Soot-covered birds could shed new light on air pollution


Black carbon samples taken from the wings of birds that lived throughout the twentieth century could change the way scientists think about climate change.

Soot collected from the feathers of songbirds that lived throughout the twentieth century could change the way scientists look at air pollution, according to new research in the Proceedings of the National Academy of Sciences.

In the study, a team of U.S. scientists measured black carbon samples taken from 1,300 larks, woodpeckers, and sparrows that existed over the last 100 years. This not only helped create a in-depth picture of air quality over industrial parts of the United States, but it also led to a new understanding of past climate change.

Black carbon — which is a major component of soot — is created through the incomplete burning of different fossil fuels like coal. The polluted air generated by that process created many environmental problems across both the United States and Europe.

When in the air, black carbon typically absorbs sunlight and speeds up atmospheric warming. On the ground, it increases the melting of both snow and ice. Though scientists have wanted to get an in-depth study of those effects for a while, they have not been able to find accurate records of black carbon emitted around the U.S manufacturing belt at the end of the 19th century.

To shed light on that time period, the team in the new study went to museums in industrialized cities and measured the amount of black carbon that became trapped in the feathers of songbirds as they flew through the smoky air. They did this by photographing the dead birds and then measuring how much light reflected off of them.

“We went into natural history collections and saw that birds from 100 years ago that were soiled, they were covered in soot,” co-author Shane DuBay, a researcher from the University of Chicago, told BBC News. “We saw that birds from the present were cleaner and we knew that at some point through time the birds cleaned up – when we did our first pass of analysis using reflectance we were like wow, we have some incredible precision.”

The researchers analyzed more than 1,000 birds during the study. That investigation revealed black carbon levels peaked during the first decade of the twentieth century. Not only that, but the air pollution levels during that time are much worse than previously thought.

In the past, researchers believed coal use fell numerous times throughout America’s history. However, the new study shows those past levels have been vastly underestimated.

While the findings are concerning, the team believes they could be put to good use. That is because the method used in the study could be used to study pollution in other parts of the world, which could then build a better picture of climate change and enable researchers to take more efficient steps towards combating the process in future years.

“This study shows a tipping point when we moved away from burning dirty coal, and today, we’re at a similar pivotal moment with fossil fuels,” added DuBay, according to “In the middle of the 20th century, we made an investment in infrastructure and regulated fuel sources—hopefully, we can take that lesson and make a similar transition now to more sustainable, renewable energy sources that are more efficient and less harmful to our environment.”


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