When India's vulture population collapsed, half a million human deaths followed: study

As It Happens6:42When India's vulture population collapsed, half a million human deaths followed: study

Vultures may not be the most popular animal in the world, but the work they do is essential for human life, a new study has found.

New research attributes 500,000 human deaths in India over the course of five years in the early 2000s to a collapse in the country's vulture populations. 

"They perform this really important function in the environment that benefits us as society, as people," co-author Eyal Frank, a University of Chicago economist, told As It Happens host Nil Köksal. "They get rid of a lot of dead animals and sanitize and clean up the space for us."

Without those sanitization services, waterways become polluted and diseases run rampant, especially in areas with a lot of livestock, according to new research due to be published in the journal American Economic Review. 

The findings are being touted by conservationists who have long been sounding the alarm about threats to the scavenger birds around the world. 

What happened to India's vultures?

India was once home to tens of millions of vultures. But in the mid-90s, the birds started dying en masse, and their population was reduced to near-extinction levels. 

For years, the sudden deaths were a mystery. But in 2004, scientists cracked the case. The birds were being poisoned by diclofenac, a non-steroidal painkiller widely used in cattle and other livestock. Even a trace amount of the drug causes kidney failure in vultures native to Europe, Asia and Africa. 

The drug's patent expired in 1994, and when cheaper generic versions hit the market, Indian farmers began using it to help sick and injured animals recover more quickly. That's when the birds, which feed on livestock carcasses, began to die. 

"That made a lot of sense for the livestock, animals and the farmers. What they didn't know is that there were inadvertently poisoning vultures," Frank said. 

Diclofenac was banned from veterinary use in India in 2006, though conservationists say some farmers and vets still use it, or other equally toxic alternatives.

How did the study calculate its death toll?

Frank and his co-author, University of Warwick economist Anant Sudarshan, estimate the loss of vultures led to an additional 100,000 human deaths per year in India between 2000 and 2005, for a total of 500,000.

They arrived at that figure by comparing the human death rates in India before and after the vulture collapse.

Areas that traditionally didn't have many vultures didn't see much change, they found. But in places where the birds once thrived, human death rates increased by more than four per cent. The effect was most dramatic in places with a high volume of livestock.  

The authors also tested water quality in the regions they studied, and found increased pathogen levels in areas where there had once been a lot of vultures. 

What's more, they tracked the sales of rabies vaccines, which rose sharply after the vultures' decline. This, Frank said, backs up anecdotal evidence that as vultures decreased in India, wild dogs — some carrying rabies — flourished. 

"I hope that people will see this as one point of evidence that highlights that the natural world, well-functioning ecosystems and biodiversity can truly have an impact on human well-being," Frank said.

What do vulture experts have to say?

Vulture expert Corinne Kendall, who was not involved in the research, cautioned that studies that rely on observational data are not strong as ones centred around experiments.

Nevertheless Kendall, the curator of conservation and research at the North Carolina Zoo, said this one "does a great job of demonstrating differences in effects on human mortality rate for areas that lost vultures versus those that did not."

It also, she says, backs up previous research that suggest vultures play a role in preventing the spread of disease. 

Not only do they clean animal carcasses from the landscape, but their highly acidic stomachs may actually destroy disease-causing pathogens, she said, which prevents the birds from spreading diseases like some other scavenger species do. 

"This work should act as a wake-up call for other areas where vultures are in decline. We need to do something now as losing these scavengers could have significant consequences on people," Kendall told CBC in an email.

"Vultures may not be glamorous or cute, but we need them."

Chris Bowden agrees. He's the vulture program manager at the U.K.'s Royal Society for the Protection of Birds, and co-chair of the International Union for Conservation of Nature's vulture specialist group.

He has been working with other conservationists and partners in India to help restore vulture populations by educating people on safe alternatives to diclofenac, running captive breeding programs and advocating for stronger pharmaceutical testing long before veterinary drugs make it to market.

Those combined efforts, he says, have pulled the birds back from the brink of extinction.

But, according to India's 2023 State of the Bird report, four species of vultures are still listed as critically endangered, and three have seen long-term population declines of between 91 and 98 per cent.

"I don't think they're ever going to come back in the same density that they were," he said. 

'Magnificent raptors' 

Both Kendall and Bowden say vultures face a myriad of threats worldwide, including hunting, accidental poisoning, and collisions with human infrastructure.

Bowden says he knows vultures have "a bit of an image problem." But as far as he is concerned, they are "magnificent raptors that are an amazing part of the biodiversity in their own right." 

"We hope that this [study] highlights that more clearly, so people take it more seriously to actually do something about conserving these amazing birds," he said. 

Frank says he hopes his work highlights the importance of biodiversity. 

"It matters for us … beyond just some fuzzy feelings we have towards, like, the more charismatic species out there," he said.