The land grows evil and corrupted ... but why?

Question

BACKGROUND

A corruption has seized hold of the land, turning great swathes of it into a poisonous waste that humans may only enter at their peril. Perhaps all who enter the waste grow sick or go mad, perhaps terrible beasts lie in wait, all that can be known is that evil has taken root in the earth.

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This is a trope that seems to have have spread throughout popular culture, (esp. fantasy fiction, movies, video games) as if it were some kind of unnatural, virulent force. This may be related to the dawn of the atomic age and environmentalism, but realistically humans have made art about the fear of pollution going back as far as I've cared to look. Personal favorites, and good examples for this question, include Dragon Age and Nausicaa of the Valley of the Wind.

But to the point, in most of these scenarios the corruption is either nuclear fallout (whether of the realistic or gonzo-mutant type), out-of-control industrialism (black coal smog and chemical spills everywhere) or supernatural (the earth turns black/purple/red and spits toxic fumes -- cue goblins). I really enjoy scenarios like this, and I was wondering if there are less trod upon naturalistic scenarios that could create a world along similar lines.

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QUESTION

• What is the best naturalistic explanation for large portions of land becoming corrupted?

Corrupted in this case means something like: polluted, toxic, perceived as eerie or unholy, like a divine plague, dangerous to humans, a wasteland.

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CRITERIA

• Earth-like world.
• Corruption. It should be dangerous, and noticeably change the landscape. Just being hard to traverse isn't enough. There's something about corrupted land that's "unholy" or "toxic". It should, in short, freak people out.
• Limited scope. The entire world can't be corrupted. Some parts remain normal and habitable.
• Not too limited. There should be enough corruption to create at least one Mordor-ish region.
• Long lasting. Ideally it should persist for at least several human lifetimes.
• Natural event. Bombs, aliens, bioweapons, etc. are all off limits. Earthquakes, volcanoes, meteors, even animal behavior, etc. are all good.

Radiation is the most common source for a corrupted land, and remains 100% valid for this question. However, the natural event requirement stands.

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Bonus points if ...

• The corruption has the potential to spread.
• The corruption is dramatic or visually interesting.
• The corruption alters local wildlife.

Answer 1

The volcanic gasses that fill the valleys near the Kikhpinych volcanos kill anything that stays in it for too long and poisons everything else that venture into it. Larger creatures like humans are known experience hallucinations, chills, and dizziness in the valley, and will die if they stay in it. Even the flesh of plants and animals that die in the valley become toxic killing anything that eats it and spreading the toxins further, dead predators and scavengers are found outside the valley all the time. There is actually a government program to clean up cadavers of dead animals to slow the spread of the toxins to the surrounding environment.

It is not just one toxic gas like many volcanoes but a whole cornucopia of nasty crap that comes out of the volcano and builds up in the surrounding area.

The area is appropriately named, the valley of death. The natural shape of the valley causes the gasses to accumulate (since many are heavier than air). So any naturally isolated basin near such a volcano would be a good candidate, and what is Mordor, a mountain rimmed basin surrounding a large volcano, and it got worse when new management came in and built a giant wall and tall gate closing off the one exit from the valley.

https://kamchatkaland.com/note/death-valley

http://repo.kscnet.ru/3697/1/Karpov-et-al_VS_1983-4eng.pdf

Answer 2

An invasive species would meet all of your requirements, but for a true corruption I would go for an invasive zombie fungus.

Meet Ophiocordyceps unilateralis a tropical fungus whose spores infect ants, grows in their brains altering their behavior, making them climb high up into the trees and attach themselves onto a major vein of a leaf and wait while the fungus grows a large mushroom fruiting body out of their dying bodies and releases new spores into the wind to infect other ants.

This real world fungus is highly adapted to influence ants, but your world could have a similar fungus that is much less picky, and can infect a wide variety of animal species. These areas of blight would be truly horrible, sickly animals prowl around, everywhere their remains sprout into more of the dreaded mushrooms, latching onto and feeding off of the nearby plants and spreading their infection to other animals. Infected humans are slowly seized by madness and hallucinations, turning on those around them until finally their own corpse feeds the growth of more fungus.

Mushrooms are known to cause mind altering effects in humans, so this is not that far fetched. Also many mushroom species are quite area specific requiring very exact environmental requirements to grow, making cultivation nearly impossible, so it could spread, but isn't likely to devour the whole world. I would imagine people would be trained to recognize the signs of infection and what the mushroom growths look like and would be ready to burn it with fire.

Answer 3

A Mazuku is probably your best bet.

A Mazuku is essentially a "blanket" of carbon dioxide that is released by any number of natural events, such as volcanic activity, landslides, tsunamis, or from natural areas like lakes.

Since carbon dioxide is heavier than air, in large amounts, it will hug the ground like a low fog, and collect into low areas. So if your large area is surrounded by mountains and the CO2 can't disperse, this will create your corruption event. Since CO2 is undetectable by eye, and odorless, any unsuspecting human walking in will likely quickly suffocate and die.

In large enough amounts, even vegetation will be affected, so you can simply change the amount of CO2 in the area in order to decide how much of a wasteland it becomes.

In terms of range, we have recorded at least a 25 kilometer radius from a single source (Lake Nyos event) - in your world, you could have an area that is filled with possible sources of carbon dioxide, where some trigger happens (an earthquake, perhaps), resulting in all those sources releasing all their carbon dioxide at once, creating an instant death zone.

Answer 4

Mud volcano.

https://pubs.usgs.gov/of/2008/1019/pdf/OF08-1019_508.pdf

https://www.youtube.com/watch?v=xSv6pO6gLpY

https://news.nationalgeographic.com/2017/10/mud-volcano-lusi-indonesia-video-spd/

More than ten years ago, rivers of mud started spewing out of the ground in five different locations on the Indonesian island of Java. And it hasn’t stopped since.The disaster, termed the Lusi mud eruption, is still spewing out mud and spans a little over six square miles. At its peak, the region was churning out over six million cubic feet of mud every day. A study published in Marine and Petroleum Geology earlier this summer reviewed the extent of the damage. The scientists found that some villages have been buried in as much as 130 feet of relentless mud. Some 60,000 people have had to abandon their homes, and 13 people have been killed.

Unlike the lahar, which is volcanic mud that comes surging down in a wave and kills everything in its path, the mud volcano produces a creeping death that covers the land, leaving it bleak and lifeless. The volcanic mud is hot when it comes out, but after it is out and covers the landscape it is difficult for plants to recolonize it, even in the tropics. This mud comes from deep in the earth and has almost no carbon or nitrogen to support plants; it is mineral clay. Also, like clay, it dries hard and roots cannot penetrate it.
https://nature.berkeley.edu/classes/es196/projects/2008final/Ross_2008.pdf

Considering how hard the desiccated regions of the mudflow are, the mud could be an used as an effective housing material.

I like the idea of mud brick structures dotting the featureless plain of mud.

You could riff on the mud theme. Volcanic muds also are full of sulfur and stunk of hydrogen sulfide. Bad for surface life but good for archons, and these can serve as the base of a food chain that supports huge numbers of flies.

http://www.desertdispatches.com/blog/2014/6/second-chance-the-owens-lake-project flies

And since this is fantasy, you could have other deep earth creatures come out with the mud. These take up residence in the thick mud beds, moving about as they did in their deep home, feeding on the rich surface life that has been covered.

The mudscape is a poisonous waste, but it is not immediately lethal to visitors. It can be traversed. There are areas of high ground that have not been covered by the flows. The mud bakes hard and you can walk across - although the crust might not be as thick as it seems, and it is a long way down underneath.

Answer 5

Invasive species of noxious plant.

You could have some plant (or fungus) that invades the area. Said plant would be resistant to removal. It could also release all kinds of "noxious" substances as defense mechanism to animals eating it etc.

Depending on your theme, this could be magic, natural, or some genetic accident brewed up in a lab.

To limit the area, you could have it vulnerable to extended periods of cold so it only affects temperate regions, or other biological reasons. If it was native in some area, maybe some animals there have adapted to eat it, but bringing them here may cause more issues then it solves.

We deal with this all the time where I am from, well not noxious plants, but invasive species.

It could even be a truly alien plant, brought here by accident or on purpose. Scientists often do things we later regret. I can name a dozen invasive spiecies that are causing biological havoc right now. Including these dang stink bugs and Japanese beetles.

Answer 6

You could go with high naturally-occurring levels of mercury -- possibly cinnabar (mercury (II) sulfide)? A high enough concentration of this would be lethal to outsiders, but local flora and fauna have evolved various adaptations to it, in weird and twisted ways.

Perhaps some plants have developed mercury storage pods that elemental mercury is diverted to as it metabolizes the compounds from the soil, and these pods periodically burst -- perhaps in windy or rainy conditions, to disperse the mercury away from the plant -- in beautiful but very toxic displays. Maybe some other plants metabolize the mercury into methylmercury and circulate it through their leaves and stems as a toxin to thwart predation. Methylmercury poisoning symptoms include numbness in the extremities, loss of balance, blindness, muscle weakness, insanity, coma, and death.

The flora and fauna of course look alien to the rest of the world as a result of their warped evolution. Anyone who lingers in the area too long will end up inhaling large amounts of atomized or gaseous mercury from the pods, and of course anyone who eats a mercury-circulating plant (or insect/animal) will quickly be poisoned as well. Some may enter for a mere day or two, and come back with lesser to moderate symptoms (weakness, blindness, etc); those who stay in the area a few days will often return insane, and/or fall comatose shortly after returning. The brave (and/or stupid) few who try to stay in or travel through the area for more than a week or so are never seen again, having rapidly accumulated mercury in their systems, falling comatose or dying while in this toxic environment.

Answer 7

Radioactive moon in a nearly geosynchronous orbit. It slowly kills or alters all life exposed to it, but it doesn't hang perfectly still in the night sky.

It travels very slowly, circling the planet once every 500+ years, enough time for the far side of the planet to recover from its ill effects. People are forced into migrating every 500+ years to avoid the bad moon.

Sometimes, the moon is over the oceans, only affecting small patches of land, these are the times of peace and plenty - then slowly it moves over one of the major continents, disrupting centuries of peace and prosperity before moving off again over the sea.

Answer 8

Mold

Effects

In particular, a subterranean mold which feeds on the roots of trees and smaller plants, and spreads beneath the floor of large forests.

After infesting a tree's root system, the mold injects a harmful chemical as a byproduct of its life cycle (adjust for sci-fi, fantasy, realism, etc.). This causes small, but noticeable effects on the host plant, and eventually will turn a huge area into a very clearly inhospitable wasteland.

Thanks to bio-accumulation, this mold is able to produce progressively more extreme and deadly effects in creatures as you move up the food chain. Naturally as a result, nothing that has managed to survive in the infected forest would be edible.

Spread

Within an area

Once a dense forest is infected, the mold is nearly impossible to stop. If caught during the absolute earliest phase of infection, it would be possible to completely extract the tree and root system.

The mold spreads invisibly underground, transferring across roots which make contact between viable host plants.

Left unchecked, the mold would spread a fixed amount per year, depending on density (i.e. More dense forests would spread more quickly).

Beyond

Periodically, the mold will inject spores into the host plant, which would spread throughout it. The spores would again travel up the food chain, until the creature they were in died and began to decompose, at which point the spores would attempt to latch onto any roots in the shallow ground beneath the corpse.

Combating the mold

Once the mold has taken hold in an area, the only way to make that space truly safe is to burn the Earth to a depth of 1m. The mold and spores die at a temperature of 200 degrees Celsius. [This could lead to some interesting cultural/religious practices depending on the setting, such as ritually burning the corpses of all wild animals one might come across.]

Answer 9

A Natural Fission Reactor would do, though one much larger than the one found here on Earth.

Oversimplifying, it's a horizontal layer of soil made of uranium, which achieves criticality.

Water is involved, which can be handy for washing fallout out into the environment.

"The natural nuclear reactor formed when a uranium-rich mineral deposit became inundated with groundwater that acted as a neutron moderator, and a nuclear chain reaction took place. The heat generated from the nuclear fission caused the groundwater to boil away, which slowed or stopped the reaction. After cooling of the mineral deposit, the water returned and the reaction restarted, completing a full cycle every 3 hours. The fission reaction cycles continued for hundreds of thousands of years and ended when the ever-decreasing fissile materials no longer could sustain a chain reaction."

Besides messing with the size and power, you might want to change the cycle times from hours to years, decades or even centuries. This can feed legends of how the corruption was vanquished by a human action, event or ritual, and is now coming back due to another human action, event or ritual. All coincidences in actuality.

Answer 10

Here's an alternative to the radioactive moon idea.

Have the planet itself be the moon, orbiting a gas giant. The moon is not yet fully tidally locked so rotates slowly relative to the primary.

The moon has a Magnetic Flux Tube with the parent gas giant and the compression of the crust also causes intense volcanic activity when the gas giant is overhead. (This would also happen on the opposite side of the planet due to tides but maybe the magnetic flux can explain why it is worse on the near side).

You would need to play with the figures but you could easily make some messy stuff happen, the main trick would be making the effected area small enough that the whole surface isn't badly affected.

Answer 11

I am going to do some 'what -if' musings here based on real events and real science.

Coal seams close to the surface have been known to catch on fire through lightning strikes, and they can burn for decades, the longest has been burning for six thousand years, both above and below ground. When they burn to the surface, they can ignite brush and trees, causing localized flareups that appear to come out of no where.

From the above article:

Even more remarkably, ancient subterranean fires shaped the very landscape of the West. "Much of the landscape of the American West—its mesas and escarpments—is the result of vast, ancient coal fires," writes Kevin Krajick in Smithsonian Magazine. "Those conflagrations formed 'clinker'—a hard mass of fused stony matter. Surfaces formed in this way resist erosion far better than adjacent unfired ones, leaving clinker outcrops."

Along with pictures of 'alien'looking landscapes.

Another description of a coal fire

Fom the back kitchen window of his little house on a ridge in east-central Pennsylvania, John Lokitis looks out on a most unusual prospect. Just uphill, at the edge of St.IgnatiusCemetery, the earth is ablaze. Vegetation has been obliterated along a quarter-mile strip; sulfurous steam billows out of hundreds of fissures and holes in the mud. There are pits extending perhaps 20 feet down: in their depths, discarded plastic bottles and tires have melted. Dead trees, their trunks bleached white, lie in tangled heaps, stumps venting smoke through hollow centers. Sometimes fumes seep across the cemetery fence to the grave of Lokitis’ grandfather, George Lokitis.

This hellish landscape constitutes about all that remains of the once-thriving town of Centralia, Pennsylvania. Forty-three years ago, a vast honeycomb of coal mines at the edge of the town caught fire. An underground inferno has been spreading ever since, burning at depths of up to 300 feet, baking surface layers, venting poisonous gases and opening holes large enough to swallow people or cars. The conflagration may burn for another 250 years, along an eight-mile stretch encompassing 3,700 acres, before it runs out of the coal that fuels it.

Read more:

Weather inversions can trap smog and pollution underneath a layer of air, that can drive air quality into dismal areas.

Carbon monoxide is poisonous to humans, is odorless, is heavier than air, and kills silently. Sulfur dioxide would also be produced in great quantities - a gas as foul smelling as you can get.

Limestone ground formations can easily be carved into underground karsts over large areas by underground streams. Coal, limestone, sandstone, and shale are oftne found in layered deposits.

A deep river valley with steep sides can produce an air trap, in that dominant winds just blow over the top.

So, let's combine then. A confluence of these separate conditions.

A deep valley, that has a permanent inversion over it. Air is trapped underneath, and there are no winds to blow it away. An extremely large coal seam ignites, producing tremendous amounts of carbon monoxide. This carbon monoxide stays heavy in the air, but there are oxidizers available to keep the coal seams smoldering. A cave system carved out from limestone and water, over a wide area, could be a source of oxygen feeding the fire.

So we have an area with very heavy air, smoke particles, the smell of sulfur, and deadly but invisible, odorless carbon monoxide gas. Humans and animals would appear to just collapse, and rescuers would suffer the same fate. Trees and shrubs burst into unexplained flame. Vegetation above the burning seams would die off. These areas would move around as the seams burned, and the karsts provided oxygen. It would be an area of mysterious, random but quick death, unpredictable and unpreventable. Animals quickly expiring, and would avoid the region.

And the ground would be black, hard, lifeless clinker.

One of the signs of initial carbon monoxide poisoning is confusion, unco-ordination, and dizziness, with effects like paralysis.

I believe this fits all of your criteria.

Answer 12

Radiation is the most obvious option; but you would need an isotope mix, and an intensity, that's next to impossible to come by naturally (or as side-effect of 'conventional' nuclear explosions or known industrial nuclear processes); moreover, it would decay pretty quickly. You would need an incredibly high contamination by middling half-life isotopes - not so active that they burn in a few months, yet active enough that tons of them aren't required to achieve effect. I don't see this occurring "naturally".

Another possibility is a hacker organism or vermigon. It needs only to mutate once to be able to change its habitat and invade, and the consequences can be as spectacular and/or horrible as desired (from a crab's standpoint, a Sacculina infestation is a zombie apocalypse).

Even so, the roaming form of the parasite - the kentrogon - is usually adapted to a specific host, and it's unlikely to be able to parasite a wide range of other organisms. If it was, though, its creep factor would shoot out of the roof.

The organism might have mutated, or might have thrived once and then been left semi-dormant for ages in the arctic permafrost, until climate changes both thaw the permafrost and allow animals to begin grazing the area. Perhaps both of them - imagine a mammal-infesting Sacculina analogue, lying in wait on the ironically named island of Vozrozhdeniya, after being mutated by the wealth of toxic wastes that were dumped in the area.

Answer 13

An ecological disaster, brought upon by over-hunting. Imagine a plant with the swift growth rate of kudzu, and the terrifyingly excessive toxicity of the Manchineel tree. A certain animal (perhaps a type of antelope) has the ability to eat this toxic vine, and keeps the plant's population density low. However, once humans discover the area, they begin hunting this antelope until- surprise! -the hard-working ungulates are all extinct. The vine then begins to grow out of control, overtaking first ditches, fallow fields, and abandoned properties. If the humans do not have sufficient technological sophistication to safely remove the plant, within a couple years their settlements and most of the land will have been overtaken by a green and deadly blanket.

Answer 14

A fungus could do it.

The largest living thing on earth is a parasitic fungus in Oregon. It stunts the trees.

http://www.extremescience.com/biggest-living-thing.htm

Imagine if that fungus also secreted a neurotoxin...

Answer 15

I don't think I've seen this mentioned yet: A Virus. IE: the T Virus

My idea is a variation on all the Zombie Virus'... with the idea that the virus (or disease) doesn't affect humans directly.

Whether man made (CRISPR Gene Editing gone wrong), alien introduced (You don't think they successfully found everything after Roswell do you?) or a naturally occurring pandemic...

What does the virus do? need? affect?

Options abound!

• It's not airborne... and started in Hawaii, Japan or some island.
• It requires dryness - water kills it. Limiting it to desert.
• It requires water - dehydration kills it. Limiting it to swampy areas like Florida or the once pristine Everglades.
• It requires: Hot/cold/fresh water/sea water/grasslands/mountainous areas/etc...
• It interacts with other ideas mentioned by others - volcanic gasses, mud-nado's, CO2 hot spots, fungi, etc
• It only affects insects - makes them aggressive, multiply faster, bigger
• It only affects plants - they now hunger for... blood.

The fight to find the vaccine/cure for the virus is intense! Will they find the cure before it mutates? Stay tune and find out next week...

Answer 16

Although I think other answers are better, I’ll throw this in for “completeness.”

Somewhere in the Rockies, there is supposedly an outcropping of uranium ore rich enough to be dangerous. There is even a story, no doubt a gross exaggeration, of someone seeing an animal jump onto this rock and immediately die.

Half-life of U-238 is 4.5 billion years. It’s plausible, though unlikely, that a young planet could have enough of it in one area for sapient creatures to figure out that there’s “something” strange about that place. Perhaps they are good at something akin to our scientific method (so they’ve noticed a correlation), but they don’t yet have the technology to identify radiation.

Answer 17

In this question I was told an explanation of how a being similar to Typhaon might exist. The details of that creature are irrelevant but the explanation can be adapted here. In fact, it could be its relative.

Your corruption is a living cloud of bacteria. As it consumes and spreads it sometimes goes dormant until something living walks by. Then it descends upon the victim and devours it whole (or worse keeps it alive for days using it for food).

So how could this develop? Well you need a few things. First you need functionally immortal cells so they don't just mysteriously die all of a sudden. There needs to be an initial quantity of them so massive that someone doesn't merely get sick. They are actually devoured. This could likely start in a tropical or densely forested region. It could've been a way to combat a mold outbreak in some protected forest that got out of control.

Such a disease could grow to have a central hive mind. Perhaps part of what made them stronger was to give them a modification that made them electrically conductive and able to store static electricity to use to kill or tear apart other cells. Essentially a bacterial version of a nerve cell but still capable of being a bacteria.

Such a bacterial hive mind could simply alter the ground as it becomes part of its massive multi-cellular colony stretching deep into the ground.

Perhaps all who enter the waste grow sick or go mad, perhaps terrible beasts lie in wait.

The first could be the bacteria messing with people to toy with them or trap them. The latter could be the results of the bacteria finding a more suitable way of moving about then mist. Essentially they could grow into a body perhaps or re-purpose lifeforms into beasts that serve the hive mind.

Giant swathes of poison could be the waste from the giant creature. It would look like normal poison since... most natural poisons come from either bacteria waste, plant secretions, or venom. It being the first isn't anything special.

I'm prepared to try and diagram such a cell if anyone wishes, but I am not a biologist so don't be upset if it isn't exactly like a normal cell looks.

Answer 18

You could consider a toxic ecosystem feeding on pollution leaving only some area untouched, protected by, say, wind as in ghibli's Nausicaä of the Valley of the Wind.

In resume:

Human pollution has transfigured nature into a highly toxic environment where everything rot but news species of insects. No human action can reduce the affected area as every violent attempt results in an equally violent reaction spreading the toxic environment even further.

To me, this idea was strongly suggested by your background but it also answers all of your criteria. For example:

• Earth-like world. It's a naturalistic explanation that could totally happen on earth (with heavy human pollution).
• Corruption. The corruption is highly dangerous. Even one breath in the deepest forest is enough to condemn your life. And that is without accounting for the territorial giant insects.
• Limited scope. There remains places where human can live, some desert, and even some high quality valley.
• Not too limited. In the movie, the whole earth is polluted and suitable for corruption spreading. The fact that places remain untouched is only due to environmental luck of human constant vigilance.
• Long lasting. The corruption has been there for nearly as long as human can remember. Time before corruption is only told through ancient legends.
• Natural event. Well, you can't be more natural than nature itself.

Annnnnd the bonus points:

• The corruption has the potential to spread. Totally.
• The corruption is dramatic or visually interesting. Beautiful shroom-like scenaries in the movie but can be adapted at will.
• The corruption alters local wildlife. You get a whole new set of giant insects on steroids (or anything more at your conveniance).

Answer 19

Great ideas so far! Since you also mentioned "evil", here's a less physical, more spiritual one:

The land is not sentient, but has some kind of inherent spiritual awareness. So, activities performed on the land effect the "spiritual atmosphere" of that area of land.

Particular acts may be tied to certain spiritual beings. These beings may influence humans toward certain actions, for their own agendas, including the furtherance of desecration, or other more direct motives. A being may "hang out" at a certain spot, causing more of the particular act, and increasing his power.

For example, a spirit of death, or spirit of violence will attempt to influence people toward violent acts. Any violent acts perpetrated, causes the land to react negatively. The land is trying to distance itself emotionally from the act, so it "shuts down".

The opposite process is also possible to create "blessed land" by sustained righteous acts on the land. Cursed land may also be "redeemed" by purposefully opposing the negative effects and causes.

Answer 20

Stage one biological life would fit the bill. life in a new location (after life kicked the bucket there for whatever reason) begins with small bacteria that do some form of terraforming: they turn conditions that are bad for most life into better conditions (turning the environment hostile to them in the process).

A very good "corruption" scenario could be the opposite : a bacteria that turns otherwise hospitable environment "bad". Ravenously unbinding nitrogens to kill plants, producing cyanide and acids to make it hostile to humans, making methane and sulfur for a bad smell. Bacteria have no problem with these things. If they can't spread airborne it would also make for a nice "front" that spreads.

As for wildlife alterations: also possible. Viruses can alter psychology to make wildlife aggressive (think rabies) and bacteria can easily cause lesions and boils and other visual indicators of "corruption".

And the best/worst part: stage one are called that for a reason. They are the "colonists". Since the changes they make usually turn the environment against them, they make way for more advanced lifeforms. This would cause a nice, progressive corruption with continuously mounting pressure on any nearby life that happens to benefit from the situations that the stage one lifeforms "fix".

This definitely has the potential to envelop a continent. Almost all land life followed the three stages of colonization at one point or another. It would require a starting point which was isolated, because life doesn't pause until convenient (ask American teen moms). Easiest would be a natural barrier like the sea or a ravine.

Reasons we don't have this problem : chance. It would have been entirely possible that some life evolved to require different conditions to sustain itself along with different stage one life, which is "assertive" enough to evict previous occupants. Perhaps it DID happen during early life and we are the corruption. Who knows.

Answer 21

A simple big herd of cow like creatures

But simply add few features to them:

1. They are in a very large number
2. They are omnivorous at a large scale (eats simply anything that is not of the same species)
3. When they don't find something else to eat become easily cannibals (eats their own species)
4. Add that their dropping is done with a gas that is unsustainable for most of other livings
5. After they have "destroyed" an area, their faeces are in the first place full of microorganism that are a vector for some really bad deseases

After some decades, the soil can become back to normal, even experiencing an incredible plant growth, so the corruption is still only located in the path of the Herd.

The bonus point would be that the herd is roaming naturally arround some kind of big mountains chains on a single continent for centuries, making the land around it experience the corruption as longer seasons.

The possibility for it to spread would be people from another continent wanting to use them as cattle because they can easily feed on a forest or even funnier, their enemies.

Answer 22

A strange bacteria has been dumped into a forest nearby the peaceful village of Talahul, The trees have become grey and drooping, their branches snagging the unwary, and the bacteria infecting all with a violence and speed unlike anthing else seen on the planet.

Spread

It can only spread with help from other animals, it transfers itself like pollen, except anything can infected, plant or animal.

Answer 23

An organism begins to metabolise an important element is a evolutionary positive, for the organism, way which is detrimental to the current life forms. Happened when photosynthesis kicked of and the increase is free oxygen cause problems for the legacy life forms.

See Peter Watts "Behemoth: B-Max" - third in a series but this is when it all happens. A bacteria (from memory) starts locking out sulfur from the ecosystem causing massive damage to the legacy lifeforms, i.e. everything alive now. Spread by contact, so at the beginning it is localised but is spread as creatures try and escape its effects.

Answer 24

I'd suggest having the magnetic poles stronger and not aligned with the cold zones of the planet. (Neptune and Uranus have magnetic axes strongly tilted to the "_vertical" axis, so its not unreasonable). Also very strong fields and some kind of suitable small companion object to the sun.....

This has some interesting side effects for your scenario.....

The magnetic poles would be located in prime habitable areas of the planet. In the area around the pole, compasses wouldn't work any more, and the effect of magnetosphere protection from cosmic particles wouldn't be present - charged particles would be attracted to those areas, and if the star system was comparatively active then a person entering these areas would find no compasses working, weird coloured sky and electrical/atmospheric effects, dangerous mysterious wasting fevers/sicknesses unlike any other after a while due to higher radiation levels (dangerously high in some cases - say the sun had a small companion star or object that gave out a large level of particles or xrays), attraction to some particles and lack of attraction for particles that might have provided proctection elsewhere, spooky absence of life (much life will leave and the flaura/fauna will be markedly different).

It would need fleshing out but in principle maybe this could provide a zone of the kind described.

Answer 25

While I am very late to the party (don't know how I missed it earlier), I'd go one step further than "noxious plants".

Noxious ecosystem. Which is spreading since it outcompetes the ones we depend on.

This has the great advantage that is has already happened, so we know it's possible.

I'm talking, of course, about the Great Oxygenation Event several billion years ago. Once photosynthesis developed, the new species outcompeted their rivals. In the process, they gave off free oxygen, which was toxic to the existing ecosystem. Eventually, the new oxygen-emitters took over the world and destroyed the existing order.

Answer 26

I'd like to throw an idea into the ring: something similar to the Messinian salinity crisis. During the crisis, it's believed that, after the Strait of Gibraltar was blocked, a large fraction of the Mediterranean Sea evaporated. What remained was a large basin that might have resembled a salt flat like the Salar de Uyuni.

Any plants or animals that lived in this basin would have had to adapt to extremely saline conditions. On top of that, since the floor of the basin lay multiple kilometers below sea level, the descending air currents compressed, resulting in increased atmospheric pressure, and temperatures well above the hottest temperatures seen on Earth today.

Any creature from the normal world would struggle to survive in a basin like this, and they would encounter huge, desolate salt flats, horrific temperatures, hyper-saline water, and they'd have to contend with whatever desperate plants and animals managed to survive in such an environment.

In regards to your question of a spreading nightmare: perhaps only part of the basin in question has evaporated, while there's a region that remains almost normal, waiting for its sea to evaporate.

Answer 27

I am surprised to see that none of the answers above took into account overpopulation. This is a natural phenomenon that leads to corruption in any setting in which biological organisms live in very close quarters. Human society is but one example.

Most of the viral pandemics are a mere manifestation of the corruption inherent to overpopulation. They usually happen in large cities or large army encampments that concentrate animals and crops as well. Take the example of large tracts of Indian soil being infected with pathogens derived from human feaces.

Overpopulation brings also psychological forms of corruption, moral blight that eventually leaves a measurable mark on the land as well. Take as an example the forests of Romania being razed for decades due to a hierarchical system of corruption that has ultimate origins into people voting for corrupt politicians. They vote like this because corrupt leaders reflect their voters own moral corruption acquired while trying to survive a world of diminished returns, ultimately caused by overpopulation (the decree by Ceausescu to forbid contraceptives in the 80s).

Edit

If an agglomeration of ants destroys a planet it is still a natural explanation (entirely possible, the first mass extinction in our planet age was arguably caused by sea sponges changing the acidity of the oceans). If the ants were sentient in a way us humans would comprehend, of course we would call it artificial, however organism agglomeration is not an artificial happening. It is called "artificial" only if you design it. Nobody designed humans to congregate in cities, they just sort of did so. So I would argue that even human overpopulation is a natural phenomenon.