Wildfires occur for ages, but they need fuel, heat and oxygen. Now, these are natural disasters, but they often don’t start from natural causes. Climate change, caused and amplified by human-made greenhouse gas emissions, extends the length of the annual fire season. Also, wildfires burn faster, just because there is more fuel to burn.
84 percent of the 1.5 million wildfires reported from 1992 to 2012 in the United States, were caused by humans, while 16 percent were sparked by a lightning strike, according to a 2017 study.
A SPARK CAN CAUSE A WILDFIRE
For a fire to start, it first needs oxygen. That is available in the air, while the fuel is anything that will burn – including grass, trees or people’s houses. The dryer these are, the more easily the fire burns. Last, the heat burns the fuel or dries the area, while the fire spreads. With the proper conditions, those three elements are all it takes to start a wildfire.
In Redding, California, for instance, a spark caused by a mere scrape of a tire rim on the asphalt, started the Carr Fire. But from just a spark to a wildfire, the air must be dry enough and the wind, strong.
“Historically, California burned more than it does now, but at [a] lower intensity and slower. Now, we are seeing fires that are unusual, like the Camp Fire that, at one point, burned through 70,000 acres in a day. We’ve never seen that before,” said Lenya Quinn-Davidson – fire analyst at the University of California.
“Fifty years ago, mid-November was wet. Maybe we would have winds, but it would be too wet to start a fire,” she continued.
California and the whole American West was plagued by raging wildfires in 2018, when some 8.5 million acres burned, the National Interagency Fire Center reported. But they burn faster than ever.
“A source [of heat] hits receptive fuel that’s dry enough to burn,” Quinn-Davidson said.
COMMUNITIES NEAR FORESTS ARE AT GREAT RISK
Wildfires are not new, though they are presently setting a record in California. They have a role in ecosystems, but the present ones are quite different from what nature produces.
Since 1975, the number of lightning-ignited fires gradually increased in the boreal forests of Canada and Alaska, likely due to snow melting earlier and fuel drying, caused by climate change – a 2017 study reports.
Today we understand that fire is a critical factor in the health of ecosystems. But constantly suppressing small fires for the better part of a century, only allowed fuel to build up. So, forests that once had big trees, became denser with brush and small trees, which, combined with the dry conditions and heat, make the perfect fuel for a fire.
The communities that were established at the edge of those forests are now at risk. Yes, people learn to “how to live with fire and design a community in a way that is not so vulnerable,” Quinn-Davidson said. And it seems we need to learn from the mistakes of the past – in preventing climate to get even hotter and be prepared with better, cleaner, greener, urban planning.
The 2018 Climate Assessment says that wildfires will continue to rise in numbers and intensity, as the climate furtherly changes.