Hi. Maybe this is a dumb question with an obvious answer, but I don’t know/remember enough to know for myself.
Lightning causes forest fires. It’s happening more and more as there are more droughts. If they can put lightning rods on buildings to protect them, could they not build a bunch of lightning rods in forests in susceptible areas? Would the lightning go into the ground and be harmless, or would it somehow still start a fire?
Cost aside, would it help prevent forest fires or no?
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TIA.
In: 6
The main cause of forest fires right now is actually arson and not natural causes.
Lightning ignited fires, but usually lightning is accompanied by rain, that slows down the spread of fire, so it’s not a problem.
Droughts of course exasperate the problem in that it accelerates the spread of fires. Yet there is another problem: overly protected forests. Most forests didn’t see large forest fires in several decades because firefighting has gone from non existent to pretty effective. That means, that fires spread faster and are more difficult to extinguish.
The solution is to simply let some fires burn and keep them away from houses and infrastructure. That way the first fire will be devastating, yet the second and third and all others after that will be slow, small and more easy to fight.
Because forest fires are actually [important](https://www.fire.ca.gov/media/5425/benifitsoffire.pdf) for the health of the overall ecosystems.
These issues with current forest fires, especially in the western USA, are actually partially caused by [preventing too many fires](https://www.nbcnews.com/news/us-news/decades-mismanagement-led-choked-forests-now-it-s-time-clear-n1243599).
Forests typically are ‘cleaned out’ by small fires which burn away dead trees and other biomass. Normally, these fires aren’t very hot (in absolute terms) and live trees tended to survive these fires. Some trees even NEED fires for their seeds to begin to germinate.
Over the years, overly aggressive fire management in the forest and other wildlands led to forests that had too much undergrowth and un-burned biomass. Now, when a fire happens, the fire has so much fuel it is able to ignite even the healthy living trees, causing immense and incredibly destructive fires.
This issue currently isn’t that we need to avoid fires altogether, its that we need ‘healthier’ fires.
Of course, this explanation does not touch on the issues of climate change, loss of groundwater and other sources that mitigate fire severity, nor the trend of building towns/suburbs/residential infrastructure inside highly forested areas (which is the forest-fire equivalent of building a major city like New Orleans/Houston directly in the path of hurricanes).
1. Forest fires help the forest long term
2. it would be impractical to put a trillion lightning rods in our forests.
3. lightning rods wouldnt work anyway because they’d have to be higher than all the trees
To add to the other great answers here, I thought I’d estimate how many lightning rods would be needed to protect a forest.
We can use the *rolling sphere method* to estimate how much protection a single lightning rod gives. This method assumes that as the *leader* of the lightning bolt descends, it’s surrounded by a spherical electric field and will jump to the first suitable object that enters that field. There are simple explanations of this method [here](https://what-if.xkcd.com/16/) and [here](https://www.bondedlightning.com/rolling-sphere-method).
I’m going to assume the sphere has a radius of 45m (150ft), which seems to be the industry standard. That means a lightning rod can protect a circle of forest with radius of 45m (so the protected area is about 6,300 m^(2)).
To get a quick and dirty estimate of how many rods we need per km^(2), I’ll just divide 1 km^(2) by the area protected by each rod. We’d need 160 lighting rods per km^(2).
The total forest area in the US is 3.3 million km^(2) ([source](https://en.wikipedia.org/wiki/Forests_of_the_United_States)). If we want to protect 10% of that, 330,000 km^(2), we’d need 53 million lighting rods.
That’s not only *a lot* of lighting rods, but the places they need to be installed, remote forests, are pretty much worst-case scenario for erecting large steel structures.
It’s a scale problem, for one thing. You’d need more lightning rods than we really have the capcity to build, because you have to build a tower and grounding equipment for each one. A lightning rod really only provides protection in a radius of about 30m (about 2800 m^2).
There are over 3million square km of forest in the US alone. That’s 3,300,000,000,000 square meters. You’d need over a billion lightning rods.
And even then, you wouldn’t prevent forest fires. The western half of North America is pretty dry, and it’s FULL of biomes that rely on regular small fires to maintain the ecology. We’ve spent 100+ years preventing fires and allowing fuel buildup through crappy management practices, so now, by July or August every year, half the continent is basically a powder keg. The lightning just happens to be the match, but once it gets to a certain point, practically anything can start a fire. If it wasn’t lightning strikes, it’d be something else.
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