Because cooler climates also tend to have lower evaporation, they tend to be moister climates, with not only moist air, but also moister (dead) biomass – and we all know wet twigs don’t burn too well…
That’s the explanation scientists of the University of Utah give for the fact that the fossil (in this case charcoal) record of North America shows a decline in forest fires and other wildfires in the period just after 1500.
For people (interested in following science news) living in West Europe the first thing that may come to mind when they hear that date is the Little Ice Age – the somewhat cooler climate timeframe that lasted until approximately 1850. People in North America however may first be inclined to think of Christopher Columbus – and the arrival of Spanish and other European settlers, which (through disease epidemics) led to population declines among Native Americans.
“The drop in fire [after about A.D. 1500] has been linked previously to the population collapse. We’re saying no, there is enough independent evidence that the drop in fire was caused by cooling climate,” says Mitchell Power, an assistant professor of geography at the University of Utah and principal author of a new paleoclimatological study that is due to appear in the journal The Holocene in August.
“The decrease in fire on a very large scale – globally and in the Americas – was controlled by this cooling climate, which began prior to the population collapse, and climate alone is sufficient to explain large scale changes in burning,” says Power.
Of course we’ll first have to wait till somewhere next month to see the actual publication, but we find these interesting quotes, because the suggested relation between climate cooling and wildfire decreases emphasizes the current risk of wildfire increases in an ever warmer world.
Upward extrapolation is supported by fossil evidence of raging wildfires at the end-Permian CO2-induced climate warming – and by other studies that warn of various possible carbon cycle climate feedbacks, with a suggested increase in forest fires (boreal and temperate) and even the new threat of large-scale wildfires in the tundra biome – climate feedbacks as such fires can become significant additional CO2 emitting sources.
© Rolf Schuttenhelm | www.bitsofscience.org