The near-extinction of vultures in India in the 1990s allowed fatal bacteria and infections from carcasses to proliferate, leading to the deaths of five lakh people over five years, according to a study published in the American Economic Association journal.

The study, The social costs of keystone species collapse: Evidence from the decline of vultures in India, estimated that the country suffered economic damages worth $69.4 billion, or Rs 58,621 crore, a year from the loss of vulture populations from 2000 to 2005.

The authors of the study noted that vultures are one of the most essential birds for the Indian ecosystem.

Despite this, there was a steep decline in their population after farmers started giving an anti-inflammatory drug called diclofenac to cattle who were suffering from diseases. The drug, which has a fatal effect on the vulture’s kidneys, remained in cattle carcasses and became deadly for the bird.

Diclofenac was banned by the Indian government in 2006.

However, its impact caused the population of vultures to decline from five crore to just thousands, according to the study. Due to this, animal carcasses were left to rot, making it easier for infections and other diseases to spread.

To understand the effect of the vulture population, researchers of the study overlayed maps of the bird’s habitats onto those of Indian administrative districts. They looked at health records for more than 600 districts, controlling for water quality, weather and the number of hospitals.

They found that before 1994, the average human death rate in districts surveyed was 0.9% per 1,000 persons. This was a baseline that accounted for whether there were large numbers of vultures in a particular district.

By the end of 2005, areas that were traditionally home to large numbers of vultures saw a 4.7% increase in human death rates on average, that is, roughly 1,04,386 additional deaths per year.

Death rates in districts where vultures were not typically found remained stable at 0.9%, the study found.

To calculate the monetary loss due to the decline of the vulture population, the authors relied on previous research that calculated the economic value of what Indian society is willing to spend to save one life at roughly $6,65,000, or Rs 5.56 crore, a person.

That put the total economic damages from the loss of vulture populations at $69.4 billion a year from 2000 to 2005.

Anant Sudarshan, the study’s co-author, pointed out that in a country like India with prohibitions on eating beef, most cattle end up turning into carcasses.

“Vultures provide an incredible disposal service for free,” said Sudarshan, an associate professor of economics at the University of Warwick in England. “A group of vultures takes about 45 minutes to turn a cow carcass into bone.”

Co-author Eyal Frank, an assistant professor at the University of Chicago's Harris School of Public Policy, told BBC that vultures are considered nature’s sanitation service because of the important role they play in removing dead animals that contain bacteria and pathogens from our environment.

According to Frank, understanding the role vultures play in human health “underscores the importance of protecting wildlife, and not just the cute and cuddly”.

He added: “They all have a job to do in our ecosystems that impacts our lives.”

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