balakrishnan, 1984). The Zoological Survey of India collected 315 species of animals, of which 28 species are new records to science (Records of ZSI, 1986). The Zoological Survey of India while carrying out their preliminary surveys concluded that the level of faunal diversity in the Silent Valley was quite high. Many species which were available in the Western Ghats 50 to 100 years ago and which have not been collected subsequently, still exist in Silent Valley. They include insects, fishes, amphibians, reptiles and mammals. A few primitive groups of animals which can throw light on phylogenetic relations of higher taxa have been collected from Silent Valley. For example, caecilians have been exterminated from many areas where they used to be available in plenty a decade ago. Their viable populations still occur in the Park. Similarly a very primitive group of beetles viz. 'ichthyurus' was also found to be abundant inSi1ent Valley. Myers, (1990) reports that only 1/6th of the estimated three million organisms of tropical rain forests have been catalogued so far. The situation may not be different in the forests of Silent Valley.
MANAGEMENT OF THE NATIONAL PARK
The Government of Kerala issued the notification on 15th November 1984 declaring Silent Valley a National Park. The then Prime Minister of India, Mr. Rajiv Gandhi, formally inaugurated the Park on 7th September 1985. After the declaration of Silent Valley a National Park, the management approach changed significantly in consonance with the policy directives for effective and efficient protection of the Silent Valley National Park. From 1985 to November 1988, the management of the National Park was looked after by the Divisional Forest Officer, Palakkad. In November 1988, Silent Valley was upgraded as a Wildlife Division with exclusive management of the Park entrusted with the Wildlife Warden, Silent Valley National Park. The first Management Plan for the Silent Valley National Park (Unnikrishnan, 1990) lists the following objectives of management.
I. To minimise all disruptive factors affecting regeneration of Silent Valley forests.
2. To study the long term successional and evolutionary processes in the rain forest ecosystem.
3. To study the plant-animal interaction in the rain forests.
4. To promote conservation awareness.
5. To study plants in relation to multiple uses for humanity.
The National Park was included in the Nilgiri Biosphere Reserve during 1986 as part of the core area. It also forms part of Project Elephant.
To ensure effective protection to the Park, the first task was to consolidate the legal boundaries. It was also necessary to create facility for staff housing, offices, wireless stations etc. However, it was also considered essential to develop infrastructural facilities outside the Park, so as to retain the inviolate status of the Park. Therefore, except for a few wireless stations, which can also be used as camping place for the protective staff on duty, all facilities were created outside the National Park at Mukkali and Mannarkkad. Some of the old structures constructed by Public Works Department (PWD) and Kerala State Electricity Board (KSEB) for the purpose of the hydroelectric project at Mukkali and Sairandhri were taken possession of and utilised for office and residential purposes. A metalled road from Mukkali to Sairandhri which was opened during project days by KSEB, was subsequently improved for use by departmental officers and for organising nature camps. However, no motor road inside the park was developed. Yet trek paths and wilderness trails, about 100 kilometre long, were taken up in the National Park to enhance staff mobility for effective patrolling against illicit activities. Fire protection measures were taken up more effectively from 1988-89 by creating firelines in vulnerable areas and keeping regular fire patrols during the fire season. Except in 1992, when there were large scale fires all over Kerala, no major fire has taken place in the Park. Protection has been further strengthened by providing wireless communication facilities at Mukkali, Mannarkkad, Sairandhri, Walakkad and Neelikkal. In addition, walkie-talkies have been provided to field staff, so that they remain in contact with the nearest wireless stations in times of emergency.
Concurrently, along with the strengthening of protection, the management has also focused on habitat improvement activities specially in areas close to Sairandhri where degradation had set in during the days of the hydroelectric project development. The habitat improvement activities include experimental trial of regeneration of forests in secondary grassland, soil and moisture conservation programmes, protection against erosion of the river banks and to a limited extent development of water holes near Sairandhri. Tribals living around Mukkali have been specially targeted for ecodevelopment activities since 1993. Although they have always remained part of Park protection teams, special schemes were formulated to engage a large number of tribals in protection and other activities in order to develop closer park tribal ties.
The value of the National Park as a learning centre has been appreciated all over. As part of the nature education and awareness programme, nature camps for school children, teachers, nature clubs etc. have been conducted since 1989. Since then more than 100 camps have been organised benefiting more than 3000 participants. An Information Centre with dormitory facility has been established at Mukkali. There is a library attached to the Information Centre and a herbarium of species collected from Silent Valley National Park is being prepared.
The local tribals have been utilising a number of plants of medicinal value from these areas since time immemorial. Steps have been taken to inventory and conserve plants with medicinal value. An area of 205 hectares at Sairandhri has been demarcated as an in situ conservation plot called 'Medicinal Plants Conservation Area.' This activity is sponsored by the Foundation for Revitalisation of Local Health Tradition (FRLHT). The FRLHT has also taken up activities like botanical profile study and identification of trees, shrubs and herbs of medicinal value. A demonstration plot has also been established at Mukkali as ex situ conservation area.
The effective and efficient protection afforded to the National Park as well as the habitat improvement works carried out in the degraded areas including secondary grasslands has helped in the regeneration of original vegetation in these areas. The regeneratioIJ.eiOf vegetation is periodically monitored. Similarly old, fire burnt areas "'are also being monitored to understand the regeneration of original vegetation.
One area which has been substantially strengthened after the declaration ofthe National Park is research. Considering the immense research potential for biological, ecological, hydrological and a range of other subjects, various
Research Institutions have taken up research works in the National Park. Presently 22 research projects are being carried out by various agencies and individuals in the Silent Valley National Park, which range from investigation on endangered species and their habitats, floristics, animal diversity, vegetation dynamics and surveys related to species of human use value. Research investments find a regular place in the budget of the National Park.
During the last 10 years, Silent Valley National Park has emerged as a signpost for the conservation efforts taken by the Government of Kerala. We have consolidated the strong foundation of conservation. However, much is left to be done. The Kerala Forest Department is aware of the values of
this unique system and of the unknown wealth of living resources within it. With a committed work force and the cooperation of scientific institutions, non governmental organisations and citizens we intend to preserve Silent Valley for posterity in a manner which is professionally competent, scientifically sound and socially acceptable.
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