Along the sandy and rocky shores of the mouths of rivers and muddy seashores, places where any other tree would perish as a seedling, lives and grows a special group of trees-the mangroves. There are many species of mangroves. They all have one common property- their tolerance to salt. What makes these trees salt resistant? Some mangroves take in sea water, extract the salt with special glands and then secrete it from their leaves. Others have roots that filter out much of the salt even as it enters the tree. The remaining salt is stored in the oldest leaves of the tree- those that are about to fall. Thus the salt does little harm.
Mangrove trees have to adapt not only to living in salty water, but also to growing in the continuously shifting sandy soil which gives little scope for the trees to get a firm hold. Mangroves anchor themselves to the soil by sending out long roots from their trunks and branches. These stilt roots support the tree and prevent it from toppling over. The muddy waters where they live contain very little oxygen. But mangroves have and ingenious solution to this problem too. The trees send out a second air-breathing root system, not downwards but popping up above the mud-like the snorkel of a diver.
In addition to the props that come down and roots that shoot up, mangroves have roots that trap the silt and debris from the sea as well as the trees' own fallen leaves. In course of time, this accumulation helps to create more land area around the trees, and a new habitat is created. Mangroves growing together create an entire ecological complex along some parts of our coast. These are also called mangals in India. Mangrove swamps perform a very important function-they nurture the seas and protect the land.
They help control floods by catching and spreading high velocity flood waters. They catch the fertile silt flowing away to the ocean with the rainwater, and trap it amongst their roots. Mangrove swamps provide vital breeding grounds and habitats for a great variety of shellfish. The nutrient rich soil provides food and shelter to innumerable organisms. The fallen leaves provide shelter to tiny shelled creatures. Floating mangrove leaves provide a base for larval growth and for micro fauna. The rotting fallen leaves of the trees provide food to insects, reptiles and shellfish. The smaller animals form food for the larger creatures that live or pass through the swamps. Many fish-eating birds come here for the abundant food and the shelter. It is a world teeming with life.
India has about 3,150 kilometers of mangrove cover. Our mangrove swamps or mangals have around 50 species of mangrove trees. The mangroves along our eastern coast are thicker when compared with those on the western coast. The best mangrove formation in India occurs in the Sundarbans in the Bay of Bengal, and in the Andaman and Nicobar islands. The Sunderbans has been designated a world heritage site- one of the natural wonders of the world.
All over the world mangroves are being degraded at an alarming rate. There are several reasons for this. There is a tremendous pressure on areas where they grow due to increasing industrialisation. Mangroves are exploited directly or indirectly, for food, duel, timber, medicines and fisheries. In India also, our mangroves are under threat. The trees are used as timber, firewood, charcoal and as a source of tannin. Honey is harvested in large quantities. Mangals have also been converted into salt pans. In the last 200 years, the area under the Sundarbans mangroves have been reduced to one third of its original size. These pressures are destroying unique ecosystems.