Adam Michael Erickson 

While radiative forcing and thus land surface temperatures have been shown to positively correlate with fire severity, precipitation, and lightning strike frequency, the effects of human activity on fire regimes remain difficult to disentangle from geophysical drivers given co-variation between these factors. Here, I analyze fire regimes in the 1919-2012 period across Canada and compare national trends to those of a latitudinal and elevational gradient in a region
experiencing exponentially increased anthropogenic activity in recent decades. Located along the Canadian Rocky Mountains, the region is intended to serve as a proxy for future continental conditions under current anthropogenic trajectories. Based on the findings, I argue that, for the first time in millennia, fire regimes in the southern boreal zone have shifted on average from large, lightning-caused fires to frequent, small, human-caused fires adjacent to human transportation corridors. While warming is known to produce more severe fuel conditions, human factors such as frequent fire ignitions, active fire suppression, industrial and recreational activity, and forestry (i.e., stand aging) likely explain the reduction in mean fire size and annual area burned. Here, I provide the first evidence of a southern boreal transition to Anthropocene fire regimes without historical analogue, representing a dramatic departure from the conditions in which these forests evolved. With ~28 Pg carbon stored in Canada’s managed forests and interspecific variation in albedo, these novel fire regimes carry direct implications for the Earth’s climate system.