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Showing posts with label mangroves. Show all posts
Showing posts with label mangroves. Show all posts

Pichavaram - the great mangrove forest of Tamil Nadu

Few people know (or care) that this favourite locale of filmmakers is a spectacular mangrove ecosystem throbbing with life
The mangrove forests of Pichavaram comprise an intriguing ecosystem

Tickets in hand, negotiations with the boatman closed, we should have been on the boat, headed for our first visit to a mangrove ecosystem. But all we could do was to gaze longingly at the dense green clumps across a vast expanse of the lagoon. The boat that was to carry us there was moored to the shore covered in blue tarpaulin. A sudden squall was depositing even more rain on the already soaked and overflowing coastline of southern Tamil Nadu and we were right in the centre of it all – at the northern edge of the Cauvery delta. 



A sudden squall threatened to drown out our much-awaited trip

Pichavaram, one of only two mangrove ecosystems located in Tamil Nadu, is approximately 75 km south of Pondicherry and 15 km from the temple town of Chidambaram. We had reached Pichavaram in the afternoon after a very enriching visit to the great living Chola temple. To be fair, the day had been fairly dry but now that we had planned to be on open water for the next four hours, it had started pouring.


Our entry into the mangroves began with the boatman negotiating one of the tamer channels
The Cauvery delta is formed when the river breaks up into multiple distributaries after Srirangam island. The northernmost distributary Coleroon (or Killidam) meets the sea near Pichavaram (the other river that drains this area is Vellar and the wetland is referred to as Vellar-Pichavaram-Coleroon wetland). The other mangrove patch is at Muthupet, which happens to be at the southernmost point of the Cauvery delta; the distance between the two is 180 km. Muthupet has a large lagoon where six distributaries discharge their waters. These mangroves are characterized by a long dry season (February to September) and high salinity.
Inside the mangroves
The shower stopped as suddenly as it had begun. We were off in a jiffy, the boatman rowing slowly and steadily across to the mangroves. Clouds streamed in from the ocean, promising more rain, but we pretended not to care. Pichavaram has almost 4,000 rivulets of varying length and width with mangroves on either side. As we entered the first, not more than six feet across, we saw the mangroves up close. They seem to grow out of water (there is not a patch of ground visible anywhere) almost like a floating forest.
The canopy weaves a tangled web, and not always a friendly one

The boatman was accomplished at clearing our way
As the boat negotiated the first turn, to our utter amazement and delight we entered a long and narrow rivulet completely wrapped in mangroves. It was like entering a green tunnel – the boatman had to row by moving the low, tangled mangrove branches out of the way. The banks of the rivulet were covered with mangrove roots reaching into the water – hundreds for every clump. The sky was swallowed up completely by the arches of these low trees and all we could see was the narrow rivulet and a vast impenetrable forest growing out of turbid water. The world had dissolved into an expanse of brown and red stilt roots (and all the shades in between) and the luxuriant green foliage of the mangroves, upon which streaks of sunlight created an impressionist canvas of rust, brown, olive, jade, lime-green and emerald.


A maze of stilt roots

In the eerie silence, as we negotiated one tunnel after another, crabs lit up the scene. They were everywhere – climbing up from the water’s edge, clinging to the trunks, hanging on to the canopy and perched in silence on overarching branches. A myriad species of crabs inhabit the forest and it was unfortunate that we knew so little about them. Soon enough we entered one of the wider channels. It was almost 100 feet across, like highways connecting the islands of mangroves. Forest towered on either side, dense and glistening in the evening sun.

The low boughs were the province of a myriad species of crabs
The east coast wetlands starting from the Sundarbans right down to Pichavaram (and Muthupet) receive a major infusion of fresh water from the rivers either throughout the year (the snow-fed Ganga and Brahmaputra) or during the northeast monsoon (Krishna, Godavari and Cauvery). Salinity levels vary through the season in proportion to the fresh water discharge but the trend is towards an increase in salinity as we move down the coast. So, while the Sundarbans have the least salinity (and the shortest dry season), the mangrove wetlands of the Cauvery delta have the maximum salinity levels and the longest dry season. Salinity (or the absence of freshwater intake) has an observed impact on biomass and species diversity. The Sunderbans and Mahanadi mangroves have 26 recorded mangrove species (out of the 33 found in India, 51 in South Asia and 68 worldwide), and high biomass due to tall low-salinity tolerant trees. But the mangrove species diversity drops to 17 for Godavari, 12 for Krishna and finally 11 for Cauvery. 


The sea-water dominated mangroves of Gujarat (with almost no fresh water infusion) have a species diversity of just eight. Further, the dominant species in all the high salinity mangroves -- those of the rivers Cauvery and Krishna and in Gujarat -- is Avicennia marina, an extremely saline water-tolerant species.

It has been observed that except in Andaman and Nicobar Islands, where the mangroves along tidal creeks, lagoons and bays are extremely diverse, those of the east coast are gradually being dominated by high salt-tolerant species like Avicennia marina due to changes in quantity and periodicity of fresh water. It has been found that the vegetation of Pichavaram and Muthupet wetlands used to be more diverse in the beginning of the 20th century but since the freshwater inflow was severely curtailed by the numerous dams and canals upstream on the Cauvery, Avicennia marina became dominant.


Mangroves receive an infusion of river water during the monsoon

We spent almost three hours in this verdant forest. It was a strangely hypnotic world. The dense forest growing out of the water, trees on stilts, and meditating crabs perched where we expected birds, puzzled our senses. But it was a real world, a shrinking and vulnerable patch of forest, and probably the last remnant of the much vaster mangrove forests that occupied the Cauvery Delta.


A strangely hypnotic world
Note:
Mangrove wetlands in India are in most cases the gift of east-flowing rivers. Other than the geological fact that India has no major west-flowing rivers, the east coast is gentler and wider and thus aids major rivers in creating large deltas and an accompanying network of tidal creeks and canals, and brackish lagoons where the mangroves thrive.

The major mangroves patches in India are Sunderbans (Ganga-Brahmaputra), Mahanadi (Mahanadi, Brahmini and Baitarani – the famous Bhitarkanika wetland), Godavari (the Gautami-Godavari system creates the Coringa wetland), Krishna (three islands located between Gollamattapaya and Nadimeru distributaries, and the Krishna river) and Cauvery (Pichavaram and Muthupet). The river dominated (tide-dominated in the case of the Sunderbans) mangroves of the east coast comprise approx 57 percent of India’s mangroves.

The west coast mangroves, all of which are in Gujarat (Gulf of Kutch and the Gulf of Khambat), comprise about 23 percent and those of Andaman and Nicobar Islands make up the remaining 20 percent. There are no statistically significant mangroves outside these five states (Andhra Pradesh, Tamil Nadu, Odisha, West Bengal and Gujarat) and Andaman and Nicobar islands, though small patches exist along the coasts of Kerala, Karnataka, Maharashtra and Goa.


We saw very few birds inside the forests but for the Striated Heron or the Mangrove Heron
The Gujarat mangroves are of a very different type. They are “sea mangroves” since they receive almost no freshwater from inland rivers during the year. These are classified as “drowned-valley type mangroves”.

Text and photographs by Sahastrarashmi
Additional photographs by Bijoy Venugopal


References: 


V Selvam, Environmental Classification of Mangrove Wetlands of India [PDF]

Beautiful Forest - Adrift in the Sundarbans

In the third episode of her Bangladesh travelogue, Jennifer Nandi enters the sinuous spiderweb of the Sundarbans, where the sluggish rivers are reluctant to lose their freedom to the sea


There are three main rivers with their tributaries that make up the Sundarbans. The River Jamuna (Brahmaputra, in India) joins the River Padma (Ganges, in India); and further down its course, joins the River Meghna, whose source is in the Sylhet hills. The western portion of this river system lies in India. Though the Sundarbans have lost half of their inland area over the last 200 years through human encroachment, over 10,000 km of continuous mangrove wilderness remain.

The myriad channels that crisscross the Sundarbans like a spider’s web draw visitors such as us. Innocent of human structure, this landscape answers to a name that means ‘beautiful forest’. One-third of its total area is permanently covered by water. Yet, it is the only mangrove forest with tigers; it harbours one of the largest remaining global population of this highly endangered species. Its coastal waters are home to the world’s largest population of Irrawaddy dolphins. It comes as no surprise that these mangrove forests are one of the two Ramsar sites in Bangladesh. But the Sundarbans is not an easy place to be in.

Twice a day, the character of the water changes from fresh to salty. And twice a day too, much of the mud is exposed to the air. Creatures that live in these stressful environments tolerate the fluctuating changes of fresh to salt water. Rewards for doing so are huge because of the nutrition that is available in such waters. Food is delivered to the estuary every day from both the sea and the land, so the creatures that are able to survive here flourish.

Water hyacinth snagged on a tree after high tide

Cleaning crabs after an early morning catch

The sandbanks being covered by water twice a day snag prodigious amounts of food that are inviting to the daytime gleaning of birds. This is particularly vital for the winter migrants that need to strengthen themselves for the ordeal of their journey to the half-frozen nesting grounds farther north. Small, short-billed waders exploit surface-dwelling organisms of the tidal mudflats. Most waders possess ear openings positioned much further forward than those in other birds. In this way, they are better able to detect vibrations in the mud.

The shifting sandbars of the rivers part the braids of their wandering channels and on this cold, damp and foggy morning, we witness life at the very edge of existence. Pastels of dawn paint the early morning water and jungle a strange hue. We are sitting on a mattress in a flat-bottomed ‘country boat’. The boatman paddles into a small creek. There are other boats like ours – though their compulsion to be out, so early, on such a cold morning, is driven by sheer necessity. They are fishing vessels – anchored with a bit of rope to a convenient snag. The men lean forward, yielding beneath a burden of life, as they lower their nets for fish; others catch crab.

Nypa palms
The forest dawn is long. The dark, impenetrable mangrove forest narrows the channels. We paddle through these tortuously twisted creeks and the mangroves press closer. The water is shallow and dark. On the harsh, sluggish grey, steep banks that lead down to the water’s edge are clear prints of tiger. If one had to emerge for a morning’s snack, I don’t think we had much of a chance, armed guard notwithstanding. Eerie sunlight sifts through curtains of fog. It’s still cold. As we paddle into wider channels, flowerpeckers and sunbirds gather on the blossoms of the flowering trees taking advantage of the cold shafts of sun that part the fog.

The river beds of the Jamuna, the Padma and the Meghna together with their tributaries are full of sediment by the time they reach their estuaries. They become sluggish in their reluctance to lose their freedom to the sea. Mingling with the dissolved salts of sea-water, their sediments clump together and drift to the bottom. These fine-grained, great, grey banks of mud trap the gases produced by the decomposition of organic debris. Earthworm-like creatures, called lugworms, ingest quantities of this mud to extract this organic material. These fat-bodied worms are in turn food for birds whose beaks are able to probe deeper into the mud. We see Whimbrels with their long down-curved bills feeding on the squelchy ooze at low tide. They also feed on fiddler crabs, probing into their burrows with their superbly adapted bills. Curlews with their even longer bills are fewer in number. But it’s still too early for any serious birdwatching and two hours later we head back to our luxury boat for some sustenance.

Sundari trees, after which the Sundarbans take their name
Ken is particularly pleased - I’d taught the cook to use the percolator, so Ken could drink Italian coffee with his substantial breakfast. We are now sailing towards Katka, a port 6 hours away at the very tip of the Sundarbans where we meet the Bay of Bengal. We move onto the bridge. It is flooded with a tide of light. We sit in its warmth and softness with mugs of the hottest coffee, and our binoculars at the ready. It is a delightful winter morning, and we waste it watching waders. We spot the rare Finfoot and then had the vessel halt for a better look! It’s a shy and secretive bird – we are lucky to see it riding high in the water. We see more Whimbrels and Curlews. The steep banks provide little space for them to stand. Brown-headed gulls tail us for a long while. Brahminy Kites circle overhead, and those great white birds, the Large Egrets, with their fierce fiery eyes and spear-like bills, fly from tree to tree in their effort to get away.

And now the true splendour of the mangrove forest reveals itself in a study in halftones. The trees are of different species that have all found ways of adapting to their very particular environment. Of the 50 mangrove species in the world the Sundarbans harbour 20. The Crab-apple mangrove is the most common species we find this morning. Each tree has its share of Fire-breasted Flowerpeckers and Sunbirds that suck nectar from the few flowers remaining. The Mangrove Apple is taller but deer are able to reach its leaves. Rhesus Macaques gather its fruit. The villagers also relish the Mangrove Apple fruit and grind it into a chutney. Local fishermen use Nypa Palm that line the water’s edge, to thatch their country boats for shelter. The Blinding Mangrove has sap, as its name suggests, that blinds. Its wood was used to manufacture safety matches and newspaper. Not anymore. It’s a tall tree which we keep a look out for perching birds. Irrawaddy freshwater dolphins show themselves as fast-disappearing dark shapes.

We settle into lazy inaction. Like light, that great zeitgeber of biological clocks, the stable rhythm of the boat’s engine lulls my body rhythms to a state so peaceful and warm that I close my eyes and hold the moment, as even the wind holds its breath, making it last till the afternoon sun yawns over the water and another sumptuous meal is served.

In the late afternoon we board the country-boat and paddle into the broader channels. We return before the falling river dusk and board our luxury boat to cruise down to Kotka in the Bay of Bengal. Ours is the only boat apart from a few crab fishermen. Here the tidal range is very large and much of the land is flooded. At Kotka we find three other large boats packed with local holiday makers. Tonight again we have an excellent view of the star stippled sky. Another good day passes.


Missed the first two episodes of Jennifer's Bangladesh travelogue?

Read them here:


Copyright: Text and photographs by Jennifer Nandi. All rights reserved.