The Social Costs of Keystone Species Collapse: Evidence from the Decline of Vultures in India

Abstract

Scientific evidence suggests the Earth is undergoing a mass extinction of species, caused by human activity. Evaluating the social costs of losing non-human species is necessary to manage biodiversity and target conservation resources. We show that the functional extinction of vultures in India increased human mortality because of a negative shock to sanitation. Vultures are efficient scavengers and feed only on carrion. In India, a country with over 500 million livestock, these birds provided an important public health service by removing livestock carcasses from the environment. In the mid-1990s, vultures experienced the fastest population collapse of a bird species in recorded history. The cause of death was unknown until 2004 when it was identified as poisoning from consuming carcasses containing traces of a common painkiller, diclofenac. The expiration of a patent led to a dramatic fall in the price of medical diclofenac, the development of generic variants, and entry into the veterinary market in 1994. We exploit this event to study the costs of losing vultures. Using habitat range maps for affected species, we compare high- to low-vulture suitability districts before and after the veterinary use of diclofenac. We find that, on average, all-cause human death rates increased by more than 4% in vulture-suitable districts after these birds nearly went extinct. We also find evidence consistent with an increase in feral dog populations and rabies, and lower water quality in affected regions. These outcomes are consistent with the loss of the scavenging function of the vultures.

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