Mangroves, our natural coast guards

Baheerathan M, Research Matters

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Photo : Dennis C J / Research Matters
If you are taking a stroll near a tropical sea shore and find a dense mat of trees that appear to be standing above the water with their roots pointing up, you are witnessing one of the rare, spectacular and prolific ecosystems in the world — a mangrove forest. Mangroves are forests present only in the shorelines of the tropical and subtropical regions of the globe. They are made up of trees and shrubs which can grow in soil with low oxygen content.

The mangrove ecosystem

Mangrove forests portray special biological characteristics — they are a class of plants that have evolved special adaptations to thrive in salt-rich sea waters. The mangrove plants and trees are known to either filter out salt from the tidal waters, or to drink in salt water and spit out the salt in them by special salt glands. Another interesting biological feature of mangroves is their seed dispersal mechanism. Many mangrove tree species germinate their seeds in the trees itself, and then disperse them, rather than dispersing the true seeds like other plants. This mechanism is called as ‘vivipary’ where a ready-to-go seedling is released into waters which are then carried by tides.

Though they represent just 1% of the tropical forests, mangroves are rich in indigenous flora and fauna found nowhere else.  They act as nurseries for fish and crustaceans like crabs, insects like dragon flies and moths. The flowers of plants that grow here are rich sources of nectar for honeybees, and the fruits and leaves are a major food source for other animals. While crabs feed on the leaf litters on the forest floors, their larvae are food for many fish species like mudskippers. The crab burrows also contribute to the roughness of the mangrove floors, which in turn, helps in more water filtering.  The mangrove canopies also serve as food sources for fruit bats, birds and many fruit-eating animals. Mangroves also serve as habitats for reptiles like crocodiles, alligators, lizards, snakes and turtles, and mammals like dolphins, mangrove monkeys, flying foxes, small clawed otters, tigers, antelopes and hippos.

“Mangroves provide home to great variety of fauna. Majority of smooth-coated otter population in Goa lives in mangroves. Mangroves form a vital part of otter habitat. They provide the necessary cover for the smooth-coated otters for their densities”, says Mr. Atul Borker, Founder Director of Wild Otters and Continental Coordinator for South Asia for the IUCN/SSC Otter Specialist Group.

Why are mangroves important?  

Apart from providing a safe haven for animals, mangroves have a major role in supporting humans too — they provide food security, forest products and sustainable fishing to local communities living around the sea shores. Shrubs like the black mangroves are used for fishing poles and in the production of mangrove flavored golden coloured honey. The red mangroves serve as firewood and the bark is used as a raw material for tannin extraction that has commercial uses in the dye industry. Mangrove swamps also offer excellent tourism destinations, supporting families dependent on tourists for a livelihood.

In addition, mangrove forests act as a natural defence barrier along the tropical coastlines, protecting them from tides, storm surges, currents and even tsunamis. They help in  reducing soil erosion and act as an effective carbon sink that have sequestered huge amounts of carbon through time.

In spite of the many advantages mangroves provide, this unique ecosystem is under threat like most other ecosystems around the world. Scientists say that mangroves are disappearing 3 to 5 times faster than the overall forest losses in the recent years. Mangroves are so sensitive that even minute changes in  temperatures, atmospheric carbon dioxide, sea levels, rainfall, wind and waves during storms can disrupt their existence.

In recent days,  development of the seashore for anthropogenic needs like housing, construction of dams and clearing of swamps are greatly contributing to the destruction of mangroves. According to the the International Union for Conservation of Nature (IUCN) Red List of Threatened species, more than one in 6 mangrove species are risking extinction due to coastal developments.

In India, mangroves cover an area of around 4500 sq. kms spanning around 11 states and 3 union territories.  The coastlines of India harbour around 3% of the total mangroves in the world. Sundarbans, the world’s largest unbroken mangrove belt, is famous for its Bengal tigers and Chittal deer, both now labelled ‘endangered’ species. No wonder then Sundarbans features in the UNESCO World Heritage List.

“Riverbank construction projects pose a great threat to mangroves. Conserving otter habitats contributes to mangrove conservation as well. If we let the mangroves be and don’t cut them; they will do well”, says Mr. Borker on the threats that face the mangroves in India.

Needless to say, a healthy  mangrove ecosystem is important for our own well-being.  If their destruction continues at the present rate, the coastal shorelines will soon become sources of carbon dioxide, which will be directly released into the oceans, resulting in great imbalance in carbon levels in the oceans and increase in ocean temperatures. Oceans, with their own marine ecosystem, are as fragile as the mangroves and a slight increase in temperature will spell doom for the myriad list of its inhabitants.

International Day for the Conservation of the Mangrove Ecosystem — A moment to spread awareness

Recognizing the threat faced by mangrove forests in 123 nations of the world, the United Nations Educational, Scientific and Cultural Organisation (UNESCO) is now promoting the conservation of mangroves through various avenues. Since 2016, UNESCO has officially proclaimed July 26th of every year as the ‘International Day for the Conservation of the Mangrove Ecosystem’.

“The protection of mangrove ecosystems is essential today. Their survival faces serious challenges — from the alarming rise of the sea level and biodiversity that is increasingly endangered. The earth and humanity simply cannot afford to lose these vital ecosystems”, said Ms. Irina Bokova, Director-General of UNESCO, on the occasion of the International Day for the Conservation of the Mangrove Ecosystem on 26 July 2016.

In that direction, UNESCO has officially declared 669 sites globally as World Network of Biosphere Reserves and 86 out of them are Mangroves. Sundarbans, which once had 32 species of mammals, has lost 4 of them including the Javan rhinoceros, wild buffalo, swamp deer and the hog deer, and many are now endangered or threatened. Conservation efforts to maintain the pristine environment are on in the form of establishing wildlife sanctuaries, controlling activities like entry, movement, hunting and extraction of forest products.

While ecologists are doing their part, how can ordinary citizens help? The first thing is to protect our coastlines by removing barriers like dams, coastal walls etc. that squeeze the mangrove forests from expanding inwards. Reducing land, air and ocean pollution by using bio degradable alternatives can help in a big way. We can also restrict overexploitation of resources by the human communities which will regulate and conserve mangrove forests.

Today, on  the 2nd International Day of Conservation of Mangrove Ecosystem, is a perfect occasion to spread the awareness about mangroves and help others appreciate this fascinating ecosystem.  It is indeed a moment to realise the harmonious relationship between humanity and nature and nurture this for the future generations to come. As Mr. Borker puts it, “International day for Conservation of Mangrove ecosystem can be the day for mangrove clean up. It can help to spread awareness regarding the importance of mangroves.” So, let’s make it a reality!

With contributions from Anushka Kale

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