Western_Ghats

The landscape of the Southern Indian tectonic shield is believed to have evolved through a slow geomorphic process (Radhakrishna 1993), which arose as a result of the movement of the peninsular region into the rest of the Asian mainland and the resulting geologic transformations. Volcanic activity over a period of 120 - 130 million years resulted in the formation of the present day Western Ghats (Daniels 2001b). Along with this, the peninsula also experienced an eastward tilt which changed the pattern of drainage. In many cases, like the river Sharavati and Kali in Uttara Kannada, the western faulting led to 'river capture' and diversion of the easterly drainage to the west (Radhakrishna, 1991). The Western Ghats, which arose from these activities, presently forms a continuous chain of small to medium sized mountain ranges running along the western coast of Southern India. Recent work by Valdiya (2001) also indicates that there have been active neotectonic movements along the NNW-SSE leading to the formation of faults and fractures. Among other geologic changes, this has resulted in changes in the flow character of all rivers and streams that flow to the west and descend across the western margins of the Western Ghats. There are abrupt drops as water falls through gorges and cascades of rivers flow along the upper reaches of the Western Ghats. Rivers show anastomosing patterns in the sinuosity of meandering in the upstream stretches. It has also lead to the formation of stream ponds as the rivers flow through these faults. For instance, in Uttara Kannada, we find the ponding of the river Bedti at the study sites of Ramanguli and Hoskambi.
The Western Ghats is a forested tract of relatively smooth, but very old, mountain ranges bordering the South Western coastline of India, starting from Central Maharashtra to the southern tip of Kerala. The Western Ghats, along with another range of smaller mountains - the Eastern Ghats, form a substantial percentage (approximately 10%) of the forested area of the Indian Subcontinent.
It runs rather continuously north- south between 8 and 210 N latitudes. It covers a distance of approximately 1600 km- being interrupted just once by the 30 km wide Palghat Gap at around 11 N. The narrow coastal strip that separates the hill chain from the Arabian sea in the west varies in width from 30 to 60 km being the narrowest between 14 and 15 N. Hills are generally of elevations between 600 and 1000 m. However there are higher hills of 1000- 2000 m between 8 and 13 N and 18- 19 N. Peaks over 2000 m are found only in the Nilgiris, Palanis and Anaimalais. The Nilgiris and Palanis are spurs from the main hill chain, which extend the Western Ghats eastwards to approximately 78 E. Annual rainfall on the Western Ghats averages 2500 mm. Rainfall as high as 7600 mm in localities such as Agumbe between 13 and 14 N is not uncommon. The Western Ghats receives much of their rain from the southwest monsoon. Hence the wettest season generally lies between June and October. The rainy season in the southern latitude is however often prolonged locally due to pre-monsoon and winter showers. Thus the dry periods in parts of the Western Ghats south of 13 N are the shortest (2- 5 months) while in the north it varies from 5 to 8 months. Mean temperature ranges between 20 and 24 C. However, it frequently shoots beyond 30 C during April- May (summer) and sometimes falls to 0 C during winter in the higher hills. The Western Ghats harbours approximately 38 east flowing and 27 west flowing major rivers. The west flowing rivers originate in the Western Ghats and drain into the Arabian Sea while the East fowing ones merge into the three major river systems- Cauvery, Krishna or Godavari- before they drain into the Bat of Bengal.

    The soil mainly consists of the derivatives of the ancient metamorphic rocks in India, rich in iron and manganese (Pascal 1988). There are exposed lateritic rocks along the coastal hills which appear black and are barren and mostly unfit for plant growth. Some granitic rocks are also present towards the southern parts of the district. One distinct feature of this region is the formation of limestone pannicles in the forests of Yanna. These are a unique feature for the Western Ghats; they are, however, common in the forests of South - East Asia.

Biogeography
    An early attempt to classify the various vegetation types of the Western Ghats was done by Champion in 1936 and was later revised and enlarged by Champion and Seth in 1968. Nagendra and Gadgil (1998) have identified 11 landscape elements (LSE) or vegetation mosaics, including some anthropogenic kinds, characteristic of the Western Ghats.
    Because of its African origin, much of the flora and fauna of the Western Ghats are shared with Africa, Madagascar and also South America. Amongst fishes, some species of catfish (Clarias), some Cyprinids (Puntius, Labeo, Rasbora and Barilius) as well as genera like Notopterus and Mastacembelus are common to both India and Africa. There are also similarities between the biodiversity of this region with the East - Himalayan region. This is found to be true of some species of fishes, mammals as well as birds (Hora 1949).
On a broader scale of the Western Ghats, studies on the biodiversity of this region have shown that the overall species diversity here is high. In fact, it has been counted as one of the world’s 18 biodiversity “hotspots”. There is also a high level of endemicity in a number of taxa in this region - with nearly 2000 species of higher plants, 87 species of amphibians, 89 species of reptiles, 15 species of birds and 12 species of mammals (Daniels, 1997). There are around 218 species of primary and secondary freshwater fishes in the Western Ghats. 53% of all fish species (116 species in 51 genera) in the Western Ghats are endemic (Talwar and Jhingran 1991, Jayaram 1999, Menon 1999, Daniels 2001a). Furthermore, freshwater fishes of the Western Ghats have a high economic value – they are caught extensively for food as well as ornamental purposes (in aquaria).
230 species of woody plants and 480 species of birds have been recorded in the Uttara Kannada district. There is a distinct gradient in species richness of plants in Uttara Kannada. The plant species densities increase both from east to west as well as north to south. This gradient of plant species richness coincides with the rainfall gradient. A similar trend in bird species diversity is also observed, but for birds, species diversity increases with decreasing rainfall, with the maximum diversity being found in the intermediate rainfall zone (Daniels 1989). Diversity patterns of reptiles and amphibians have also been studied by Daniels (1991). The central Western Ghats are rather rich in butterfly species. While 249 species are known from the state of Goa, the Uttara Kannada district alone is known to harbour 300 species (Gaonkar, 1996). Species richness data for fish and aquatic invertebrates have, however, not been documented in the recent times. A number of species have been introduced into the waters of this region, most of which are in the reservoir areas of dams. Many have naturalised in the streams, ponds and tanks of the region. Species like Oreochromis mossambics, Gambusia officinis, Poecilia reticulata etc. are exotic species which are originally from Africa and South America. Species like Rohu, Catla, Mrigal (carps which are from the northern parts of India) have been introduced recently, mostly for commercial purposes.

Daniels, R J R (1989). A conservation strategy for the birds of the Uttara Kannada district. PhD Thesis: Indian Institute of Science, Bangalore. pp238.
Daniels, R J R (1991). The problem of conserving amphibians in the Western Ghats, India. Curr. Sci., 60(11): 630-632.
Daniels, R. J. R. (1997). Taxonomic uncertainties and conservation assessment of the Western Ghats. Curr. Sci. 73 ( 2): 169- 170.
Daniels, R. J. R. (2001a). Endemic fishes of the Western Ghats and the Satpura Hypothesis. Curr. Sci., 81 (3):240-244.
Daniels, R. J. R. (2001b). A Report on the National biodiversity Strategy and Action plan- the Western Ghats Ecoregion: Submitted to the Ministry of Environment and Forest, India. pp 129.
Gaonkar, H. (1996) Butterflies of Western Ghats, India including Sri Lanka: a biodiversity assessment of a threatened mountain system. Unpublished Report submitted to Centre for Ecological Sciences, IISc, Bangalore.
Hora, S L (1949) Satpura Hypothesis of the Distribution of the Malayan Fauna and Flora to Peninsular India. Proc. Nat. Inst. Sci. India, 15(8):309-314.
Nagendra, H and Gadgil, M (1998) Linking regional landscape scales for assessing biodiversity: a case study from the Western Ghats. Curr. Sci., 75(3):264-271.
Pascal, J P (1988). Wet evergreen forests of the Western Ghats of India. Pondicherry: Institut Francaise.
Radhakrishna, B P (1991) An excursion into the past - 'the Deccan volcanic episode'. Curr. Sci., 61 (9&10):641-647.
Radhakrishna, B P (1993) Neogene uplift and geomorphic rejuvenation of the Indian Peninsula. Curr. Sci., 64 (11&12) :787-793.
Samant, J. S. Ajit Kumar, C.R., Thomas, R. and Biju, C. R. (1996). Ecology of hill streams of the Western Ghats with special reference to fish community. Annual (draft) submitted to Bombay Natural History Society.
Valdiya, K. S. (2001). Tectonic resurgence of the Mysore plateau and surrounding regions in cratonic Southern India. Curr. Sci., 81 (8): 1068-1089).