Insights into Editorial: Bio-restoring degraded patches of Sunderbans
Increasing anthropogenic activities along with natural stresses have led to massive degradation of one of India’s World Heritage Site the Sunderbans.
A team of researchers from West Bengal State University, Kolkata, set out with the herculean task of identifying the major reasons for the decline and also devising new restoration strategies.
The Sundarbans is a protected wetland under the Ramsar Convention and is also a UNESCO World Heritage site.
Small coastal patches of mangroves are highly vulnerable and fragmentation of the ecosystem is creating barriers to species movement and dispersal.
Mangroves and Sunderbans in India:
The total forest cover of the Indian Sunderbans as assessed by remote sensing studies for the year 1986 was about 2,246.839 sq. km., which gradually declined by 2,201.41 sq. km.
In 1996, then down to 2168.914 sq km in 2001 and to 2122.421 sq km in 2012. The loss in the mangrove forest in the Indian Sunderbans is about 5.5 %.
The continuation of this process in response to climate change and sea level rise poses a serious threat to the carbon sequestration potential and other ecosystem services of this mangrove forest in future.
Using satellite imagery, the study reveals that the rate of coastal erosion is higher than the rate of accretion in the estuarine zone.
In other words, the entire island system is faced with a rapid loss of land area and embankment, flooding, and salinization of drinking water.
Cause of decline of Sunderbans:
- The increased population with few alternative livelihood opportunities poses a serious threat to the Sundarbans as it is the main cause of mangrove destruction.
- Excessive exploitation and negligence of restocking are the main cause of Overall depletion of growing stocks of Sundarbans forest.
- A team of researchers surveyed 19 shoreline mangrove patches, collected soil and water samples and studied them.
- The results published highlight that lack of essential nutrients and increasing salinity were the main problems in Sunderbans.
- “Nutrient depletion especially phosphorus and nitrogen were found to be directly connected with the decline in forest cover.
- They are now trying to understand what is causing nutrient depletion.
- They also planned to expand this analysis to a larger area, so as to cover the whole mangrove region and get a complete picture.
- They also saw a change in the species distribution salt-sensitive ones such as Heriteira fomes, Xylocarpus species and Phoenix paludosa were not able to cope up with the increase in the salinity and declined while the tolerant varieties thrived.
Solutions: Route to restoration
The team then established an on-site mangrove nursery and during each season collected mangrove propagules or buds and maintained in the nursery till transplantation.
About 22 species of mangroves were restored in the region which included threatened, endangered and vulnerable species.
High salt-tolerant varieties were planted near the shoreline and the moderate ones farther.
The team notes that the present ecosystem in the studied patch is almost brought back to the original pristine condition.
They have already identified many degraded mangrove patches in the western part of Indian Sundarbans and have planned to restore them by the application of this technology.
Ecological Restoration: New Technology needs to be implemented:
- A new technology developed by Indian scientists for ecological restoration is helping in revival of mangroves degraded due to rising sea levels, climate change and human intrusion in the Sunderbans in West Bengal.
- Ecological restoration means reviving native ecosystem in degraded areas while maintaining diversity of original flora and fauna through regeneration but bringing down the regeneration period to four-five. Natural regeneration takes longer time.
- The restoration technology, involves plantation of native salt-tolerant grasses and a diverse set of carefully identified mangrove species in different zones of degraded mangrove patches. It also involves the use of growth-promoting bacteria.
- The restoration process begins with stabilising entire site of restoration by planting native salt tolerant grasses.
- Besides local mangroves and associate species, the nursery also grew threatened, endangered and vulnerable species. In all, 22 species of mangroves and associate plants were grown so as to maintain native diversity.
In a development that will ring alarm bells for both environmentalists and policy makers, the mangrove forest cover in the Indian Sunderbans has been depleting alarmingly over the past few decades.
Mangrove Forest Cover Changes in Indian Sundarban (1986-2012) Using Remote Sensing and GIS, a publication by the School of Oceanographic Studies, Jadavpur University, reveals that from 1986 to 2012, 124.418 sq. km. mangrove forest cover has been lost.
The disappearing shoreline of the Sunder-bans can be saved if immediate action is taken to plant mangrove along the banks, monitor sea-level conditions, maintain embankments, and tone down the “so-called poverty alleviation measures”. It’s either this or a countdown to catastrophe.