JOIN USConservation Mangroves form one of the most important ecosystems in our planet. K S Someswara discusses the advantages of allowing the mangrove forests to thrive.
The mangrove ecosystem is a peculiar habitat which can be seen at the interface of land and sea. The term ‘mangrove’ is applied to a specific ecosystem of the intertidal world in the tropics and sub-tropics and the plant community of the ecosystem is termed as mangrove vegetation.
Mangroves are called ‘flood buffers’. They help stabilise the climate by moderating the temperature, humidity, wind and even giant waves. They are specially adapted to withstand salinity, wave action and can grow even in poor soil. They are the natural protectors of the land from the impact of the sea. While there is a general feeling that these are dwarf weed plants, they actually act as a buffer between sea and land. They really are friends that nature has provided not just to humans, but also to many water borne species. However, their importance is either not understood or ignored by mankind.
Richest mangroves
The richest mangrove grow in tropical and sub-tropical areas. They can also be seen on mountain ranges. This ecosystem can be found in almost all the continents except Europe, Arctic and Antarctica. The best of them can be seen only in India and Bangladesh.
The Sunderbans are the largest mangrove forests found in the world, both in system and biodiversity. India accounts for 70% of the total mangrove forests in the world.
Sunderbans accounts for nearly 80% (4000 sq km) of the total area (about 6740 sq km) of mangroves present in India. The remaining are spread over Andaman and Nicobar islands and about 20% are seen on the estuaries of other large rivers like Mahanadi, Krishna, Cauvery, etc and a small percentage grows on the west coast from Kutch to Kerala. The peculiar coastal structure and the nature of estuaries are some of the reasons for scalene mangrove structure along the West coast. We have a long stretch of mangroves, even in Karnataka, along the coastal lines of Karwar, Honnavar, etc where the locals call it kandla or sundari.
Pioneer plant species initiate the process of establishment of mangroves by way of forming mud-flats and stabilisation of the same. The roots of these plants help in building the soil and establishing micro-organisms which further help in stabilisation. This starts from the side of the land and later gradually shifts toward the sea. Some of the major mangrove plants are porterasia coarctata and some members of Cyprus family. Other forms are rhizophora apiculata, rhizophora mucronata, brugeira gymnorrhiza, B-cylindrica, luminitzeria and many more. The stabilisation slowly reaches a stage called climax vegetation. If represented by a complete circle of life with different species of plants, animals (terrestrial and aquatic) and micro-organisms, it forms an ecosystem called the tropical salt mesh or mangrove ecosystem. Every species has its own salinity level tolerance.
Highly adaptive
Mangroves are adaptive, even in hostile conditions such as high salinity, hypoxic (deficiency of oxygen), water logged soil strata, tidal pressure, strong winds and sea wash. To cope with such hostile environments, the mangroves exhibit highly evolved morphological and physiological adaptation to extreme conditions. They have special root systems like arial roots, stilt roots and breather roots. They share two forms of reproductive strategy. One is by dispersal by means of water and the other is vivipary.
Vivipary means that the embryo develops continuously while attached to the parent tree and during dispersal. They may grow in place attached to parent tree for one to three years. Their length will increase up to one meter before they break from the parent tree and fall into water. These seedlings (propagaule) then travel in an amazing method. In the buoyant sea water, they lie horizontally and move quickly. Upon reaching fresher (brakish) water, they turn vertical, set down roots and bud, making it easier for them to lodge in the mud at a suitable less salty area. Once lodged in the mud they quickly produce additional roots and grow.
Crucial ecosystem
The mangrove ecosystem is crucial for coastal areas. Since estuaries are highly populated, one slight ecological imbalance can create havoc. They play an important role in stabilising the area. The coastal line faces problems of erosion and threat of rising sea level.
Mangroves are also called ‘tropical littoral ecosystem’ more dynamic than the sea itself. They not only act to prevent soil erosion but also as a catalyst in retaining land from the sea. They are a breeding and nursery grounds for a number of varieties of marine organisms including shrimp, crab and fish. Hence, the loss of mangrove not only affects us indirectly but also there is a direct economic repercussion through the loss of fishing.
If managed properly they can be an alternative to timber, and help in reducing environmental degradation. In India, since ancient times, they have been used as firewood, for boat building and brick burning. Honey collection in the mangrove forest is another important economic activity and the Sunderbans produces the largest quantity of honey. In spite of its diversified utility, mangroves are threatened by the possibility of extinction.
Large demographic pressure is creating extreme stress on the coastal environment. The destruction level has reached a stage of no return. Land reclamation like concrete construction, development of industries are the leading culprits, where large quantities of industrial affluents and debris have been dumped continuously in the mangrove area, creating a barrier with which sea water is unable to enter the mangrove area.
There is a dire necessity to save this precious ecosystem. An action plan on war footing is the need of the hour to educate the people about the importance of mangrove ecosystem and its necessity, so that in the long run, this savior of the earth is saved from extinction.