What natural force would prevent dragons from burning all the forests in the world?

Question

So, dragons. Considering the classic wyvern depiction, they are large flying carnivores that breathe fire. Considering not only the fact that flying animals have much higher metabolisms than their ground-based counterparts, but that these dragons breathe fire, they need to eat a lot.

Due to the mechanics of flight, and the fact that these dragons are specialized for flying, the most efficient way for them to eat would probably be to swoop on large herds of herbivores... or, if they are fast enough, surround them with a wall of fire, sit outside, and wait for them to burn before waltzing in to eat.

For this to work, there can't be very many trees; a large flying animal won't be able to turn quickly, and prey animals can easily hide in the trees, where the dragon cannot reach them from the air. (Considering that the dragons are specialized for flying, they are unlikely to be very fast on the ground, making a ground chase infeasible.)

Because of this, the dragons will be incentivized to burn down forests anywhere in their territory, to make room for the grasslands they need to hunt.

So, the question... In a world where dragons exist, why would there be forests? what would those forests look like, and what defenses do they have against dragons?

Answer 1

I propose a Frame Challenge

In reality, herd animals are frequently found in meadows and large open areas despite eons of hunting, which, presumably, would lead to the animals that survive being those that were more likely to stick to the trees.

The problem is that herd animals need a ton of grazing space — which is very difficult to find in forests.

Add to this that you have areas like the African Savannah that's chuck full of tasty treats with very few trees about.

My challenge:

William of Ockham, an English Franciscan friar (1287–1347), is credited with formulating the Law of Parsimony that we know better today as Occam's Razor, which can be simplistically stated: "All things being equal, the simplest answer is usually correct."

The simplest answer is that your dragons would populate in areas with large open spaces where herd animals dwell rather than seek the more fantasy genre driven habitat of forested mountains. This is especially true as dragons, like most herpetological critters, will be fond of warm areas. That means closer-to-the-equator latitudes, lower elevations, and open/rocky areas for habitation. If they must have caves, they'll be volcanic (warmed by the earth, not the sun).

Conclusion

You don't have a problem because no dragon in its right mind would try to hunt in a forest. Unless they have human or near-human intelligence, the idea that burning down the forest before chasing an animal into the area simply wouldn't happen. The burning part would be as a consequence of chasing something into the forest — but that's not going to burn down the world's forests. In fact, once the prey is in the forest, despite having ignited it, the hungry dragon would turn around and chase down something easier to see.

They'd favor large open spaces and avoid forests completely. It's how they'd evolve.

And this assumes they use fire-breathing as a means of obtaining a meal. Fire is destructive, so unless they live on ash (see the movie "Reign of Fire," which brilliantly used this as a way of justifying why dragons burn everything they see), the use of fire would be defensive, not offensive. Like eagles and other raptors, they'd want large open spaces to swoop in, snag breakfast, and haul it back to the kiddies.

Edit

@User3445853 brought to my attention Australia's Firehawk Raptor, a remarkable bird that will pick up burning brands in their claws and beaks to intentionally set fires, forcing their prey to bunch up and run in one direction. This certainly weakens my frame challenge — but I'm going to stand by it anyway because I don't think it's without merit. But that was some great insight!

Answer 2

Grasslands already prevent forests through the tolerance of grass for fire.

Grass is not ancient. In many areas, the evolutionary master stroke of grass that klet it take over large parts of the world is that it can tolerate fire by hiding its biomass underground. By tolerating (and encouraging!) fire, grass can outcompete taller plants that would shade it out.

Burning the grass keeps out the forest. Forest invades on grasslands where fire is suppressed as we are learning in spades over recent years. Dragons in your scenario perform a role which has been performed by native people in other circumstances. In the American West (and also, I think, Australia) native people realized grassland supported more prey animals and so would burn it to keep it as grasslands. Or (here I anticipate comments!) if those ancients were not so farsighted as their descendants the result of their burns to flush out prey was the same. Here your dragons play this role.

Forests grow in lands which cannot support grass - wrong soil, so wet that fire cannot spread, terrain limits fire spread. In a scenario where dragons do what native people did, or lightning did, you will have a balance of grassland and forest similar to what there was before people practiced fire suppression.

** side note: I am not entirely clear what about the ecosystem allowed the former great forests of N America and Europe to resist the influx of grass. I suspect it is reliable moisture. In the US South, grass does very well but trees will quickly recolonize a meadow and I think the extent of a wildfire was historically limited by high ambient moisture. Probably true for Europe as well.

Answer 3

Burning down all the forest is a massive investment for uncertain return. If you burn down more than you need, another dragon may move in and exploit your effort to feed itself to your active harm as it's a competitor. And destroying forest is a never-ending battle. You end up with trees that NEED to be burned to sprout.

There are grasslands. Hunt there. Minimal investment for maximum calorie intake.

Domesticating the herds would probably be a better long-term strategy than burning all the forest, and if you do burn down some, it's probably carefully calculated to provide more pasture.

Answer 4

Forest fires are a natural part of the cycle in their own right. There's a selection of pyrophilic trees around the world, many requiring fire as part of their reproductive cycle. Though the eucalypts could be considered more pyromaniac than pyrophilic, effectively taking the place of your dragons in deliberately starting fires.

A planet that has evolved forest dragons which use fire would have parallel evolution bringing more pyrophiles and fire resistance in both flora and fauna. So remember to place your dragons in a full blown fire ecology, not as lone fire users in the world, or as you suggest, there wouldn't be much but ash to see.

The trees become more fire resistant, the smaller plants use fire to distribute their seeds over a wider area. The birds fly ahead of the fire and hunt the insects and mammals that are driven out. The mammals can burrow, climb out of, find water to swim in, or run ahead of the fire. Fire is a fundamental part of your world, for every creature or plant you put in it, you have to consider its response to fire.

In short, dragons trying to burn the forests down as an evolved behaviour is a requirement for the forest to regenerate and expand.

The Hare runs into the fire.
The fire, it takes her, she is not burned.
The fire, it loves her, she is not burned.
The hare runs into the fire.
The fire, it loves her, she is free...
-Terry Pratchett, I Shall Wear Midnight

Answer 5

They are not smart enough

Your dragons are not smart enough to make the (very long term) connection behind burning down a forest and having a better food source. After all it takes months or years before the burned wasteland of a forest turns into a meadow.

This is entirely believable since humans are the only animals that can think ahead such a long time.

In a comment you mentioned beavers. Google-fu says that Beavers instinctively pile up sticks wherever they hear running water. They do this even if they were raised in captivity and have never seen a dam in their life. Even if the sound of running water is coming from a speaker system and not a river. They pile up sticks because that's what beavers do.

They don't make the conscious connection between piling up the sticks and blocking the river because they don't need to. They have a straightforward instinctive prompt that doesn't require a big brain. Big brains cost a lot of energy to maintain. Why bother?

You are free to say your dragons have no such prompt.

Answer 6

1. Dragons are bound to some specific location. Maybe some kind of volcano where they need to sleep to recharge their fire batteries or whatever.

2. Therefore, Dragons can only go a limited distance from this location, simply because they need to return there every night to not die.

3. Therefore, Dragons have a limited area of action in which they need to find enough animals to eat so they don't starve to death.

4. Therefore, Dragons have to make their area of action as attractive to animals as possible, or else they won't breed enough or just leave. Animals like big patches of grass, but also need some forest in between for some reason like their babies or whatever.

5. Therefore, Dragons can't burn down all forest.

qed

Answer 7

In a world where dragons exist, trees will have evolved to be extremely fire resistant.

And, breathing fire must come with a high energy cost and be very tiring, so a dragon is only going to start fires where it has the immediate motivation to do so.

(It's also possible that dragons like trees. They provide shade, and good hiding places for their young.)

Answer 8

I have to agree, if dragons are very intelligent and cooperative, they would burn all the dry forests; it's the strategic thing to do.

It won't force the forest animals to live on grassland. That doesn't work for most of them, they'd be extinct within years because they aren't adapted as well as their many, many competitiors.

But I'll decrease the number of forest animals and increase the number of grassland animals, after a few generations. So still a win for dragons.

So perhaps the reasons that the dragons don'tt do that is that they are not cooperative and/or highly intelligent (some comment mentions that they aren't intelligent enough for herding).

If they're intelligent but not cooperative, they might realize this problem, but also realize that they are investing heavily in forest burning, while another dragon is probably going to move in and benefit.

If they're cooperative but not intelligent, they simply won't know that it's useful to invest in burning forests to the ground. It'd have to have an immediate benefit, like catching a monkey immediately. But that's probably not as efficient as going somewhere else and catching a zebra. Flying over forests would be inefficient, and burning trees to catch someting would be too.

Note that in a world with more fire, many plants would be harder to burn. That's already the case in our world (Google 'fire-resistant plants'), and with more evolutionary pressure, such traits would prevail.

So if California or Australia make it seem easy to burn huge areas to the ground - it probably wouldn't be in your world. Depends a bit on climate.

Answer 9

Burning all the forests is not a trivial task. Otherwise, they would burn down even without any dragons.

The forest fires have a lot of mechanisms to self-extinguish and that's why we (in the real world, sans dragons) have forests, despite also having thunderstorms, dew-started fires, human neglect, volcanoes, etc., etc...

There are broad-leaved forests that are not trivial to light in the first place. There should be a limit of the firepower a single dragon has.

There are also coniferous forests that are somewhat easier to light and burn down, but they are unwelcome to dragons because it is too cold for a dragon to live and way too cold for a dragon to reproduce.

This leaves us with dragons living in some "moderate climate belt" and at least partially migrating with the season. There will also be a patchy pattern of forest fires moving with them.

p.s. a plot twist may be that more powerful dragons live in the favorable belt and don't migrate and less powerful ones migrate with the seasons, crossing the powerful dragons land twice a year.

Answer 10

Trees would have evolved alongside fire breathing dragons. Over eons trees could have evolved defenses, such as thicker bark that is flame retardant. Maybe the trees do lose their leaves and a lot of the thinner branches but the tree itself survives and regrows.

Note this as well, https://www.nps.gov/yose/learn/nature/fireecology.htm :

Researchers began to study the effects of fire in the wilderness in the 1930’s. They demonstrated that fire was essential to many plant and animal communities.

Fire dependence refers to plants and animals that are adapted to and rely on the effects of fire to survive. For example, lodgepole pine and giant sequoia trees use fire to help open their “serotinous” or sealed cones, to remove litter and duff from the ground to allow seeds to germinate, and to burn open the canopy, affording seedlings the sunlight they need to grow big and tall.

Answer 11

Burning "all the forests in the world" would release a huge amount of smoke and water vapour into the atmosphere. This would drastically reduce the amount of sunlight reaching the earth and in turn this would disrupt cold blooded reptilian metabolisms to the point where dragons would find it difficult or even impossible to reproduce.

Answer 12

There are plenty of places on Earth that are naturally pretty devoid of forest, and have plentiful grassland and large grazing herbivores, (the central Asian steppe, the African savannah, the American west, etc, etc), and dragons are highly mobile creatures, so I don't see why these dragons wouldn't just migrate to where their food is already plentiful rather than seek to alter existing unideal environments.

Secondly, I'm not sure hiding in a forest would ever be a viable defence mechanism for, say, a herd of wild cows. Natural forests contain densely packed vegetation and it would be challenging for the cows to physically manoeuvre themselves around all the trees and branches and exposed roots without causing themselves distress and injury. But also, these animals are highly specialised grass grazers, and without grass to graze on in the forest, they're not going to be able to stay in there long before hunger drags them back out into the open grassland. I really don't think it would occur to the dragons at all that there is anything hiding in the forests that it would be worth their effort to eat.

Answer 13

Other apex predators didn't, why would dragons?

Widescale destruction isn't really a great strategy. Predator populations that overhunt often rapidly decline. Even human beings, by far the most destructive single species this planet has ever seen, don't generally resort to broadscale destructive behaviors as a default. Natural selection favors populations that don't have these behaviors, even in the presence of extremely adaptable species that are capable of migrating to arbitrary biomes.

See Humans - Humans have not typically had devestating impacts on any ecosystems absent the use of agriculture or industry - in absentia of those behaviors, human populations don't generally overhunt their habitats. Notably, the history here indicates that human beings only start to exterminate animal populations for reasons OTHER than eating them.

Another analogous example here is the Orca - Orca are extraordinarily well adapted predators. They are the fastest animal in the ocean, they're incredibly intelligent, they hunt in packs, they have huge ranges, and they live in every ocean on the planet. In other words, they are an intelligent and highly adaptable apex predator.

Orca generally do not over hunt regions they inhabit. Their population typically achieves a sort of stasis with regards to their available prey, as do most predator populations on earth.

So even the most adaptable, intelligent, and lethal hunters on this planet don't eat so much from one territory that they're forced into suboptimal territories. I see no reason to suspect the ecology of dragons would be any different.

Answer 14

Forest in your world would develop to be highly resistant to fire, as mentioned in other answers. Moreover, the predominant trees there (or perhaps it's a local plant growing beneath your trees) would release a fragrant smoke which is very unpleasant for dragons.

Thus, while they could burn the trees (and should you endanger their offspring a bit, it won't be a protection at all) they will make an effort to not burn any tree (or even leaves) when hunting. If he was desperate, a dragon might do that, after a week of not catching any animal, a disgusting prey would be preferable than none at all, but they would try hard to avoid burning any tree.

Answer 15

Poison

Fire can produce or release many toxic compounds, depending upon the material burned. Over the eons, the trees of your world evolved to take advantage of that (though, of course, not knowingly or intentionally).

A certain type of tree had a random mutation that caused it to given off a poisonous compound when burned. Two normally harmless chemicals combined into something deadly. Not just deadly but unpleasant. When dragons tried to burn those trees, the smoke was very painful to the dragons, and those who breathed to much of it died. Not to mention, even if the dragons persisted in burning them down, it meant grass didn't grow as well and animals the grazed there died. Or maybe the poison didn't kill the herbivores. It just settled into their tissues, killing dragons who ate them.

Over time the dragons learned not to burn those trees, which in turn meant they were the ones to grow and spread. Until a point was reached wherein dragons don't burn down forests, because they gain nothing from it.

Answer 16

Forest will grow in and around wetlands

A wetland (saline or fresh water) will be too costly for the dragon too heat up. It will also not burn easy. Forests will thus grow in wetlands.

So will no forests grow outside of wetlands? Well, any forest close enough to a wetland will allow the prey to escape to the wetland once the dragons starts burning. Wasted effort for the dragon so the dragon will stop doing it.

Why can the dragon not eat the animal once it is in the wetland? Either the wetlands will be covered with very dense wet forest or otherwise only animals that can hide under the water will survive.

But wait, so big animals that cannot hide underwater can still be captured in a wetland? Yes if a dragon is suddenly introduced in a ecosystem these bigger animals will indeed go extinct together with a lot of forests (but the forests might regrow once the megafauna is extinct). Something similar happened actually when human arrived on the Eurasian and American continents.

Answer 17

I would offer that trees don't have an individual survival instinct. They are not flame-resistant or even fire-proof. They are, of course, filled with a species survival instinct.

Perhaps over the millennia of dragon-fire, the scorched forests had but one species that kept continuing on and that species (with variations) now dominates the forest biome. These trees explode when burned...explode with a huge cloud of seeds that catch the hot updraft and swirl away in their thousands to float down across wide expanses. Give these trees some fast-growth bamboo-like qualities and the dragons will eventually realize the newly burned open country is a short-term proposition. If the rains and weather are favourable, there could well be a newly sprouted forest even bigger than the previous one!