The Western Ghats, also known locally as the Sahyadri, is a mountain chain that runs parallel to the western coast of the Indian peninsula. This geological feature is much older than the Himalayas, representing a history of continental drift and ancient ecology. Spanning approximately 1,600 kilometers, the range holds immense ecological significance for India, influencing the climate and supporting a vast array of life forms. Due to its unique biophysical and ecological processes, the Western Ghats have gained international recognition. The mountain chain is a UNESCO World Heritage Site and one of the world’s most significant ecological regions, underscoring its importance for conservation and scientific study.
Geographical Extent and Geological Origin
The range stretches from the border of Gujarat and Maharashtra in the north, extending south through Goa, Karnataka, Kerala, and Tamil Nadu. It covers an approximate area of 140,000 to 160,000 square kilometers, forming a continuous natural barrier along the western edge of the Deccan Plateau. The average elevation of the crest line is about 1,200 meters. The highest point in the entire range is Anamudi in Kerala, soaring to 2,695 meters.
Geologically, the Western Ghats are not a traditional fold mountain range formed by tectonic compression. They are considered a great escarpment, representing the faulted and eroded edge of the Deccan Plateau. This formation began around 150 million years ago during the break-up of Gondwana, when the Indian plate separated from Madagascar. Faulting and uplift created a steep, cliff-like western slope facing the Arabian Sea.
This tectonic uplift caused the entire Deccan plateau to tilt gently eastward. The resulting structure features a sharp, abrupt rise on the western side and a long, gradual slope descending towards the east. This eastward tilt dictates the drainage pattern of nearly all major peninsular rivers. The underlying rock structure is a mix of ancient basalt in the north, related to the Deccan Traps, and older gneiss and charnockite rocks in the south.
Defining Climatic Influence
The Western Ghats exert a profound influence on the climate of the Indian subcontinent by acting as a formidable barrier to the Southwest Monsoon winds. Starting in June, moisture-laden winds sweep in from the Arabian Sea and are intercepted by the mountain wall. This interception forces the winds to rise rapidly, causing them to cool and condense, which results in intense orographic rainfall along the western slopes.
The windward western side, including the narrow coastal plain, receives exceptionally heavy rainfall, often exceeding 2,500 millimeters annually. This high precipitation supports a dense growth of tropical wet evergreen forests. Once the air currents crest the peaks and descend onto the eastern side, they have shed most of their moisture content.
This creates a stark contrast, known as the rain shadow effect, on the leeward eastern slopes. The descending air warms and holds moisture more effectively, drastically reducing precipitation in the interior plateau region. Consequently, the eastern slopes receive significantly less rainfall, supporting drier vegetation types. Ecosystems transition dramatically from lush tropical evergreen forests on the west to moist and dry deciduous forests, and eventually scrublands, further inland.
Status as a Global Biodiversity Hotspot
The Western Ghats are recognized as a Global Biodiversity Hotspot, a designation reserved for regions with a high concentration of species found nowhere else on Earth. The long geological history and varied microclimates have fostered an extremely high degree of endemism across multiple plant and animal groups. For example, over 50% of the tree species, 65% of the amphibians, and 62% of the reptiles found here are endemic to the region.
The flora is characterized by unique ecoregions, such as the shola montane forests. These are stunted patches of evergreen forest nestled in valleys, interspersed with rolling montane grasslands. A notable example of endemic flora is the Neelakurinji (Strobilanthes kunthiana), a shrub that flowers only once every twelve years. This high-altitude mosaic supports specialized species adapted to the cool, misty conditions of the peaks.
The fauna includes a range of rare and charismatic endemic mammals. The amphibian diversity is unparalleled, with numerous endemic species like the Purple Frog, which emerges only during the monsoon to breed. Exceptional endemism is also seen among reptiles, including the Malabar Pit Viper and various shield-tailed snakes.
Endemic Fauna Examples
The region is home to several endangered species:
- The Lion-tailed Macaque, a primate with a distinctive silver mane that inhabits the rainforest canopy.
- The Nilgiri Tahr, a mountain goat that lives exclusively among the high montane grasslands and rocky cliffs of the southern Ghats.
Role as a Major Hydrological Source
The Western Ghats function as the primary watershed, often termed the “water tower,” for peninsular India. The heavy monsoonal precipitation captured by the western slopes is the source of numerous river systems that sustain the ecology and economy of several states. The mountain range acts as a significant water divide, directing the flow of rivers in two distinct directions.
Short, fast-flowing rivers originate on the steep western slopes and rush directly into the Arabian Sea. In contrast, the eastward tilt ensures that the major river systems of peninsular India begin their long journeys here, flowing across the plateau to drain into the Bay of Bengal. These rivers include the Godavari, Krishna, and Cauvery.
These major rivers are rain-fed and perennial due to the consistent water storage capacity provided by the Ghats’ forests and soil. Their basins drain approximately 40% of India’s total land area. The water collected and regulated by the Ghats is integral to massive irrigation networks and provides water for agriculture, domestic consumption, and hydroelectric power generation.