Thousands of migratory birds die in Sambhar Lake, a Ramsar site

In November 2019, thousands of migratory birds were found dead at Sambhar Lake, about 80 km southwest of Jaipur city in Rajasthan.

Sambhar Lake is India’s largest inland saltwater lake, 230 sq km in area, spread mostly across Jaipur and Nagaur districts. It has a catchment area of 5700 sq km, with the water depth fluctuating between 60 cm in the dry season to about 3 m at the end of the monsoon.

Every year, the lake attracts thousands of migratory birds. A total 83 species of water birds have been recorded at the lake, the most abundant of which are little grebe, great crested grebe, great white pelican, little cormorant, black stork, and darter, apart from various species of plovers, egrets, herons, and geese.

Beginning on November 10, 2019, birds of about 25-30 species were found dead, including northern shoveller, Brahminy duck, pied avocet, Kentish plover and tufted duck. By November 20, 2019, the Rajasthan government had buried 18,422 bird carcasses to prevent the spread of infection. The number of dead birds being found each day began declining after November 20.

What are the possible reasons for the bird deaths?

The cause of death seems to be avian botulism, but this has not been officially confirmed. After a Division Bench of the Rajasthan High Court took cognisance of the deaths, the state government listed likely reasons:

·      Viral infection

·      Toxicity, as a new area has been filled up after almost 20 years, and there could be higher concentration of salts along the edges;

·      Bacteriological infection

·      Higher temperature and high water levels due to a good monsoon: This might have led to an increase in competition for resources. The weaker individuals, exhausted from the long journey, perhaps were unable to compete, and may have succumbed to stress emanating from the shortage of food, susceptibility to disease/pollutants/toxins and other habitat-related factors in the wintering grounds, the government suggested. If that is the reason, the government said it is expected that with fall of temperature and lowering of water levels, incidence of such mortality will go down

Is there a concern for human health? Humans are primarily at risk from avian botulism only if they eat infected fish or birds.

What are the reasons that make salt concentration a concern?

In a 2016 directive, the National Green Tribunal had noted the impact of the salt industry, including unauthorised salt pans, on the ecosystem of Sambhar Lake and asked the state government to cancel allotment of salt pans. The Wildlife Institute of India, the State Pollution Control Board and Sambhar Salts Ltd have collected samples to test for water quality. Part of the lake has been leased to Sambhar Salts, a joint venture of Hindustan Salts Limited and the state government. Sambhar Salts produces 196,000 tonnes of clean salt every year, which is around 9% of India’s salt production.

The lake was recognised as a wetland of international importance when it was designated as a UNESCO Ramsar Site in 1990. Today, as per NGO Wetlands International, it has the worst possible Wetland Health Score.

What should the government do?

The government should pass legislation to create a Sambhar Lake Development and Conservation Authority. This authority should be given full responsibility of Sambhar Lake. Currently, no one is responsible and every government department passes the buck, be it Forest or Irrigation. The Revenue Department says they had the land once; Panchayat says that they had the land but gave it to Hindustan Salts Limited, and Hindustan Salts is not ready to talk.

What are the issues at Sambhar that need to be addressed immediately?

There is no document about management of Sambhar Lake. We should study why the water from four rivers, which flows into the lake, has decreased over the years. We should also study the hydrology, sedimentation, the increase or decrease in depth of the lake, as well as birds, animals, their food sources, etc.

(This post is based on articles in the Indian Express.)