As usual, my writing keeps getting overtaken by events. I was working on the next part of my "Preparing for Nuclear War" series but this was further put off when Australia suffered something that was comparable to a nuclear war in its effects - at least in terms of the country's wildlife. I decided to write about this, but before I could post anything a freaking new plague descended on us.
I think it would be a pity to let what I'd written go to waste, so here it is. It's no longer topical, but I suppose it will at least be in time for next bushfire season. Climate Change is not going away.
Comparing the bushfires to a nuclear war
It is instructive to compare the devastation caused by the recent bushfires with that of a nuclear war:
It is instructive to compare the devastation caused by the recent bushfires with that of a nuclear war:
The immediate effects of a nuclear bomb are very similar to that of an intense fire. In comparison to a conventional bomb, a nuclear bomb puts out a lot more heat in relation to blast. With the Hiroshima bomb, about two thirds of the initial casualties were from burns. Modern high-yield nuclear weapons put out even more heat in proportion to blast than the Hiroshima bomb, so would arguably cause an even greater proportion of burns casualties. [Reference]
Yes, the comparison between bushfires and nuclear war breaks down when we consider radioactive fallout. Actually, a bushfire does have hazardous fallout of its own - smoke, ash and so on - and some of it is even radioactive (more on this later), but certainly a nuclear bomb is very much worse in this respect.
Also, in human terms, a nuclear war is going to be much worse than a bushfire which devastates the same area because nuclear bombs are going to be targeted mostly at cities where humans live, whereas a bushfire will mostly destroy the bush where there are many fewer people. But from the point of view of wildlife which lives in the bush the situation is reversed.
So - if we exclude the effects of fallout and concentrate on the actual level of destruction rather than just the human casualties - how do the recent bushfires compare to a nuclear war?
First, we need to define what we mean by a nuclear war. Here are my assumptions:
1) The country launching the attack is Russia.
2) Only long-range "strategic" nuclear weapons are used, so this would include all of their ICMBs (Inter-Continental Ballistic Missiles) and SLBMs (Submarine Launched Ballistic Missiles), but would exclude "Tactical" (i.e. short-range battlefield) nuclear weapons and "gravity bombs" (i.e. bombs dropped from aircraft).
3) We will only consider missiles which are currently fielded and ready to launch. This is an important factor because at any one time most of a country's nuclear arsenal is in storage or is unable to be used at short notice (or at all) for various reasons. The assumption I am making is that retaliation would be launched and that would devastate the attacking country to the extent that it would not be practical for it to bring any of these extra weapons into use.
4) No failures occur and no anti-missile defences exist; each missile that is launched hits its target.
5) Where ambiguity about the yield of a nuclear weapon exists, I have chosen the largest known value.
6) All weapons explode at the optimum height for maximum fire damage. In reality, some weapons would be ground burst - either to guarantee the destruction of a hard target or to generate fallout - and a ground-burst weapon creates much less fire damage.
7) None of the explosions overlap. This is unrealistic; any target worth destroying would probably be targeted by at least two weapons.
My information on Russia's nuclear arsenal comes from the document "Russian nuclear forces, 2019" [Reference: Hans M. Kristensen & Matt Korda (2019) Russian nuclear forces, 2019, Bulletin of the Atomic Scientists, 75:2, 73-84, DOI: 10.1080/00963402.2019.1580891]
The useful information is on Page 74 (page 3 of the PDF).
It say that Russia has 1165 ICBM warheads, but says that "Only about 860 of these warheads are deployed. The rest are in storage for potential loading." There are also 720 SLBM warheads, but also says "At any given time, two thirds of the 10 SSBNs [submarines] are in overhaul and do not carry nuclear weapons, so not all 720 warheads are deployed."
So adding up the available data we get the following warhead count:
444 x 800 kt
88 x 400 kt
552 x 100 kt
16 x 50 kt
This is a total of 1100 nuclear bombs with a combined explosive power of nearly 30,000 Hiroshimas. While this falls far short of the figure of 4500 or so weapons often quoted for the Russian arsenal, it's a more realistic assessment of what might actually be launched, and it's not something that any country would want to be on the receiving end of. Imagine 30 Hiroshima bombs falling on each of a country's thousand biggest cities and towns.
How much area would these burn?
The Nukemap site gives information on the effects of nuclear weapons. Nukemap is not some amateurish or joke site; it was produced by Prof Alex Wellerstein using declassified cold war documents and considerable effort has gone into making it as accurate as possible. Check out this site and see what the effect of a nuclear weapon on your city will be.
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What is relevant to us is the "Thermal Radiation Radius". While obviously there are a lot of variables when it comes to something like this, this area is roughly what would be destroyed by fire. This seems to be quite a good approximation; Nukemap says the area within the Thermal Radiation Radius of a Hiroshima-sized (15 kt) bomb is 10.7 square km. The actual area of the firestorm in Hiroshima was said to be "about 11" square km. It's worth noting that Hiroshima had a high proportion of wooden houses and was particularly vulnerable to fire damage, so this most likely overestimates the amount of fire damage that would be caused.
Combining the data from Nukemap with the warhead sizes and numbers gives us:
| Bomb Size | No. of bombs | Area Burned per bomb | Total Area Burned |
|---|---|---|---|
| 800 kt | 444 | 38,400 ha | 17,049,600 ha |
| 400 kt | 88 | 20,800 ha | 1,830,400 ha |
| 100 kt | 552 | 6,030 ha | 3,318,560 ha |
| 50 kt | 16 | 3,220 ha | 51,520 ha |
| Total | 22,260,080 ha | ||
Comparing this to the bushfires:
The area of bushland burned by the bushfires has been estimated at 18.6 million hectares.
This is 83% of the (very generous) figure I calculated for an all-out nuclear war.
So, while the human cost of the bushfires has been relatively little, from the point of view of the wildlife in the bush it has been pretty much the equivalent of a full-on nuclear war. And the death toll of wildlife - estimated at over a billion animals - certainly bears this out.
What was that about radioactive fallout from a bushfire?
There is reason to believe that bushfire smoke and ash contains more than just trace quantities of radioactive material. Here's my reasoning:
There is a certain amount of uranium-238 in the earth's crust. This radioactive element decays through a number of other radioactive isotopes until it ultimately ends up as stable lead. This sequence of isotopes is known as the Uranium decay chain.
For the most part, the isotopes in this decay chain stay in the ground, however one isotope - the inert gas radon-222 - is an exception. Because it is inert, it isn't bound chemically to the ore body in which it is formed, and because it is a gas, it's free to seep out of pores in the ground into the environment.
Mostly, the level of radon in the environment is very low, but it can potentially be a hazard in poorly ventilated houses in some areas.
Anyway, radon-222 has a half-life of about 3.8 days and most of its daughter products have even shorter half-lives - with the big exception of lead-210, which has a half-life of about 22 years. Lead-210 decays via bismuth-210 to polonium-210, and then finally to stable lead-206.
Lead-210 and bismuth-210 aren't much of a hazard but polonium-210 is very nasty stuff. It's a strong alpha emitter and dangerous if breathed in or ingested. If the name sounds familiar this is because it was the substance used to assassinate Soviet defector Alexander Litvinenko.
So what we have is radon seeping out of the ground, dispersing in the air and decaying quickly to lead-210, which then settles out to accumulate in the soil, on foliage and so forth. This lead-210 continually generates polonium-210 as it decays.
This might sound like bad news and we're all going to be poisoned when we eat our fruit and vegetables, but the quantities of these isotopes are very small indeed. Even an animal which consumes large amounts of plant matter is ingesting such a tiny amount of polonium-210 that it will suffer no measurable harm (that I am aware of) from this source.
However, polonium-210 on foliage can be problem in some cases. Apparently, smokers get a significant dose of radiation from polonium-210 on tobacco leaves, and it appears likely that a portion of the lung cancers suffered by smokers is attributable to this cause.
So now the problem with bushfires becomes apparent: millions of tonnes of foliage gets burnt. Its smoke is breathed in by people (and animals, who don't have the luxury of smoke masks) and its ash falls into creeks and water supplies. Depending on what ends up where, the lead-210 and polonium-210 - which previous existed at harmless levels through thousands of hectares of forest - might end up concentrated to uncomfortable levels in places where it's not wanted, including in people's lungs.
Is this an actual problem in practice?
I don't think anyone has studied this effect with regard to the recent Australian bushfires, however I have turned up a 2011 conference paper from the Technical University of Lisbon: "Vegetation fires and release of radioactivity into the air".
[Reference: Fernando Carvalho, João Oliveira & Margarida Malta (2011), DOI: 10.2495/EHR110011 Conference: ENVIRONMENTAL HEALTH AND BIOMEDICINE 2011, Volume: 15]
This tells us:
"Concentrations of both radionuclides [lead-210 and polonium-210] in the smoke samples increased in average by a factor of about 100 compared to the reference sample. Moreover, in all these smoke samples the 210Po concentrations were systematically higher than those of 210Pb, with 210Po/210Pb ratios up to 12."And that:
"The inhalation exposure to the smoke from vegetation fire over a one day may represent for a fireman a 210Po inhalation about 80 times higher than a cigarette smoker and about 4000 times higher than inhalation of atmospheric background 210Po by a member of the public."So this is not a problem which can be dismissed out of hand.
I believe it would most likely be a relatively small issue compared to the toxic chemicals and particulate matter in smoke, but could still contribute a few extra lung cancer deaths and it's something that would be worth studying further.
Probably not anything specific.
I don't believe a hand-held Geiger counter will help you detect if there's a problem. The radioisotopes involved have relatively weak gamma emissions and will exist in relatively low concentrations. Maybe you could pick something up with an alpha-sensitive Geiger counter, but drawing any useful conclusions from this would be very difficult.
A smoke mask which filters out the toxic chemicals in bushfire smoke will also deal with the radioactive stuff, so if you have a mask you probably don't need to be concerned. And if you don't have a mask you're at a greater risk from the other components in smoke anyway.
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