The Sundarbans has lost almost 130 square-kilometres of area in its Bangladeshi portion due to erosion, said a Sparso study that analysed almost four decades of satellite data on the region.
The study “Time-series Analysis of Coastal Erosion in the Sundarbans Mangrove” found that from 1973-2010, approximately 233 sq-km of area has been lost exclusively to erosion while 104 sq-km of sea-water has been converted to vegetation by the mangrove.
The rate of coastal erosion, widespread in many parts of the peripheral zone, is variable in different parts of the forest. The average rates of erosion in the western and eastern parts of the forest are 14 metres and 15 metres per year respectively, the study measured.
A prior study, published in the journal “Estuarine, Coastal and Shelf science,” said between 1970-1990, The Sundarbans (in total, including Bangladeshi and Indian portions) had balanced out its erosion (32 sq-km) and accretion (29 sq-km), and only 3 sq-km of area was lost. That study found that between 1990-2000, the difference between erosion (42 sq-km) and accretion (6 sq-km) had increased seven times. Accretion is increase of land along the shores of a body of water, as by alluvial deposit.
The total area of vegetation in the Sundarbans, listed in the study, in 2010 was 4,034 sq-km whereas in 1973, the area was 4,178 sq-km.
The Sparso (Bangladesh Space Research and Remote Sensing Organisation) study focused only on erosion as a cause for deforestation, and sought to determine its nature and pattern, but did not directly attribute causes like global warming, sea level rise, siltation from the Himalayan river system, or anthropogenic (man-made) hazards for this phenomenon. The scope of this study was limited to the Bangladeshi portion of the Sundarbans.
Speaking about the findings of the report, hydrology expert Professor Ainun Nishat said: “We have to acknowledge that the Sundarbans is under threat for different reasons including excessive human interventions and salinity intrusion that directly affects the different floral species of the mangrove forest by hindering their growth.”
Dr Ahsan Uddin Ahmed, a panelist at the Inter-governmental Panel on Climate Change, opined that even though land erosion and accretion is nature’s law in an active river delta, forest land depletion due to human intervention should not be tolerated.
“If the projection of the study is true, then we have to be more conscious about protecting the forest from its threats,” warned Ahsan, also the executive director of Centre for Global Changes.
