Forest fires

[kbs2244]

From today’s news page.

http://www.physorg.com/news190561417.html


I remember reading that one of the amusements of the early European inhabits of New York City was boat trips up the Hudson into “Indian Territory” to watch the fires that were set to clear the wood lands.

They would burn for weeks.

[Minimalist]

I have a recollection of someone ( Mann, perhaps?) discussing this very issue.

I'll have to leaf through 1491 to see if I can find it.

[wxsby]

I live in an area in Southern California where the ecology is fire based. There had been large scale annual burning for thousands of years until a few hundred years ago, and much of the native vegetation requires fire to propagate. The common reason given for this is that the fires started naturally, but I find that hard to believe. I've lived here for over twenty years and have seen very few thunder storms, and I can't think of a lot of other natural causes for starting fires. The fact that it did burn annually meant the fires weren't as intense as they are when we have them now. We were at ground zero when the Cedar Fire burned over 3000 homes in San Diego County, and the area had not burned in over 50 years before that. That was only seven years ago and the fuel is ready for another disaster.

There are stories that everything from the desert to the ocean was intentionally burned every year to control the environment. I'm not sure how, but that would be the only reason it would have burned every year.

[Minimalist]

Funny how there is always money to put out fires but never enough to thin the brush before they start, huh?

[Rokcet Scientist]

There had been large scale annual burning for thousands of years until a few hundred years ago, and much of the native vegetation requires fire to propagate. The common reason given for this is that the fires started naturally, but I find that hard to believe. I've lived here for over twenty years and have seen very few thunder storms, and I can't think of a lot of other natural causes for starting fires.

If the climate was different, the vegetation would have been too. Possibly simpler to self-ignite from natural causes?
Also, in many parts of the world 'veld brush' (low growth) is purposefully lit once every few years*, in order to promote fresh grass growth for herd animals.

*like the heather in western Europe, and the undergrowth (bushveld) in South Africa.

[wxsby]

Funny how there is always money to put out fires but never enough to thin the brush before they start, huh?

We ask that question every year.

[wxsby]

in many parts of the world 'veld brush' (low growth) is purposefully lit once every few years*, in order to promote fresh grass growth for herd animals.

]

Most of the native vegetation here is low growth, as long as it burns every year or so. And if it does burn, fresh grass grows quickly. That would make sense.

[wxsby]

If the climate was different, the vegetation would have been too. Possibly simpler to self-ignite from natural causes?

Fall Santa Ana winds... humidity below 5%, hurricane force winds for days, temps in the 100s... how much simpler to ignite could it be, but what would ignite it?

[Rokcet Scientist]

If the climate was different, the vegetation would have been too. Possibly simpler to self-ignite from natural causes?

Fall Santa Ana winds... humidity below 5%, hurricane force winds for days, temps in the 100s... how much simpler to ignite could it be, but what would ignite it?

Sparks and lightning. From dust devils. They create their own electrical system with (sometimes very localized) thunderstorms. Plenty of sparks and lightning flying around.

[Minimalist]

If the climate was different, the vegetation would have been too. Possibly simpler to self-ignite from natural causes?

Fall Santa Ana winds... humidity below 5%, hurricane force winds for days, temps in the 100s... how much simpler to ignite could it be, but what would ignite it?

Usually some idiot with a cigarette.

[wxsby]

Not buying the natural causes...

Usually some idiot with a cigarette.

In twenty plus years here all the fires have been 'manmade'. Arson leads the menu. Cigarettes are second, I think. The Cedar was from a 'lost hunter', trying to start a signal fire so someone could find him. In 75 MPH winds. The Witch fire in 2007 was from power lines blown down in major winds. We have never had a naturally caused fire, much less one every year. Occam says they burned it off because they could for a positive result.

[dannan14]

We have never had a naturally caused fire, much less one every year. Occam says they burned it off because they could for a positive result.

That could be true down south, but in NorCal after a big storm you can look across one valley and see multiple lightning caused fires. i've seen electrical storms in other desests, do they really not happen in SoCal?

[Rokcet Scientist]

Not buying the natural causes...

Usually some idiot with a cigarette.

In twenty plus years here all the fires have been 'manmade'. Arson leads the menu. Cigarettes are second, I think. The Cedar was from a 'lost hunter', trying to start a signal fire so someone could find him. In 75 MPH winds. The Witch fire in 2007 was from power lines blown down in major winds. We have never had a naturally caused fire, much less one every year. Occam says they burned it off because they could for a positive result.

Just because you have never witnessed fire by natural causes doesn't mean it doesn't happen, barry!

Ask the people whose homes burned down because of lightning strike...

[Minimalist]

http://forestfire.nau.edu/lightning.htm

Nationwide, humans cause almost 80% of wildfires, but in the American Southwest, 60% to 70% of forest fires are ignited by lightning. The region leads the nation in the average number of forest fires due to lightning strikes and the number of acres burned by these fires each year (Pyne 2001, p. 6).

Even so, by some estimates, 10% to 25% of all wildfires might be deliberately set. And the number of human-caused fires in the West, intentional or not, is rising because more people are moving into the wildland-urban interface, where private homes border on forests and other public lands.

[wxsby]

http://forestfire.nau.edu/lightning.htm

The map refers to the Southwest as West Texas, New Mexico and Arizona. I have seen some of the most powerful thunderstorms, with the most lightning, in those places. The San Diego area is not included. This is not thunderstorm territory. I have witnessed them in the mountains, but not where I live. I am a ham radio operator, and I have never bothered to put lightning protection on my antenna feeds. No one here does. Lightning is not an issue here. If the evidence is correct, and this area burned annually for a few thousand years, it was not lightning caused... unless the climate was very different. That is a possibility.