Restore mangroves to save Sundarbans

Recent cyclones — Yaas, Amphan, Bulbul and Aila — have devastated and displaced millions of marginalised people in the Sundarbans. Climate change is increasing the frequency as well as the intensity of the cyclones that impact the Indo-gangetic delta. Mangroves, a special group of plants that can survive in salty soil and tides, act as an effective barrier against such disasters by protecting the earthen banks as well as reducing the damage. Restoration of native mangrove species needs to be prioritised to save the Sundarbans.

Mangroves proliferate in many coastal regions. Indonesia has the largest mangrove cover scattered across its islands. The Indo-Gangetic delta houses the world’s largest contiguous mangrove forest — the Sundarbans. The Sundarban mangrove ecosystem is shared between Bangladesh (60%) and India (40%). The Indian part of the Sundarbans is also inhabited by 96 tigers.

The history of conservation in the Sundarbans can be traced from the Mughal period (1526–1765) to British colonial rule (1765–1947). Mangrove forests have often been considered a hindrance to human settlement and have been indiscriminately cleared to facilitate agriculture.

After independence in 1947, various laws and policies have been implemented to conserve this habitat. The Sunderbans were turned into a tiger reserve in 1973 under the Wildlife Protection Act 1972. The core area of 1,700 square kilometre was designated a National Park on May 4, 1984. The Indian Sundarbas received international recognition as a World Heritage Site in 1987. Nationally, it was designated a biosphere reserve in 1989. In February 2019, the Sunderbans became the largest wetland site in India.

English Lord Daniel Hamilton established the ‘Gosaba’ cooperative model around 1903. This colonial scheme initiated mangrove deforestation in India’s islands. Currently, 54 out of 102 islands are colonised by humans without any trace of mangrove forests. This makes these islands vulnerable to floods and the breaching of earthen river banks during natural disasters. These islands are under constant pressure of erosion that also destabilises the earthen dams.

The recent cyclones have devastated large tracts of land by breaching unstable embankments. Concrete dams can be a temporary solution but are costly, ecologically unfriendly and unsustainable. Erosion can wash away the underlying soil and breach any concrete structure. Mangrove seeds that float in with tides cannot establish themselves in concrete-covered banks, making the natural regeneration of mangroves almost impossible.

Mangroves are the only natural solution to this issue. Restoring mangrove vegetation can stabilise banks, attenuate wave pressure and hinder the wind damage during cyclones. Mangroves have been proven to be the best ecosystem-based disaster risk-reduction model across the globe. A study indicates that a density of 30 mangrove trees per 100 square metre can reduce the flow of a tsunami wave up to 90%.

When Cyclone Bulbul hit in 2019, Sundarban mangroves reduced the wind speeds by 20 kilometre per hour. And during Amphan super cyclone, a 10 year old multispecies mangrove plantation saved a part of Satjelia Island in the Indian Sundarbans from intense flooding and wind damage. Restoration ecologists must be careful to use only the locally available species for mangrove restoration. Exotic, invasive species can replace the local flora and result in an ecological disaster.

Mangroves are known to render other ecological services such as increasing the fish catch and serve as breeding ground for fish, prawns and crabs. Fishing is the second most important livelihood of the economically marginalised communities living in the Indian Sundarbans.

Scientists have indicated that after oceans, mangrove and sea grasses are the best carbon sink. Hence, mangrove plantation can be instrumental in sequestering GHG gases and halting the progress of harsh climate change impacts. Restoration of mangroves is the only option to save the 4.6 million people residing in the Indian Sundarbans from natural disasters. Natural methods are sustainable, eco-friendly as well as economically viable over technological alternatives. Policy makers must prioritise mangrove restoration to cope with the impending climate change crisis.

(Chowdhury is associate professor and Rosencranz is the Dean at Jindal School of Environment & Sustainability, O P Jindal Global University, Haryana)