Mangrove plants live in hostile environmental conditions such as high salinity, high waterlogged soil strata, tidal pressures, strong winds and sea waves. Now a question needs to be asked. Do mangroves need salt? The answer is in the negative. Generally, mangroves are facultative halophytes, meaning that they do not require salt water to live but are able to tolerate it. They do so, thereby out-competing freshwater plants by the processes of microfiltration and salt excretion.

Their intricate root systems are covered with tiny pores that filter out salt from the water that surrounds them. At the same time, any of the salt that finds its way into the plants is excreted through salt glands located on the base of mangroves leaves. These processes work so well that a thirsty traveller could cut the root of a mangrove and obtain fresh drinkable water. Mangroves reduce the height and energy of wind and swell waves passing through them, reducing their ability to erode sediments and to cause damage to structures such as dikes and sea walls.

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Loss of energy varies from 13 to 66 per cent over 100 meters of mangroves. Moreover, waves lose their ability to scour the sea bed and carry away sediments. Winds across the surface of water get reduced and propagation or reformation of waves is also prevented. Many mangroves have stilt roots, which are aerial and act as anchoring structures to withstand wave action. Since most of the islands of Sundarbans are below sea level, the 3500-km long stretch is the only protection against incursion of saline water.

Watching brick embankments crumble to the hungry tide, villagers have now realised that mangroves provide the only protection to dykes that are critical to the Sundarbans’ survival. Truly, during Aila villagers noticed that embankments that had mangrove plantations had weathered the storm while others had been breached. Mangroves are considered ‘land builders’. All coastline waves and currents create change, sometimes bringing sediments to the coast, but sometime causing erosion and the loss of lands.

The mangrove vegetation reduces wave energy and slows the flow of water over the soil surface, reducing the water’s capacity to dislodge the sediments and carry them out of the mangrove’s area. At the same time, the slower water flows can allow already suspended particles to settle out from water resulting in increased deposition of sediments. The tangles of slit roots also help the sedimentation of the particulate matter. Networks of mangrove roots provide firm anchorage to the banks of tidal rivers, creeks and also to the coastline. Moreover, it is believed that the roots of the mangroves secrete  a substance which modifies the coarse particles into fine ones and helps in soil formation.

Mangroves are important to many local coastal species, both terrestrial and aquatic. For many organisms, mangrove forests serve as the starting place for their food web. Its detritus (fallen leaves and organic material) serves as a nutrient source for planktonic and epiphytic algol food web. These microorganisms and macroinvertebrates then supply the remaining members of the food web with tremendous amounts of nutrients and energy. Mangroves are the breeding and nursery grounds for several marine organisms including commercially important shrimps, crabs and fish species.

Mangroves stop contaminants like excess amounts of nitrogen and phosphorous, petroleum products and halogenated compounds from polluting the ocean waters through a process called rhizofiltration. Apart from nature’s fury,  the land degrading anthropogenic activity is one of the prime factors for destruction of mangroves. In the forestsociety interface, unplanned overexploitation of natural resources is very common. In case of Sundarbans also, as a result of continuously increasing population pressure almost half of the mangrove forests have been cut down to supply fuel wood, land reclamation for settlement and aquaculture  and various other purposes.

There remains the striking imbalance between exploitation and replacement, thereby making the ecosystem fragile. Indiscriminate prawn seed collection, refuse and sewerage discharge discharged from urban areas, spillage of toxic pollutants as well as trash in the tourists spots and other anthropogenic factors are responsible for environmental degradation. Sundarbans is famed for its biological diversity. It is not just an environmental asset or ecological treasure. Its mangrove forests act as a bio shield between the ocean and land. It is also a unique part of this country because this region has immense geo-political importance.

Sundarbans should be saved. To save the Sundarbans we need to leave it alone. Only thing we can do is to minimise human intervention. The development dilemma around the Sundarbans is a dilemma about preserving nature and preserving man in an environment that is extremely fragile. The Sundarbans is not a just a matter of development. It is the matter of conservation of man and the beast; of vegetation and the unique world in which each component contributes to the overall ecological balance, and to natural regeneration.

Nature in the Sundarbans commands and demands far more respect so that there is neither a ruthless dispossession of the rights of the indigenous people of the region, nor a blatant violation of its environment. One of the best-known aphorisms of Mahatma Gandhi ~ “Earth (Nature) provides enough to satisfy every man’s need, but not for every man’s greed” ~ is in effect an exquisitely phrased one-line environmental ethic. Everybody should properly be made aware of the ethic.

(Concluded)

(The writer is a retired IAS officer)