A couple of months ago I wrote about a new paper linking warming temperatures and more extreme forest fire danger.

At the time, the paper drew criticism because its data was drawn from the 20th century, when the climate signal in the trend of increasing wildfire might be confounded by fire management policies. Are we having more and larger fires now because it’s a warmer world, or because we’ve so mucked up the forests through fire suppression and overgrazing that they’re now tinderboxes ready to go up?

It’s likely that both variables are involved, but teasing them apart is difficult.

Enter Jennifer Pierce and Grant Meyer (sub. req.), with a paper today in Nature that reaches far back in time to overcome that problem. Using burn debris in alluvial deposits, Pierce and Meyer were able to distinguish and date different fire regime environments. And, no surprise, they found that in the days before our land use practices began altering the system, large, stand-replacing fires were prevalent during warmer climate periods while more frequent but far less destructive surface fires – essentially burning the grass off – were common during cool periods.