<p>There was an interesting paper on this for the United States a couple of years ago:</p>

<p>Balch et al (2017) <a href="https://doi.org/10.1073/pnas.1617394114" rel="nofollow noreferrer">Human-started wildfires expand the fire niche across
the United States</a>, PNAS, doi: 10.1073/pnas.1617394114</p>

<p>They estimate that in the coterminous U.S. human-started events account "for 84% of all wildfires and 44% of total area burned".  There is a marked spatial variation, with lightning-started wildfires occurring mainly in the more sparsely populated western forests.  If you have access, the paper's worth a read, it has lots of interesting figures picking apart the details.</p>

<p><a href="https://i.sstatic.net/Lcz7m.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Lcz7m.png" alt="enter image description here"></a></p>

<p>It's worth noting that there are a number of reasons for human-started wildfires, which are could be classed as accidental, deliberate or careless:</p>

<blockquote>
  <p>Human-started wildfires were caused by a variety of sources, including the US Forest Service-designated categories of equipment use, smoking, campfire, railroad, arson, debris burning, children, fireworks, power line, structure, and miscellaneous fires.</p>
</blockquote>

<p>They also note that their data contains this, perhaps not unsurprising, feature:</p>

<blockquote>
  <p>There was also a notable mark of American culture on the distribution of wildfires, with the peak day of wildfires occurring on July 4th, concurrent with Independence Day fireworks displays (Fig. 2). Indeed, Americans start over twice as many wildfires on July 4th as any other summer day.</p>
</blockquote>

CC BY-SA 4.0
2019-08-08T17:04:53.653Z
We need to find some way of dealing with it. There's nothing we can do about lightning, but we need to find and punish the pyromaniacs responsible. I bet Hitler would soon have had the problem under control if it had happened in Germany. Not everything he did was bad. A pyromaniac burned down the Reischstag in 1933,and he had his head chopped off! Do gooders, bleeding hearts and pioneers of political correctness got frogmarched to a concentration camp.
Michael Walsby
CC BY-SA 4.0
2019-08-09T09:34:34.930Z
@MichaelWalsby Even as a Brit, I think that capital punishment for celebrating Independence Day is a bit much.
Deditos
CC BY-SA 4.0
2019-08-09T09:44:09.327Z
I agree, but I'm just telling you what Hitler would have done with pyromaniacs who started fires deliberately. Those guilty of starting them through carelessness would have got more lenient treatment, but would not have gone unpunished if the fire was a serious one, and especially those fires which caused loss of life.
Michael Walsby
CC BY-SA 4.0
2019-08-07T13:31:08.200Z
2019-08-07T13:31:08.200Z
Deditos
<p>At a very rough estimate, what proportion of wildfires are caused by natural events like lightning? I am absolutely sure that in Europe, where there are often wildfires, the sun is never hot enough to set fire to vegetation directly, though it obviously makes things tinder dry and easily combustible. The broken bottle theory has been disproved. Experiments involving broken glass among highly combustible straw or hay were unsuccessful in causing combustion, though manual focussing of the suns rays with the lens-shaped bottom of a bottle were on rare occasions and with much difficulty successful. Although lightning undoubtedly causes the occasional wildfire, the majority have no connection with lightning. It should also be remembered that lightning is usually accompanied by torrential rain. These fires often start in several places at once, which is stretching the long arm of coincidence a bit too far. </p>

<p>Apart from the very rare instances of volcanos causing wildfires, what other natural causes could there be?
Comparison of wildfire frequency in tinder-dry uninhabited areas, well away from civilisation, versus frequency in or near similar but populated areas should give a good idea of the scale of the problem.  </p>

CC BY-SA 4.0
2019-08-06T01:06:56.653Z
Only the first sentence is the actual question. The following wall of text are various claims, opinions, and thoughts with differing relatedness to the question. Can you please focus and edit your question so it is answerable?
Gimelist
CC BY-SA 4.0
2019-08-06T19:04:33.943Z
This is what I suspected. It's disgraceful that people could do such things. I won't go into a list of all the environmental damage done by wildfires, but the list is long. Perhaps worse, people are often killed by these needless fires, just to entertain a few nut cases.
Michael Walsby
CC BY-SA 4.0
2019-08-06T19:36:31.403Z
Someone in the space station could count the fires which start in areas far from human habitation and compare with similar areas within easy reach of nut cases.
Michael Walsby
CC BY-SA 4.0
2019-08-07T15:04:24.093Z
"... lightning is usually accompanied by torrential rain..."  In the arid western USA, where I was a wildland fire fighter for eight summers, lightning storms are commonly accompanied by very little rain (the regional colloqiualism is "dry lightning").  Even with torrential rain, a lightning-struck tree may smolder internally for a long time only to reignite as conditions dry out.  As a fire lookout, I would remain especially vigilant for up to two weeks following a "wet" lightning episode.
Stu Smith
CC BY-SA 4.0
2019-08-08T00:08:18.730Z
At least one near me in southern California was caused by a lawn mower hitting a rock and throwing off sparks.
mkennedy
CC BY-SA 4.0
2019-08-08T16:47:00.553Z
You might want to review the [Global Fire Atlas](https://earthobservatory.nasa.gov/images/145417/a-new-global-fire-atlas)
Fred
<climate-change><climate><air-pollution><forest><wildfire>
Origin of Serious Wildfires
Michael Walsby
# Origin of Serious Wildfires

(Asked by: username_0 on 2019-08-05)

At a very rough estimate, what proportion of wildfires are caused by natural events like lightning? I am absolutely sure that in Europe, where there are often wildfires, the sun is never hot enough to set fire to vegetation directly, though it obviously makes things tinder dry and easily combustible. The broken bottle theory has been disproved. Experiments involving broken glass among highly combustible straw or hay were unsuccessful in causing combustion, though manual focussing of the suns rays with the lens-shaped bottom of a bottle were on rare occasions and with much difficulty successful. Although lightning undoubtedly causes the occasional wildfire, the majority have no connection with lightning. It should also be remembered that lightning is usually accompanied by torrential rain. These fires often start in several places at once, which is stretching the long arm of coincidence a bit too far.

Apart from the very rare instances of volcanos causing wildfires, what other natural causes could there be?
Comparison of wildfire frequency in tinder-dry uninhabited areas, well away from civilisation, versus frequency in or near similar but populated areas should give a good idea of the scale of the problem.

**Tags:** climate-change, climate, air-pollution, forest, wildfire

> **Comments:**
> **username_1**: Only the first sentence is the actual question. The following wall of text are various claims, opinions, and thoughts with differing relatedness to the question. Can you please focus and edit your question so it is answerable?  
> **username_0**: This is what I suspected. It's disgraceful that people could do such things. I won't go into a list of all the environmental damage done by wildfires, but the list is long. Perhaps worse, people are often killed by these needless fires, just to entertain a few nut cases.  
> **username_0**: Someone in the space station could count the fires which start in areas far from human habitation and compare with similar areas within easy reach of nut cases.  
> **username_2**: "... lightning is usually accompanied by torrential rain..."  In the arid western USA, where I was a wildland fire fighter for eight summers, lightning storms are commonly accompanied by very little rain (the regional colloqiualism is "dry lightning").  Even with torrential rain, a lightning-struck tree may smolder internally for a long time only to reignite as conditions dry out.  As a fire lookout, I would remain especially vigilant for up to two weeks following a "wet" lightning episode.  
> **username_3**: At least one near me in southern California was caused by a lawn mower hitting a rock and throwing off sparks.  
> **username_4**: You might want to review the [Global Fire Atlas](https://earthobservatory.nasa.gov/images/145417/a-new-global-fire-atlas)  

---

## 1 answers

### Answer by username_5 on 2019-08-07. Score: 3

There was an interesting paper on this for the United States a couple of years ago:

Balch et al (2017) [Human-started wildfires expand the fire niche across
the United States](https://doi.org/10.1073/pnas.1617394114), PNAS, doi: 10.1073/pnas.1617394114

They estimate that in the coterminous U.S. human-started events account "for 84% of all wildfires and 44% of total area burned". There is a marked spatial variation, with lightning-started wildfires occurring mainly in the more sparsely populated western forests. If you have access, the paper's worth a read, it has lots of interesting figures picking apart the details.

[![enter image description here](https://i.sstatic.net/Lcz7m.png)](https://i.sstatic.net/Lcz7m.png)

It's worth noting that there are a number of reasons for human-started wildfires, which are could be classed as accidental, deliberate or careless:

> Human-started wildfires were caused by a variety of sources, including the US Forest Service-designated categories of equipment use, smoking, campfire, railroad, arson, debris burning, children, fireworks, power line, structure, and miscellaneous fires.

They also note that their data contains this, perhaps not unsurprising, feature:

> There was also a notable mark of American culture on the distribution of wildfires, with the peak day of wildfires occurring on July 4th, concurrent with Independence Day fireworks displays (Fig. 2). Indeed, Americans start over twice as many wildfires on July 4th as any other summer day.

> **Comments:**
> **username_0**: We need to find some way of dealing with it. There's nothing we can do about lightning, but we need to find and punish the pyromaniacs responsible. I bet Hitler would soon have had the problem under control if it had happened in Germany. Not everything he did was bad. A pyromaniac burned down the Reischstag in 1933,and he had his head chopped off! Do gooders, bleeding hearts and pioneers of political correctness got frogmarched to a concentration camp.  
> **username_5**: @username_0 Even as a Brit, I think that capital punishment for celebrating Independence Day is a bit much.  
> **username_0**: I agree, but I'm just telling you what Hitler would have done with pyromaniacs who started fires deliberately. Those guilty of starting them through carelessness would have got more lenient treatment, but would not have gone unpunished if the fire was a serious one, and especially those fires which caused loss of life.  

---

