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Study: 83% Sundarbans’ mangrove landscape changed for Cyclone Amphan

  • Published at 08:54 am August 25th, 2021
Aftermath of the extremely severe cyclonic storm Amphan in the Sundarbans on Thursday, May 21, 2020 | Dhaka Tribune

Due to the increase in salinity, many Sundari trees in the forest area have died of disease after the cyclone

Cyclone Amphan hit the coastal area of Sundarbans, stretching towards both Bangladesh and India in May 2020.  It was the strongest tropical cyclone since the Sidr in 2007.

Despite its disastrous meteorological caution, Amphan made a more boisterous impact on the Indian side than in Bangladesh.

The Bangladesh government has estimated that the cyclone has cost the economy a loss of nearly $130 million (Tk 1,100 crore).

The Sundarbans is considered as the main safeguard which protects lives and properties in times of natural disasters again and again. Yet, little attention is paid to prevent the destruction of the mangrove forest itself, as this time Amphan has defaced 83% of the forest landscape, according to the information of National Environmental Satellite, Data, and Information Service of USA.

This change includes decrease in mangrove vegetation, croplands, erosion of embankments, increasing salinity in soil and water. Around 63% of shorelines along with the Sundarbans in Bangladesh were eroded and on average, the shoreline moved 30.66m towards land.

The findings came out from a combined research of a group of researchers from India, Brazil and Bangladesh which were published in the “Estuarine, Coastal and Shelf Science” journal of Elsevier Publication.

Erosion went on destroying many districts in the coastal region along with 63.82% in Satkhira range, 49.15% in Khulna range, 52.86% in Sarankhola range, and 56.19% in Barisal subdivision, the report stated.

The research titled “Geo-ecological impact assessment of severe cyclonic storm Amphan on Sundarbans mangrove forest using geospatial technology” was done through image analysis collected from United States Geological Survey (USGS).

The two ecological indicators Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) which were used to calculate the damage of greenery, demonstrate that almost all parts of the Sundarbans mangrove forest experienced degradation and fragmentation due to severe category cyclonic storm Amphan, the researchers found.

On the Bangladesh side, the degradation is primarily seen in the central and western sections of the Sundarbans forest.

“Whenever we calculate the destruction in the aftermath of a super cyclone such as Amphan, our focus usually remains on the people and properties. The ecological destruction and imbalance it creates --we often forget to calculate that,” said Dr Manoranjan Mishra, associate prof of Department of Natural Resource Management & Geoinformatics of Khallikote University, India, also the lead researcher of this study.

“But this is important as a balanced and healthy ecological environment of the mangrove is important for us to be protected from future natural catastrophe,” he added.

The loss

The dense mangrove areas, which are the swamp forest portion of the Sundarbans, have suffered the most significant loss. According to the Land Use Land Cover (LULC) data, the croplands of both countries were significantly decreased, said the prof.

Vegetation lands were damaged significantly in the northeastern and central region of the country, where the most affected regions were the Sarankhola range of Bagerhat and coastal areas around Barisal. 

Although the flora and faunas in the Sundarbans are habituated with the salinity of the Sundarbans, some mangrove vegetation including the Amur, Dhundul, Sundari, and Golpata, require low salinity.

Among these, the Sundari trees are at significant risk of extinction. Due to the increase in salinity, many Sundari trees in the forest area have died of disease after the cyclone.

MA Hasan, assistant conservator of Forest of Sundarbans West Division of Khulna, disagreed with the severity of the mangrove due to Amphan.

“Sundari is decreasing in our region. That is not new information, in fact it has been declining in the region for a long time due to the scarcity of freshwater. The situation has arisen because of Farakka dam,” said Hasan.

There is a difference area-wise, Bagerhat district is still in good condition to grow Sundari trees whereas Satkhira has been continuously submerged with saline water, hence the soil here losing the ability to maintain a standard growth of Sundari trees,” he added.

The report also stated that people who lost their livelihood sources due to the cyclone are being forced to encroach upon core mangrove areas for the collection of fish, timber, honey, etc, thus, not only putting the remaining mangrove at risk but also inflicting possible human-wildlife conflict.

“Such human-wildlife conflict we see on our part too. And it will continue to increase unless nature gets the scope to heal itself. But as we see, after these cyclones there is very little initiative to restore nature, said Prof Mishra.

“So, even the natural process of revival gets hampered. At the same time, the geographical location of Sundarbans and proneness of natural disasters of this region are making the resuscitation process difficult,” he added.

The Department of Forest has not yet done any comprehensive study about the ecological impact in Sundarbans after Amphan. Regarding this matter, the Chief Conservator of Forest Md Amir Hossain Chowdhury was contacted by Dhaka Tribune multiple times but he could not be reached.

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