Rising salinity of Hooghly river helps regrowth of mangroves in Kolkata

The Hooghly river bank has gradually been turning into a natural habitat for mangroves as a result of rising salinity of the water.

'The Farakka treaty and resultant low down flow are pushing up the salinity. Because of the rising sea level, more saline water is flowing in during high tide. Over the past decade or so, we have noticed natural regeneration of mangroves in the city's vicinity,' Botanical Assistant of Acharya Jagadish Chandra Bose Indian Botanic Garden, Basanta Kumar Singh was quoted as saying by a local daily.

The mangroves had started taking roots along the Ganga, also known as the Hooghly here, in such numbers that the Botanical Garden has taken up a plantation project along a 1.6 km stretch.

The project, 'Ex situ Conservation of Mangroves', was on the drawing board for the past three years. On July 6 the plantation drive was launched on a four acre area, the newspaper said.

Howrah Police Commissioner Gaurav Sharma, present on the occasion.

The daily quoted AA Mao, Botanical Survey of India director, as saying that their objective was to stop soil erosion and conserve some mangrove species to create a new biodiversity zone.

'In the last fifty years, no mangrove plantation drive has been successful at the Botanic Garden since it is difficult to grow mangroves unless the water salinity is high,' according to Garden in-charge MU Sharief.

Singh added that over the past ten years mangrove seeds that flow up to Kolkata from the Sunderbans during high tide had started regenerating. 'Now you can find mangroves from Babughat to Belur,' he was quoted as saying.

The regeneration of the seeds prompted botanists to check the salinity of the river here and suitability was found to be enough to start a mangrove plantation.

Tuhin Ghosh of Jadavpur University's School of Oceanographic Studies said, 'The Farakka barrage project has reduced the river flow and triggered siltation in the lower course of the Hooghly. The riverbed is becoming shallower and water level is rising during high tides. This high tide water is travelling more towards the north and the brackish zone is shifting towards the north.

'Regarding the effect of climate change, I do not know if any study has established the correlation between rising sea level and the increase in salinity,' Ghosh was quoted as saying.