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.)
