Mitchell Power, of the University of Utah and Natural History Museum of Utah, pulls a sediment core out of Spring Lake near Delta, Utah. The sediment core showed a reduction in charcoal – and thus fire – in the area during the Little Ice Age, a time of global cooling that began sometime between that A.D. 1200s and 1500s and ended in the early 1800s. A new study led by Powers suggests the Little Ice Age led to a worldwide reduction in fires after 1500, and that reduction was not caused by decimation of New Word populations by European diseases in the wake of Columbus. (Credit: University of Utah.)
n the years after Columbus’ voyage, burning of New World forests and fields diminished significantly — a phenomenon some have attributed to decimation of native populations by European diseases. But a new University of Utah-led study suggests global cooling resulted in fewer fires because both preceded Columbus in many regions worldwide.
“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 the study’s principal author, Mitchell Power, an assistant professor of geography at the University of Utah.
“The implication is that climate is a large-scale driver of fire. That’s a key finding. Climate is driving fire on global and continental scales,” says Power, who also is curator of the Garrett Herbarium at the Natural History Museum of Utah, which is part of the University of Utah.
The new study analyzed worldwide charcoal samples spanning 2,000 years. It will be published online during August in the journal The Holocene, which is the name of the geological epoch covering roughly the last 11,500 years of Earth’s history. It was funded by the National Science Foundation and the Natural History Museum of Utah.
The study deals with the Little Ice Age, a period when Earth’s climate cooled, causing New York Harbor to freeze over in 1780, among other effects. Estimates of when the Little Ice Age started range from the 1200s to the 1500s. It ended in the early 1800s. Possible causes include some combination of increased dust from volcanic eruptions, decreased solar activity, and changes in circulation of the ocean and atmosphere.
“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.
“In a cooler atmosphere, you tend to get reduced convection, so you get reduced thunderstorms and ignition from lightning,” he says. “Cooler climate also tends to maintain high levels of fuel moisture and soil moisture.”
Today, warming climate and drought have been tied to increasing fires in the U.S. West and elsewhere. “In a world where climate is rapidly changing we need to pay more attention to this relationship between climate and fire,” Power says