Bird feathers are especially good at picking up particulate—just think about how effective feather dusters are. When a bird flies through the sky, the same thing happens. Their feathers pick up all the little particles in the air, including black carbon pollutants. If some of those birds eventually end up as specimens in museums, their feathers serve as records of air quality for the year they were taken. Shane DuBay and Carl Fuldner, PhD students at University of Chicago, studied bird specimens from the last 135 years at museums across the American Manufacturing Belt (the Midwest and Great Lakes area). By examining the carbon preserved in the birds’ feathers, Shane and Carl found that air pollution was likely worse during the early American industrial era than previously thought.
Shane is a student in the Committee on Evolutionary Biology while Carl is in Art History. When they first met, Carl and Shane found that they shared a lot of ideas about how the records that field naturalists make (such as photographs or field notes) retain information about past environments. They both felt strongly that this was also the case with specimen collections also, but in less obvious ways. “So, we set out to demonstrate that the severed link between these bird specimens and the historical environments they were taken from could be restored,” explains Shane. “That was the inspiration for the project.”
Not only did this project help contextualize the bird specimens in their historical environments, it also revealed a lot about how pollution levels fluctuated over the past 135 years. Shane and Carl measured a time series of the black carbon (the light-absorbing component of soot) they found on the preserved birds. As the birds flew through sooty skies, their feathers darkened and soiled. Shane and Carl took pictures of the birds’ chests and wings and measured how well they reflected light. Sootier birds reflected less light than ones that flew through cleaner air. Carl and Shane were then able to track the relative changes in feather reflectance year by year. The fact that most bird species moult annually means that the specimens contained soot only from the year which they were collected (as opposed to a lifetime of accumulation). By looking at hundreds of these bird, they were able to estimate temporal trends in black carbon pollution.
They noticed a dip in soot pollution on feathers that coincided with the 1929 Stock Market Crash. During this time, coal consumption dropped leading to a reduction in soot emissions. “When we saw this in our sample, we realized that our method was sensitive enough to really track meaningful changes in atmospheric soot through time,” says Shane.
Through their work, they reconstructed historical levels of soot pollution, filling major historical gaps in the sampling record. Their research allows for quantitative assessment of the efficacy of historical environmental policy and a better understanding of black carbon’s role in climate change. “One question I’ve been tackling in my independent work is how photographs can be used to advance an environmental ethic,” Carl adds. “A vivid photograph of a soot-covered bird from the early 1900s conveys our findings in a concise, visually-powerful way.”
Shane and Carl each brought distinct skill sets to the project, but as it evolved they were both struck by how it pushed them outside of their academic comfort zones toward environmental history and atmospheric science. “The project has been a very rewarding experience because it has been collaborative and genuinely interdisciplinary. It is a historical study, but it also feels urgent and relevant to contemporary discussion around climate and public health,” says Carl.
There are a number of follow up projects Shane and Carl have planned for this research. They would like to expand their sampling to the UK and Western Europe since they are areas with long histories of industrialization. They would like to explore the size and shape of the black carbon particles on the birds. The size and shape determines the particles’ effect on the climate, and little is known about their shapes pre1950. Finally, they are looking into how pollution directly affected the birds. Soot pollution increases respiratory illness and mortality rates in humans and there is no reason not to believe the same thing would happen in other animals. “By understanding our past, we can better prepare for the future,” says Shane. “Atmospheric pollution is still a pressing global issue, but an issue we have dealt with for over a century. Better understanding our past efforts to mitigate soot pollution can help inform our current efforts.”