Looking back through the history of our world, it is unfortunately easy to spot where humans started to build societies. On the one hand, we have a history of killing things, and as humans trekked across the world, we killed a lot of life forms, and things like the woolly mammoths disappeared in lockstep with our arrival. We also did need uniquely human things like fires, which give off smoke, ash, and other air pollutants. As someone who has lived in snowy places most of my life, I know snow, if nothing else, is good at showcasing pollutants as it collects various bits of auto exhaust, fireplace exhaust, animal biproducts, and other pollutants. It turns out that what I grew up seeing in the snowbanks of Boston can be studied in the “didn’t completely melt” snows of the extreme north and south.

An ice core collected in Iceland contains 4,500 years of data on how fires did and didn’t flare up in the North Atlantic. And here is where I remind you that not all fires are man-made. About 1,100 years ago, according to this ice, fires sharply decreased in number. Researcher Delia Segato explains: The Viking colonisation of Iceland caused one of the first environmental disasters in history and even today, after a millennium, the Icelandic forests have not fully recovered. The Vikings deforested extensively, causing the loss of more than 25% of vegetation in less than a century. The settlers, following the customs of their native lands, used to cut down birch tree forests to collect wood and to remove the shrubs to open grazing lands

So for many centuries, we saw a decrease in smoke pollution in the ice that reflected humanity’s ability to log anything into looking like pasture land. Unfortunately, things have changed in more recent times. Segato goes on to say: In the two most recent centuries, we have found that fires have increased due to climate change and emissions caused by human activity. The results of the study show that regions at extreme latitudes represent one of the first places on Earth where climate change is having the most catastrophic effects. At the end of summer 2020 alone, fires in the Arctic Circle caused the emission of 244 megatons of CO2, exceeding by 35% those recorded in 2019. In these areas it is therefore essential to improve the understanding of climate trends and the history of fires.

This work appears in the journal Climate of the Past.

More Information

Ca’ Foscari University of Venice press release

“Five thousand years of fire history in the high North Atlantic region: natural variability and ancient human forcing,” Delia Segato et al., 2021 July 20, Climate of the Past