Natural protection from natural calamities in the Indian Sundarbans

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Natural protection from natural calamities is one of the effective ways to protect the Sundarbans from the vagaries of nature. This has been amply clear from the events leading to and following the cyclonic storm, Yaas. Cyclone Yaas formed in the Bay of Bengal made landfall on 26 May 2021 and wreaked havoc in Odisha and the coastal areas of West Bengal spread across South 24 Parganas, North 24 Parganas, Purba Medinipur and Paschim Medinipur. Several other inland districts were also affected. However, the present discussion is centred around the Indian Sundarbans spread across the districts of South and North 24 Parganas.

Strategy for the Sundarbans

Prior to cyclone Yaas, West Bengal faced large-scale devastation from Amphan in 2020 and two severe cyclonic storms, Fani and Bulbul in 2019. Also, the scar of the severe super cyclone Aila is still not completely healed for the residents of North and South 24 Parganas.

After Cyclone Aila of 2009, there came out a series of articles in several journals and newspapers on the impact of the mangrove forest in preventing greater tragedies. It has been claimed that the Sundarbans mangrove reduced the fury even in the city of Kolkata. However, the mangrove forest, while saving the people and their properties, suffered huge loss and lost its density. Post-Aila, there were efforts in reviving the mangroves in the West Bengal Sunderbans, both from the Department of Forest and Mahatma Gandhi NREGA.

In 2019, two major cyclones Fani and Bulbul, hit the Sundarbans with varied degrees of intensity. A commentary by Amrita Sen and Jenia Mukherjee in ‘Mongabay’ runs like this, “Although there have been tangible losses to lives and assets in the Sundarban region, it has been palpably witnessed how the mangrove ecology naturally safeguarded people and the inland against the severe storm surges of Bulbul.”

How does the mangrove ecosystem protect land and people from the storm surges, from wind, from erosion of soil? There are several ways in which the system operates.

  1. Pneumatophores, a halophytic shrub variety which predominates in coastal mangrove forests, have extended prop-roots which stabilize the soil and protect land from strong tidal waves.
  2. Mangroves also reduce the wind speed, by attenuating the energy of the wind while passing through the dense tree cover. They act as natural buffers between the land and the sea, and apart from sequestering carbon, they also shield against riverbank erosion by stabilizing soil and sediments through organic depositions.
  3. Mangroves safeguard low-lying land near coasts by checking excess salt deposition from storm surges and flooding.
  4. The uniqueness of Sundarban mangroves primarily lies in its ability to absorb the storm steam through the impenetrably thick cluster of prop-roots, extricating the cyclone of its severest effects. Parts of the islands, where the mangrove cover is less, have been found to be affected badly by the cyclones, whereas the eastern peripheries with a dense cover usually suffer lesser devastation.

While there are several studies on the positive impact of the mangroves in protecting the coastal areas from erosion, storm surges and cyclonic storms, human intervention in mangrove plantation usually does not follow any scientific pattern where the protection angle is prioritised. The interventions are made either by the Forest Department or by the Panchayats through MGNREGA. While Forest is focused on improving the green cover, MGNREGA is keen on creating employment opportunities. Naturally, the science of coastal protection is not prioritised by either of the programmes.

After the massive Indian Ocean Tsunami of 2004, an international technical workshop titled ‘Coastal protection in the aftermath of the Indian Ocean Tsunami: What role for forests and trees’ organised by the Food and Agriculture Organisation (FAO) of the United Nations at Khao Lak, Thailand from 28 to 31 August 2006 arrived at several conclusions, which are extremely important in our context. Following are the excerpts from the FAO publication:

  1. Coastal forests and trees can, under certain conditions, act as bio-shields to protect lives and valuable assets against coastal hazards including tsunamis, cyclones, wind and salt spray and coastal erosion.
  2. The degree of protection offered by coastal bio-shields depends on a number of variables, including
      1. the characteristics of the hazard itself (e.g. type, force, frequency)
      2. the features of the site (e.g. bathymetry, coastal geomorphology) and
      3. the characteristics of the bio-shield (e.g. type of forest/tree, width, height and density of the forest)
  3. Care may be taken to avoid making generalisations about the protective role of the forests and trees based on evidence from one or a few areas; the many factors that influence the protective role of the forests/trees must be understood and taken into consideration before lessons can be learned and applied elsewhere.
  4. Coastal forests and trees are not able to provide effective protection against all hazards; provision for other forms of protection and for evacuation must be relied upon. Care must be taken not to create a false sense of protection against coastal hazards.
  5. The importance of incorporating coastal protection as an integral part of coastal area planning and management is recognized.
  6. The options of protection include: soft and hard solutions and a hybrid of the two. If none of these is appropriate and viable, it may be necessary to zone coastal land use and prevent further settlement and construction of valuable assets in the vulnerable zone.
  7. It is important to match the species with the site in order to avoid high mortality and low performance of the planted trees. Some forest types and tree species cannot survive or thrive in areas exposed to specific coastal hazards; therefore, they are not candidates for protective measures.
  8. Development of bio-shields is not possible in all situations owing to, inter alia, biological limitations, space constraints, incompatibility with priority land uses and prohibitive costs.
  9. The level of knowledge and understanding of the functions of forests and trees in coastal protection is still insufficient and there is a lack of multidisciplinary research and cooperation in this field. Specific areas needing further attention include research in non-mangrove coastal forests and collection of data and development of models on interaction between the physical and ecological parameters.
  10. There is a need to recognize that many years are required to establish and grow bio-shields to a size and density that could offer protection against coastal hazards.
  11. Considerable research and field initiatives related to forests and coastal protection have been carried out over the past several years; they provide a useful foundation for further work to improve understanding of the protective role that forests can offer.

The recommendations are equally important. These are grouped in several categories. We might be interested in the set of recommendations on assessment and design of bio-shields. Here it goes:

“ The following analysis sequence is recommended to assess the potential for protection:

  1. Identify the areas that are subject to coastal hazards and the characteristics of the hazards
  2. Identify and prioritize the assets that need protection
  3. Identify the options for protection (hard, soft and hybrid measures)
  4. Consider the costs and benefits of protective measures.”

In fine, for the Sundarban areas, our thrust might be on the following:

  1. Form a multi-disciplinary team of experts involving engineers from the Irrigation & Waterways Department, foresters,  academics and social engineers
  2. Take a thorough survey of the area to identify the areas prone to hazards, nature of hazards, intensity of hazards, present status of embankments, the spill areas, the assets needing protection
  3. Specifically identify the areas where Aila-type embankment strengthening measures are required and go for such hard engineering solutions
  4. Even in Aila-type embankment construction designs, keep provision for mangrove plantation, in forward sea/river side mudflats as well as in the countryside spill areas, wherever land is available and such plantation is feasible
  5. Instead of monoculture, always try to develop a mix of plants of different root systems, height, leaf size and leaf density and develop that by following a scientific pattern
  6. Instead of plunging into action without proper planning, may consider preparing detailed project reports (DPR), embankment-wise based on the survey findings and design parameters.

For the entire initiative, support might be sought for from international organisations like the Food & Agriculture Association (FAO), the World Conservation Union (IUCN), the United Nations Development Programme (UNDP), Wetlands International, World Wildlife Fund for Nature (WWF) and several Universities and Institutes within the country and abroad.