Why birds are dying in Rajasthan’s Sambhar?

Why birds are dying in Rajasthan’s Sambhar?

• Over the last 10 days, thousands of migratory birds have been found dead at Sambhar Lake, about 80 km southwest of Jaipur city.
• Officials have buried over 18,000 carcasses from 25 different species so far including migratory and have rescued around 750 birds of which 400 are still alive.
• Considering the size of the lake there are fears that the toll may be much higher as there are areas that the officials haven’t reached till now.

Sambhar Lake

• Sambhar Lake is India’s largest inland saltwater lake at 230 sq km, spread mostly across Jaipur and Nagaur districts and also a part of Ajmer.
• It has a catchment area of 5,700 square km, with the water depth fluctuating between 60 cm in the dry season to about 3 meters at the end of the monsoon.
• Every year, the lake attracts thousands of migratory birds and a total of 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.
• The lake was recognized 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 at E.

How much is known so far about the cause of death?

• The clinical signs exhibited by affected birds included dullness, depression, anorexia, flaccid paralysis in legs and wings, and neck touching the ground due to which the birds were unable to walk, swim, or take flight.
• There was no rise of body temperature, no nasal discharge, no respiratory distress, or any other sign.
• On the basis of history, epidemiological observations, classical clinical symptoms and post-mortem findings, the most probable diagnosis is avian botulism, but this has not been officially confirmed.

Other possible reasons for the bird deaths at Sambhar Lake

• After a Division Bench of the Rajasthan High Court took Suo Motu cognizances of the deaths, the Rajasthan government has listed likely reasons:
  • Viral infection
  • Toxicity, as a new area has been filled up after almost 20 years, and there could be a higher concentration of salts along the edges
  • Bacteriological infection
  • Higher temperatures 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.

But why is it taking so long to establish the cause of death?

• The government is waiting for reports from various sources to establish the exact cause.
• It has so far engaged eight institutions and agencies but has received complete reports from only two: RAJUVAS and the National Institute of High-Security Animal Diseases (NIHSAD) in Bhopal.
• While RAJUVAS has suggested avian botulism, NIHSAD has ruled out bird flu.

Is there a concern for human health?

• Humans are primarily at risk from avian botulism only if they eat infected fish or birds. While NIHSAD has ruled out bird flu, this was what was feared initially.
• Personnel was directed to adopt appropriate prophylactic measures such as the use of masks and gloves and burial of carcasses in deep pits with limestone.

How common is avian botulism?

• There have been several waterfowl botulism outbreaks. Between 1995 and 1997 in Canada, an estimated 1,00,000 birds died in Alberta, 1,17,000 in Manitoba, and 1 million in Saskatchewan.
• In 1997, another 5,14,000 birds died due to botulism in Green Salt Lake, Utah, US.
• In 1952, an epizootic outbreak killed 4-5 million waterfowl across the western US.

What are the possible reasons for deteriorating ecology at Sambhar Lake?

• The (partial) handover to Hindustan Salts Limited and the lack of management in the region has been cited as reasons for the deteriorating ecology.
• In a 2016 directive, the National Green Tribunal had noted the impact of the salt industry — including “unauthorized salt pans” — on the ecosystem of Sambhar Lake and asked the state government to cancel the allotment of salt pans.
• However, numerous illegal salt pans are still active in the region.

Way Ahead

• The government should pass legislation in the Assembly to create a Sambhar Lake Development and Conservation Authority along the lines of Odisha’s Chilika Development Authority.
• This authority should be handed the entire responsibility of Sambhar Lake and the chief minister should be made its Chairman.
• There is no document about the management of Sambhar Lake. World Wildlife Fund had created a document about 22 years ago, and it is now outdated.
• A fresh document should study why the water from four rivers, which flows into the lake, has decreased over the years.
• It should study hydrology, sedimentation, the increase or decrease in depth of the lake, as well as birds, animals their food sources, etc.