SEA-LEVEL RISE AND REAL CHALLENGES FOR INDIAN COASTS

Author: Rahul Wankhede

The accelerated heating of our planet has led to an unprecedented rise in the average sea levels world over primarily by: (1) mountain glaciers and polar ice sheets that store much more water in them than any other source on land are melting at an accelerated rate over the last few centuries due to anthropogenic activities, and, (2) warm water expands thereby causing an increase in its volume. Presently this increase has been estimated as 3 mm per year but, this being an average value it does not reveal the regional variations occurring due to local factors like wind flow, ocean currents, subsidence or emergence of the ground, land erosion, etc. Rising sea level has an adverse effect on the entire coastal ecosystems and entities dependent on them. As saline water penetrates freshwater bodies and living areas, it disrupts the local ecosystem, most of which is irreversible.
As the planet traps more heat due to GHG emissions and other reasons, mean sea levels will rise over a few more centuries before reaching an equilibrium level; the rate of which will depend on the future levels of emissions and ice melting. The peninsular position of India with its coastline of 7516.6 kilometres gives it a geostrategic location on Earth, but has also put the entire subcontinent at risk of rising sea levels and related climatic change-induced disasters. Almost 17 crore people in India are at the front lines of rising coastal erosion and mean sea levels, shore-line loss, and natural calamities like cyclones. The Coromandal coast, Malabar coast and most of India’s eastern coastline is a ‘coast of emergence’, created land upliftment and/ or by receding of the ocean waters. Konkan area oppositely, is a ‘coast of submergence’ formed by subduction of land under the ocean water. The western coast of India exhibits both the phenomena of emergence and submergence, due to faulting of the sedimentary rock bed, which makes these areas more susceptible to inundation by increasing sea levels.

Historically as well, in the past sea level rise has caused the submergence of huge areas: 1. Dwarka in the western sector is a popular example, wherein increased sea levels caused flooding and submergence, which was later proven by archaeological studies, a few miles into the sea. 2. About 25km east of Poompuhar on the Tamil Nadu coast, scientists discovered an ancient harbor-like structure under the sea, estimated to be around 15000 years old along with the original Poompuhar city that shifted location four times due to continuous sea level rise. Both these examples are evidence of the continuous process of geological changes that the planet undergoes continuously in a value-neutral manner; the natural balance is now being disturbed by pollution and global warming.

The Green Climate Fund estimates that around 25 crore of the Indian population lives within a radius of 50 kilometres from the sea shores and therefore are most threatened by the impacts of global warming making them more susceptible to be affected by extreme temperature variations, rainfall pattern disruptions, etc. Climate scientists from Stanford University calculated the economic impact of climatic change on India and found that the Indian economy would have been 31% bigger than its present size, had it not been affected by unusual climatic changes.