An analysis of old bird fossils, that also seem to be dusty or dirty doesn’t really seem like a good indicator of how air pollution levels have evolved. But a new study from a team of University of Chicago graduates comes to contradict this.
The researchers, Carl Fuldner and Shane DuBay, analyzed over 1,000 bird specimens collected by US museums over the last 135 years. All of the fossils where the remains of the Eremophila alpestris or the horned lark. They looked to quantify and determine the effects of airborne soot in the US Rust Belt cities, including Chicago, Detroit, and Pittsburgh.
The team did so by calculating the amount of soot that still remained on the feathers of the larks. This is a trace of the black carbon that has been floating in the air over time.
The Relation Between Larks and Soot
Some likened the analyzed specimens to air filters as soot was noted to accumulate and store in their wings similar to dust n feather duster. Horned larks were the perfect study candidates as this species is known to change its plumage annual.
As these molt and grow a new set of feathers every year, the soot collected on them can be longer than that.
“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, says DuBay.
According to the study results, black carbon levels matched the nation’s coal consumption up until around the mid-20th century. Following this point, although the coal use increased, the black carbon levels started and are still going down.
The research team then determined that this latter is the effect of an improvement in the burning efficiency, rather than in the coal emissions control.
Based on their results, the scientists believe that following the evolution of atmospheric black carbon might help researchers better study the changing climate and global warming.
Also, DuBay and Fulder consider that their study also points out the importance of museum collections and their scientific and research importance.
A paper with the detailed study findings is available in the journal Proceedings of the National Academy of Sciences.
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