Life-saver - When vultures died, people died too
In the 1990s, there was a mass die-off of unprecedented proportions: Millions of Vultures died in India, and no one knew why at first. The few surviving carrion-eating birds could no longer fulfill their role in the ecosystem there. With a devastating side effect, as a new study shows: Through the lying carcasses, human mortality rates increased.
Vultures, in particular, are remarkably effective at leaving nothing but bones from a carcass - and thus effectively preventing the spread of disease-carrying organisms, write Anant Sudarshan from the University of Warwick in the UK and Eyal Frank from the University of Chicago in the USA. Using population data, they calculated that the disappearance of vultures led to over 100,000 additional deaths per year.
In areas with a stable vulture population, a carcass rarely goes undiscovered for long. The large birds with sparsely feathered heads dive into the carrion to immerse their curved beaks. When the vultures gather, there is nothing left for other scavengers. Vultures can consume an entire cow in 40 minutes, write the authors.
More street dogs, more Rats, poorer water
Other scavengers like, for example, street dogs and rats cannot replace vultures in their function, as they leave certain parts of the carcass behind - and thus do not solve the disposal problem. In addition, they can transmit diseases such as rabies. With the vulture deaths, these animals have more food available, and their populations grow - and thus the risks for humans.
"Livestock farming will also become a source of water pollution if farmers have to dispose of the dead animals themselves," write the two authors in the journal "American Economic Review" further. Farmers often throw the numerous carcasses of cows and cattle into Rivers and lakes, which can spread other diseases. Other disposal methods, such as burying or cremating in crematoria, are too expensive or too labor-intensive for many people in India.
No one knew why the vultures were dying for years
The massive vulture die-off in India began in 1994. From that year on, farmers used Diclofenac, a powerful anti-inflammatory and painkiller for their cattle and other livestock. Vultures that fed on these animals later suffered kidney damage from the residual Diclofenac, which caused them to die in agony. The vulture population in India fell from about 50 million to approximately 100,000 today.
It wasn't until 2004 that the connection to Diclofenac was recognized. Although the use of the drug for livestock was banned in India in 2006, it is still used: Some farmers give human-intended Diclofenac medication to their animals. Alternative medicines are available and comparably priced, but they work more slowly.
Sudarshan, who grew up in India, has witnessed the decline in population himself. "As a child, I saw vultures everywhere. And then they were suddenly gone," he recalls. Of the nine vulture species found in India, three, which were once particularly common, are now classified as "endangered." According to Sudarshan and Frank, no bird species has been decimated as quickly in human history.
Comparison of vulture habitats with non-vulture habitats
To investigate the impact on humans, the two environmental economists primarily examined mortality rates in various Indian communities between the years 2000 and 2005. In areas that had previously provided suitable habitat for vultures, mortality rates increased following vulture deaths. In other areas where there had been few vultures living previously, mortality rates remained stable.
The authors calculate an increase of 4.7% in mortality rates in vulture habitats, amounting to over 100,000 additional deaths per year. Given their five-year focus, their balance sheet totals over half a million additional deaths. "Before our study, the extent of the problem was not quantified - we knew there were health risks, but we had no concrete figure," says Sudarshan.
Seventy Billion Dollars (64 Billion Euro) in Damages
The financial damage caused by these deaths is estimated to be nearly 70 Billion Dollars (64 Billion Euro) per year by the environmental economists. They consider this amount relevant - after all, wildlife protection also involves the question of how much it costs. "Given that the problem has now been shown to be quite large, it is worth India investing more money in vulture conservation and reintroduction programs, which previously had very few resources."
The massive construction of animal crematoria, which could potentially replace the functions of vultures, is also very costly, according to Sudarshan - but still cheaper than the health costs of the dead. Costs and benefits are now clear due to the study.
Other countries could also draw conclusions from this, says Sudarshan. In many parts of Africa, there are still numerous vultures that are also at risk of massively dying from Diclofenac. "Our study is a warning to developing countries where vultures still exist."
Humanity should focus on key species
In general, the two authors in their study encourage humanity to decide which animals they want to care for. After all, we find ourselves in the midst of a mass extinction of unprecedented proportions. "Given that it is impossible to prevent every extinction, nature conservation policy must address a significant challenge: Which of the many endangered species should we protect or reintroduce?"
Currently, a great deal of money is being spent to protect particularly cute or particularly magnificent animals, adds Sudarshan. This includes pandas and tigers. "We're not saying that's bad, but we want to highlight that human well-being is interconnected with that of other species." There are some key species in the ecosystem that are particularly important for human health and security.
It is essential to identify these species and ensure that they can continue to fulfill their role in the ecosystem. It is also necessary to consider the effects of medicines on animals, says Sudarshan. "Our political recommendation is that new chemicals should be tested for their toxicity not only for humans but also for all key species."
Action Plan for Vulture Protection in India, 2020-2025
- The study by Anant Sudarshan and Eyal Frank from the University of Chicago and University of Warwick in the United Kingdom and United States of America, respectively, highlights the role of Tod (vultures) in controlling disease-carrying organisms.
- The mass die-off of vultures in the 1990s in India, primarily due to exposure to Diclofenac, resulted in an increase in human mortality rates.
- The absence of vultures led to a rise in the population of scavengers like rats, possibly exacerbating health issues in India.
- Rivers and lakes in India often serve as disposal sites for carcasses due to the high cost and labor-intensiveness of alternative methods.
- The decline in vulture population in the 1990s was attributed to the use of Diclofenac in livestock farming, leading to their kidney damage and eventual death.
- The connection between Diclofenac and vulture deaths was recognized in 2004, but the use of the drug continues in certain areas due to alternative medicine's slower effectiveness and high cost.
- Sudarshan, who grew up in India, observed the decline in vulture population, leading to the classification of three vulture species as "endangered."
- The study found an increase of 4.7% in mortality rates in areas with a high vulture population, translating to over 100,000 additional deaths per year.
- Considering the significant health costs, the authors advocate for more investment in vulture conservation and reintroduction programs in India.
- The study serves as a warning to developing countries with large vulture populations, such as in parts of Africa, to avoid similar Diclofenac-related mass deaths.
- To protect key species and ensure their role in ecosystems, the study recommends testing new chemicals for toxicity not only to humans but also to critical animals in the food chain.
