Biology of the Western Ghats

Tragically for mankind, most of the forest cover of the Western Ghats has disappeared. The few remaining stretches of natural forests and protected areas, however, still house a biological wealth matched only by the North-east. The famous forests of Silent Valley which were saved from the clutches of an ill-advised hydroelectric project form a part of this vital forested swatch. A wide climatic (rainfall and temperature) and geographical (altitude and associated mountain spurs) gradient exists in this zone. This is manifested in a tremendous diversity of vegetal communities and animal associations. From the coastal plains along the western flanks, the zone rises up to a maximum altitude of 2,735 metres in the south, while falling gradually (sharply in a few places) along the eastern side, towards the dry Deccan Peninsula.

These climatic and geographical gradients have resulted in major habitat variations in this Zone. There are tropical evergreen forests in the central and southern regions; semi-evergreen and moist deciduous forests, wherever left untouched, clothe the mountains almost all along their length; dry deciduous forests of teak and associated species clothe the coastal plains in the northern and central regions as also along the eastern rain-shadow slopes. There are extensive rolling grass-hills in the south-central portions of the Ghats. Of the total area of 160,000 sq. km., just less than one-third is currently considered to be forested and only about nine per cent (15,000 sq. km.) is estimated to be tropical evergreen forest. The rest are moist and dry deciduous forests, dominated by teak.

The Western Ghats Zone covers barely five per cent of India's area, but its biological richness can be best understood when one realises that 27 per cent of all the species of higher plants recorded in the Indian region are found here (about 4,000 of 15,000 species). Further, almost 1,800 species are endemic to the region. The Nilgiri-Travancore-Anamalai-Palni-Cardamom hill areas in the southern parts of the zone exhibit the highest degree of endemism. Further, several interesting plant associations are observed in the evergreen forests of the Zone. There are montane 'shola' forests, riverine or swamp forests and nearly half a dozen other evergreen-species associations, mostly observed in the southern half of the Zone, where numerous ancillary mountain ranges converge to produce a region of exceptional diversity. Because of the heavy rainfall and healthy soil conditions that much of the Zone's southern half enjoys, cash crops like coffee, cocoa, cardamom, rubber, tea and pepper are extensively grown, setting in their wake additional man-induced habitats.

The Western Ghats Zone is also characterised by a series of forest gaps or breaks, that are actually valleys that break the continuity of the mountain ranges and accordingly of the biological components as well. Some of the major ones are the Palghat Gap, the Moyar Gorge or Gap and the Shencottah Gap. These series of gaps have resulted in preventing the spread of certain species and have hence, facilitated local speciation and endemism. The associated mountain ranges such as the Anamalais, the Nilgiris and the Agastyamalais are all separated by clear-cut barriers and besides the interesting floral speciation, a distinct faunal endemism and/or local speciation, is also found. Areas such as this are in urgent need of study and documentation.

Though this zone has healthy populations of much of the animal species characteristic of peninsular India (tiger, elephant, gaur, dhole, sloth bear, panther and several species of deer), it also exhibits a fairly good degree of endemism among primates, ungulates, carnivores, rodents, squirrels and several birds. Amongst amphibia, most of the species and nearly half the genera are endemic, while a good degree of endemism is visible also amongst reptiles, fish and insects, most faunal endemism and restriction being only in the central and and southern parts of the zone. Several of the zone's faunal components are of great interest (and importance) in that they have helped provide justification for what is called The Hora Hypothesis. This explains the spread of several species from the Himalaya and North-east along a once continuous central Indian mountain range into the Western Ghats, giving rise to several interesting biological linkages between the Western Ghats, the Himalaya and North-East! More natural history field research would reveal vital clues to the management of such areas.

Source: Sancturay Asia Magazine