Mangroves are the very lifeline of nature. Regrettably, these vital ecosystems are under threat of extinction with growing urbanisation, infrastructure development and human intrusion. Let us have a look at how mangrove forests are vital to human survival and the challenges they face of late.
Mangroves are wetland ecosystems formed by the assemblage of specialised plants and animals adapted to semi-saline swamps along coasts. Mangrove forests of the Indian state of Kerala are highly localised, but the species diversity of these mangroves and its associates are comparatively rich. It is confined to the upper reaches of estuaries, lagoons, backwaters and creeks.
However, the grim reality is that this vital ecosystem is under threat owing to the so-called urbanisation and infrastructure development.
In Kerala, mangroves are distributed in all the districts except Idukki, Pathanamthitta, Palakkad and Wayanad. Maximum extent is reported from Kannur district. The total extent of mangrove forests in the state is estimated to be less than 50 sq km.
Mangroves play an important role in the economy of coastal people through various ways. Mangroves provide excellent habitat for migratory birds, serve as breeding ground for many species of fishes and prawns, and helps in controlling pollution, rutting of husks, etc.
Mangroves are the less understood sister community of forests. If forests are getting a bad deal, you can imagine what mangroves are going through. In a state like Kerala where backwaters run through bursting human habitats, mangroves have been cherished for long, though lately they have been considered dispensable impediments in the way of economic development.
It is heartening that, of late, several enthusiastic, lay naturalists are taking up the protection of mangroves. Also, there are some new state laws aimed at protecting this valuable ecosystem.
How vital are mangroves?
Along the edges of backwaters and closer to the sea is nature’s inventive exuberance called mangroves. Central to it are many species of halophytes, which are plants adapted to thriving in salt water. Their roots grow up out of the saline, oxygen-starved mud to breathe. Seeds grow into seedlings while still attached to the tree, and, when mature, spear themselves into the soft mud. Roots of trees are, in fact, a network of tall stilts in the ebb and flow of tides.
The important mangrove plants are Acanthus cillicifolius, Acrostichum aurem, Aegiceras corniculatum, Avicennia officinalis, Azima tetracantha, Bruguiera gymnorrhiza, B cylindrica, B sexangula, Excoecaria agallocha, E indica, Kandelia candel, Rhizophora apiculate, R mucronata, Sonneratia caseolaris, and Calophyllum. Some of the species that disappeared from the Kerala coast are Azima tetracantha and Ceriops tagal. Heritiera littoralis and Flagellaria indica have discourteous distribution. Calamus rotang and Syzygium travancoricum are some of the rare and endangered species found in the mangroves.
In 1969, biologists of University of Florida discovered the detrital cycle: within hours of the leaves falling from the trees, they are colonised by marine fungi and bacteria that convert difficult-to-digest carbon compounds into nitrogen-rich detritus material. Feeding on the detritus and evolving outward is a parade of species in a food chain: worms, snails, shrimp, molluscs, mussels, barnacles, clams, oysters, crabs, fish, birds and marine animals, culminating in man.
Until recently, man had not understood this productive ecosystem that in fact makes it possible for him to live an amply endowed life. Mangroves give him fish to eat, small timber to cook with and shade against nature’s fury. They turn seawater into a better-tolerated brackish water which he can use for agriculture. They trap nutrients brought down by rivers. They are recyclers of pollutants. They prevent erosion and silting of the channels.
In Kerala, people may not have scientifically understood it, but they have lived in harmony with mangroves and derived much pleasure from it. Mangroves are known as Kandal Kadu in Malayalam. Of the 1,700 hectares of Kerala’s mangroves, more than half are in Payyanur.
(Read the full article in the February issue of Safety Messenger Magazine 2016)