Scientists have long established the link between low snowpack years and wildfire seasons that start earlier and burn more acres.
But a new study out of Western Colorado University found that those fires are also more likely to be “high severity fires.”
“When you've got a winter with a really low snowpack that's not holding much water as snow, the subsequent fire season tends to have more area that burns at high severity,” said lead author Jared Balik. “That correlation is much stronger than we would have hypothesized it to be.”
Balik said low severity fires are the kind forest managers try to achieve with prescribed burns, igniting forested areas during shoulder seasons to clear out excess fuels like dead tree limbs.
“If you have a high severity fire though, those living trees can be killed, and the seed source that would propagate the next generation of that forest would also be consumed by the fire,” Balik said.
Those highly destructive fires can transform a forest to a grassland or shrubland, the study notes. In addition to lost habitat, those landscapes also store less carbon dioxide and burn more easily than forests.
The timing of the paper’s release during Colorado’s lowest snowpack year on record was coincidental, but Balik said the table has been set for a highly destructive fire year.
“Those low snow winters, like the one we just went through, really precondition our forests for some of the most damaging wildfires,” Balik said.
Multiple fires have already broken out across Colorado this spring, with the 24 fire burning more than 7,300 acres near Colorado Springs. Denver was recently blanketed with smoke from historically large fires in Nebraska, burning more than 800,000 acres.
Balik emphasized that this summer’s fire season is still to be determined. A rainy spring or a strong monsoon season could help, and the vast majority of wildfires are started by humans and are preventable.
“If you don't get the ignitions at the right time and place, you're not going to have a catastrophic wildfire season,” Balik said. “So if we can act responsibly when we're out on our public lands recreating, that could help avert a lot of catastrophic fire.”
The study suggests that forest managers take advantage of high snowpack years to do as many prescribed burns as possible, since those will likely remain low severity fires.
Climate change is driving long-term snowpack decline, and Balik said the effect is most pronounced in Colorado River Basin states.
But regional variations from the El Niño-Southern Oscillation cycle should still bring good snow years.
“Here in the southwest, El Niño tends to bring wetter conditions that might reduce fire severity. But at the same time, El Niño brings drier conditions to the northwest that could increase fire severity there, and then the La Niña phase is the opposite,” Balik said.
