Research Highlights Featured Chart

October 15, 2024

The costs of species extinction

Public health implications of the decline of vultures in India.

Tyler Smith

Source: Sari ONeal

Nearly five hundred vertebrate species have gone extinct over the last 100 years, a rate that outpaced the last five mass extinction events on planet earth. Some of these species, known as keystone species, help to hold entire ecosystems together.

In a paper in the American Economic Review, authors Eyal Frank and Anant Sudarshan studied the sudden collapse of vulture populations across the Indian subcontinent as a result of farmers’ unintentionally poisoning the birds by using the painkiller diclofenac on their cattle. They found that when vultures in India died out, human mortality increased significantly. 

The researchers argue that when vultures disappeared and were no longer scavenging dead livestock, carrion were more likely to be either dumped in rivers, leading to deadly water pollution, or eaten by other scavengers, such as feral dogs and rats, that are more prone to transmitting diseases to humans.

Using a differences-in-differences approach, they compared changes in human mortality in areas that were highly suitable habitats for vultures to areas that were less suitable around the time the vulture populations disappeared. 

Figure 4 from the authors’ paper shows the event-study estimates between 1988 to 2005.

Figure 4 from Frank and Sudarshan (2024)

The estimates in the chart compare the all-cause death rates per 1,000 people in districts with high suitability for vultures to districts with low suitability. The dashed vertical line indicates the introduction of the generic painkiller used by farmers on cattle, diclofenac, in 1993. The vertical bars are 95 percent confidence intervals.

Before 1993 and the steep decline of vulture populations, there was no significant difference between how mortality was evolving in high- and low-suitability districts. But by 1996, the first year in which the decline in vulture populations gained widespread recognition, the all-cause death rate was higher in the high-suitability districts by 0.65 deaths per 1,000 people. By 2005, death rates were higher by about 1.4 deaths per 1,000 people.

Overall, districts that were highly suitable to vultures saw an average increase in all-cause human death rates of 4.7 percent, compared to areas that were poorly suited to vultures. The results imply an average of over one hundred thousand additional deaths per year and the equivalent of almost $70 billion per year in mortality damages.

The findings suggest that increased awareness of anthropocentric benefits from biodiversity may promote better policies prior to a species becoming extinct.