A recent study of mangrove forests in Sunderbans has revealed a change in their vegetation pattern, with the high salt-tolerant Avicennia species being edged out by Ceriops decandra, a relatively less-salt tolerant variety of mangrove, suggesting an evolution of the mangroves.
The study titled ‘Benchmark Studies on the Status of Mangrove Forest’ has been conducted by the Nature Environment & Wildlife Society (NEWS), sponsored by the Sunderban Biosphere Reserve under the ‘Mangrove For Future’ theme of the International Union for Conservation of Nature.
“It was earlier believed that salinity is the main determining factor for the mangroves in the Sunderbans. But the study points to pH ( which determines the acidity and alkalinity of water) also being an important factor,” Himadri Sekhar Debnath, principal scientist involved with the project and former Joint Director of Botanical Survey of India ( BSI) told The Hindu .
A change in the mangrove species may lead to change in biodiversity, ecology species variation and finally to the variation in gene pool, Ajanta Dey, project director (NEWS) said.
She pointed out that the first-of-its-kind study in Sunderbans used GPS technology and was conducted over a period of nearly two years. Using the transect method, the abundance, frequency and density of individual mangroves species were observed and analysed from over 400 samples collected from the creeks of Sunderbans.
Overall, Ceriops decandra was the most abundant species, followed by Excoecaria agallocha and Ceriops tagal mainly in the blocks under the Sunderban Tiger Reserve. While Ceriops species are referred to as Garan , the other predominant species Avicennia alba is called Kalo Baine in local language.
“A well marked succession pattern of mangroves in newly silted char lands has been observed. Succession is observed with the first appearance of Porteresia caorctata in newly formed stable lands, followed by appearance of species of the genre Avicennia, Ceriops, Rhizophora, Xylocarpus and others,” the summary of the report shows.
During the study, the researchers found 33 angiospermic plants species in the Sunderbans. There are about 85 species of mangroves in India — the last, Acanthus albus, was discovered a year ago during the field study for the project.
Thriving despite stressAlthough Sunderbans, a UNESCO world heritage site, is believed to be under stress, the study has revealed that mangroves are thriving in the unique ecosystem.
