Once, vultures were a common sight in India, frequently seen scavenging over large landfills for cattle carcasses. Occasionally, these birds even posed a hazard to aircraft during takeoffs. However, over two decades ago, vultures in India began dying off due to a drug used to treat sick cows.
By the mid-1990s, the vulture population, once numbering around 50 million, had nearly vanished. The culprit was diclofenac, an inexpensive non-steroidal painkiller for cattle, which is deadly to vultures. Birds feeding on the carcasses of treated livestock suffered kidney failure and died. Despite a ban on veterinary use of diclofenac in 2006, the decline has only slowed in some areas, with at least three species experiencing long-term population losses of 91-98%, according to the latest State of India’s Birds report.
A new peer-reviewed study highlights further consequences. The study, published in the American Economic Association journal, reveals that the drastic reduction of these scavenging birds has led to the spread of harmful bacteria and infections, resulting in about half a million human deaths over five years. “Vultures serve as nature’s sanitation workers by removing dead animals that harbor bacteria and pathogens. Without them, diseases can proliferate,” explains Eyal Frank, co-author of the study and an assistant professor at the University of Chicago’s Harris School of Public Policy.
Frank and his co-author, Anant Sudarshan, analyzed human mortality rates in Indian districts with formerly large vulture populations compared to those with historically low vulture numbers, both before and after the vulture decline. They also looked at rabies vaccine sales, feral dog populations, and waterborne pathogen levels. They found that as anti-inflammatory drug sales increased and vulture populations collapsed, human death rates rose by more than 4% in areas once abundant with vultures.
The researchers observed that the impact was most significant in urban areas with high livestock populations and frequent carcass dumps. They estimated that between 2000 and 2005, the loss of vultures resulted in approximately 100,000 additional human deaths annually, translating to over $69 billion per year in economic damages due to premature deaths. These deaths were linked to the spread of diseases and bacteria that vultures would have otherwise removed.
Without vultures, stray dog populations surged, leading to an increase in rabies among humans. Although rabies vaccine sales increased, they were insufficient. Unlike vultures, dogs did not effectively clean up decomposing remains, causing bacteria and pathogens to contaminate drinking water through runoff. As a result, fecal bacteria levels in the water more than doubled.
“The vulture collapse in India starkly demonstrates the severe and often irreversible costs to humans resulting from species loss,” says Sudarshan, an associate professor at the University of Warwick and co-author of the study. “While chemicals caused this decline, other human activities such as habitat loss, wildlife trade, and climate change also impact animals and, consequently, us. Understanding these costs highlights the need to focus resources and regulations on preserving keystone species.”
Among India’s vulture species, the white-rumped vulture, Indian vulture, and red-headed vulture have seen the most dramatic declines, with populations falling by 98%, 95%, and 91% respectively since the early 2000s. The Egyptian vulture and migratory griffon vulture have also declined significantly, though less drastically.
The 2019 livestock census in India recorded over 500 million animals, the highest number globally. Historically, farmers relied on vultures to efficiently dispose of livestock carcasses. The rapid decline of vultures in India is the fastest recorded for any bird species and the largest since the passenger pigeon’s extinction in the U.S., according to researchers.
Currently, India’s remaining vulture populations are concentrated around protected areas, where their diet includes more wildlife than potentially contaminated livestock, according to the State of Indian Birds report. Ongoing declines suggest persistent threats to vultures, raising concerns about their impact on human well-being. Experts warn that veterinary drugs continue to pose significant risks to vultures. The dwindling number of carcasses, due to increased burials and competition from feral dogs, exacerbates the issue. Additionally, quarrying and mining activities disrupt nesting habitats for some vulture species.
Is there hope for the vultures’ return? It’s uncertain, but there are encouraging signs. Last year, 20 vultures bred in captivity, fitted with satellite tags, and rescued were released from a tiger reserve in West Bengal. A recent survey in southern India recorded over 300 vultures. However, more action is needed to ensure their survival.
