A Review on the Status of Sambhar Wetland Bird Tragedy

Ecological Importance

Sambhar has been designated as a Ramsar site (Figure

2) (recognized wetland of international importance) because the wetland is a key wintering area for tens of thousands of pink flamingos (Figure 3)and other birds that migrate from northern Asia and Siberia.

The specialized algae and bacteria growing in the lake provide striking water colors and support the lake ecology that, in turn, sustains the migrating waterfowl.

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In November 2019, nearly 20,000 of migratory birds were found dead mysteriously in the lake area. The salt (NaCl) concentration in this lake water differs from season to season. The salt concentration in the pans Kyars varies and, accordingly, the color of the brine ranges from green, orange, pink, purple, pink and red due to the bloom of haloalkaliphilic microorganisms. More recently, haloalkaliphilic microalgae namely Dunaliella, Euhalothece, Nitzchia, etc. have also been isolated [1].

The Human Connection

Sambhar is known as a source of salt production. Over the decades, salt extraction in the lake has undergone a transformation. The traditional process is monsoon- dependent. The lake taps water from seasonal rivers, streams and rivulets. This water reacts with the lake sediments and becomes brine. It evaporates over 50 days leaving behind crystallized salt. Today, most salt production units use deep bore wells to extract groundwater, reducing the entire process to barely two weeks.

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Cause of Bird Tragedy

Thousands of birds, including this Pallas’s Gull, have been found dead around Rajasthan’s saline, Sambhar Lake, triggering alarm among birders. This incident needs immediate investigation and remediation.The deaths of over thousands birds in Sambhar Lake have been attributed to Avian botulism. Attached is the detailed report by the Indian Veterinary Research Institute (IVRI), Bareilly. A potential cause of the presence of the bacteria could be toxicity of the water possibly due to excessive salt extraction by illegal salt units around the lake.

Avian botulism is a neuromuscular illness caused by a toxin produced by a bacteria-Clostridium botulinum. It is a paralytic, often fatal, disease for birds. Heavy rains that lashed northern India this July reduced the salinity of the lake. However, when the water evaporated, it increased the salinity around the edges of the lake bed. The bacteria that caused the present outbreak-_C. botulinum-_is an anaerobic bacterium, meaning it can grow and produce toxins only in the absence of oxygen. The low-levels of warm, saline water in the lake are further estimated by ecologists to have provided an ideal location for the manifestation of botulism.

The decaying plant or animal materials are capable of hosting the bacteria for a longer period of time. A bird-to- bird cycle: Since only insectivorous and omnivorous birds were affected and not herbivores, the birds feeding on dead birds could have been a possible cause of such mortality. In studies conducted by the USGS National Wildlife Health Center, several environmental factors, including pH, salinity, temperature, and oxidation-reduction potential in the sediments and water column, appeared to significantly influence the likelihood of botulism outbreaks in wetlands.

For several years activists have highlighted commercial and other activities detrimental to the eco-system of the wetland were being carried out contrary to the provisions of the Wetland (Conservation and Management) Rules framed under the Environment Protection Acts of 1986 and 2010.

The Rajasthan state hosts one of India’s largest migratory bird populations. On November 20, the Rajasthan High Court took notice of the tragedy and sought a report from amicus curiae Nitin Jain (Figure 5).

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Authorities are burying the piling bird carcasses in pits after wrapping them in polythene sheets. This has raised concerns about the risk of contamination of soil, water and salt produced in the area. Experts also suspect poisonous algae and dumping of waste and carcasses in the lake behind the epidemic.

Sambhar Bird Diversity

A total of 71 species of wetland birds have been recorded (Tables 1&2).

Anatids were largest in number and 27 species have been sighted for the first time from the lake waters. Under Ramsar definition, some twenty families of water birds have been designated as birds ecologically dependent on wetland. Out of 20 families recognized, 15 families are recorded from Sambhar Lake. The other two families also form the part of wetland dependent birds. All the 17 families recorded from Sambhar Lake are taxonomically categorized to define clearly the nature of dependence and status of wetland birds.