At first glance, you might regard a Jamaican cave that has been continuously inhabited by bats for thousands of years as one of the last places to learn how the chemical content of regional air and water have been changing. But for Jules Blais, a biologist with the University of Ottawa, the countless strata of guano deposited there by these animals provide an ideal record of this information.

Blais specializes in gauging the influence of environmental contaminants on the metabolism of various species, using evidence such as bat excrement, or guano. “We can see the history of leaded gasoline,” Blais offers by way of example. “We think we can also see evidence of pollutants from gold mines. The legacy of gold mining in Central America is recorded in here.”

The Jamaican cave work is just the latest in a decade’s worth of similar investigations Blais has conducted with longtime colleague John Smol, a biologist at Queen’s University in Kingston, Ont. Together they have used nitrogen isotopes to answer questions about the role of spawning salmon in carrying polychlorinated biphenyls (PCBs) from the ocean to pristine wilderness settings far inland. The pair has also been able to analyze sediments found along the Arctic coastline where local hunters have carved up their catch at different times over the centuries, using this same isotopic technique to draw inferences about changes in the state of marine mammal populations during that time.

Blais’ and Smol’s collaboration was honoured earlier this year by the Natural Sciences and Engineering Research Council’s Brockhouse Canada Prize for Interdisciplinary Research in Science and Engineering. “We would like to build on the idea of using natural archives to reconstruct past events,” Blais says, noting that the award’s $250,000 research grant will provide the necessary resources to complete a book dedicated to the subject.