Mangrove forests of Sunderbans are threatened with extinction. In order to address this challenge, DBT has supported an on-site mangrove nursery harboring total 22 species of mangroves and their associates.
Restoration of mangrove has been done in considerable area of the degraded site which was earlier completely barren, with established grassy patches of Porteresia coarctata, Myriostachya withiana, Paspalum vaginatum and Sporobolus virginicus.
Mangrove seedlings are regularly multiplied in the nursery depending on the availability of propagules in different seasons. The team has started transplanting the already well grown seedlings to the site of restoration at Zone II of patch II following the distributional patterns of natural mangroves along the mudflat.
Technologies to multiply Heritiera fomes (endangered), Xylocarpus spp., Phoenix paludosa (near threatened), Lumnitzera racemosa and Nypa fruiticans (both very rare locally) in large scale have been developed to be utilized for mangrove restoration.
The site of moderately degraded patch II in the Zone II has been transplanted with 600 saplings of Heritiera fomes with 76.6% rate of survival so far. It is hypothesize that the loss of adaptive plasticity in mangroves is behind their gradual disappearance under degraded ecosystem.
Study data established that synthesis of nitrogen-rich and energy-intensive organic solutes to achieve full osmotic adjustment becomes challenging for mangroves under degraded soil conditions. Impaired nutrient cycling under degraded mangrove soil limits the synthesis of all osmolytes and photosynthates.
The researchers at DBT are presently studying the loss of mangrove ecosystem homeostasis based on three aspects:
We expect to get a definite trend to distinguish between degraded and non-degraded mangrove ecosystems, which might help us to explain the phenomenon of loss of ecosystem homeostasis for mangroves under degraded soil. This result is to be validated by mangrove gene expression study, which is planned in later part of this project.
The Sundarbans is the largest mangrove forest in the world. About 300 species of trees and herbs and about 425 species of wildlife including the Bengal Tiger survive in this ecosystem. The Sundarbans is also a World Heritage Site. Out of a total area of 0.6 million hectares of the Sundarbans, 0.4 million hectares are forest areas, with the remaining part comprising water bodies mostly flowing through to the sea at the south. This mangrove forest is predominantly a salt-tolerant forest ecosystem with the exception of an estimated 856.7 million Sundari (Heritiera fomes) trees, which are less salt-tolerant.
Mangroves are threatened with extinction, primarily due to suffering from top-dying disease caused mainly due to increasing salinity in surrounding waters. The mangrove forests of the Sundarbans provide an important defense in limiting climate change impacts, providing protection to coastal areas from tsunamis and cyclones. Mangroves serve each year as a biological shield protecting coastal communities from the worst effects of storm surge. Loss of mangroves escalates the disaster risk for local populations from storm surge and flooding.