A new study has found a direct correlation between the collapse of the vulture population and the rising human mortality by over a lakh per year in India besides increasing the burden on the economy. As per the study, over 5 lakh additional people died, which caused $350 billion loss to the country’s economy between 2000-2005 due to the collapse of the vulture population.
Vultures were once ubiquitous across the country with a population that may have exceeded 50 million birds. But by the second half of 1990 decade, the number of Indian vultures in the wild fell by over 95%. The only parallel to the fastest decline of vultures in recorded history is the extinction of the passenger pigeons in the US.
The sudden collapse of populations of the scavenger birds was attributed to the use of a painkiller medicine, Nonsteroidal anti-inflammatory drug (NSAID) Diclofenac, to treat cattle. Vulture deaths triggered a sanitation shock, led to increased incidents of the spread of diseases like rabies, diminished water quality and impacted human health.
The new research, “The Social Costs of Keystone Species Collapse: Evidence From The Decline of Vultures in India” by Eyal Frank of the University of Chicago and Anant Sudarshan of the University of Warwick, underlined that the all-cause human mortality rate increased by more than 4%, which implies mortality damages of around $69.4 billion per year.
The research quantified an average of over 1,04,386 additional deaths per year due to the collapse of the scavenger population. It analysed the human death rates between 1994-1999 and 2000-2005 by keeping in mind the factor of rising livestock numbers and sharp decline in vulture numbers in selected districts. The researchers found that the all-cause death rate was double per 1,000 in the two periods. Between 2000 and 2005, the price of Diclofenac was too cheap and was in rampant use.
Three years after the Centre approved the generic use of Diclofenac in 1993, the decline in vulture populations was first recorded. The government first recognised the negative impact of the drug on vultures in 2004 and banned its use in 2006.
Critical role of scavengers
According to the study, the ecological and epidemiological dynamics of scavengers, pathogens and infectious diseases help explain the causal link between diminishing vulture populations and human health. In the natural set up, vultures efficiently evolved to feed on carrion. Since the stomach acidity levels in vultures are hundreds of times more than humans, they enable the birds to consume carrion while not allowing most bacteria to survive in the digestive system.
The research shows that vultures can consume the carrion of an entire cow within 40 minutes whereas other scavenging species such as dogs and rats not only leave the flesh behind and therefore do not solve the sanitation problem, but also transmit various diseases, including rabies. Vultures also control the population of other scavengers, such as dogs and rats that transmit diseases. Recent experimental evidence confirms that vultures do not have a good functional replacement in the ecosystem.