Ecosystem Based Disaster Risk Reduction at Indian Sundarbans: A Lesson Learned from AMPHAN Supercyclone

Ecosystem based Disaster Risk reduction is the sustainable, green method to minimize cyclone damages at tropical coasts. As a part of a climate change resilience project initiated in 2012, 102 hectare of multispecies mangrove plantation was established at eastern corner of Indian Sundarbans. The AMPHAN supercyclone, have caused immeasurable destruction in the region, between 16-21st May, 2020. This research brings forward the field observations on effectiveness of community managed mangrove plantation in ameliorating disaster impacts. Study revealed that mangrove bio-shield minimized property damage during the cyclone by reducing flooding through earthen embankment stabilization and managing the wind speed, direction.


Introduction
Sundarban biosphere reserve, India (9630 sq km) is situated at the largest delta of the world, dominated by the largest contiguous mangrove forest of the globe and is the only abode of mangrove tigers. It has been designated as the Ramsar wetland conservation site with an area of 4,23,000 hectare, which is the largest amongst all other wetland conservation sites in the nation.
It is a UNESCO world heritage site. The south-eastern part of the forest has been designated as a  [7]. Seasonal migration of labors from the areas of Sundarbans is also a major source of income to the locals after the economic pressure generated due to drop in agricultural produce in the region because of salt water intrusion during AILA cyclone in 2009. Approximately, one member from each 75% of families must have migrate and working in inter and intra states of India [6,7].
Sundarbans has to bear the brunt of natural disasters which is ever increasing due to the vagaries of climate change and sea level rise impacts at the Ganges-Brahmaputra-Meghna delta.
Measures have been taken to limit the impact of cyclones on the lives and livelihood of the socio-economically marginalized population of the delta. Ecosystem based disaster risk reduction is a popular initiative adopted across the globe to limit damage to resources [8,9]. In this context, mangroves are proven to have enormous ecosystem services. One of the foremost of which is to save the vulnerable coastline from furies of cyclones, storm surges and tsunami by acting as a natural bio-shield [10-13]. As part of a social work and climate change resilience venture mangrove plantation activities were initiated through community participation in 2012, at Satjelia Island located in the remote corner of Indian Sundarbans (Figure 1). COVID 19 outbreak caused a huge public health crisis throughout the globe. Eventually it leads to nationwide lockdown to contain the disease but has also resulted in huge unplanned migration of mostly unorganized labor population [14,15]. During this COVID-19 pandemic, between 16-21 st May 2020, the region was hit by a devastating super cyclone, AMPHAN having the highest wind speed of 260 km/h. This resulted in untold destruction and official report suggests that 28% of the Sundarban area was devastated by this cyclone and 1200 sq km of mangrove reserve forest impacted out of 4263 sq km [6]. This perspective gives an outlook on how a social work venture facilitating community based mangrove plantation has saved around 3000 families at Satjelia island from after effects of the AMPHAN cyclone.

Community based mangrove plantation
As a social work initiative a mangrove restoration activity was started at Satjelia island of Indian

Case selection and research methodology
In the current AMPHAN super cyclone, the parts of Satjelia and Lahiripur Gram panchayet   Mangroves have physiological and anatomical adaptations to survive in the saline environment and generally exist between land and sea (Table 1a). They can consolidate the mudflat soil and hinder erosion activity during tidal regimes or storm surges [12]. In case of AMPHAN eight year old mangrove plantation cover has resisted the wind speed of the cyclone and also protected the mudflat from caving in, resulting in a barrier against the storm.Mangroves are a group of salttolerant trees or shrubs that grow in water, with their roots emerging from the water. Mangrove ecosystems provide important ecosystem services for flood protection in coastal areas and also benefit the region economically.
The growth and type of mangrove forests depend on: hydrological connectivity and topographical features. Hydrological connectivity consists of the quality, quantity and timing of freshwater and sediment inflow. This is responsible for deciding the height of the mangroves.
Tidal conditions, coastal landscapes and marshes decide the path of the mangroves, i.e., their growth in the horizontal direction [18]. Therefore, mangroves can adapt to rising sea levels and changing land use because of the ability to move horizontally and vertical accretion.
Mangroves are connected to each other and form an integrated system linking the coast and the ocean. Though they thrive in saline conditions, the deltas where mangroves are found also depend on freshwater supply. Deltas have been shrinking in areas where freshwater is scarce, leading to loss of mangrove forests. These ecosystems are being threatened by unsustainable human activities for development.
A qualitative exploratory case study, using in-depth interviews, official documents, and literature review has been used to understand the role of community-managed mangrove plantations in saving families from problems resulting after a natural disaster. Verbal interviews were conducted with the villagers residing along the mangrove protected river banks also indicated the role of mature mangrove strands in ameliorating flooding and cyclone intensities. The interviewers were selected from the island in consultation with local Non-Governmental Organization (NGO) who was residing along the mangrove plantation cover and without the same. A total of 65 respondents expressed their views during the month of June 2020, after the damages due to the cyclone (Table 1b)  Found on coastlines and low-lying land. This species has aerial roots (prop roots) that are emerge from water. This helps to host aquatic and coastal wildlife and prevent soil erosion at the coastline. These are the tallest mangroves, so they provide the best protection against cyclones and storm surges. Most suitable for aquaculture due to fish and shrimp found among the roots.

Black Mangroves (Avicennia spp)
Located inland, after red mangroves. It gets its name from the bark of the trees, which are black. The wood is used as charcoal, fuel and harvested for construction purposes. This variety of mangroves has pneumatophores, i.e, roots originating upwards from the roots in the soil. These help the plants and underwater root systems receive oxygen.

[21]
Central America White Mangroves (Laguncular Racemosa) These are located at higher elevations, near inland water bodies. They do not have aerial roots, but produce flowers and fruits. The leaves have pores which transpire saline water. Therefore, white mangroves play an important role in preventing inland water sources from becoming saline.

Result and Discussion
The interview sessions and on-site visits clearly suggest that the flooding during the aftermath of the cyclone was considerably low in the houses along the vicinity of the mangrove plantation cover. The mangrove bio-shield not only has checked the breaching of earthen embankment by 60% but has also resulted in lesser flooding. The tube wells near the mangrove cover were one of the only sources of local fresh water for more than a month, following the disaster. The area was not flooded during the storm because of the mangrove bio-shield. Most of the respondents (23  25), residing away from the mangrove cover reported massive damage of their houses and ponds during the cyclone incident. 14 out of 25 of these respondents reported their roofs been blown away or house infrastructure damaged during the cyclone. Only 5 respondents from the mangrove sheltered region reported of such damage. Mangrove cover has acted as a bio-shield against the strong winds and has reduced the wind speed during this disaster. Similar evidences also suggests that mangrove patch has the capacity to reduce the wind speed by acting as wind Currently, rainfall patterns are changing and the frequency of cyclones has increased due to climate change. The role of a mangrove ecosystem in providing resilience and risk management to coastal communities is rising. Bangladesh, India and Vietnam rely on mangroves to protect them from annual floods and cyclones, while the United States, China, Mexico and India also reap economic benefits [13]. Past researches also focused on how mangroves have proved effective in managing or ameliorating disaster impacts during several disaster events across the globe (Table-2) and same trend has been also noticed during AMPHAN supercyclone at Indian Sundarbans. This devastating event triggered the study and acceptance of mangroves as important barriers between the land and sea. A study was conducted at the Cuddalore district in Tamil Nadu. This location was ideal as it had a flat, even coastline with patches of dense mangrove forests and cleared land. Satellite images proved that a density of 30 trees per 100 sq. metres can reduce the flow of a tsunami up to 90%. These also showed that villages exposed to the coast faced maximum damage as opposed to villages behind mangroves, where damage was minimal. Also, villages that were far inland, but without mangroves were equally damaged. In Sri Lanka, it was observed that around 6,000 people were killed in a settlement that had lost mangroves whereas only 2 individuals were killed in a village that had dense mangrove forests.

Conclusion
The Ecosystem based Disaster Risk reduction initiated by mangrove plantation has shown positive results in protecting the lives and livelihood of the marginalized population of Indian Sundarban during the impact of AMPHAN super cyclone. It also acts as a reservoir of fish and the area accounts for more catch particularly crustaceans than region devoid of mangrove cover.
In-spite of the international efforts in restoring mangroves for their 'blue carbon sequestration', plantation efforts are not gaining much momentum at The Sundarbans. This work substantiates the need of community based mangrove plantation initiative in a poverty impacted, disaster vulnerable, and densely populated region like the Ganges-Brahmaputra-Meghna Delta focusing on its ecosystem services. Community managed mangrove plantations proved to be an effective as an initiative to sequester 'blue carbon' but to build disaster resilience along the coastline.
Mangroves are also used for ethnobotanical purposes by local communities [33]. Further research on the mangrove patch will shed light on the mechanism by which mangroves can reduce the effect of natural disasters and how this community based mangrove plantation model can be optimized in different other tropical-sub tropical coastline impacted by mangrove loss.

Acknowledgment
Authors acknowledge the project team of 'People's empowerment and Mangrove restoration'  table-1a and table-2, as a part of the winter internship project-2020-21 with TSRD. And, Bhattacharyya, S-Is the coordinator of the KKS-BMZ-TSRD funded project that initiated, managed the multispecies mangrove plantation mentioned in the case study and has been the main contact person for the post AMPHAN survey on disaster impacts.