Perhaps one of the most versatile ecosystems on our planet, the mangrove swamp forest straddles land and ocean, equally dependent upon both. As July 26th, 2018 was the first International Day for the Conservation of the Mangrove Ecosystem, as declared by UNESCO, let us take a belated dive into the mysteries of this little-known ecosystem, one which only accounts for <0.4% of our planet’s total forest cover.

Mangroves are a group of shrubs that grow in brackish or saline water. In order to survive, they must be fed year-round by a steady source of both fresh- and sea-water. They occur globally between 25 degrees N and S (tropics and subtropics) in estuaries or marine wetlands.

With approximately 110 species around the world, the mangrove is specially adapted to anoxic environments, high salinity, and frequent inundation. Individual mangrove species show strong zonation, where different species are found at different benchmark distances from the shoreline, representing their different tolerances of salinity, anoxia, and inundated soil. Mangrove roots, once established, provide habitat for many species and slow water movement, thereby enhancing sediment deposition in certain areas. One species, the Red Mangrove (Rhizophora mangle), can survive in highly flooded areas and are able to exclude salt from their water intake due to their highly-impermeable roots. In species where salt is intaken through the roots, it is then funneled into decaying leaves, which then drop off the plant having acquired ample salinity. Thus, mangrove internal salinity is preserved. Black Mangroves (Avicennia germinans) prefer higher ground and have pneumatophores , which are specialized root-like structures that poke out of the soil, allowing the mangrove to breathe. Reproduction is also facilitated by their watery location – mangrove seeds are dispersed by water and, in many species of mangrove, the seeds germinate while attached to the parent plant. Hardy and adaptable, the mangrove flourishes in a habitat hostile to most other plants.

But this fascinating ecosystem is no safer from threats than are other terrestrial forests. The World Mangrove Atlas (2010) indicated that one-fifth of the world’s mangroves have been lost since 1980, with Southeast Asia clocking the highest rates of loss. Mangrove forests are disappearing at three to five times the rate of other forest losses, creating serious ecological and social impacts in their wake (UNESCO). Much is at stake if we lose these swamp forests that, like so many other habitats, are felled under the banner of development and in the race for resource acquisition. Mangroves provide vital ecosystem services such as forest produce, timber, aquaculture, coastal stabilization, reducing erosion, and attenuating coastlines against storm surges and flooding. The dark tangled depths of a mangrove swamp also provides habitat to incredible biodiversity, most of which is shielded from the human eye, from crabs and aquatic life to fish to large mammals such as swamp deer, spotted deer, monkeys, and – in the Sundarbans – the world’s largest wild cat, the Bengal tiger. An additional ecosystem service provided by mangroves, as by all wetland ecosystems, is carbon sequestration. “Blue Carbon,” as it is popularly known, is the carbon sequestered by coastal and marine ecosystems, with wetlands and mangroves in particular serving as prime carbon sinks. Mangroves capture atmospheric carbon and store it within the soils beneath their roots. However, as rates of mangrove loss continue to increase, there is enormous risk of releasing these reserves of stored carbon into the atmosphere, further accelerating climate change and posing threats to continued survival of multiple species and ecosystems.

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This may be the first time that the planet celebrates this lesser-known ecosystem, but the mangrove has played a vital role in the livelihoods and culture of coastal communities in the tropics for centuries. It is time that the rest of us recognize the value of this delicate ecosystem, one that provides so many benefits for our species, and in turn raise our voices and lend our hands to mangrove protection and reforestation efforts.

Five incredible mangrove systems in India that are a must-see:

1. The Sundarbans Biosphere Reserve, West Bengal/Bangladesh
2. Pichavaram mangroves, Tamil Nadu
3. Bhitarkanika mangroves, Odisha
4. Godavari-Krishna mangroves, Andhra Pradesh (Pulicat Lake Bird Sanctuary & Calimere Wildlife Sanctuary)
5. Baratang mangroves, Andaman & Nicobar

Sources:

Michel, Jacqueline. (2014). Oil Spills in Mangroves; Planning & Response Considerations.

http://www.unesco.org/new/en/unesco/events/prizes-and-celebrations/celebrations/international-days/int-day-for-the-conservation-of-the-mangrove-ecosystem/mangrove-ecosystem-2016/