[thedoc (OP)]

Fire-fighters were killed in Arizona this week tackling a wildfire that got out of control. But how do blazes like this begin...

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[werttty]

I know that some forest fires due to lightning

[CliffordK]

How accurate is the "80% figure"?  Perhaps it depends on where one is.

There were several large forest fires in Oregon this year.  I believe all of them were caused by lightning.  In particular mid-summer storms with lots of lightening, and very little rainfall. 

The majority of large Fir trees, and other evergreen trees can withstand the occasional forest fire, and it is not uncommon to see ancient trees with old fire scars.  However, it does depend on how hot the fire is.  There are estimates that fires once a decade or so can be healthy for a forest, and I believe the forest service does manage Yellowstone National Park by building small intentional fires.

Anyway, fires like the 2002 Biscuit fire can grow to be truly enormous.  I suppose I'd rather see small fire scars than seeing fires covering hundreds, or perhaps thousands of square miles.