How vultures keep ecosystems healthy
How vultures keep ecosystems healthy
The vulture crisis demonstrates the connections between wildlife health and human health
How vultures keep ecosystems healthy
The vulture crisis demonstrates the connections between wildlife health and human health
The decline of vulture populations had fatal consequences for humans and other animals that depended on their vital role in the ecosystem.
During the 1990s, the vulture population of South Asia experienced a rapid decline. This near-extinction event was so dramatic that it came to be known as the “vulture crisis.” While scientists raced to find the cause, the plummeting numbers of vultures caused profound ripple effects through entire ecosystems. Human and animal health also declined, and in regions of India where vultures had previously been most widespread, the human mortality rate increased by up to 4%.
Autopsy results showed widespread kidney failure among deceased vultures, which was soon attributed to diclofenac poisoning. Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) used in veterinary medicine. Although diclofenac is perfectly safe for humans and most other mammals, it is highly toxic to vultures. When vultures consumed the carcasses of animals that had been treated with diclofenac, they suffered acute kidney failure. Diclofenac also caused visceral gout, or the accumulation of uric acid crystals within the kidneys, ultimately leading to renal failure.
Vultures are carrion eaters, arguably the most important species of scavengers. With fewer vultures consuming the carcasses of dead animals, they were instead often left to decompose in the open, endangering public health and sanitation. The situation could become dire when decomposing carcasses contaminated water sources, regardless of whether these water sources were consumed by animals or used by human communities. There were also profound shifts within wider ecosystems, as population of feral dogs and other scavenging animals increased. This contributed to the spread of diseases like rabies, as well as to increased dog bite incidents and other conflicts between humans and animals.
The vulture crisis was initially not well understood. However, as researchers explored the link between diclofenac and the decline in vulture populations, regulatory measures were implemented to ban or restrict the use of this drug in veterinary practices. Some countries introduced alternative drugs that were safe for vultures. The importance of vultures to their wider ecosystems also prompted conservation organizations into action. Captive breeding programs were established to breed vultures in controlled environments and later release them into the wild. While this helped the population of vultures recover, their numbers still remain depressed. Vultures are slow-reproducing birds with low reproductive rates. As well as remaining low in South Asia, the population of cultures have also declined in other parts of the world.
The vulture crisis highlights the connections between human and animal health. The decline in vulture populations had profound impacts felt throughout their wider ecosystems. Some scavengers flourished as a result of decreased competition for food sources, but humans were not the only species to experience increased mortality alongside that of vultures. The vultures crisis also underscores the impact of human activities on ecosystem health and the importance of understanding the potential impacts of veterinary drugs throughout the food chain.
