Western Ghats, India – Biodiversity

From the book  ”The Western Ghats” by Mohan Pai (2005).



The term biodiversity encompasses the variety of all life on the Earth. It is identified as the variability among living organisms and the ecological complexes of which they are part, including diversity within and between species and ecosystems.

Biodiversity manifests itself at three levels:
1. Species diversity which refers to the numbers and kinds of living organisms.
2. Genetic diversity which refers to the genetic variation within a population of species.
3. Ecosystem diversity which is the variety of habitats, biological communities and ecological process that occur in the biosphere.

Brahmagiri Forest, Coorg – Pic by Mohan PaiBiological diversity affects us all. It has direct consumptive value in food, agriculture, medicine, industry. It also has aesthetic and recreational value. Biodiversity maintains ecological balance and continues evolutionary process. The indirect ecosystem services provided through biodiversity are photosynthesis, pollination, transpiration, chemical recycling, nutrient cycling, soil maintenance, climate regulation, air, water system management, waste treatment and pest control.


Biodiversity is not distributed equally among the world’s 170 countries. A very small number of countries, lying wholly or partly within tropics, contain a high percentage of the world’s species. These countries are known as megabiodiversity countries. Twelve countries have been identified as megabiodiversity countries. These are : India, Brazil, Colombia, Ecuador, Peru, Mexico, Madagaskar, Zaire, Australia, China, Indonesia and Malaysia. Together, these countries contain as much as 60 to 70 percent of the world’s species.
Tea Gardens of Munnar – Pic by Mohan PaiIndia is one of the 12 megabiodiversity centres of the world. The country is divided into 10 biogeographic regions: Trans Himalayas, Himalayas, Indian desert, Semi-arid zone, Western Ghats, Deccan peninsula, Gangetic plains, North-East India, islands and coasts.


Fisher Women of Devbagh – pic by Mohan Pai

In India we have 320 million hectares of land and 200 million hectares of exclusive economic zone in the sea, within which are distributed some 1,20,000 known and perhaps 4,00,000 as yet undescribed species of microbes, plants and animals.
Biogeographically, the hill chain of the Western Ghats constitutes the Malabar province of the Oriental realm running parallel to the west coast of India. Rising up from a relatively narrow strip of coast at its western borders, the hills reach up to a height of 2,695 m before they merge to the east with Deccan plateau at an altitude of 500-600 m. The average width of the mountain range is about 100 km. This bioregion is highly species rich and is under constant threat due to human pressure.
The rain forests of the Western Ghats are unique vegetation forma-tions as they exist in an environment where there is considerable seasonality in distribution of the rainfall. These forests are found in the areas where the rainfall is distributed from 4 to 10 months, as a consequence, there are 2 to 8 dry months in a year. Of this, most of the precipitation takes place during a 3 month period of June to August.

The orographic effect of these mountain ranges brings in considerable variation in precipitation. The total rainfall along the coast is in the region of 3,000 mm and it touches its maximum around 7,500 mm per annum in certain places on top of these ranges and there is abrupt fall in the rain on leeward side. The high altitudinal zone also gives rise to a kind of forest which has primarily Lauraceous vegetation.

The tropical rain forests of the Western Ghats have considerable diversity in vegetation types both with respect to their altitudinal locations and also because of edaphic and altitudinal variations. There is a school of thought that the parent rocks in these areas have given rise to such good soils which are rich in nutrients and have a very high moisture holding capacity which has given rise to these rainforests.

Global Biodiversity Hotspots in India

Hotspots are areas that are extremely rich in species, have high endemism and are under constant threat due to human pressure. Among the 18 Hotspots of the world, two have been identified in India; the Eastern Himalayas and the Western Ghats. These are particularly rich in floral wealth and endemism, not only in flowering plants but also in reptiles, amphibians, swallow-tailed butterflies and some mammals.


Of India’s 15,000 plant species with 5,000 endemics (33%), there are 4,050 plants with 1,600 endemics (40%) in a 17,000 sq. km strip of forest along the seaward side of the Western Ghats in Maharashtra, Goa, Karnataka, Tamil Nadu and Kerala. Forest tracts up to 500 m in elevation, comprising one fifth of the entire forest expanse are mostly evergreen, while those in the 500-1500 m range are semi-evergreen. There are two major centres of diversity, the Agasthyamalai Hills and the Silent Valley/New Amarambalam Reserve basin. (Source : Teri, New Delhi)

Flora and Fauna

The area has an estimated 3,00,000 hectare (37%) under forest cover and is characterised by a rich diversity of flora and fauna.
* The region has about 4,500 species of flowering plants. Of these about 1,700 are endemic to the Western Ghats. Nearly a third are rare or threatened and several are believed to be extinct.

* Amphibians:
Over 117 species belonging to 21 genera are recorded in the forests and coastal areas of this region, of which 76% are endemic to the region.

* Invertebrates:
A large variety of insects including some of the spectacular butterflies and moths occur in the dense evergreen highland and lowland forests. It is estimated that India has over 1,400 species of which the Western Ghats harbour nearly 320 species including 37 endemics and 23 others shared with Sri Lanka. The area is host to a large variety of fresh water mollusca, some of which are specific to the region.

* Fish: The fish fauna of both fresh water montane and lowland river streams and water bodies as well as coastal lagoons and backwaters are very many and varied in this region. There is large commercial coastal fishery of finish and shell fish in this region.

* Reptiles: Dense forests of the region are the home of the King Cobra and Rock Python apart from other smaller reptiles. Many species of tortoises including the endemic cane turtle, and terrapin are also found in the Western Ghats. The marsh crocodile or mugger was once widely distributed in swamps and larger water bodies of the forested areas.

* Birds : About 508 species of birds occur in the Western Ghats (590 if sub-species are included). Among these about 16 species are endemic. Many endemic birds are exclusive to evergreen and Shola forests.

* Mammals: The forests of the area have large herbivores such as gaur, spotted deer, sambar, barking deer, elephant, etc. Carnivores are represented by tiger, leopard, jungle cat, leopard cat, fishing cat, Malabar civet, brown palm civet, small Indian civet, two species of mongoose and wild dog.
Several genera of mammals are endemic and representatives include slender lorris, the Lion-tailed macaque, 2 species of mongoose, 2 species of civet, Nilgiri langur, Nilgiri tahr, grizzled giant squirrel and the rusty spotted cat.

Biosphere Reserves in the Western Ghats. 

The concept of a biosphere reserve emerged from the Man and Biosphere programme sponsored by the UNESCO during the early seventies. Prior to this, conservation efforts had a tendency to focus on a few animals like the tiger, while ignoring the overall diversity of living organisms. They also did not successfully reconcile the need for development with conservation. The Biosphere Reserve is an attempt to rectify these lacunae and make conservation more meaningful given the socio-economic realities of the region.
Lion-tailed Macaque

Biosphere Reserve is an international designation term made by the UNESCO for representative parts of natural and cultural landscapes extending over large areas of terrestrial or coastal/marine ecosystems or a combination thereof.
The network includes significant examples of biomes throughout the world. The Biosphere Reserve finally aims at conserving and use of resources for the well-being of people locally, nationally and internationally. So far about 360 Biosphere Reserves have been established in about 90 countries.
In 1978, an advisory group of the Indian National Man and Biosphere programme identified 12 sites ranging from Nanda Devi in the Himalayas to the Gulf of Mannar in the Bay of Bengal, representing the diverse biogeographic provinces in the country. Of this the project proposal for the Nilgiri Biosphere Reserve was first prepared in 1980, but it took six years for the reserve to be officially established.

Covering an area of 5,500 sq. km in the states of Karnataka, Kerala and Tamil Nadu, the Nilgiri Biosphere reserve has been designed to encompass extremities of habitat. From 100m above MSL in the Nilambur plains, it goes up the vertical slopes of New Amarambalam to the rugged heights of Makurti peak (2,554 m) and drops in the east to 250 m in the Coimbatore plains. The western slopes get over 5,000 mm of precipitation annually while the sheltered eastern valleys receive less than 500 mm. Corresponding to their altitudinal and climatic gradients, the natural vegetation changes from tropical wet evergreen forest along the western slopes to montane stunted Shola forest amidst the grassy down on the upper plateau and on the east, progressively drier deciduous forests ending in thorny scrub. This setting is home for a variety of animals – the Lion-tailed macaque in the evergreen forests, the Nilgiri tahr in the grassy downs, the black buck in the dry scrub and the tiger and the elephant throughout the region.

Paniya Tribal Woman, Wyanad, Kerala – Pic by Mohan Pai

To the north, the Biosphere Reserve begins in the Nagarhole National Park of Karnataka and the adjoining Wayanad sanctuary of Kerala. The moist deciduous forests and teak plantations of Nagarhole harbours abundant population of gaur, spotted deer, sambar and wild pig which support a sizeable number of carnivores such as tiger and leopard. Nagarhole is perhaps the best place in south India for sighting these large cats. The forest cover along the Kabini river has been reduced due to the construction of an irrigation dam. It was along the banks of this river that elephants were regularly captured for nearly a century by the Khedda method until 1971. Even today an evening ride on coracle along the riverbanks during the dry months may be rewarded with the sight of over a hundred elephants.

South of the Kabini, the dry deciduous forests of the Bandipur National Park were declared as a Project Tiger area in 1973. Contiguous with Bandipur lie Madumalai sanctuary of Tamil Nadu and portion of the Wayanad sanctuary in Kerala. The natural vegetation of this tract is moist deciduous forest. The fauna is similar to that of Nagarhole with elephants in large numbers.

East of Madumalai, the vegetation over the Sigur plateau and the Moyar river valley lying in the rain shadow of the Nilgiri massif, becomes drier. Thorny plants such as Acacia dominate. In addition to the fauna of the deciduous forests, striped hyena, jackal and four-horned antelope are seen here. The black buck has disappeared from the Sigur plateau but a viable population of 300 to 500 is still found in the Moyar valley. They can be easily seen in the evening along the foreshore of the Bhavani reservoir.The Moyar valley is the junction of two great hill chains of the peninsular India – The Eastern Ghats and the Western Ghats. A portion of Talamalai-Satyamangalam plateau has been included in the Nilgiri Biosphere Reserve as representative of the Eastern Ghats.

Over the eastern slopes of the Nilgiris, the forest cover extends southwards as a narrow belt into Balampatty and Siruvani hills. The Siruvani reservoir on the Kerala side provides water to Coimbatore city. A good stretch of evergreen vegetation covers the higher reaches of Siruvani hills. Adjoining these hills to the north-west, the Attappady valley is mostly under cultivation. The large tribal population here has been practising shifting cultivation for a long time. As a result, the forest covers over the surrounding hills have largely degraded. A well preserved stretch of evergreen forest with Dipterocarpus, Mesua and Palaquium is seen west of the Attappady Reserve, extending into the Silent Valley, New Amarambalam and through a narrow corridor into Nilambur.
The endangered Lion-tailed macaque of the Silent Valley fame is highly adapted to such evergreen habitats. The controversy regarding the proposed dam across Kanthipuzha in the Silent Valley was laid to rest with the entire area being declared as a National Park in 1986. But the Government of Kerala has proposed Pathrakkadavu Hydro Electric Project in the Kunthi river, once again threatening the Silent Valley.

Tribal Hut, Wyanad, Kerala – Pic by Mohan Pai

Perhaps the largest pristine evergreen forest in peninsular India is the New Amarambalam Reserve, which has escaped the axe simply because its steep terrain is inaccessible. This is home to Chalamekans, the only genuine hunter-gatherers in the peninsula. The upper Nilgiri plateau has been altered by human activities into one vast stretch of cultivated land and settlements around Udhagamandalam (Ooty).
Both slopes and valleys here grow tea, coffee, cinchona, fruits and vegetables such as potato. Extensive plantation of Blue gum (Eucalyptus), Wattle (Acacia) and Pine have also been raised. These have resulted in enormous loss of top soil. To tap the potential for generating hydro-electric power, a series of dams have been constructed across the Bhavani river and its tributaries.
A major portion of the upper plateau has been excluded from the Biospere Reserve. Only the western and the southern ridges, which retain some natural Shola and grass land vegetation along with monoculture plantations have been included. A sanctuary has been declared to protect the Nilgiri tahr.

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