Survey sights good signs: High biodiversity in 49% of Ganga main river


Written by Esha Roy
| New Delhi |

November 8, 2020 6:13:14 am





Survey sights good signs: High biodiversity in 49% of Ganga main riverThe Ganga and its tributaries flow through 11 states and cover 26.3 per cent of the country’s total geographical area. (File photo)

With celebrations of the Ganga Utsav — to mark the 12th anniversary of declaring the Ganga as a national river — having come to an end, the Wildlife Institute of India (WII) in the second phase of its survey of the entire main stem of the Ganga river (the main river without its tributaries), has found that 49 per cent of the river has high biodiversity and that biodiversity sightings, including of the Gangetic Dolphin and otters, have increased in the river. Scientists at the institute say that this indicates reducing pollution levels and a healthier state of the river.

The WII will next week kick off the second part of the Ganga survey and in the coming months collate data and information of these increased sightings to ascertain how much the river habitat has improved and how this has affected the species living in the Ganga.

The study was initiated by WII on behalf of the National Mission for Clean Ganga, one of the flagship projects undertaken by the Ministry of Jalshakti, and the first phase of the survey was carried out between 2017-2019.

“This is the first study ever done in the country on the entire river, and the first also of all its biodiversity,” says project in charge Dr Ruchi Badola. “The sightings of biodiversity have increased. While it is unlikely that any river can be completely pollution free, there is a certain standard necessary for life to exist and thrive – and the goal is to achieve this standard,” she said.

Explained

Why the threat to the Ganga’s biodiversity is real

Freshwater ecosystems account for 0.01% of the earth’s surface water but 10% of species. According to the UN Environment Programme World Conservation Monitoring Centre (UNEP-WCMC), decline in diversity of freshwater species is the highest, and surpasses losses in marine and terrestrial species – globally 20% of all known freshwater fish, 44% waterbirds and 42% amphibian species are under threat of extinction. The highest loss of freshwater biodiversity has been reported from the Indian subcontinent, specifically the Gangetic plains. Reason why the government has taken up the project of biodiversity conservation in the region.

The Ganga and its tributaries flow through 11 states and cover 26.3 per cent of the country’s total geographical area.

But its main stem flows through five states — Uttarakhand, UP, Bihar, Jharkhand and West Bengal.

“There was a commonly held belief that there are areas in the Ganga that had no biodiversity. This is not what we have found – the entire river has some biodiversity or the other, and 49 per cent has very high levels of biodiversity.

Ten per cent of the high biodiversity areas fall alongside national parks and sanctuaries such as Rajaji national park in Uttarakhand, Hastinapur wildlife sanctuary in UP and Vikramshila gangetic Dolphin sanctuary in Bihar,” said WII scientist Dr Shivani Barthwal.

The high biodiversity stretches have been divided into six zones – Devprayag to Rishikesh (61 km), Makdumpur to Narora (147 km), Bhitaura to Ghazipur (454 km), Chhapra to Kahalgaon (296 km), Sahibganj to Rajmahal (34 km) and Baharampur to Barackpore (246 km).

“We have been tracking biodiversity through some key aquatic and semi-aquatic species such as the Gangetic Dolphins, gharials, otters, turtles and various species of water birds. One of our findings has been that many species that used to be found in the main stem and had disappeared, are now coming back. We have found nesting colonies of the Indian Skimmer. Seibold’s, a species of water snake, disappeared 80 years ago and has now resurfaced. We have found new distributions of the puffer fish. Many other species have started travelling back from tributaries to the main stem of the river, indicating improving water quality,” said Dr Barthwal.

Rapid biodiversity of the Ganga had revealed that the distribution and density of key aquatic species such as the Gangetic Dolphin, the gharial and the mugger had in earlier years, significantly reduced due to loss of suitable habitat conditions, and change in the river’s morphology due to the construction of dams and barrages, bank alteration, agriculture and sand mining. In the early 19th century, 10,000 Gangetic Dolphins were estimated which reduced to 3,526 by early 2000, disappearing entirely in Haridwar and most of the Yamuna and becoming extinct in smaller tributaries.

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