(CN) – Scientists who want to study the effects of pollution and climate change don’t need to look any further than a feather.
Researchers from the Field Museum of Natural History and the University of Chicago released a study Monday in which they document their use of discoloration of bird feathers in museum collections to determine the amount of pollutants in the air when the birds were collected.
The paper, published in the Proceedings of the National Academy of Sciences, details changes in feather colors of five species of birds that are widespread in North America.
The birds – selected for their lighter-colored feathers – had historical counterparts that were darker due to coal pollution that deposited soot onto the feathers.
"The soot on these birds' feathers allowed us to trace the amount of black carbon in the air over time, and we found that the air at the turn of the century was even more polluted than scientists previously thought," said Shane DuBay, one of the authors of the paper.
DuBay said that the feathers acted as collectors of soot and black carbon.
"When you touch these birds, you get traces of soot on your hands,” DuBay said. “We'd wear white gloves while handling them, and the gloves would come away stained, like when you get ink on your fingertips reading a newspaper.”
Researchers examined birds from the past 135 years to analyze the historical amount of pollution in Rust Belt cities. Since the birds grow a new set of feathers every year, they make excellent measurement tools to determine the levels of pollution in the United States year by year.
"We were surprised by the precision we were able to achieve," DuBay said. "The soot on the birds closely tracks the use of coal over time. During the Great Depression, there's a sharp drop in black carbon on the birds because coal consumption dropped – once we saw that, it clicked."
The researchers noted the amount of soot found in the feathers increased during World War II when coal use ramped up due to the war effort, and then decreased again after the war was over.
In order to analyze the yearly changes in levels of soot, researchers photographed the birds and used the light reflecting off the feathers to measure the sootiness. They then looked to how environmental laws changed to see if there was a correlation.
"The changes in the birds reflect efforts, first at the city level but eventually growing into a national movement, to address the smoke problem," said Carl Fuldner, co-author of the paper. "We are actually able to go back and see how effective certain policy approaches were."
DuBay said the research effectively shows how changes in environmental laws and technology can affect wildlife.
"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," DuBay said. "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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