The Palghat Gap, a substantial discontinuity in the Western Ghats, frequently features in news. This geographically mesmerizing region stretches around 40 kilometers in width, carving a separation between the Nilgiris and Anamalai hills. Elevated more than 2,000 meters above sea level, these hills give the Gap a dramatic presence.
Origins and Formation of the Palghat Gap
The birth of the Palghat Gap is attributed to the separation of continental shelves following the drift of Australia and Africa from the Gondwana landmass. Notably, the division of India and Madagascar observed about 100 million years ago contributed significantly to its formation.
Vegetation within the Gap
Contrary to the lush tropical rainforests that generally characterize the Western Ghats, the vegetation characterizing the Palghat Gap can be classified as a dry evergreen forest.
Historical Importance: A Gateway to Kerala
Over history, the Palghat Gap has served as a crucial entrance into Kerala, enabling both road and rail transportation between Coimbatore and Palakkad. Further enhancing its importance as a transport passage is the Bharathappuzha river, which flows through the Gap.
Geographical Characteristics: The Shear Zone
Regarded as a geological shear zone, the Palghat Gap stretches from the east to the west and indicates a weak region in the earth’s crust. This geological feature could provide an explanation for the occasional tremors experienced in the Coimbatore region.
Climate Variation
Interestingly, the climate varies around the Palghat Gap. While the northern region of the Western Ghats receives a higher annual rainfall, the southern part experiences rainfall more uniformly throughout the year.
Ecological Implications: Biogeographic Distinctions
The unique and distinctive flora and fauna on either side of the Palghat Gap are thought to be a result of ancient river systems or previous incursions of the sea.
Genetic Variations
Specific genetic studies have found differences in the mitochondrial DNA of elephant populations living on the Nilgiris side compared to those in the Anamalai and Periyar sanctuaries.
Bird Species Variation
Research conducted by IISc Bangalore revealed genetic divergence in the White-bellied Shortwing, an endemic and threatened bird species. For instance, variations in appearance between Nilgiri blue robin and White-bellied blue robin populations were discovered, dependent on their location around Ooty and the Anamalai hills.
Species Richness and Phylogenetic Diversity
Recent research by groups from CCMB at Hyderabad and multiple other institutions unveiled that the southern region of the Western Ghats, specifically located south of the Palghat Gap, is rich in diverse species. Home to over 450 tree species, including fossil species like Magnolia champaca (Champa; Tamil: Sambagan), this region has witnessed these species thriving for over 130 million years.
Other Significant Gaps
Besides the Palghat Gap, other gaps that have been identified include Thalghat (between Mumbai and Nashik) and Bhorghat (between Mumbai and Pune).
The Palghat Gap is recognized as a significant element in the Western Ghats’ ecology and geography. Its existence and unique features have implications for various aspects like transport and communication, biodiversity, climate, and genetics.
