GR: When it’s warmer, there is greater possibility of fires starting, spreading, and intensifying. As the climate system strives to reach a new equilibrium, droughts, heatwaves, and fires will become more frequent.
As burned areas grow, weeds will spread. As fire frequency increases, fire-tolerant ecosystems dominated by weeds will become persistent. This will occur when there is not enough time between fires for trees to replace the weeds. We’ve already seen this happening in the western U. S. as fire tolerant cheatgrass has replaced much of the sagebrush ecosystem. New hyperactive fire regimes are in the global forecast for nature’s shift to a new equilibrium in the warmer Earth of the Anthropocene. Fires added to farms, domestic livestock, and all the other human impacts will shift the land from forests to weedlands of reduced diversity, stability, and carrying capacity. More about weeds.
The increase in forest fires, seen this summer from North America to the Mediterranean to Siberia, is directly linked to climate change, scientists say. And as the world continues to warm, there will be greater risk for fires on nearly every continent.
“On a single hot, dry day this summer, an astonishing 140 wildfires leapt to life across British Columbia. “Friday, July 7 was just crazy,” says Mike Flannigan, director of the wildland fire partnership at the University of Alberta. A state of emergency was declared. By the end of summer, more than 1,000 fires had been triggered across the Canadian province, burning a record nearly 3 million acres of forest—nearly 10 times the average in British Columbia over the last decade. As the fires got bigger and hotter, even aerial attacks became useless. “It’s like spitting on a campfire,” says Flannigan. “It doesn’t do much other than making a pretty picture for the newspapers.”
“Forest fires are natural. But the number and extent of the fires being seen today are not. These fires are man-made, or at least man-worsened.
“Evidence is becoming more and more overwhelming,” says Flannigan, that climate change is spreading fires around the world. Globally, the length of the fire weather season increased by nearly 19 percent between 1978 and 2013, thanks to longer seasons of warm, dry weather in one-quarter of the planet’s forests. In the western United States, for example, the wildfire season has grown from five months in the 1970s to seven months today.
“The number-crunching now shows an increased risk for fire on nearly every continent, says Flannigan, though most of the work has focused on North America, where there is a larger pot of funding for such research. In the western U.S., where fires ravaged Oregon this summer, the annual burned area has, on average, gone from less than 250,000 acres in 1985 to more than 1.2 million acres in 2015; human-caused climate change has been blamed for doubling the total area burned over that time.
“Similarly, for fire-ravaged British Columbia, an analysis from this July estimates that climate change has made extreme fire events in western Canada 1.5-6 times more likely.
“So how much worse are things set to get? Scientists are getting far better at untangling the relationship between extreme weather and climate change.
“Pinning any specific environmental event on climate change is a tricky business, though the science of weather attribution has grown in leaps and bounds over the past decades. Individual wildfires are still near the bottom of the list of things that can easily be pegged to a changing climate, thanks to all the other factors in the mix. If people break up forests into smaller chunks through logging or agriculture, that can limit the spread of forest fires; on the other hand, some trees burn faster than others (younger trees are greener, so burn slower), and shrubs under a tree canopy can make fire more intense. A particularly rainy year can paradoxically increase fire risk if the rain comes in springtime, by boosting the volume of vegetation available to burn later in the season. Natural weather patterns like El Niño can have a dramatic effect on precipitation, and so on fire.”
“If we have higher temps, we have a greater probability of fire starting, fire spreading, and fire intensifying.”