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Sambhar lake may have been lethal electric trap when birds arrived

An investigation by The Indian Express has revealed that a vast network of live wires running thousands of bore wells could have created a submerged electric trap and the carcass of electrocuted birds could have served as the biomass for the toxic bacteria to thrive.

Written by Jay Mazoomdaar |
Updated: December 26, 2019 7:09:34 am
Sambhar lake, migratory birds, sambhar lake birds dead, Siberian cranes, Rajasthan, Veterinary Research Institute, india news, Indian Express Due to record rain, a vast network of live wires running thousands of bore wells remained under lake water well into the migration season.

More than 20,000 migratory birds died since they began congregating at Rajasthan’s famed Sambhar lake late October, their carcass samples testing negative for avian flu and poisoning. The Indian Veterinary Research Institute (IVRI) attributed the deaths to avian botulism, a lethal paralytic disease caused by a bacterial neurotoxin produced in rotting organic matter. What led to the outbreak remains unclear.

An investigation by The Indian Express has revealed that a vast network of live wires running thousands of bore wells could have created a submerged electric trap and the carcass of electrocuted birds could have served as the biomass for the toxic bacteria to thrive.

Read | What’s behind Rajasthan’s bird crisis?

When the birds arrived in October at Sambhar, India’s largest saltwater lake, they were greeted, thanks to heavy rain, by water levels at a two-decade high. Under the surface was a messy network of cables that came alive every night to power thousands of illegal bore wells that keep Sambhar’s innumerable private salt pans in business.

There is no official count of these but an estimated 5000 to 20,000 illegal bore wells extract saline groundwater across a 25-45 km stretch along the north-western shores of Sambhar lake. From this assembly of submersible pumps, electric wires and water pipelines stretch 2-5 km between the lake and the surrounding villages where thousands of salt pans draw brine.

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Away from tourists’ gaze, this throbbing illegal network has been expanding in and around Sambhar. The pumps are run mostly in the night so that the leaking current does not endanger labourers who work through the day.

Also read | Memories of Sambhar

The bore wells are active round the year, except in July-August when rainfall expands the lake’s boundaries and reduces salinity. Post-monsoon, between Dusshera and Diwali, the pumps resume groundwater extraction. Until last year, lake water would recede laying bare most of the cable network by the beginning of the migration season in late October.

But this year, Sambhar received its heaviest rain in two decades. Result: pumps and power lines remained under lake water, leaking electricity, when the birds arrived — among the most common species in the flock were Northern shoveler, plover, black-winged stilt and the common teal.

Denial is the dominant response. “All of us are very concerned but please don’t link the bird deaths to the salt industry. Salt is not produced in the areas where most of the dead birds were found,” said Rajasthan Refined Salt Manufacturers Association’s president Anil Gattani.

Local rescue workers, however, said that nobody went looking for dead birds in the “bore well zone” for days after dead birds were spotted in the “tourism areas” near Sambhar. “Forget birders, very few locals venture into the bore well areas. Officials did not bother to check there until mid-November when thousands of dead birds were found in the Nawa belt. Many suspect that Nawa is where the deaths began,” says local activist Pawan Modi who was among the first birders who reported the mass die-off on November 10.

In the villages of Nawa, there are clues. “Yes, salt keeps eroding our wires and there is some leakage of current. If the (wire) joints come off, we switch off and rewire,” said a local salt pan owner, insisting “par waise gunguna-ta paani se chidiya nahin marti (a little tingling in the water does not kill birds).”

Studies on the impact of electro-fishing — stunning fish with electricity — show that water birds exposed to a low-intensity shock immediately take flight to resettle at a safe distance. In a shoreline like Sambhar’s this year, strewn with live wires, a safe perch may not have been easy to find.

“No sign of electric shock was found in the postmortem…why did no flamingo die?” asked a senior forest official in Jaipur. Told that flamingos stick to open waters away from the shoreline, he declined to comment.

To identify internal signs of an electric shock in the absence of external injuries, a carcass needs to be examined within 48 hours, explained a senior veterinarian who did not wish to be named. “From the development stage of maggots found in the carcasses spotted on and after November 10, one can tell that the die-off began around Diwali (October 27). After so many days, decomposed samples won’t show if the birds suffered electric shock,” he said.

As reporters and officials came rushing after dead birds were spotted on November 10, most salt pan owners stopped running the bore wells. Two weeks later, botulism was declared the killer.

Said V K Gupta, joint director, Centre for Animal Disease Research and Diagnosis (CADRAD), IVRI-Bareilly, who signed the report diagnosing botulism: “Botulism toxin cannot be found in a carcass unless the bird died of botulism,” he said.

But the presence of an electrical current in the lake water when the birds arrived, said the senior vet, might explain what triggered botulism in the first place.

For, botulinum spores are found everywhere in nature. To germinate and produce toxin, these otherwise harmless spores require temperatures above 25 degrees C, non-acidic pH level (7.5-9), low or no oxygen, and, most importantly, decaying biomass.

While the IVRI report inferred that rotting plankton and invertebrates in and around the lake fostered the outbreak, multiple studies show that mere decaying vegetation is a poor substrate (substance) for the bacteria’s growth. In fact, decaying animal material — in this case dead birds — is more suited for generation of toxin.

N V K Ashraf, chief veterinarian and senior director at Wildlife Trust of India, said that the carcasses of birds or animals that may have died due to reasons other than botulism could also provide the organic material required for bacterial germination under anaerobic conditions and cause a botulism outbreak.

“It is impossible to pinpoint the initial trigger since samples were collected several days after the outbreak set in. Once established, botulism is self-perpetuating. Maggots feed on carcasses and accumulate the toxin. When other birds feed on the toxic maggots, they die, setting off the carcass-maggot cycle until all infected carcasses are removed,” Ashraf said. He added that bore wells should never have been allowed to operate under lake waters.

As late as November 24, almost two weeks after the deaths were reported, the state government began removing illegal bore wells and wires from the lake bed in Nawa. Officials maintained that the move was long overdue since the National Green Tribunal had ordered their removal in November 2016.

“We will continue looking for dead birds all of December and keep removing illegal bore wells. We have stated digging a three-foot-deep trench to guard against pipelines and power cable,” said Nawa SDM Brahm Lal Jat.

Said Rajesh Oza, general manager (works) of government-owned Sambar Salt Ltd: “In the past, our efforts to remove those illegal bore wells were unsuccessful. While we produce around 2.5 lakh tonnes a year, they (the private firms) produce 15-20 lakh tonnes. You can imagine the clout they have.”

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