How do the California fires start?

Are humans causing it? OR do fires just spontaneously occur somehow? All these fires we hear about, has anybody been held accountable for them?

Some are careless campfires or cigarettes. Some are caused by lightning. The last I heard, the current Paradise fire may have been caused by sparks from a broken electrical transmission line. California Power (I don’t recall the exact name) said it was going to shut down lines due to high winds to prevent such, but then did not.

More than once it’s been Pacific Gas & Electric neglecting proper safety and maintenance.

theres been many reasons for some of the fires …… from intentional arson to a campfire not put out or cigarette or pipe sparks or being tossed down while still hot or someone with an ax or saw creating the right amount of sparks…

hell one year most of riverside ca burned down because pf some guy didn’t listen to the city ban on power tools mows his yard hit a rock and it started a fire

another time it was a lit joint someone hid when the rangers came by

mother nature does her part with electrical storms and rockslides and critters playing with powerlines

And yes if your at fault the state will take you to the cleaners even if your not criminally liable and if you are they throw lengthy stays in jail too

I read of one case where a fire was started by a flat tire on a camp trailer. The steel rim riding on the road was throwing off sparks.

Lots of ways to start fires. That isn’t the important part. The important part is stopping them.

Note that while it is inevitable that little fires start, it is not at all inevitable that these little fires turn into massive ones. For example when you immediately put all the little fires out a massive amount of dead wood gradually builds up–so when this pile catches fire and there are massive winds you end up with massive fires–frequent controlled burns are the alternative. The state government could require substantial firebreaks between urban areas and forests. The state government could require tile roofs on houses so they don’t immediately catch fire.


I was recently in the Sequoia NP visitor center, where displayed is a cross section of a giant redwood tree. These trees are notably compatible with fire - unsurprising in a plant that can live over 3000 years. The section on display is something like 1000 years old and shows many instances of growth in response to minor fire damage. On average, this tree coped with a significant fire once every 13 years. Essentially all of those would have been caused naturally - mostly by lightning.

In 13 years - or even some multiple of that - the amount of growth available for a fire to consume is limited, so the natural fires are rarely intense. When humans show up and build structures (which rarely exhibit even a small fraction of a sequoia’s fire tolerance) they tend to strongly favor the idea of extinguishing fires when possible. This is an effective way to have less frequent and much more intense and damaging fires.

And the San Ana winds themselves are probably the number one way that a small fire which might be contained quickly spreads. These out-of-control fires only happen during Santa Ana conditions.

Just read that humans cause 84% of all wildfires. That’s both deliberate and inadvertent.

That’s a misleading statistic because acreage burned by lightening strike fires is higher than human caused. From an NFPA source:

Here’s an acres burned vs numbers comparison:

Many human caused fires are very small fires that are quickly put out, partially because they are near human habitation, so they are reported and dealt with shortly after they start. Lightning caused fires often occur in remote areas, and are not noticed until they produce a significant smoke plume. If they aren’t likely to come near human habitation, the fire services may just let them burn until they go out on their own.

Of course, the ones that make the news because they destroy a lot of property and take human lives are more likely to have been human started.

And yes, we’ve buggered up the natural fire ecology in a lot of places and let deadwood / underbrush growth build up. In untampered forests, wildfires often don’t burn as hot, and don’t crown. They take out all the excess clutter in the understory, the mature trees survive, and a new growth cycle can occur.

And in CA, we’ve got too many groves of non-native eucalyptus near human habitation. 200 foot tall tiki torches.

When we were living in Carson City there was a ridge between our neighborhood and the city proper, across a small valley. One summer a lightning strike ignited a fire at the very top of the ridge, We watched the smoke thicken and a growing black patch for about 45 minutes when a fire bomber arrived. It took two passes along the length of the ridge, then came back in earnest to drop its load. No more smoke and all the black was now pink. About an hour later a green forest service firetruck stopped and a half-dozen firefighters climbed out and hiked to the top of the ridge to overhaul the remains.

Total burned area, maybe half an acre.

Another piece of evidence for completely naturally-caused fires is species like the lodgepole pine. They’re so adapted to quickly colonizing recently-burned areas that they literally can’t reproduce without fire: The pinecones are sealed shut with a resin that only releases once the temperature gets hot enough. Such a species couldn’t have possibly evolved without natural fires at least every few decades or so.

It’s also worth mentioning that humans used fire for a very long time before we learned to make it ourselves. Someone would get a burning piece of wood from a naturally-started fire, use that to start their own fire, save some embers from that fire for starting the next one, and so on, for generations on end. But we couldn’t have done that if there weren’t any natural fires to start with.

That’s also a misleading statistic. It’s looking at the forest as a resource rather than an ecosystem. One in which, as you point out, fire is a natural part. So who cares if a lot of remote acreage burns?

The answer is these people as well as logging companies. And unfortunately, much of the Forest Service. Call it a fire-industrial complex.

The real answer to wildfires is twofold: 1) modify the urban-forest interface so that fires in the wild will not move into the towns. 2) Let the wildfires burn themselves out.

People do not like #1 because it means thinning trees and removing brush near their houses. That’s a lot of work. They also have to modify their houses so that firebrands (burning bits of trees blown in the wind) do not set them on fire. That’s potentially expensive and may uglify the house.

But if we do #2, it means a lot less money spent on fire suppression. The benefits to the forest ecology will be great. Fire will eventually return it to its natural state and we won’t have all those fire suppression chemicals poluting the waterways.

Pacific Gas & Electric is usually ordered to pay home owners for burned homes when it’s proven that their wires caused the fires. So PG&E wants to pass on the fines to their customers, and the state has said no, they can’t do that. So PG&E has now taken to turning off the power to their customers in areas where there are high winds.

So these fires burns hundreds and thousands of acres even with all of the modern firefighting equipment we have. I’m curious what happened before such equipment existed. The fires must have just burn thousands and even millions of acres unabated before dying out naturally, right? Are there any records of massive fires like that?

As noted above, when active firefighting wasn’t happening, fires burned regularly, keeping the amount of accumulated fuel low, which tends to significantly limit the extent and severity of the next fire. *

For a good chance of truly damaging fires, one thing that helps is a lot of active fire suppression.

  • This is an oversimplification. Over thousands of years, occasional long periods of cooler, wetter weather would have produced few fires and much growth. At some point this would end with an extensive fire.

I recall reading years ago a quote from some firefighter who said the way to fight a forest fire is to “pour money on it until it goes out.”

There were a couple very large widfires in Tillamook County, Oregon during the 1930s that gave a lot of impetus to the current practice of suppressing wildfilres. They were called the Tillamook Burn.

I understand they also gave the Japanese the idea to burn forests in WWII. They first tried with a float plane launched from a submarine that dropped bombs near Brookings, Oregon and when that didn’t work, balloon bombs

You don’t need to look very far.

Australia’s worst fires (probably the world’s) were the Black Saturday fires in February 2009 when even modern equipment and organisation was overwhelmed by the combination of 46C, 100km/hr winds on areas under prolonged drought with up to 400 fires started by Power lines, Arson, Lightning and Machinery often converging such as the most devastating blaze which destroyed the Kinglake Marysville townships. These fires burned about 1,1million acres.

The Black Friday fires in January 1939 burnt nearly five million acres through the Victorian Alps at a time when there was no organised fire fighters and equipment wasn’t much more than beating flames with a damped hessian bag.