Metric loss

Vultures prevent tens of millions of metric tons of carbon emissions every year

Vultures are difficult birds for humans to love. They are one obligatory scavenger, meaning they get all their food from already dead prey – and this association has presented them as a harbinger of death since ancient times. But in reality, vultures are nature’s flying sanitation team. And new research adds to this positive picture by detailing the role of these birds in a surprising process: mitigation of greenhouse gas emissions.

With their impressive vision and the range they can cover during their long gliding flights, the 22 species of vultures found around the world are often the first scavengers to discover and feed on a carcass. This cleaning provides a vital service to both ecosystems and humans: it maintains nutrient cycling and controls pathogens that might otherwise spread from dead animals to living animals.

Decomposing animal bodies release greenhouse gases, including carbon dioxide and methane. But most of these emissions can be avoided if the vultures get to the remains first, a new study in ecosystem service shows. It calculates that an individual vulture eats between 0.2 and one kilogram (kg) of carcass per day, depending on the species of vulture. Not consumed, each kg of naturally decomposing carcass emits approximately 0.86 kg of CO2 equivalent. This estimate assumes that carcasses not eaten by vultures are left to rot. But many carcasses are composted or buried by humans, resulting in more emissions than natural decomposition, so eating vultures can avoid even more emissions when replacing these methods. Avoided emissions may seem small, but multiply those estimates by the estimated 134 to 140 million vultures worldwide, and the number becomes more impressive: tens of millions of metric tons of avoided emissions per year.

But this ecosystem service is not evenly distributed around the world. It mainly occurs in the Americas, says the study’s lead author, Pablo Plaza, a biologist at the National University of Comahue in Argentina. According to Plaza and his colleagues, three species found only in the Americas – black, turkish and yellow-headed vultures – are responsible for 96% of all vulture-related emissions worldwide. Collectively, the vultures of the Americas keep about 12 million metric tons of CO2 equivalent out of the atmosphere each year. Using estimates According to the US Environmental Protection Agency, that’s equivalent to taking 2.6 million cars off the road every year.

The situation outside the Americas is quite different. “The decline of vulture populations in many parts of the world, such as Africa and Asia, has resulted in a concomitant loss of ecosystem services produced by vultures,” Plaza says. The white-rumped vulture, once one of the most common vultures in India, has been brought to the brink of extinction in recent decades. Between 1992 and 2007, its population fell by 99.9%, from millions of birds to a few thousand survivors. This steep decline was largely due to poisoning with diclofenac, a veterinary drug to which vultures are exposed when they eat dead livestock. In India alone every year the atmosphere gains at least 2.9 million metric tons greenhouse gas emissions that the vultures would have avoided before their population collapse.

The value of vulture services can be even greater in times of weather or other disasters. Carolina Baruzzi, a postdoctoral researcher at the University of Florida, who was not involved in the new study, documented vulture scavenging after wildlife mass mortality events such as disease outbreaks. “Without vultures,” she explains, “we have carcasses decomposing at a slower rate, which can cause a range of problematic issues,” including increased greenhouse gas emissions and disease. . Baruzzi’s work has shown that the difference between ecosystems with and without vultures is not subtle. If the vultures were there, “in two weeks, [carcasses] were usually gone,” she says. “Where we didn’t have vultures, they stayed there for over a month and a half or two months, which is really striking.”

Vulture conservation is of course not a major climate solution in itself. But according to US Forest Service scientist Grant Domke, this factor and others add up. “I think the biggest piece here is this idea of ​​a portfolio approach to emissions reductions,” says Domke, who leads a team reporting US forest carbon data as part of the government’s commitment. country to the United Nations Framework Convention on Climate Change. He points to studies of large-scale wildfires that show their detrimental impact on emissions and sequestration is of the same order of magnitude as the beneficial effect shown by vultures in the new paper. “Everything has to be on the table,” he says, “and the more we understand the contributions of plants and animals as part of the whole economy, the better.”