A geologist from the Natural History Museum of Utah has been studying the charcoal found in lakebed sediments around the world. Mitchell Power has discovered that the number of wildfires dropped significantly from about 1400 AD until about 1800. That corresponds with the so-called "Little Ice Age," when tree rings and other evidence shows global temperatures were considerably cooler than they are today.
Power says this evidence also argues against the idea that burning forests for crops dropped off drastically after Europeans came to the Americas and much of the indigenous population was wiped out by disease.
"The loss of human populations around the arrival of the Europeans," Power tells KUER, "did not necessarily answer this question about decreased fire after about 1500 AD. And we saw, in fact, that the amelioration of climate, so climate started to cool much earlier than the arrival of Columbus."
In hot weather, Power says vegetation is more susceptible to fire because of low fuel moisture and humidity and because more convection in the atmosphere leads to thunderstorms and lightning.
He says that cold be a warning for today as global temperatures rise. "I think it's an interesting analogue for what's happening now in the West and in Utah. We're seeing higher temperatures every month than in the previous year, or previous records of any kind. And so it's interesting to think about, 'Well, if it's going to continue to be hotter and drier we should expect to see more fires.'"
Professor Power's study will be published online in the journal The Holocene this month.