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Soot laden Birds Reveal the Extent of Historic Air Pollution

The nature of the air quality in America since the dawn of the industrial age has been largely a matter of conjecture. It was known that the air quality had been dangerously poor in the past. But how do you measure something which no longer exists? A team of researchers realised that birds might provide the answers they were looking for.

Birds Provide Clues to Pollution

Scientists have looked at the bodies of horned skylarks, woodpeckers and sparrows which were collected from inside and outside industrial areas in the early 20th century. They looked at specimens held at museums across the land to gauge the extent to which the birds’ plumage had been covered by soot. Their findings have produced the most complete picture to date of the historic air quality in the industrial areas of the United States. This information enhances our understanding of climate change.

Insights into Climate Change

The soot trapped in the feathers of the songbirds over the past 100 years is causing scientists to revise their records of air pollution. The burning of fossil fuels such as coal filled the air with carbon deposits which resulted in issues with pollution across the industrialised world. Cities became coated in sooty air thanks to the unregulated burning of coal in both homes and factories. The effect of this pollution on humans has been known for decades but scientists are revealing how the soot also contributed to global warming.

When soot is suspended in the air, the carbon absorbs sunlight and increases warming in the atmosphere. When it hits the ground, it increases the rate at which snow and ice melts and has been linked to the loss of ice in the Arctic region.

Analysing the Birds

For the new study, scientists explored the collections of numerous museums to find specimens which they could investigate. They then measured the level of carbon deposits which were trapped in the birds’ feathers. The researchers were able to accurately measure the amount of soot on each bird by photographing them and looking at the amount of light reflected off them.

The scientists were able to analyse over 1,000 birds and the tests showed that black carbon levels peaked in the first decade of the 20th century. It became obvious that the air quality at that time was worse than previously thought. During the Great Depression, the use of coal fell and then boomed once more during World War II. At the conclusion of the war, new fuels ensured that the use of coal went into decline.

The study helps enlighten us as to the role of black carbon in past climate change and by understanding this we can more accurately model future climate scenarios.
Similar research may now be undertaken in Europe. The available resources in the UK boast a longer history and so offer the potential for further revelations.

The Good news

The good news is that the most recent avian specimens were much cleaner than those of previous eras and so they have served to demonstrate that the industrial world has cleaned up its act.


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