Flowing for 2,525 kilometres from the Himalayas to the Bay of Bengal, the Ganga is at the heart of the 800,000 square kilometre basin which supports around 300 million people in India, Nepal and Bangladesh.
This cradle of the 5,000-year-old Indo-Gangetic civilisation is also India’s richest basin in terms of fish species – a World Bank study published in 1996 had estimated around 350 species, while a 1991 study by P.K. Talwar of the Zoological Survey of India had reported 375. This diversity is at its richest at the myriad mouths of the Ganga, where it forms the world’s largest mangrove forest, the Sundarbans. Upstream, estimates of freshwater fish species vary between 104 and 161.
The Ganga basin is the second richest in Asia in terms of biodiversity, following the Mekong. With a length 60% of that of the Mekong, it has 74 types (or genera) of fish, whereas the Mekong has 77.
Species under threat
Four freshwater fish species in the Gangabasin are threatened to various degrees. Of them, the Tor tor of the Himalayan foothills, once famous among anglers, is now endangered, according to the International Union for Conservation of Nature (IUCN).
Other freshwater animals are in even more serious danger. The upper reaches of the Ganga – from Rishikesh in the Himalayan foothills to Kanpur– is home to 12 freshwater turtle species, six of which are endangered. The two species of crocodile found in this stretch are listed in the IUCN Red Data Book as endangered. So are the Common Indian otter and Smooth Indian otter. Other crocodile species, known locally as mugger (literally “crocodile of the marsh”) and gharial, are well-known to fans of the British hunter turned conservationist, Jim Corbett.
And then, of course, there is the famous Ganga dolphin, now declared India’s national aquatic animal. Platanista gangetica – to give it its zoological name – is the blind freshwater dolphin that is unique to the Ganga-Brahmaputra-Meghna (GBM) basin. It is also highly endangered.
The upper stretch of the Gangain the north Indian plains is home to over 100 species of birds, both migratory and residential. Several are endangered, and Salim Ali – the doyen of India’s ornithologists – had proposed way back in 1978 that a bird sanctuary should be set up in the area close to Narora in Utter Pradesh. This stretch is home to 51 species of insects and 15 species of molluscs as well. But there has been a marked decrease in the last two decades in the diversity of the zooplankton at the base of the food chain, thanks to industrial and domestic effluents being dumped into the river largely untreated.
Downstream of Kanpur– an industrial centre notorious for lack of pollution control – the number of fish and animal species drop dramatically. But biodiversity picks up once the largest tributary of the Ganga – the Yamuna – flows in at Allahabad. But there are still increasing numbers of species under threat in these mid-Gangetic plains. Eight species have been classified as vulnerable, one as rare and one as endangered in this stretch. In the lower Gangetic plains, three species have been classified as rare and five as vulnerable.
The Ganga is the river millions of Hindus consider the holiest, the river in which the faithful seek to wash away their sins and on whose banks they wish to die. Added to almost unchecked flow of domestic and industrial effluents, millions of bathers and thousands of bodies that are cremated every day creates a huge pollution load on the Ganga, which has very serious detrimental effect on the biodiversity in the river.
Clean-up efforts fall short
Some clean-up efforts have been made, including the very expensive and much critiqued Ganga Action Plan. It started in 1983, and the pollution levels in the river have only gone up since then. The plan is now in its second phase under a new name, and results are awaited.
Designating protected areas on and around the river – or its tributaries – has had better results. The 2,073 square-kilometre Hastinapur Wildlife Sanctuary abuts the Ganga, close to the Bijnor barrage. Though the forest in the area has been degraded, the establishment of the sanctuary in 1986 has provided protection to the two-toed Barasingha (swamp deer), Sambhar, Cheetal, blue-bull, wolf, leopard, hyena and wild-cat. The area has a number of bird colonies, including migratory birds from northAsia and those on the IUCN red list – Greater Spotted Eagle, Swamp Francolin, Sarus crane and Finn’s Weaver.
In November 2005, the stretch of the Gangain the upper plains – between Narora and Brijghat – was declared a Ramsar Site, which means it is a “wetland of international importance.” The declaration came largely thanks to WWF India’s dolphin conservation programme. This 85-kilometre stretch is habitat for several species of turtles – and infrequently, game fish like the Tor tor – as well as theGanga dolphin.
The most important protected area of the mid- and lower-Gangetic plains is the Vikramshila Dolphin Sanctuary. But even in the sanctuary, the dolphin population continues to decline at around 10% per year, mirroring the overall decline in the basin.
Reasons for biodiversity decline
There are long-standing reasons this decline in biodiversity. All aquatic ecosystems are highly sensitive to a reduction in the water flow. Since the 1850s, the Ganga has been diverted for irrigation as soon as it enters the plains. In most barrages leading to irrigation canals, the diversion is about 50% of the flow. In most stretches, the river ecosystem has acclimatised to such diversions.
However, in some places the river has dried up. This happened between Bijnor and Narora when there was no water coming in from the Kalagarh canal. This obviously leads to increased stress on the ecosystem, especially on species like dolphin that need deep pools fast moving water, according to Sandeep Behera, associate director of the River Basin and Biodiversity Programme in WWF-India. Scientists have identified reduced river flow as one of the primary threats to the populations of dolphin, mahseer, crocodiles, turtles and fish in this stretch.
For millennia, the Ganga basin has been one of the most intensively farmed regions in the world. Despite that, until the nineteenth century, it had thick forest cover along the Himalayan foothills, the area known as the Terai. But that was systematically deforested, mainly in the first half of the twentieth century, to build South Asia’s rail network and for the British Army during World War I.
About 80% of the original forest cover in theGangabasin has been lost, according to a joint study carried out in 2003 by IUCN, International Water Management Institute, World Resources Institute and the Ramsar secretariat. This means loss of habitat for terrestrial species, plus the freshwater species dependent on them. It also means a higher sediment load in the rivers, as the tree roots that used to hold the soil together are no longer there. The water becomes even more turbid, and many species are unable to cope.
Another problem is that in the upper stretches of the river, only about 10% of the original floodplains of the Ganga remain, the rest having been taken over for farming, factories or houses. That is a serious loss of habitat. With 532 people per square kilometre, this is already one of the most densely populated river basins in the world, and that figure is projected to rise.
For decades, the level of pollutants in the Ganga has been well above the permissible value. Basic indicators of the state of the water, such as biological oxygen demand and dissolved oxygen, also show water quality is nowhere near what it should be.
While impacts of climate change on the aquatic ecosystem are expected to vary over the long term, global climate model data show an increased run-off with longer dry periods for all the sub-basins of Ganga. The impact of this on aquatic ecosystems would vary depending on individual species preference and these need to be investigated now. The increased dry weather flows predicted by most models can affect nesting sites of turtles and the seasonal habitats of the dolphin. This is an area where more information is required to ensure that the results of current conservation efforts are not destroyed.
Stepping up conservation efforts
A mix of strategies will be essential to preserve freshwater biodiversity in theGangain the long term. It must include reserves that protect key biodiversity-rich water bodies and their catchments, as well as species-or habitat-centred plans that reconcile the protection of biodiversity and use of water resources in ecosystems altered by human activities.
Designation of Ganga as India’s National River, formation of a dedicated National Ganga River Basin Authority and a new phase of the Ganga Action Plan will hopefully help protect this river. Transboundary cooperation between the basin countries is also important for conserving the biodiversity of this unique river system. Proposals have been mooted for designation of the upper stretch of the Ganga as a World Heritage Site, to protect the intrinsic culture and nature link of the river and the landscape it flows through.
Archana Chatterjee is national project coordinator for the World Heritage Biodiversity Programme, India at UNESCO’s New Delhi office and trustee of Conservation Sciences India.
Homepage image by Xavier Pelletier at WWF