Vultures reduce greenhouse gas emissions

Photo by: slowmotiongli / iStock

A study published in the journal Ecosystem Services found that vultures have a positive impact on reducing greenhouse gas emissions.

There are 23 species of vultures worldwide and they are common in almost all countries. These birds are scavengers. They are able to travel considerable distances in flight and have a vision that allows them to see carrion from great heights. Often vultures find their prey in a fairly “fresh” state, i.e. not yet heavily decomposed. By eating animal carcasses, vultures have been found to prevent carbon emissions. The fact is that decomposing animal bodies emit greenhouse gases, including carbon dioxide and methane. “Cleaning” the air from emissions by vultures does a vital service to both ecosystems and humans: it maintains nutrient cycling and controls pathogens that might otherwise spread from dead animals to living ones.

The authors of the study estimated that one vulture (depending on the bird species) eats between 0.2 and 1 kilogram of carcass per day. Each kilogram of naturally decomposing carcass not eaten by the birds emits about 0.86 kilograms of CO2. At first glance, the amount of carbon monoxide emissions avoided may not seem great, but there are an estimated 134–140 million vultures worldwide, which means that their contribution to emissions reduction is in the tens of millions of metric tons per year.

However, the study’s lead author, Pablo Plaza, a biologist at the National University of Comahue in Argentina, argues that the amount of CO2 emissions reduced by birds is not evenly distributed on the world map, as much depends on the vulture species. The three bird species with the greatest impact on emission reductions are the black, turkey and yellow-headed vultures, found mainly in South and North America. These species are the main “sanitarians” as they are responsible for reducing 96% of emissions credited to vultures globally. For example, America’s vultures retain about 12 million tonnes of CO2-equivalent from the atmosphere each year. The US Environmental Protection Agency estimates that this is equivalent to the emissions of 2.6 million cars.

Unfortunately, the situation outside the Americas is different. “The decline in vulture populations in many regions of the world, such as Africa and Asia, has led to a concomitant loss of the ecosystem services that vultures produce,” says Plaza. For example, the white-backed vulture, once one of the most common vultures in India, has been on the verge of extinction over the past few decades. Between 1992 and 2007, its population fell by 99.9%, from millions of birds to just a few thousand. Such a dramatic decline in numbers was mainly due to poisoning with the veterinary drug diclofenac, which vultures consume when eating dead livestock.

Cover photo: Goddard_Photography / iStock