The Mangroves of Andaman Islands and Tamil Nadu
Updated: Apr 3, 2022
Text by Yuvan Aves and photos by Dhritiman Mukherjee
In times of rapid climate change, protecting the mangroves of India is more crucial than ever before
Havelock island is rich in mangroves just like the rest of the Andaman archipelago. When the tide was high, I would snorkel around these ‘octopus plants’ and peer through the lattice work at the life among them. The long green seeds of these plants floated away into the clear blue of open ocean. Fish would congregate here to feed on the fallen, soaking foliage, and on the algae growing on the roots. Shoals would zip into them to hide, if a predatory needlefish passed by or if I swam too close. But now the tide is low, and one can walk a good distance into the ocean.
The stick-like seeds of rhizophora plants drop into the water from the trees. They are then dispersed by waves and ocean currents to shores, where they may germinate and grow. Cover Photo: Sometimes called “walking trees”, rhizophora are a genus of mangroves that grow in intertidal zones, such as the fringes of Havelock Island. The stilt roots of rhizophora keep their crowns above water during high tide and are uncovered as “spidery” forms during low tide.
As I walk to explore the ocean bed I see the rhizophora plants, their crowns and their roots growing such that it is difficult to say where one begins and one ends. They are a mass refuge for creatures waiting to roam the revealed seabed each time the tide falls. Now they are crawling down. Nerite snails, a motley bunch of crabs and hermit crabs are descending to the soil beneath. In little tidepools in the shade of root matrices, fingerlings of fish swim around. Collared kingfishers and reef herons perch around these and feast.
Mudskippers are an amphibious species of fish that spend their time divided between the ocean and the seashore. Researchers believe they might help us understand how the first fish may have moved out of the ocean, over 375 million years ago.
The earth under a mangrove tree is a thriving, fertile feeding ground. Blue fiddlers and sand bubbler crabs are here scavenging organic matter from the sand and strewing around tiny spheres of silt everywhere. Mudskippers bask on the curves, where the stilt roots ran horizontally. They quarrel over a preferred lazing spot — raising their dorsal-fin warning flags and smacking each other. These pugnacious little creatures also feed on pieces of soft decaying stalk and leaf bits. The arms of a brittle star from its inundated burrow is scooping in more organic matter.
Without our noticing, mangrove forests or mangals, do phenomenal things. They build new coasts, and make fresh land. Each time the tide moves in and out, the dense root networks trap soil, add organic matter to it for future seeds to flourish. Over millennia, they can significantly build, modify and stabilise coastlines and seashores.
The mottled lightfoot crab (Grapsus albolineatus) is a regular mangrove-dweller of Havelock Island.
One of the leading experts of mangroves in India, Professor K. Kathiresan from Annamalai University in Tamil Nadu has done extensive research on them. He and his team have found over 4,100 species of fauna which live within these unique coastal forests — from little polychaete worms to the saltwater crocodiles of the Andamans and Odisha, from horse-shoe crabs to the royal Bengal tiger of the Sundarbans.
He was part of the group of scientists who visited Odisha after the super cyclone which ravaged it in 1999. He often narrates what he witnessed. All along the coast, he saw lost lives — bodies lying scattered or heaped in mounds. The death toll was 10,000. 3.5 lakh houses were destroyed, including the chief minister’s. Astonishingly, he found that the surroundings of Bhitarkanika were barely touched by the disaster. Bhitarkanika is a vast protected mangrove forest with a large community of fishermen, tribes and locals living in, and around it. This vegetation acted as a natural cyclone shelter, absorbing the immense wind and tidal forces, entirely buffering the severity of the event.
Having witnessed this, Dr. Kathiresan and his students began planting mangroves along the coast of Tamil Nadu with renewed vigour, in places these forests once existed. The Bay of Bengal is known to be the most unpredictable and perilous part of the Indian Ocean, conjuring up the highest number of storms and cyclones, and spewing them inland. But interestingly, the eastern coast of India hosts among the greatest mangrove diversities, starting in the Gulf of Mannar to Pitchavaram in Tamil Nadu, Coringa in Andhra Pradesh then Mangalajodi and Bhitarkanika in Odisha and the Sunderbans in West Bengal, the largest mangrove forest in the world. His team planted mangrove saplings in Ariyakuppam, Pondicherry and all along the coast of Chidambaram, Tamil Nadu, among other places. Their planting initiative didn’t go completely undisturbed. In some places, fishermen regarded the plants as a nuisance and uprooted many saplings from their vicinity. But in various other places, the mangroves grew to maturity.
Organic matter shed by mangroves provide a substrate for coral reef to grow. In this way, the species indirectly supports the health of the seabed.
In December 2004, a massive tsunami hit the lower coast of India, triggered by an underwater earthquake in Sumatra. It was considered to be one of the most severe natural disasters to hit the country. New records were set by the damage and casualties caused by the colossal waves which pummelled the coast, some over 13 feet high. After the incident, however, fishermen and locals from around the mangrove afforested regions flocked before Dr. Kathiresan’s office, wept and thanked him profusely. The trees had buffered the beating of the giant waves. Their villages had been spared, their families saved. Mangroves made big news.
WHERE I LIVE by the Adyar river’s estuary in Chennai, tracts of rich mangals once existed. Now they do only in pockets inside creeks, some shores and mudflats. During the monsoon, when the river swells, excavator machines work day in and day out, at the river mouth where it flows into the ocean, to remove sand and constantly widen it. The shores of the river are flanked now by high rise buildings, a result of poor urban planning. The water’s current erodes its banks and brings enough sediment to fill up and choke the estuary in no time, causing the flooding of adjacent areas. Initiatives like the creation of the Adyar Eco-park which has restored the natural vegetation of the river creek and its surroundings though have contributed to mitigation of flooding and erosion markedly, and also bringing back living communities which once existed here.
All along the Indian peninsula, mangrove forests have proven to be crucial buffers of cyclones and other natural disasters arising from the ocean.
Mangroves are also fondly known as “walking trees” from their typical appearance, or “dancing trees of the sea”. They offer far too many services to be ignored, especially in a country like ours, with a long coastline full of diverse life and people. Mangrove wetlands also act as sieves of seawater, filtering it and protecting underground freshwater reserves from salt intrusion. Their stilt roots have been found to precipitate and bury toxic heavy metals, thereby purifying water.
Across the peninsula, millions of fishermen are dependent on them, as mangals are crucial breeding grounds for economically important fish, shrimp and crabs. Time and again they have also proven to be indomitable coastal sentinels against calamities surging in at us from the seas.
is a Chennai-based naturalist, writer and activist. He enjoys introducing the natural world to children and is the author of A Naturalist's Journal - a collection of essays on countryside wilderness.
Yuvan is a "Human Book" for our children who live by and off the Bay of Bengal. In his most generous heart, he has a place for every child.
Want to be a "Human Book"? Write to us at email@example.com to join our family!