Vultures Prevent Tens of Millions of Metric Tons of Carbon Emissions Each Year

An anonymous reader quotes a report from Scientific American: Vultures are hard birds for humans to love. They are an obligate scavenger, meaning they get all their food from already dead prey -- and that association has cast them as a harbinger of death since ancient times. But in reality, vultures are nature's flying sanitation crew. And new research adds to that positive picture by detailing these birds' role in a surprising process: mitigating greenhouse gas emissions. With their impressive vision and the range they can cover in their long, soaring flights, the 22 species of vultures found around the world are often the first scavengers to discover and feed on a carcass. This cleanup provides a vital service to both ecosystems and humans: it keeps nutrients cycling and controls pathogens that could otherwise spread from dead animals to living ones.

Decaying animal bodies release greenhouse gases, including carbon dioxide and methane. But most of these emissions can be prevented if vultures get to the remains first, a new study in Ecosystem Services shows. It calculates that an individual vulture eats between 0.2 and one kilogram (kg) of carcass per day, depending on the vulture species. Left uneaten, each kg of naturally decomposing carcass emits about 0.86 kg of CO2 equivalent. This estimate assumes that carcasses not eaten by vultures are left to decay. But many carcasses are composted or buried by humans, which result in more emissions than natural decay, so vulture consumption can avert even more emissions when replacing those methods. The avoided emissions may not sound like much, but multiply those estimates by the estimated 134 million to 140 million vultures around the world, and the number becomes more impressive: tens of millions of metric tons of emissions avoided per year.

But this ecosystem service is not evenly distributed around the world. It occurs mostly in the Americas, says the study's lead author Pablo Plaza, a biologist at the National University of Comahue in Argentina. Three species found only in the Americas -- the Black, Turkey and Yellow-headed vultures -- are responsible for 96 percent of all vulture-related emissions mitigation worldwide, Plaza and his colleagues found. Collectively, vultures in the Americas keep about 12 million metric tons of CO2 equivalent out of the atmosphere annually. Using estimates from the U.S. Environmental Protection Agency, that is akin to taking 2.6 million cars off the road each year. The situation outside of the Americas stands in stark contrast. 'The decline in vulture populations in many regions of the world, such as Africa and Asia, has produced a concomitant loss of the ecosystem services vultures produce,' Plaza says.

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