Wildfire questions answered

Wildfires growing deadlier, more destructive

By Leah Asmelash, CNN
Copyright 2019 CNN

(CNN) - Firefighters in California are battling over a dozen wildfires that have displaced thousands of people and left over a million without power.

Wildfires are growing deadlier and more destructive each year. For those outside of the area who might be unfamiliar with the phenomenon, here's everything you need to know about wildfires.

How do wildfires start?

There's no single answer.

Most wildfires are actually man-made -- 84%, according to a NASA study. It doesn't take much: a campfire, a tossed cigarette or even a firework can spark a massive blaze. Those Amazon fires a few months ago? Many believe they were lit by cattle ranchers and loggers who wanted to clear the land for use.

Remember that old Smokey Bear saying, "Only you can prevent wildfires"? He has a point.

But human carelessness isn't the only thing causing wildfires.

California's largest public utility, Pacific Gas & Electric, might be in part to blame. In 2017 alone, PG&E equipment caused 17 fires, often after branches of falling trees hit power lines, according to state fire officials.

In some places, a falling branch may not be a big deal. But in California, where the land is so dry and the winds so strong, fires caused like this can spread with astonishing speed.

That's exactly what happened in last autumn's Camp Fire in Northern California. It left 85 people dead and thousands of structures destroyed. It was the deadliest blaze in state history, and it was caused by PG&E equipment.

Why do they always seem to happen in California?

More wildfires actually occur in the eastern part of the U.S., but wildfires in the West tend to be larger and more destructive, according to data compiled by the Congressional Research Service.

Here are the numbers to put it in perspective. Nearly 36,200 fires burned 1.7 million acres in the East in 2018. In the West, just 22,000 wildfires burned more than 7 million acres.

So even though wildfires happen in the East, we don't hear nearly as much about them because they aren't as devastating as they are in the West.

What makes California unique is a combination of factors. The air is already dry. On top of that, there are the Santa Ana winds, a weather event where high pressure builds over the western U.S., forcing air over California's deserts. It all results in super strong winds combined with low humidity, allowing wildfires to spread rapidly.

Texas actually had the most wildfires out of all the states in 2018 -- 10,541, according to the Insurance Information Institute, which pulled data from the National Interagency Fire Center. California, which came in second place, had 8,054 wildfires.

But the differences in damage are striking. Despite having fewer fires, California's flames burned more than 1.8 million acres, while Texas' affected 569,811 acres, according to the insurance institute.

For comparison, Nevada only saw 649 wildfires in 2018 -- just a fraction of what California and Texas experienced. But those flames were responsible for over a million acres burned.

How many wildfires happen every year?

In 2018, there were around 58,100 fires that burned 8.8 million acres in the U.S., according to the Congressional Research Service.

The number of wildfires has been decreasing slightly over the last 30 years, whereas the number of acres burned is increasing slightly, according to the research service's report.

Is climate change to blame?

In a nutshell, climate change creates drier air and drier vegetation.

So even though it doesn't directly cause fires, it does help create conditions conducive to feeding them -- and that contributes to more extreme fire events, said CNN meteorologist Brandon Miller.

In its fourth climate change assessment, issued in August of last year, California reported that the state's forests will become more vulnerable to wildfires because of climate change.

And the assessment states that, if greenhouse gas emissions continue to rise, by 2100 extreme wildfires will occur more often -- and the average area burned statewide will jump by 77%.

CNN's Madeleine Ayer, Scott Glover, AJ Willingham and Ralph Ellis contributed to this report.

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