When Vultures Nearly Disappeared in India, Half a Million People Died, Too, Study Finds (2024)

Vultures often get a bad rap. But these bald-headed scavengers play a vitally important role in their ecosystems, serving as nature’s clean-up crew after other animals die.

Now, new research has estimated precisely how important these birds are to the humans who live alongside them. After vultures nearly went extinct in India, an extra 500,000 people died in five years at the start of this century, according to a new study that will soon be published in the American Economic Review.

Vultures don’t simply get rid of unsightly, decaying flesh on the side of the road. By feasting on animal carcasses, they also help limit pollution and keep diseases at bay, the research finds. The conclusions are a reminder that “biodiversity and ecosystem functioning do matter to human beings,” says study co-author Eyal Frank, an economist at the University of Chicago, to the New York Times’ Catrin Einhorn. “And it’s not always the charismatic and fuzzy species.”

These birds were once abundant in India—tens of millions of them flew freely throughout the country. But starting in the mid-1990s, they began to disappear. By the early 2000s, their population had dropped by 95 percent.

At first, the vultures’ decline was a mystery. But eventually, scientists realized the birds were being poisoned by a painkiller given to cattle and other livestock. When vultures swooped in to eat the livestock carcasses outside tanneries, they unintentionally ingested the drug, called diclofenac, which caused their kidneys to fail. Diclofenac use became more widespread starting in 1994, when cheaper generic versions became available after the drug’s patent expired.

Researchers had heard stories of humans being negatively affected by the disappearance of the vultures. But they wanted to see whether the ripple effects of the birds’ decline would show up in data.

To do so, they compared human death rates in India before and after the birds disappeared. In places that didn’t have many vultures to begin with, human death rates remained relatively constant. But in places that historically had large vulture populations, human death rates increased by more than 4 percent. The change was the most noticeable in areas with high livestock numbers.

They estimate that the loss of the vultures contributed to an extra 104,000 human deaths per year, for a total of more than 500,000 additional deaths between 2000 and 2005. That translates to $69 billion per year in economic costs related to the premature deaths, per the study.

In areas that once had abundant vultures, they also found that water quality had gotten worse. The extra pollution likely came from the bacteria and pathogens that proliferated in rotting animal carcasses that formerly would have been picked clean by vultures in less than an hour. Some of the contaminants also came from chemicals used to dispose of the carcasses once the birds weren’t around to take care of them, per Science’s Vivian La.

“In a country like India with prohibitions on eating beef, most cattle end up turning into carcasses,” says study co-author Anant Sudarshan, an economist and environmental policy expert at the University of Warwick in England, to CBS News’ Arshad R. Zargar. “Vultures provide an incredible disposal service for free. A group of vultures takes about 45 minutes to turn a cow carcass into bone.”

Without vultures around to provide competition for carcasses, wild dogs had access to more food. As a result, those dogs—and the rabies they often carry—flourished.Sales of rabies vaccines, the researchers found, also increased.

The death of the vultures was “the largest sanitation shock you could imagine, where you have 50 million carcasses every year not being disposed of,” Sudarshan tells Vox’s Dylan Scott.

Diclofenac has been banned from veterinary use in India since 2006, but conservationists say farmers are still using it illegally, per the New York Times. In addition, other drugs that are toxic to vultures are still approved for use in livestock.

Today, vultures make up less than 1 percent of their previous numbers in India, reports the Times. And four species—the red-headed vulture, the white-rumped vulture, the Indian vulture and the slender-billed vulture—arecritically endangered.

“This work should act as a wake-up call for other areas where vultures are in decline,” says Corinne Kendall, curator of conservation and research at the North Carolina Zoo, who was not involved in the study, to CBC Radio’s Sheena Goodyear. “We need to do something now, as losing these scavengers could have significant consequences on people. Vultures may not be glamorous or cute, but we need them.”