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In my world, I'd like to place a region of permanent forest fire, but I'm having trouble coming up with the minute details of the biome.

For example, my first idea was that it started when a lush, humid forest was exposed to a volcanic eruption, followed by a permanent but slow lava flow, lasting long enough that some plants have adapted and evolved into flora that relies on the constant fire and is itself so slow to burn it can outgrow whatever is lost to the fire.But how plausible is that, biologically speaking?

What is a better approach to creating a permanently burning forest?

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    $\begingroup$ This has been done in fiction: en.wikipedia.org/wiki/The_Player_of_Games $\endgroup$
    – Humphrey
    Sep 27, 2021 at 11:31
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    $\begingroup$ The problem with this idea is that burning happens at the edge of the forest and a short distance away, the plants have a very different environment. That reduces the opportunity for evolving something that thrives in fire. If you think instead of pulses of lava instead of permanent, you can have an environment where evolution can happen. Have plants that quickly break down the cooled lava and grow. $\endgroup$
    – David R
    Sep 27, 2021 at 14:05
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    $\begingroup$ @DavidR reminds me of redwood trees, which evolved to survive forest fires so they can thrive off the nutrients left afterwards. $\endgroup$
    – Drake P
    Sep 28, 2021 at 0:54
  • $\begingroup$ Do you need just fire or you need burning trees? Because fire can come from natural or swamp gases, or from underground fires of coal, or from petroleum leaks, and exist separately from trees (who maybe even got adapted to the extent of not catching fire). $\endgroup$
    – Anixx
    Sep 29, 2021 at 14:54
  • $\begingroup$ Closed loop burning path - miles or tens or hundregd of miles long. Fire burns as a hot face at slow rate. Plant growth is rapid and fertilised by fire results - maybe nitrogen release in ash plus other sources. Something like hemp with a very rapid regrow rate. Fire takes maybe months to circle the burn track. With a burn rate of say 1 metre per hour it travels less than 1 kilometre per month. A 10 km loop should be very adequate. $\endgroup$ Sep 30, 2021 at 11:49

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Yes there is a better approach

Gas pockets feeding the fire...

https://en.wikipedia.org/wiki/Darvaza_gas_crater#/media/File:Darvasa_gas_crater_panorama.jpg

...or underground coal seam fires.

https://www.globalforestwatch.org/blog/fires/embers-under-the-earth-the-surprising-world-of-coal-seam-fires/

The volcano essentially did a naturally occurring version of fracking, creating channels to the surface for gas, while land slides exposed coal seams, in some instances laying the coal bare on the surface.

These fires ebb and flow with the seasons, especially effective if they are not the four seasons we have on the temperate parts of the Earth (Winter, Spring, Summer, Fall) but instead Wet and Dry seasons like in the tropics.

The biology would have to...

  1. Grow fast
  2. Spread Effectively
  3. Survive Scorching

Vines and brush — where the roots go deep — would work, the plants survive having the surface parts scorched off because when the water comes, the roots shoot and grow new surface parts and send vines in all directions.

https://tallcloverfarm.com/3547/brambles-gone-wild-how-to-remove-blackberries

Blackberries are infamous for forming brambles and spreading quickly


So, to summarize:

  • The fires are fed by subsurface sources, like gas and coal, not by "new" biomass
  • The biology does not so much "adapt" to the fires as it is just very good at spreading and "ignoring" the fires by hiding underground.
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    $\begingroup$ I love this answer, especially the idea of using vines and bushes rather than trees. Who says a forest fire must involve trees? I've helped neighbors clean out bushes and vines that were three feet taller than I am. That's a forest to me! $\endgroup$ Sep 27, 2021 at 11:11
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    $\begingroup$ I like the idea you put forward! Let's see if it can be developed... Currently I'm thinking of combining it with Ash's answer (to a less extreme degree). $\endgroup$ Sep 27, 2021 at 11:29
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    $\begingroup$ There are plenty of places on Earth where the seasons are more like "wet and dry" than spring, summer, winter, and fall. $\endgroup$ Sep 27, 2021 at 19:04
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    $\begingroup$ TIL that "blackberry" and "bramble" are not synonyms. $\endgroup$
    – Gh0stFish
    Sep 27, 2021 at 19:45
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    $\begingroup$ Uhhh. Excellent for a horror version. Let's say at the end of the rain season someone lands in this biome thinking it looks lovely lush, but the plants are weirdly low in height... After a couple of days hiking, they awaken at night to a deafening rumble, the horizon glowing in an eerie orange... 😱 $\endgroup$
    – jan.sende
    Sep 28, 2021 at 0:15
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Quite a few plants - mostly trees - have evolved to require fire to germinate! This seems like the seed of what you might need - combined with a geography that's appropriate.

Annual fires are common in several areas; but what makes them not permanent is the weather cycles. This could possibly change, though, and become permanent in a way - if your geography allows the fire to "travel".

Imagine a Pangea type world, a single large continent taking up 30% of the surface area of the globe, say. If that Pangaea is ringed by forest, and if the weather patterns comply, it's possible that you could have a travelling fire, which, say, is on the east from March to June, the north from June to September (northern summer), the west from September to December, and the south from December to March (southern summer). (West/East could easily switch, of course.)

The fire could literally travel in that way, ringing the globe every year. Then, cultures would possibly come up that would worship the "renewing fire", have rituals based on it, etc.

I'm not sure what you'd need for the weather to work out this way (you'd need the rainy season to not coincide with the fire, but to coincide with the end of the fire, for example), so that part might be a bit handwavy - but it seems like a possibility, if you're not going into meteological science fiction, at least!

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    $\begingroup$ What makes them not permanent is really fuel consumption, not weather. The fire will only be actively burning around the edges, where there's new fuel. Even if you have a travelling fire in a grassland (with fuel like cheatgrass, that grows rapidly, then dies) any particular spot will only burn for a few minutes. $\endgroup$
    – jamesqf
    Sep 27, 2021 at 18:28
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    $\begingroup$ California (and Australia) are evidence that it's definitely possible to have effectively permanent fires - fires that start in summer have tended to last until the rainy season. Hence, weather. $\endgroup$
    – Joe
    Sep 27, 2021 at 18:31
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    $\begingroup$ From my understanding, it's common here to present solutions that are close to the requested idea, but more practical - it may well be that the world-builder can use this for their needs and the practicality suits. If not, that's fine :) $\endgroup$
    – Joe
    Sep 28, 2021 at 5:52
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    $\begingroup$ @jamesqf I think that OP does not require the fire to be in the same spot all the time. Citing the question "[the fire is] so slow to burn [that the plants] can outgrow whatever is lost to the fire" - I guess it fits Joe's answer! $\endgroup$
    – ciamej
    Sep 28, 2021 at 21:44
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    $\begingroup$ In other words, the fire burns the plants, goes away, the plants regrow, the fire slowly returns and the process repeats. Nowhere it is mentioned that the plants grow directly in the fire. Quite the opposite, the plants burn in the fire, and can regrow only when the fire is temporarily not here. $\endgroup$
    – ciamej
    Sep 28, 2021 at 21:57
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t started when a lush, humid forest was exposed to a volcanic eruption, followed by a permanent but slow lava flow, lasting long enough that some plants have adapted and evolved into flora that relies on the constant fire and is itself so slow to burn it can outgrow whatever is lost to the fire.

I don't think that can work. Evolution for something to adapt to those conditions would take several generations, even assuming an annual reproduction cycle for something like grass that would take decades or centuries.

Over that time span a lava flow would involve volumes so huge that it would annihilate any volume organically produced in the same time. And don't forget that, though volcanic soil is fertile, it cannot straightforwardly grow anything on it without some weathering.

Weathering requires time to happen and, most importantly, exposure to weathering agents, which is going to be difficult or impossible with new lava flowing on the old one.

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It's science-based.

But how plausible is that, biologically speaking?

Nope, for each additional 10°C temperature, the speed of chemical reaction roughly doubles. Between, say, 40°C ambient for normal life to a 600°C for a puny fire temperature, you have 256 difference in the chemical reaction speed**. There's too much of a difference for the life forms to be based on biochemistries close enough to evolve one from the other.

** Citation Raising the reaction temperature by 10 °C can double or triple the reaction rate. This is due to an increase in the number of particles that have the minimum energy required. The reaction rate decreases with a decrease in temperature.

Is there a better approach to creating a permanently burning forest ?

Your only chance, by direct evolution in hot conditions.

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    $\begingroup$ And the problem is worse than that, with the exception of the carbonatites lava flows are 1000°C or more. $\endgroup$
    – Ash
    Sep 27, 2021 at 7:41
  • $\begingroup$ Let's see if I understand your answer: You are proposing that, to create a permanently burning forest, flora that evolved in hot conditions be (artificially) transplanted into a region with permanent lava flows and supported until it is able to sustain itself? $\endgroup$ Sep 27, 2021 at 8:02
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    $\begingroup$ @BurnytheDinosaur nope. Keep your lava flowing for billion of years and let some totally different chemistry evolve a specific life to the energy gradients of the area. $\endgroup$ Sep 27, 2021 at 8:07
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    $\begingroup$ High temperatures are problematic for life not because biochemical reactions happen too fast, but rather because the cellular machinery does not survive high temperatures. Increasing a human's body temperature to 47C won't double the speed of reactions, it'll grind them to a halt as the necessary proteins and enzymes denature and become useless. $\endgroup$ Sep 27, 2021 at 19:58
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    $\begingroup$ @NuclearHoagie maybe I should have been clearer. The speed of the reaction is a measure of average energy available for the substance molecules to engage in reactions. Of course, with such a notable increase in this energy, other reaction will become possible and more favorable, with a result of a complete change between the two biochemistries. You can't have free water to solve and carry the molecules between cells at 600C and normal atmospheric pressure - a lot of "normal" biochemistry will simply not happen even at only 20C increase in the reaction temp, much less a 500+ one. $\endgroup$ Sep 28, 2021 at 2:05
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You can't have traditional trees they're too slow you need something that grows far faster, probably faster than Bamboo or even Kudzu, something with a growth rate in the 10s of metres a day range, more importantly 10s of kilograms per day. I don't think osmosis allows for absorbing, moving and just chemically processing that much material but lets go with it. What is this plant going to be like:

  • It will have a metabolic focus on producing thick porous bark that starts with a high water content and dries and burns and crumbles off while being replaced continuously. It will be the bark rather than the stems of the plant that smolder continuously.

  • The tissues of this plant are going to be high in silica and chromium as flame retardants.

  • It's roots are going to be deep and extensive and exude acids to mobilise growth nutrients, these root adaptations exist individually in nature but not in any one plant that I know of.

All of these adaptions do exist in nature; Oak trees survive grass fires in meadows by having a thick spongy bark. Willows have high silica in their wood making it slower burning, which is not why it is there but is a useful side effect. Many grasses in fire prone environments have deep roots to survive burn over. Clover roots exude acid primarily to balance their pH in light of nitrogen fixation but it has the side effect of mobilising nutrients from dissolved soil particles as well.

Such a plant won't give you a big flashy crown fire but it could smolder continuously pouring smoke and ash into the environment and burning anyone who ventures that way.

I reiterate that I do not believe that this is within the reach of the biological systems we understand and share our world with but maybe if it smoldered slowly enough without burning out it could work.

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You can't. It's simply a matter of energy input and output. The sun delivers about 700 W/m^2 to the Earth's surface. Plants convert a small fraction of that into biomass. (Photosynthesis is at best only about 5% efficient: https://en.wikipedia.org/wiki/Photosynthetic_efficiency#Typical_efficiencies )

A fire will convert many years worth of plant-produced biomass into CO2 & H2O in minutes to hours*, releasing the stored energy in the process. Then no more fire until the plants have a chance to regrow.

Even the coal seam & natural gas fires mentioned in another answer demonstrate this. It took probably millions of years of plant growth to produce that coal or natural gas, which is now burning at a rate far greater than production.

*Generally speaking. You can have situations, like tree roots, where there's limited access to oxygen, so the fire might smoulder for months.

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    $\begingroup$ The fire doesn't have to consume huge portions of the forest - we have annual forest fires in various places on the globe here such that we probably have a forest fire somewhere all the time, and yet we manage to still have forests; it's just a matter of percentage. Yes, if 50% of the forest burns every year, that's not going to keep up long term; but maybe 1% is feasible (or if not, just keep moving that number down!). $\endgroup$
    – Joe
    Sep 27, 2021 at 17:28
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    $\begingroup$ @Joe: Sure, but that having a constant state of occasional fires somewhere is not my understanding of what the OP was asking for. Indeed, it's a perfectly normal state of affairs in for instance much of the western US. But in any particular spot, you might get a low-level fire for a few days every few decades. Even the major fires that have been burning for months are only actively burning around the edges. $\endgroup$
    – jamesqf
    Sep 27, 2021 at 18:24
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You can do one better than a permanently burning fire - a natural fission reactor. The best part? It isn't science fiction, it's history: https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

OK, maybe "permanent" is a bit of an overstatement, the one that existed on Earth only ran for hundreds of thousands of years. It required a high concentration of fissile Uranium and some groundwater. You could do all sorts of things with the water coming as part of a rainy season, or a river meandering to the wrong spot....

You also have a fuel in a fixed location and life won't exist right next to it, but there will be a fringe that is just at the boundary of survivability, and is changing little for thousands of years, which seems ripe for evolution. If you want to keep the evolutionary challenge as heat rather than radiation, then the specific locations will be cracks in the rocks where the steam escapes, some could be hot enough to produce flames whenever burnable material is available.

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  • $\begingroup$ How does steam cause fires? $\endgroup$
    – L.Dutch
    Sep 28, 2021 at 3:07
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    $\begingroup$ Do a search for "superheated steam". The steam you make in your kitchen will give you burns, but won't start fires. However, in the right conditions steam can be heated to much higher temperatures, where it can start fires. $\endgroup$ Sep 28, 2021 at 5:11
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    $\begingroup$ @L.Dutch youtu.be/YjzFStira-k?t=130 Steam igniting a fire. The one caveat which the video goes on to note is that steam will immediately deprive the flame of oxygen and make it go out - to get around this they recommend something with its own chemical oxygen source like the head of a match, so maybe you'll need some strange deposits of potassium chlorate secreted by the trees or another source of oxygen combined with the steam $\endgroup$
    – Greedo
    Sep 28, 2021 at 10:52
  • $\begingroup$ Super heated steam over Farenheit 451 could indirectly heat a rock surface from the other side to the point that it will ignite cellulose. $\endgroup$
    – KalleMP
    Sep 29, 2021 at 6:55
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Fire loops around the globe

Your planet has its landmass as a band around the equator. (or, alternatively, there's [almost] no open water, poles are covered in snow, leaving only the equatorial zone available to the biomass)

Somehow, there are no large rivers. (plants still need to get moisture, and there's evaporation, which means there ought to be rain- or snowfall, which usually means runoff, but fires tend not cross large bodies of water... figure this out).

The equatorial zone is dry-ish, and e.g. typically covered by grasses.

The fire started (magically in only one direction), spread the entire width of the equatorial zone, and continues to burn, e.g. westwards.

By the time the fire has reached it's origin, that part has already sprouted new mature (and dry) grass, with seeds either preserved deep in the soil, or spread by wind, or spread by birds or even migratory animals.

Thus the fire continues to burn in a circle around your planet.

The long-lived plants died out, what remains are grasses and maybe shrubs.

The plants have therefore evolved to live in this cycle, and so have the insects and the animals.

P.S. some math

Fire boundary speed: 10% of wind speed (https://link.springer.com/article/10.1007/s13595-019-0829-8)

Typical wind speed: 10km/h (https://sciencing.com/wind-speeds-tropical-rainforest-23367.html)

Thus, for a planet the size of the earth, the fire circumnavigates in ~4½ years, leaving enough time for plants to germinate, go through several life cycles and accumulate large amount of stale, dry biomass.

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Biology already knows plants that got adapted to periodic fires. These include either fire-resistant trees that just do not catch fire because of some non-burning composition or seasonal plants which get burned but keep roots and/or seeds intact so to re-grow.

A permanent forest fire with burning trees is likely impossible, because it would require much more energy than can be produced.

So, you are confined only to a choice of either periodic, seasonal fires or fires with fuel supply other than trees.

That fuel supply can be natural gas, petroleum, underground coal or peat deposits, or gas produced by microorganisms on swamps (burning methane is common in swamps, producing "lights").

The underground peat deposits can burn for years in Moscow area, even under snow, producing smoke. But, of course, this does not mean the trees are burning all that time.

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