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Hostile Terraforming

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"The atmosphere contains high concentrations of methane, carbon monoxide, and fluorine. [...] Population approximately nine billion...all Borg."

"There is a notion called 'terraforming' that has held popular theoretical cachet for some time. It holds that given the correct level of technology, the potential is there to change the environment of another planet into one like our own. This is nothing the human race has yet been able to put into practice. It's never been considered that someone might do it to us. These central positions look less and less like someplace a human could survive. They have been un-terraformed."

Imagine you are a leader of an alien race currently at war with another race, and your natural habitats are drastically different. How would you perform a hostile takeover of a planet?

By making it so the planet is now inhabitable by you and not by the natives, of course! Convert the atmosphere, reshape the land and sea, overrun the native ecosystem with one more suitable — whatever is necessary to make the very ground your enemies tread on no longer their ally. If successful, this can turn the targeted planet into a Death World.

A specific context for Terraforming, and if it's Earth or an Earth-like world being changed to another ecosphere, the term would be "xenoforming". When specific species are involved this may be an Introduced Species Calamity. Often overlaps with Atmosphere Abuse, though the latter doesn't have to occur specifically for terraforming purposes. Depending on methodology, it can involve Grey Goo, Gaia's Vengeance, The Night That Never Ends, Alien Kudzu, or Meat Moss. Due to the destruction, this is an Apocalypse How of the Planetary Species or Total Extinction variety, depending on how much of the planet's multicellular life is replaced.


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    Anime & Manga 
  • Astro Boy: This is the alien robot Mazin Garon's modus operandi. After he's activated by one of the scientists who found him he goes about remolding the rocks, air and even gravity of the island he crashed on, killing everything for miles around with the poison gas meant to be the planet's new atmosphere. Although in Garon's case it's not really hostile, as he was only doing what he was programmed to do before the space mail order package he was in crashed on Earth by accident instead of the planet he was supposed to help his owners colonize.
  • Digimon Adventure: The Dark Masters warp the Digital World to their liking, forming the Spiral Mountain, consisting of four sections, one for each Dark Master to rule according to their environmental preference. As a consequence, previous locations in the Digital World got destroyed, such as Primary Village, the place where Digimon are born.
  • Lord Slug wanted to freeze the Earth because of this in Dragon Ball Z: Lord Slug. "Deterraforming" was discussed in the Dragon Ball Abridged movie version.
  • Godzilla: Planet of the Monsters
    • Godzilla has inflicted this on the Earth's biosphere in the 20,000 years since humanity's Homeworld Evacuation; making the planet a Death World for humans with unbreathable air and with extensions of Godzilla in place of plant life which are hard enough to break knives, which release metallic pollen that interferes with radio communication, and can produce Flying-type Servum monsters. It's suggested the Hostile Terraforming is the work of Mother Nature herself purging the planet of humanity's ecologically-destructive ways rather than the work of an invasive species. However instead of reverting to a 'pristine' state of Nature, the world has been transformed to serve the needs of this new apex predator.
    • The landing party do their own small version by carpet-bombing the forest with thermobaric bombs in order to clear a landing site. Brings a whole new meaning to Coming in Hot!
  • Neon Genesis Evangelion: Adam and Lilith are revealed in supplementary materials to be alien terraforming biotechnology called Seeds of Life created by a long dead precursor race. The problem is, if one Seed lands on a planet that already has a Seed (in this case, Lilith landing on Earth after Adam has already done so), it would risk a "forbidden union" between the two Seeds' respective offspring that would give rise to a race of godlike entities rivalling the aforementioned precursors. The precursors were aware of the possibility of this happening, and added control rods (the Lances of Longinus) to each Seed's vessel that would automatically seal one of the Seeds in such a situation. This is what happened to Adam, as Lilith's Lance was apparently destroyed in the process of her arrival to Earth. Then a bunch of humans removed the Lance...
  • Space Battleship Yamato:
    • In both the original anime and the live-action film, the Gamilas have reduced Earth into a radioactive wasteland by meteor bombing, and the main characters discover that this would leave a world more suitable for Gamilan life.
    • The 2012 reboot, Space Battleship Yamato 2199, puts more focus on this aspect of the Gamilas attacks on earth, describing the effects as "pollution" instead of explicit radiation like the original series and live-action movie. The Planet Bombs also seeded poisonous Alien Kudzu that's shown penetrating the underground cities, which is discovered as identical to the plant life on the Floating Continent. However, that ecosystem is not suitable for Gamilan life in this version; the Hostile Terraforming is strictly a way to Salt the Earth. This was RetConned, however, in Space Battleship Yamato 2202, where it's shown the Gamilas attacks were meant to transform Earth into a state more habitable to the Gamilons all along.
  • Tekkaman Blade: The Radam Invasion seeds the earth with strange fungus-like plants while they decimate the Earth Military. However, the plants aren't there to terraform Earth, they're there to forcibly terraform us into the best possible Hosts.

    Comic Books 
  • The Authority battles God ("The Outer Dark," issues 9-12). Earth's creator is a moon-sized alien being that created the planet as a retirement home. Since Earth's creation, changes to its orbit and ecosystem caused by the asteroid impact which formed our moon led to the rise of life as we know it and to an atmosphere which is poisonous to its creator, instead of somewhere God would be comfortable. God immediately sets about "fixing" that by dropping organic machinery to restore God's preferred atmosphere. Or as The Engineer calls it, "turdscaping".
  • Bucky O'Hare and the Toad Wars!: The toads have a machine which can completely change the climate and ecology of a conquered planet into a swamp. Given what we see of the cities on such converted worlds, this cannot be a pleasant experience for anything currently on the surface when this happens.
  • In the Mars Attacks! comic book the Martian overlords have conquered Earth and are in the process of xenoforming Earth into a more Martian-like planet as so to let them live better at the expense of the largely expendable humans.
  • The first issue of Sillage/Wake involves an alien called Heiliig who intends to terraform a jungle planet by moving it closer to the sun and burning everything to suit his species, the Hottard, which require extreme heat, although in this case he's unaware that there's one sentient being (the human girl Navis) and lots of semi-sentient animals already living there. When he learns of Navis, he decides he doesn't care and proceeds with his operation, and tries to kill Navis when she tries to save her home, saying his people are more important. He is stopped and arrested by the Sillage fleet because it is illegal to terraform an inhabited planet without asking the natives for permission and making accommodations for them. After adopting Navis into the Sillage fleet, the terraforming process is continued and the planet is turned into a paradise for the Hottard.
  • Superman: In various media, villainous Kryptonians often attempt to remake Krypton on Earth. In Krypton No More, he and Supergirl fight two villains with radiation-fueled powers who intend to turn Earth into a radioactive wasteland to suit them.
  • In Teenage Mutant Ninja Turtles (IDW), Krang attempts to terraform Earth into "New Utrominon" using the Technodrome, but the Turtles manage to thwart his plans so they don't extend any further than the small Atlantic island where the Technodrome was located. Whenever it shows up later in the series, the island's new environment is so hostile to non-Utroms like the Turtles that they have to wear respirators the whole time.

    Fan Works 
  • In Abraxas (Hrodvitnon), San's memories reveal that Ghidorah has conquered many alien worlds (some if not all of which were home to sapient life that Ghidorah wiped out), and it converted their atmospheres into endless global storms. According to the author, if Ghidorah decides to stick around on a conquered planet longer than usual after it's exterminated the opposition and decimated the biosphere, then that's when the real xenoforming will begin.

  • In The Conversion Bureau and many of its Recursive Fanfictions, Equestria is surrounded by an expanding barrier that is spreading magic over the earth, and magic is portrayed as harmful to humans, necessitating the eponymous bureaus and the Mutagenic Goo that turns them into ponies. The many Deconstruction Fics that arose in response to these stories liken the whole process to genocide.
  • Project Sunflower: An unintentional version - according to supplemental notes, the Black Tide that served as one of the two main antagonists of the story was a "repair nodule" for a terraforming process used by a long-extinct alien race. Essentially, they dropped a biomass and control nodules onto uninhabited planets, which used nanomachines to spread out and create an artificial organic "computer" layer that would let the aliens control the weather and other environmental features, then form a crust on top for the aliens to live on. A "repair nodule" from one of these worlds was accidentally blasted into space by an asteroid strike, and eventually hit Earth and, not realizing it was on the wrong planet, started consuming all surface matter to convert it into a computer layer.
  • Daughter of Fire and Steel: As soon as General Zod is debriefed about the effects of the Earth's environment on Kryptonian bodies, he decides he'll turn Earth into a New Krypton, whether its inhabitants like or not.
    Zod skimmed through it and saw the usual readings. Atmospheric composition, geological elements, temperature and weather conditions. But as Zod continued reading, he realized what his scientist was so interested in. By itself any one of these readings was irrelevant but taken together they showed a world that truly perfect for Kryptonians to settle on. Add the nurturing radiation provided by the local star and you have the best prospect for terraforming. No wonder Jor-El sent his son here. This was world was perfect for them to start anew and with the codex they could do just that.
  • Rocketship Voyager. During their melding-of-minds with Nee'Lix, Captain Janeway and Tech Lieutenant TuV'k see images of his homeworld and the subsequent deforestation and genocide via terraforming by an invading alien race.

    Film — Animated 
  • Battle for Terra: The humans sends a machine that can convert the air on Terra to be human breathable in seven days. This would leave the air unbreathable for the Terrians.
  • Darksied tries to do this to Earth in Justice League: War.

    Film — Live-Action 
  • The Arrival: Aliens are causing global warming in order to kill off humans and make the planet more comfortable for their kind. When confronted, one of them points out that humans are doing the same exact thing, only much slower. The aliens are simply speeding up the process.
  • Color Out of Space (2020): A bit more Eldritch than most examples, but the Apocalyptic Log speculates that the mutations the Color causes to the environment (mutating and/or amalgamating all terrestrial life that comes into contact with its influence, and seemingly turning the main setting into an Eldritch Location) are the Color attempting to reshape the environment into something which the Eldritch Abomination can better understand.
  • In The Crawling Eye, a mysterious fog on the side of a Swiss mountain turns out to be the result of alien invaders, trying to create more hospitable conditions for a large-scale invasion.
  • In Guardians of the Galaxy Vol. 2, the "Expansion" combines this with Assimilation Plot. Ego the Living Planet planted seeds on various worlds across the universe that would expand and convert those worlds into extensions of himself. The process would displace and kill every living thing on those worlds, leaving only Ego. The only problem was that he lacked the power to do it himself...which is why he attempted to create hybrid offspring that he could use as batteries. Enter Peter...
  • DC Extended Universe:
    • Man of Steel: General Zod and his followers attempt to use a device called the World Engine to convert Earth into a new Krypton. Not only is the process incredibly destructive, but Krypton's atmosphere is toxic to humans. When Jor-El tries to persuade Zod not to do this, appealing to the fact that Earth's environment gives Kryptonians super powers and they can live side-by-side with humanity, Zod says he doesn't care about the humans and he doesn't want to have to adjust to the enhanced senses.
    • Justice League (2017): Steppenwolf seeks the three Mother Boxes in order to conclude the terraforming process that he attempted thousands of years ago. This process summons gigantic crystaline tentacles that tear the ground apart and turn the skies red, presumably turning any planet it takes place on into a mini-Apokolips.
    • Zack Snyder's Justice League: there's an attempted hostile terraforming by the Mother Boxes' Unity in the ancient times battle as Darkseid invaded Earth.
  • Mortal Kombat: Annihilation: When Shao Kahn launches his invasion of Earthrealm, Sonya and Jax notice that nature is slowly dying because of the merging process. If completed, Earth would become a Mordor-like realm just like Outworld.
  • In Pacific Rim, the Kaiju creators learned from their first attempt during the age of dinosaurs, that they were incompatible with Earth's atmosphere. However, this trope is inverted, as instead of colonizing and ruining our planet, they waited and went to other worlds for 65 million years. Eventually, we destabilized our world enough to their liking in 200 years that they could just walk right in.
  • Neil Blomkamp's short film Rakka has the aliens that invaded Earth in 2020 do this, building megastructures to release methane into the atmopshere, melting the ice caps, flooding cities, and poisoning the air to make it more suitable for them. According to the narration it's getting harder to breathe, and is almost impossible near the megastructures. On top of this they're sowing their own crops onto the planet and choking our own native plant life, and are even burning down forests.
  • In Star Trek II: The Wrath of Khan, after viewing the description of the Genesis Device, Dr. McCoy raises the possibility that it could be used to destroy an existing ecosystem while creating a new one. In Star Trek III: The Search for Spock the Klingons saw the device as a weapon, whether it was used for Hostile Terraforming or simply to increase the wealth and power of the Federation. An interesting twist here is that, due to the relatively human-like physiology of most Star Trek aliens, the terraformed planet would still for the most part be habitable to the original inhabitants... it's just that the ones who are actually on the planet when it is terraformed would be used as raw materials for the terraforming transformation.
  • In Star Trek: First Contact (pictured above), the Borg travel back in time and assimilate Earth while it's recovering from World War III. Three centuries later, nine billion Borg are living there, and the planet is poisoned and industrialized almost beyond recognition. The main plot of the movie is about traveling back in time again, to stop this from happening.
  • In Superman Returns, Kryptonian technology causes an island to grow that would have grown over America if Superman hadn't flown it into space. The Expanded Universe says this then started growing into a planet, implying it might have converted Earth into a new Krypton.
  • They Live!: One of the members of the Resistance says in a TV broadcast that the alien infiltrators have caused the release of certain gasses (such as flourocarbons and methane) in order to make the Earth's atmosphere more like that of their home planet ("turning our world into theirs"). Since the aliens are capable of surviving on Earth even with its current atmosphere, it clearly isn't necessary for them to live here, so it's probably just to make them feel more comfortable.


  • This is the purpose of the Mimics in All You Need is Kill, though in fairness they don't know the Earth has intelligent life.
  • The Alectors of the Corean Chronicles carried this out against the Ancients when they began colonizing Corus.
  • In the Cold War thriller A Cage Of Ice by Duncan Kyle, the Soviet Union is using aircraft to spray black powder on the Arctic icecap to increase its absorbing of sunlight and melt the polar icecaps, with the aim of creating an ice-free Northern port as well as flooding coastal cities in the West. The novel is Harsher in Hindsight, as Western politicians might be more willing to take measures to combat Global Warming if it was a Dirty Communist plot!
  • Cthulhu Mythos: Allies of the Great Old Ones and Outer Gods are occasionally found trying to work towards "clearing off the Earth" for their masters.
    • This was Wilbur Whateley's goal in The Dunwich Horror, for instance.
    • Cthulhu's Reign, edited by Darrell Schweitzer, is an anthology of short stories on what existence on Earth would be like when the Old Ones return. There are several references to the Eldritch Abominations 'terra-deforming' the Earth to make it more suited to themselves.
  • The Culture of Ian M Banks considers all terraforming hostile for this very reason. Also inefficient. Turning dead rocks into tailor-made Orbitals and Rings is much more desirable, on all points.
    • Formic Wars (prequels to Ender's Game): The "Scouring of China", first mentioned in the original novel, is shown in the "First Formic War" trilogy to be an example of this - the Formics are defoliating the ground and scooping the dead biomass up, as well as dumping bacteria in the ocean. This conclusion is independently reached by Victor Delgado (a space miner who lost family to the Formics when they first entered the solar system) and Bingwen, a young Chinese boy with genius-level intelligence. Bonus points for never heard of such a concept before but deriving it based on his knowledge of farming. The officer escorting him to a school for children like him (and his future instructor) commends Bingwen not only for reaching this conclusion but also for even asking why the Formics are attacking (not a question that most people ask).
  • Daystar and Shadow: This turns out to be the motivation of both the Hemn and the Others. The Others want to turn the world into a desert, kill most humans, and infect everyone else with a parasite that turns them into plants the Others can eat. The Hemn want to use runaway Global Warming to create a hot, humid ocean planet where their civilization can flourish.
  • The Genocides by Thomas M Disch has aliens reconfigure Earth for cultivation, with the subsequent destruction of humanity being more along the lines of pest control.
  • Hayven Celestia: The sulfur-breathing krakun have attempted to terraform inhabited planets before. A notable failure was their attempt to introduce additional sulfur to the geroo homeworld, which unintentionally turned it into a volcanic hellscape.
  • The History of the Galaxy: The tactic of "combat terraforming" involves bombarding an entire planet with thermonuclear bombs to wipe out all indigenous lifeforms. The planet is then decontaminated and reseeded with terrestrial life. This is why Terran Alliance isn't concerned with keeping cities on the colony world of Dabog intact. They plan to combat terraform the planet anyway in order to resettle billions of people from the overpopulated Earth. This is also their plan for Cassia, although one of the planet's three continents has already been terraformed to Earth norm by the colonists. The other two were left untouched, but Earth is having none of that.
  • Humanx Commonwealth: The villains of The Deluge Drivers attempt to heat up the ice world Tran-ky-ky to make it habitable to humans, even though this will decimate the native Tran. Ironically, such warming would've happened naturally eventually, but the culprits don't want to wait ten thousand years for the place to warm up.
  • Isaac Asimov's In a Good Cause— has information on the sulphur-reducing Diaboli terraforming the obscure human colony of Chu Hsi to be fit for Diaboli life falling into the hands of a group of human anti-Diaboli Federalists, who intend to release it to break up a Diaboli-sponsored all-human conference. Subverted: Except it turns out the information was a forgery by Earth's government, as part of a long-running scheme to manipulate things so that when the human-Diaboli war comes, no human power is on the Diaboli's side. Then double-subverted: Earth's government had found out the Diaboli eventually planned to terraform human-populated worlds, but they weren't going to do it yet.
  • In The Keys To December by Roger Zelazny the homeless protagonists are cooling down a planet too hot for them. This forces the local humanoids to evolve civilization on par with Ice Age humans. The main point of the story is the Catforms' dilemma, if they should doom the intelligent natives. There are multiple hints that Ice Ages on Earth may have been a similar terraforming project, which somehow was reverted.
  • In The Kraken Wakes by John Wyndham it turns out that the alien invaders are triggering global warming to melt the ice caps, presumably to increase the amount of ocean deep enough for them to live in.
  • Last and First Men, the Fifth Men escape a dying earth by terraforming Venus. Halfway through the process, they discover that Venus is inhabited and oxygen is lethal to the natives who furthermore need radioactive materials to survive, but the Fifth Men keep at it anyways.
  • In The Long Utopia, this appears to be the aim of the insectoid "Manipulators" who have managed to step (in a different way than previously seen in the series) from an intersecting universe. In this particular instance, standard terraforming is too inefficient to deal with the existing flora and fauna, and so the creatures devise a way to essentially shake the planet apart to harvest raw materials for terraforming-from-scratch efforts.
  • In the short story Occam's Scalpel by Theodore Sturgeon, the personal physician to a recently-deceased powerful businessman reveals to the man's successor that their employer was actually an alien, whose species naturally breathed smog, and that recent trends in pollution are all part of a plot to make Earth habitable for them. It's actually a hoax by the doctor and his brother, who had created a fake alien corpse to fool the businessman into taking action to save the environment. At the end, though, the brothers realize that it would provide a single explanation for everything, and start to wonder if maybe they were right.
  • In Philip K. Dick's "Oh to Be a Blobel!", humans have terraformed Mars by converting the atmosphere to be bretahable to them, unaware until the terraforming had begun that Mars was already inhabited by Titanians who couldn't breathe an oxygenated atmosphere.
  • Paradox Trilogy: Hyrek gives a wry commentary on the various types of terraforming performed by different governments. Paradox uses robots to terrform planets for colonization, blithely wiping out all indigenous species. The Terran Republic, by contrast, takes great care to catalog all native life on potential colony worlds... then wipes it all out in order to transplant human-friendly organisms.
  • Brian W. Aldiss' The Saliva Tree has a pair of aliens landing near a farm somewhere in England and spreading a chemical that greatly increases crop yield and starts changing the local animal life, including humans, to better suit the invaders' tastes. It starts when everyone at the market complains of the milk being spoiled, and the farmhand who's selling it tastes it as perfectly fine. The main character barely has time to take his lady friend (later fianceé) before the mutagenic effects of the chemical become irreversible (as is, she spends some time violently ill as her body struggles to resist the chemical). The others who stayed were not so lucky.
  • The prehistory of The Seventh Tower has a self-inflicted version: after a devastating war with the Spirit World Aenir, whose denizens can manifest in the physical world as Living Shadows, humans created a Veil of enchanted darkness to block off the sun. It made most of the planet lethal to Spiritshadows but turned it into a frozen wasteland. When the Big Bad briefly destabilizes the Veil, it causes a mild ecological disaster for the peoples who had adapted to the Ice.
  • The Southern Reach Trilogy: The Crawler's misguided purpose is to revive the world of its creators by terraforming Earth through returning it to a primeval state even though said creators are long dead.
  • The Space Trilogy: In That Hideous Strength, the 'civilized' people of Sulva became disgusted with their flesh, so they razed the surface of their planet to rid it all of the uncleanness of biological life. Now Sulva is a pristine, smooth Death World which orbits the Earth and shows its face in the dead of night.
  • In The Taking, a 2004 novel by Dean Koontz, characters speculate that this may be the goal of whatever has arrived with the storm that sweeps across the West Coast. After the discovery that the aliens are in fact demons that have (possibly) come into the Universe through a black hole, it becomes clear that their intention was to reverse terraform the world into a literal Hell on Earth.
  • The Tripods: Xenoforming is on the Tripods' agenda somewhere after 'enslave humanity'. The alien Masters' ultimate plan is to replace the Earth's atmosphere with one they can breathe.
  • In George R. R. Martin's Tuf Voyaging the Ecological Engineering Corps used 30-km "seedships" to wage ecological warfare on an alien race called the Hrangans. The ships cloning all sort of plagues and flora and fauna to devastate worlds. A couple thousand years later the last known seedship is in the possession of one Haviland Tuf who offers his services for hire, often using the ship for beneficial terraforming but sometimes using it for its intended purpose.
  • Vorkosigan Saga: The colonists of Barrayar just had to dump Earth soil and Earth-descended plants in place and burn away the native stuff while terraforming the planet for human habitation.
  • The War Against the Chtorr features an invasion by an alien ecosystem, almost all of it deadly to man. However, an Assimilation Plot appears to be the ultimate goal rather than genocide.
  • The War of the Worlds (1898): Possibly an Ur-Example. Intentionally or otherwise, the invading Martians use areoforming as a weapon, introducing "red weed" that chokes out all other plants and sucks up Earth's water. Fortunately, it's as susceptible to Earth microbes as the other Martians.
  • A minor example in Harry Turtledove's Colonization books: when the Race's Colonization fleet finally arrives, they bring with them plants and animals from Home, a desert world. The plant life thrives in Earth's desert regions and spreads faster than weeds. Since the Race also happens to control most of Earth's desert regions, this works out for them. However, arid American states are also being taken over by the alien plants. Home's animals are even worse. Since they're used to food being scarce, they eat all plants down to the roots, leaving not a blade of grass in their wake. Many characters compare them to goats, only much worse. When the US complains to the Race about their animals crossing into American territory, Fleetlord Atvar simply tells them they're free to destroy any plants and animals in their own territory as they wish. Of course, while a farmer with a rifle may scare off and shoot a coyote, good luck doing that to a brontosaurus or a whole herd of them. Neither the plants nor the animals are likely to move into the colder regions, though.

    Live-Action TV 
  • Andromeda: The Pyrians (aliens that live in super-hot, toxic, Venus-like environments) "pyroform" planets by burning them to their tastes, and the old Commonwealth has to seriously fight them not to lose precious human habitable worlds. In the episode "Point of the Spear", they try to forcibly pyroform a Commonwealth world.
  • Defiance had a somewhat unintentional example, when the Votan Ark ships were destroyed the terraforming equipment they were carrying fell to Earth and malfunctioned, creating deadly hybrid creatures such as Hellbugs and those bear-spider-armadillo things.
    • Towards the end of the second season it turns out that the Votan sent the Kaziri ahead of the main fleet to terraform Earth, but the crew aborted the mission and buried the ship when they found that Earth was inhabited. However the AI is determined to complete its task and attempts to destroy both the humans and all but a few Votan it chose to preserve in capsules.
  • The Lord of the Rings: The Rings of Power: Adar's plan is to set off Orodruin to erupt. The ash in the sky would protect orcs from sunlight while rendering the Southlands uninhabitable to everyone else.
  • The Outer Limits (1995):
    • In "Corner of the Eye", the aliens plan to destroy Earth's atmosphere to make the planet habitable for them.
    • In "Birthright", the alien infiltrators' long-term plan is to use a chemical to terraform Earth over the course of 30 years by giving it a methane atmosphere which they can breathe. Of course, this would result in humans being wiped out. The aliens claim that said chemical, BE-85, is a fuel additive designed to clean up the atmosphere, meaning their plot entails tricking humanity into releasing the chemical themselves on a global scale.
    • In "To Tell the Truth", the native population of Janus Five view the human colonists' terraforming of their planet as such.
    • In "Manifest Destiny", the UFS Rhesos wiped out the indigenous population of Trion, millions of beings at an early stage of evolutionary development, using neutron bombs in order to terraform and eventually colonize the planet.
  • In Quatermass II, an alien vanguard takes over selected humans so they can build a chemical plant to make an atmosphere that will support their kind of life, and kill off all terrestrial life.
  • Stargate SG-1:
    • In the episode "Scorched Earth", an alien vessel was terraforming a planet recently inhabited by a colony of displaced Human Aliens into something hostile to their form of life. In a twist, it's not hostile terraforming — the alien vessel didn't even know the Human Aliens were there, and in fact picked the world because there was no native intelligent life. The episode's conflict is due to the terraforming ship carrying the genetic samples needed to restore an extinct race and having already expended too many resources to start over elsewhere, while the Human Aliens require a fairly specific set of environmental conditions to survive in, so they can't simply be relocated either. The ship's AI exposits that it passed over another, similar world because it did have intelligent life which happens to be the Human Aliens' homeworld, and the ship offers to give them a ride back home before continuing with its work.
    • By connecting to every Stargate in the Gate network simultaneously, the Dakara Superweapon is capable of seeding life across the entire galaxy (and did, millions of years ago)... or can completely wipe it out.
  • In the Star Trek: Deep Space Nine episode "For The Uniform", the Maquis use a special chemical concoction to make planets uninhabitable to Caradassians. In retaliation, Benjamin Sisko has a concoction made to make planets uninhabitable to non-Cardassians in order to force Maquis leader Michael Eddington to surrender himself and the chemicals. And, to prove he wasn't bluffing, he launches a torpedo towards a planet where one Maquis cell was living at to force their evacuation.
  • The apparent intention of the Mind Flayer in Stranger Things. It builds a complex network of tunnels under Hawkins, killing everything above them and infecting even the soil itself with its spores. The adolescent demogorgons (nicknamed demodogs) that follow with it in its arrival on Earth are the first soldiers in a new army that it attempts to build before being shut out of the human world.
  • The War of the Worlds (2019): After the End, the red weed introduced by the Martians has turned Earth into a Mars-like world with an Alien Sky and a red weed-coated, otherwise-barren landscape (called "the Red World" by Word of God), whilst completely choking the land and oceans' terrestrial ecosystems which has in turn put the resource-scarce survivors on the brink of extinction. Though it's not shown, Word of God supports the implication that the Martians deliberately introduced the weed to fulfil this trope rather than bringing it to Earth by accident.

    Multiple Media 
  • Doctor Who:
    • The Ice Warriors do this a couple times. In "The Seeds of Death", they attempt to xenoform Earth using a fungus that will extract oxygen from the atmosphere. The novel "The Resurrection of Mars" shows them successfully Hostile Terraforming another planet, making it hostile to both humans and its once-abundant native life within a year.
    • And from the other direction, "The Mutants" has a group of evil human colonists plotting to terraform an inhabited planet in a way that will genocide the indigenous sentient culture.
    • "The Fires of Pompeii": It's briefly indicated that the Pyroviles would've done this to Earth once they started merging with and converting with millions of humans for their Alien Invasion. Lucius shoots down the Doctor's pointer that the planet they're trying to invade is 70% water by stating water can boil.
    • "The Sontaran Stratagem"/"The Poison Sky": Weakened by their eternal war with another race of Scary Dogmatic Aliens, the Sontarans hatch an uncharacteristically circuitous plan to bathe the Earth in gas which is poisonous to native life but nutritious to themselves, so that they can turn the Earth into a clone world for themselves on which to mass-spawn more soldiers.
    • In the audio story "The Runaway Train", an aquatic alien race to whom oxygen is poisonous sent a terraforming device to Earth which would've turned it into a water world so they could use it as an outpost.
    • Doctor Who New Adventures: In the Alternate Universe in "Blood Heat" where the Silurians are retaking the Earth from humanity, they've been reverting Earth to a similar prehistoric state as it was in when they originally ruled it. They've brought back extinct plants and animals which now coexist alongside their modern counterparts in new ecosystems, mutated fruit which is inedible to humans grows now, they're heating up certain parts of the planet, and they're converting deserts into rainforests. Unusually for this trope, the Silurians aren't introducing an alien ecosystem to Earth but rather are reverting the landscape partly to what it was like in prehistoric times, although the conditions are still very much hostile to humans.

  • MonsterVerse: Generally, it's theorized by Monarch that most of the hostile Titans — the MUTO species, Ghidorah, Camazotz — respectively seek to alter the local or planetary environment to suit themselves, detrimental effects on other species be damned. Emma Russell notes in the graphic novel Godzilla: Aftershock that it's essentially the same kind of thing the human race has already been doing to the planet. In Godzilla: King of the Monsters, King Ghidorah commands the other Titans to join him in tearing down humanity's cities and causing a global Natural Disaster Cascade, on top of Ghidorah himself covering the skies in massive storm systems: the films' novelizations note that Ghidorah's agenda will most likely strip away all multicellular life down to the Earth's bedrock if Ghidorah sees it through to the end. In the graphic novel Kingdom Kong, Camazotz permanently envelops Skull Island in a perpetual superstorm which blocks out all daylight (as he finds the sun intolerable) so that he can turn the island into his new territory — although Camazotz is defeated, the changes he made to Skull Island's climate are permanent, and Skull Island's ecosystem and terrain is breaking down due to the lack of sunlight, constant downpours and gales 24/7.
  • Star Trek:
    • Star Trek: Deep Space Nine: In the episode "For the Uniform", Sisko uses a specialized warhead to poison the atmosphere in such a manner that it would be uninhabitable for human life, but functional for Cardassian in an attempt to force Eddington to surrender. The Maquis did pretty much the same thing (except rendering it uninhabitable to Cardassian life but safe to human) to multiple Cardassian colonies.
    • Star Trek: The Next Generation: In the episode "Home Soil", the Enterprise tries to help terraform a desert planet by pumping water for irrigation. Unfortunately, the planet is occupied by sapient lifeforms who are annoyed enough at the attempt to terraform to sabotage the drill. It takes a while for everyone to figure this out because they're microscopic silicon lifeforms, and thus mistaken for parts of the sandy scenery. However, Federation Terraforming regulations require a planet to be devoid of any trace of life, so that not even possible future species might be prevented from evolving naturally.
    • In Star Trek: The Genesis Wave, the titular Wave is designed to do this, transforming planets into new homes for Plant Aliens the Lomarians. Fired from the Lomarians' hidden base, the energy wave transforms worlds in its path into swampy hellholes through use of Genesis technology stolen from Dr. Carol Marcus. The Lomarians even go as far as to program their own genetic profile into the genesis matrix, combining colonization with reproduction by having new Lomarians spontaneously generated on transformed worlds.
  • Star Wars Legends: The Yuuzhan Vong in the New Jedi Order use Organic Technology exclusively and "Vongform" many of the planets they conquer, including Coruscant. In the Legacy comics a century later the Jedi and Vong shapers attempt to use their technology to re-terraform several devastated planets in the galaxy, but the Sith sabotage the effort.
  • Transformers: This crops up quite a few times with the Decepticons and/or other hostile Transformers planning to remake organic worlds such as Earth into mechanical replicas of Cybertron.
    • In the The Transformers, episode "The Key to Vector Sigma", Megatron finds out the titular key has the ability to turn the planet Earth into metal, but fortunately, the damage is limited to a few poor trees.
    • In Transformers: Generation 2, the Cybertronian Empire's modus operandi was to kill all the inhabitants of each planet and then mechaform the planet itself to make replicas of Cybertron.
    • Transformers: Twilight's Last Gleaming: With control of the Allspark, Megatron's Evil Plan at the series' start is to use it to transform Earth into a new Cybertron. Although he's killed and the Allspark destroyed before he can complete the plan, the humans and Autobots were too late to stop the Allspark's influence poisoning the Earth to its core, threatening to destroy the planet anyway.
    • Transformers: Prime: Specifically Hostile Cyberforming. The Omega Lock in Season 2 is capable of producing pure "cybermatter" to rapidly transform planets into environments similar to Cybertron. The Autobots and Decepticons both pursue it the hopes of restoring Cybertron to its former glory, but the victorious Megatron announces that he intends to use it on the Earth as well, which would destroy all existing life upon it. Optimus Prime makes the hard decision to destroy the Omega Lock, but it still functions long enough to provide Megatron with a massive, technologically-advanced fortress on Earth, dubbed "New Kaon". Towards the end of Season 3, the Decepticons rebuild the Omega Lock and attach it to the Nemesis, producing their own raw cybermatter with the aid of Ratchet's synthetic energon formula, and attempt once again to cyberform Earth.
    • On a smaller scale, Decepticon pirate, Hammerstrike of Transformers: Robots in Disguise (2015) causes oil spills to try to recreate the Cybertronian seas that he's accustomed to.
    • Transformers: Devastation: Megatron's Evil Plan is to use the Plasma Core Generator on the Proudstar, an ancient Cybertronian ship, to transform Earth into a new Cybertron (which will naturally have lethal consequences for all life on Earth). Megatron believes that Optimus Prime will balk at destroying the Proudstar because it's a repository for ancient Cybertronian knowledge that were lost long ago due to Cybertron's war.

  • In the second season of Earthsearch, Angels One and Two force the humans off the planet Paradise and back onto their spaceship by using its terraforming technology (the spaceship was originally designed to find a new planet for humanity to settle on) to melt the icecaps, causing massive flooding.

    Tabletop Games 
  • Dungeons & Dragons:
    • The Hulks of Zoretha intend to colonize and spread their kind over the world. In order to do this, they will attempt to destroy all life currently existing on it, in order to ensure that there will be nothing left to compete for resources with their descendants.
    • Abyssal incursions also work like this. When a group of demons crosses into the material world and stays in one place for a while — the number needed grows inversely with their individual demons' power — their presence wears away the boundaries between the mortal world and the Abyss. The natural world's affected first — plants twist into monstrous shapes, the weather grows chaotic and unpredictable and animals flee or are killed by the demons — and if the infection remains for long enough portals begin to open into the Abyss itself, allowing more demons through and hastening the corruption. At this point, the weather goes from hostile to outright supernatural phenomena such as rains of fire and multidirectional winds. The infection begins to spread as demons move into the wider world and carry the Abyss' taint with them, starting new leaks in other areas, and if this goes on for long enough one or more demon lords take notice and move in as well. The lord's presence vastly accelerates and magnifies the corruption, eventually drawing the world into the Abyss as a new abyssal layer.
  • Empire of the Petal Throne: Long ago, humanity adapted the world of Tékumel for human colonisation. Then, stuff happened. 50,000 years later, the original inhabitants still bear a grudge.
  • Metagaming's MicroGame 12 Invasion of the Air-Eaters: An alien race invades and uses Atmosphere Converters to change Earth's air to sulfur dioxide, which they can breathe but humans can't.
  • Magic: The Gathering: A single drop of Phyrexian oil can corrupt anything but it has an easier time with metallic objects. Karn the Silver Golem unknowingly spread Phyrexian oil on his travels throughout the planes thanks to the Phyrexian heartstone that Urza used to give him life. Then he created an artificial plane Mirrodin full of metal structures and metal-infused people. The oil he left behind quickly corrupted Mirrodin and turned it into New Phyrexia.
  • Transhuman Space: The reason why environmentalists are blocking the Green Duncanites' efforts to terraform Europa is because it would threaten the moon's indigenous microbes.
  • Warhammer 40,000 has three kinds of this, all distinct from one another.
    • Chaos energy, which is spread into the Materium from the Warp through Warp rifts, is the pure destructive kind, making the material world hospitable to demons. Ground tainted by Chaos can be distinguished through its deadened or charred appearance, the horrifically mishapen people, animals and plant life caused by spreading through contact, and the crazy effects on the sky. Standing on such ground and not going crazy requires considerable mental fortitude.
    • "Tyrantforming" is the first stage of devouring a planet by the Tyranids: the spores dropped onto the surface merge with local plantlife, turning it into Hungry Jungle - rapidly draining the ground of all nutrients. The Tyranids then devour the plants. By the time they're finished with a planet, the lack of a breathable atmosphere and any oceans makes the planet inhospitable without substantial effort, while Tyranid organisms left behind make that prospect extremely unwise. They eventually want to do this to all of the galaxy, though there is at least one system they're avoiding because it scares even them.
    • Orks are described as "an invasive ecosystem by themselves"; thanks to their spore-based biology. Left unchecked, Ork spores will gradually "Orkyform" entire planets. Orks are, in fact, even more virulent than the 'Nids in this regard. Once a spore lands in a spot with the appropriate resources, it will first form plants and fungi, then lesser orkoids like Squigs and Gretchins and finally proper Orks. The only thing that stops them from orkyforming the entire galaxy, let alone completely overtaking the ecosystems of most planets they wind up on, is that, unlike the hive-minded Tyranids, the Orks are Chaotic Stupid incarnate and they quickly resort to killing each other whenever there's nothing else around to fight.
    • In fact, the Necrons' idea of creating the perfect environment is to purge it of any and all life, down to the molecular level if necessary.

    Video Games 
  • Eris' "Harmony" in Agent Intercept. By using the transforming technology of the Sceptre (which she obtained by stretching the Agency thin with her Loki AI) on the tectonic plates, she renders the Earth capable of reshaping to her whims. Torpere isn't wrong when he says this could kill millions and irreparably damage the planet, and the scope of it is witnessed firsthand in the final level - fittingly named The End of The Earth - as you weave through roads, canyons, and rivers in pursuit of the ever-shifting route to deactivate it.
    Eris: Can't you see the order this will bring? Warring nations separated, new lands created, threats buried beneath the sea! Everything in a perfect harmony - of my design!
  • All K-D Labs RTS games employ combat terraforming to some extent.
    • All sides in Perimeter and two sides in Maelstrom can terraform the battlefield to create passages and so on. Both sides in Perimeter II (Exosus being waterborn, Comeback being landlubbers) and Hai-Genti in Maelstrom instead make parts of land inhabitable only for themselves.
    • In Perimeter, terraforming is out-and-out weaponized. The Exodus' superweapon, the Scum Disruptor, creates a volcano wherever it's targeted, and Scum Splitters create a localized earthquake.
  • In 1986 FPS tank simulator Arcticfox your task is to destroy alien installations that convert oxygen to elements aliens can breathe. The process starts when you enter their base, and Earth air becomes unbreathable in about 40 minutes.
  • Aurora (4X): Terraforming can add or remove any gas into a planet's atmosphere. Hilarity Ensues as well.
  • Champions Online. A mid-level quest features chain fights against the froglike Gadroon, who are seeking to Xenoform Earth into a much warmer, swampier habitat — starting in the middle of Canada.
  • In Civilization: Beyond Earth colonies following the path of Purity intend to replace their new planet's ecosystem with that of Earth's, rather than adapting themselves like Harmony and Supremacy. In fact, Harmony-leaning factions will demand that Purity and Supremacy factions stop clearing the miasma (a highly-toxic alien gas) near their lands, showing that they view this act as this trope.
    • On a tactical level, Harmony factions can engage in some Hostile Un-terraforming by deploying Miasmic Condensors, orbital units that create miasma (which heals and powers up their units, but damages those of other affinities). Their workers can also do the same to individual hexes as a defensive measure. This can also screw up any non-Harmony faction's trade, as their trade routes can't go through miasma hexes.
  • The Command & Conquer: Tiberian Series centres around humanity's adjustments to a world being transformed by the eponymous Toxic Phlebotinum, which not only converts the atmosphere, the people and the ecosystem, but also extracts useful minerals from the Earth's crust for easy harvesting when the invaders finally arrive in person.
  • Dawn of the Monsters: It's assumed that the Nephilim Monarchs and Nests are altering the environment in their vicinity to make the planet more hospitable for Nephilim and less hospitable for humanity... but then it's discovered that the Nests were actually cleansing the surrounding environment of the rampant pollution caused by humanity, leading the characters to speculate whether the Nephilim are actually Gaia's Vengeance.
  • de Blob: Interestingly, neither the Raydians nor the Inkies seem to be able to tolerate the environment that is suitable to the other; A world full of color and lacking ink is downright chaotic for the Inkies (and deprives them of the ink they need to replicate themselves), while the Inky world of black and white is painfully dull and polluted for the Raydians, even more so if they are forced into the suits that impede their movements and are the only known way that the Inkies can generate new ink. So it follows that in the areas that the Inkies take over, they dramatically alter the environment in addition to altering / bleaching buildings. This is often seen in the first console game in the form of massive spills / slicks of ink on the surface of formerly clean water and stunted vegetation. In the second game these effects are much more pronounced - Prisma City has suffered both heavy water and air pollution even before the formal Inky takeover, some buildings / landforms are submerged underground to impede Blob's progress, and perhaps most dramatically of all, the canyon leading to the Inktron Collider (formerly Prisma City's hydroelectric plant) is near-completely submerged in frozen ink. Of course, as Blob makes progress, he alters the landscape in a fashion that is detrimental to the Inkies.
  • Destiny: The alien Vex have xenoformed worlds in the system, including reversing the Traveler's work on Mercury to make it into a massive machine-world.
  • The villains in Destroy All Humans! 2 are a race of alien lobsters called the Blisk who seek to turn Earth into a new homeworld more habitable for them, which they plan to accomplish by causing World War III in order to leave the planet waterlogged and irradiated. Before, the Furons did this to the Blisk's former homeworld of Mars by nuking it into oblivion, turning a former aquatic paradise covered in oceans into the red dustbowl that we now know it as.
  • The Inferno DLC for Endless Legend adds the Kapaku faction, who seek to convert Auriga into a volcanic wasteland like their home planet. It turns out though that said home planet was also the victim of a different version of this, with invaders having converted their preferred scorching landscapes on it into verdant forested lands.
  • In Evolve, this is part of the process of a monster invasion. While the defenders are busy fighting the beasts, they fail to notice the atmosphere becoming toxic and the weather becoming unstable. Once there are no more humans, structures are razed and the planet is practically immolated as the monsters use key positions as nesting grounds.
  • The Korath Clan in Galactic Civilizations 2 are Absolute Xenophobes whose signature weapon is the Spore Ship, which eliminates a planet's entire biosphere and turns it into a toxic world that they can colonize.
  • In Haegemonia: The Solon Legacy, high-level spies can reverse-terraform enemy planets. It's not permanent (the enemy can simply terraform it back if they have the tech) but as planet quality is the primary factor in maximum planet population, killing off a few hundred million colonists or at least inciting revolution due to massive overpopulation with a single spy can really wreck someone's day.
  • Half-Life 2: The game in its released form contains hints of this. Most notably, the Combine drain the Earth's oceans and use Xen species such as Headcrabs and Leeches as biological weapons. The original beta however went much further - a key location in the game was the "Air Exchange", which replaced the air with noxious gases breathable by the Combine, and which meant that all human characters in the game had to wear gas masks.
  • Halo: As part of their process of absorbing a world's entire biomass, the Flood will convert the planet's atmosphere to one more suitable for expansion.
  • Horizon Zero Dawn:
    • This is the ultimate goal of HADES. Specifically, he was designed as a subroutine for GAIA, the AI responsible for terraforming Earth back to habitability after Zero Day. Building an ecosystem is complicated, but if she got something wrong, she was too much of an All-Loving Hero to do what needed to be done. HADES was designed to take control away from her if necessary, use the terraforming system to reset everything back to zero, and then give control back to her so she could start again. Unfortunately, nineteen years before the start of the game, a foreign signal of unknown origin caused HADES to activate unnecessarily. GAIA sacrificed herself to destroy him (while also creating a way to have herself rebooted eventually), but he managed to upload into a damaged Titan and continue his work to destroy everything. Worse, if he succeeds, GAIA won't be around to re-terraform the Earth again.
    • Horizon Forbidden West reveals the previously unknown origin of that signal. It was sent by Far Zenith, a mission organized by humanity's elite who, before the Robot War that destroyed Earth, tried to colonize the Sirius system. Unfortunately, their attempt to terraform a planet in that system failed, so they returned to Earth, hoping to use HADES to reset Earth to a primordial state so that they could colonize it without any complications from human societies on the surface.
  • The page quote comes from the 2001 video game Hostile Waters: Antaeus Rising. In it, the genetically-engineered "alien" species, after having Turned Against Their Masters, begin to drop the ambient temperatures of the island chain where they operate, in addition to pumping toxins into the air and increasing ground radiation levels, to bypass their in-built sensitivity to heat (which in itself was a safety feature to prevent them from spreading too far). The effects become more and more pronounced with every mission, until the final islands come to resemble nothing on Earth (and, indeed, the very last one was not even there in the first place):
    Sinclair: Sinclair, First Officer's log entry two-zero-three-two-kappa. The air is changing in composition. Radiation levels are shifting, altering in frequency and power. Something's growing in the rocks. The ground is scabbing over, shuddering with intense fungal infection. It's freezing. Humans couldn't live in an environment like this. Oh... God... That's the point!
  • Jak 3: Jak has to fight the Big Bad operating a massive machine called a Terraformer, meant to be used to fix the unfinished planet. Unfortunately, as it's Dark Maker technology, "fix" here means "ruin and make completely uninhabitable to current life".
  • Jeff Wayne's The War of the Worlds: Much like the novel, the Martians engage in xenoforming with their red weed.
  • In Justice League Heroes, Darkseid uses the Mother Box to warp reality and converts Earth into a new Apokolips.
  • In Lost Planet: Extreme Condition NEVEC is planning to terraform E.D.N. III in a way that would instantly thaw out the planet and kill the native Akrids and the rebelling colonists. Fortunately Wayne discovers an alternative that won't fry the colonists and by Lost Planet 2, ten years later, most of the frozen wastes of E.D.N. III have been replaced by deserts and jungles, and several new Akrid species are coming out of hibernation.
  • The planned fate of Earth in Manhunter.
  • The Shroobs do this to the Mushroom Kingdom in Mario & Luigi: Partners in Time. After raiding Peach's Castle and Toad Town, they proceed to cover it all in their native purple mushrooms — and also harvest vim from Toads, turning them into those mushrooms as well.
  • Phazon from the Metroid Prime Trilogy tends to do this. It turns out to be a Sentient Phlebotinum Planetary Parasite that originates from the planet Phaze, which deliberately seeds the universe with phazon meteors.
  • Resistance has massive temperature shifts - most obvious in Resistance 3 - due to the Chimera terraforming the planet to be more suitable to their own needs.
  • Shatterline has the earth's surface deteriorating into an endless Crystal Landcscape as result of a space virus that converts most matter into silicon, with the world's surface covered in gigantic crystal spikes that rips through entire cities.
  • Sid Meier's Alpha Centauri plays this trope every possible way, both in terms of mechanics and actual story. Humanity as a whole is trying to survive on alien planet. Said planet is a sentient being, which treats human activity as symptomes of a disease and reacts accordingly, mobilising immune response. With sufficent technology, it's possible to melt polar caps or cool down the planet, directly influencing sea level. This may lead to drowning of numerous cities, most likely belonging to unprepared enemy factions or render all ports facitilies useless (which can hit really hard pirate faction). There are also tectonic warheads, perfectly capable of causing local tectonic shift. And last, but not least, are fungal payloads, which cause a massive outburst of native lifeforms where they hit - usually with mind worms ready to attack everything outside their new habitat.
  • Spore: De-terraforming planets of an enemy empire to reduce the level of colony that planet can maintain is one of the simplest strategies for wiping out or conquering the home-world of a hostile race before your ship has top-tier weaponry available. It's especially effective against enemy home-worlds, as it reduces them from thriving T-3s with extra settlements (as many as 10 fully defended sites with fleets of defending ships), to a basic T-2 with two settlements at best and making them far more vulnerable to invasion. Empires will regard this as an act of war. More in line with this trope, the Grox, Enemy to All Living Things, can be killed by terraforming their planets, and likewise they specialize in deterraforming.
  • In Star Control II, Mycon Deep Children reshape planets they collide with, stimulating their volcanic activity to the point where it's comfortable for Mycons — obviously, since they enjoy temperatures above 600 Kelvins, it's less than comfortable for pretty much everyone else. Mycons don't seem to care.
  • StarCraft:
    • The Zerg cover the surfaces of planets with Creep on which they are able to "build structures" and get a bonus to their healing speed. Other races cannot build on Creep until it clears away after the source of the Creep (Hatcheries, Creep Colonies, Creep Tumors, or Overlords) is destroyed.
    • In StarCraft II: Legacy of the Void Amon starts terraforming Aiur with corrupted Void crystals that suck the life out of the surrounding life forms and summon Void entities.
  • In Stars! (1995) Claim Adjuster trait can undo enemy terraforming via Retro Bombs. Claim Adjuster races also can use Orbital Adjuster on a planet without conquering it, and Packet Physics races terraform planets they bombard with mineral packets. If environmental requirements of the sides are different (frequently, as it's 3 independent values), it's deterraforming for the target.
  • Stellaris:
    • The Prethyon Scourge can do this to worlds. The only solution is Orbital Bombardment; if they're caught mid-process, simply wiping out the terraformers from orbit will suffice, but if the world's been completely altered, the entire biosphere has to be glassed into oblivion. Even worse, the Extradimensional Invaders turn any successfully invaded planet into a Shrouded World that is lost to the galaxy forever, with even the most advanced terraforming tech being unable to make them habitable again.
    • Before update 1.3 it was possible to terraform inhabited planets to an ecosystem the population wasn't suited for, making them uncomfortable. After that patch only uninhabited (or stone age) planets can be terraformed by playable factions, but the process removes all tile blockers including hostile fauna or flora, suggesting that terraforming is a global extinction-level event.
    • A mild example is the possibility to terraform your own inhabited worlds into something better (usually a Gaia world). While it doesn't lead to any noted extinction events, it does incur a severe happiness penalty from that planet's population while the process is ongoing, implying that the whole affair isn't exactly pleasant to live through.
    • One event chain uncovers ancient terraforming machinery on one of your colonies. If you choose to reactivate it there's a decent chance it will terraform the planet into a sub-optimal environment for your species, possibly even a toxic world, or spawn hostile mutant monsters, but there's a small chance it'll become a Gaia world. On the other hand if you dismantle the machinery you will get a terraforming tech.
    • The Synthetic Dawn DLC added Machine Worlds as a terraforming option for robotic empires. They are entirely uninhabitable by organic populations, and any that are still on a planet when it is terraformed to a Machine World die instantly.
    • Similar to Machine Worlds, Hive Minds can create Hive Worlds, which are basically Expies of fully zergified planets. Their description says that the entire Hive World is one single giant organism linked to the Hive Mind, and any foreign being that makes planetfall is instantly attacked by the very ground itself.
    • Fanatic Purifiers and Determined Exterminators can change the type of an enemy planet via Armageddon-level Orbital Bombardment. Initially the planet became an uninhabitable barren world when the last POP died, but later it was changed to a Tomb World that can be colonized by robots or Tomb World-native species, or terraformed with late-game terraforming tech. With the Apocalypse DLC it is possible to create a Fanatic Purifier empire that originated on a Tomb World.
    • The Aquatics species pack comes with a new type of Colossus weapon that fits this trope even better: with the Hydrocentric ascension perk you can simply flood your enemies' worlds with water, instantly wiping out the inhabitants and creating an ocean world that is ideal for your species to colonize.
    • In the Toxoids species pack the Toxic God that devastated the homeworld of the Knights of the Toxic God turns out to be a Colossus that turns planets into toxic worlds. Upon completing their quest to find it the Knights can choose to destroy it or commandeer it as a weapon against their enemies.
    • Toxoids also has the Relentless Industrialists civic, which allows constructing a building on colonies that gradually terraforms them into Tomb Worlds while producing immense resources. Less of a problem for species adapted to Tomb Worlds.
  • In Sword of the Stars the different species have differing environmental tolerances. After the third expansion pack made it possible to occupy planets inhabited by "civilian" populations of different species the player has to choose between terraforming conquered planets to make them more hospitable to their imperial population, or keep it in a state the civilian aliens would prefer.
  • Warcraft III: While not on a different planet, the Undead faction produces Blight from its buildings, which kills the ground around them and turns trees into dead wood (though it's just as useable as before). Undead units only regenerate while on blighted ground, and unlike creep other factions can put their buildings down on it (it even dispels the blight in a wide radius).
  • Warframe: The Orokin covered Earth with a massive forest, with trees hundreds of meters tall, in order to render it completely unusable. And according to the Silver Grove quest, it wasn't doing so great even before that. Vast cities and technological ruins dot the planet, but they have been completely consumed by the forest. One mission type revolves around stopping the Grineer from poisoning the forest as they plan to use it as an industrial base to finish their conquest of the system. Despite all this, the primitive Ostron tribes have adapted to life, and are staunch allies of the Tenno.
  • XCOM 2:
    • This is seen on some maps. It's not a stated goal of the aliens and the effect is pretty patchwork, so it's probably more of a matter of the Elders being careless or lazy than malicous destruction. Nevertheless, the imported plants grow over everything to the near total exclusion of anything from Earth. These spots tended to be isolated out in the wildnerness, usually near ADVENT facilities the populace was never meant to see.
    • What is active policy is the euthnasia of nearly all animals, domesticated or otherwise. It's so bad that finding a pack of wild dogs is a rumor that can take almost a week to follow up upon. It also raises the question where those legendary ADVENT burgers come from.
      Shen: Nobody seems to be asking the hard questions, like when was the last time anyone saw a cow?
  • In the X-Universe's distant past, humanity launched fleets of self-replicating, self-improving terraforming starships to make the uninhabited planets of the precursors' Portal Network habitable. A glitched software update in 2146 caused the Terraformers to return to the Solar System in force, "terraforming" anything they found. New York City was leveled by a redirected comet or asteroid impact. In the games, most of the planets found in Terraformer (now "Xenon") territory have been heavily scarred by Xenon experiments.

    Visual Novels 
  • In Saya no Uta, the ultimate goal of the villain deuteragonist, Saya, is to convert all life on Earth into the sort of creature that she is. This inevitably creates a world that would be completely uninhabitable for unconverted human beings, populated by grossly mutated mockeries of normal life, and by twisted people likely driven insane by the pain of their transformation.

  • In Homestuck, the Troll Queen aka Betty Crocker's attempts to recreate Alternia on Earth lead to mass flooding and the extinction of humanity. Among other things, she tried to force humans to adopt troll culture and romance which was impossible due to basic biological differences. Humans don't mix their genetic material in buckets to make new larva, for example.
  • White Noise had this happen in the backstory. The aliens who killed off everyone on Earth's surface then attempted to terraform the planet to suit them, resulting in a clouds of toxic Murk that roam the surface.
  • xkcd: In "Marsiforming", a human suggests to terraform Earth to resemble Mars.

    Web Original 
  • Afterlife SMP: Goolien Lizzie turns half of a modded Yellowstone biome into a blue, gooey land reminiscent of "her home planet" of Zorgensploosh 12. This confuses Lauren as she lives in the other half of the biome that wasn't Zorgensploosh-formed.
  • In The Magnus Archives, servants of the fourteen Powers try to complete occult rituals that will re-shape reality to be more hospitable for their gods. The Magnus Institute has managed to sabotage thirteen of the fourteen rituals, leaving the way clear for them to summon their own patron, the Ceaseless Watcher.
  • In Nat One Productions's story-line Denazra, the machine fleets that are slowly cleansing the galaxy of organic life do this to every suitable planet they come across. They usually start work as soon as they arrive, regardless of anybody still living there.
  • Orion's Arm: Happened on occasion due to many early colonists preferring to adapt to new environments rather than terraform, putting them into conflict with later waves who would rather change the planet than themselves.
    • Most notably when the original Martian Tweaks were forced to leave their homeworld when the atmospheric pressure and oxygen content were raised to intolerable (for them) levels. However, the terraforming of Mars took long enough that a second clade of Martian tweaks emerged, and managed to halt the process at a level they are comfortable at.
    • A similar thing happened on Venus, despite the extremophile tweaks wiping out the baseline colonists (the former were then banished from the solar system).
    • When Zarathustra, one of the first exosolar colonies, was settled there was minimal terraforming and the tweaked colonists went feral. A couple centuries later Jupiter Transsystems arrived, enslaved the natives, and set up terraforming stations that would have killed off the tweak population if they hadn't also awakened and pissed off the original colony AI.

    Western Animation 
  • Oglethorpe and Emory of Aqua Teen Hunger Force tried to "deterraform" Earth in the episode "Bad Replicant". Except they have no idea how to do it.
  • Ben 10: In Season 3, Zs'Skayr's Evil Plan to make Earth his domain involves covering the planet's skies in a Corrodium shell from space which will block out the sunlight (which is deadly to Zs'Skayr), and enable him to rule at full power in the darkness. The fact the Corrodium shell will also mutate all human and animal life on the planet into monsters is believed to be a mere side-effect.
  • In Ben 10: Omniverse, the Kraaho attempted to detonate a nuclear device on Earth to heat it up and make it more comfortable for them, not caring that this would kill off the humans.
  • DC Animated Universe:
    • The Imperium in the series premiere of Justice League are Weakened by the Light, and so make machines that blanket the Earth's sky in perpetual darkness.
    • In Superman: The Animated Series, the forces of Apokolips attempt to cause a volcanic reaction that will turn Earth into a lava-spewing Mordor like their own planet. They try it again during the invasion in the finale of Justice League Unlimited. Neither one serves much of a practical purpose; Darkseid basically just wanted to mark Earth as his own.
  • The Irken Empire from Invader Zim employs a procedure dubbed "Organic Sweep" to terraform an already conquered planet. This consist of the entire Irken Armada bombarding the planet's surface with all their artillery, eradicating all the organic life and structures that might have survived the previous conquering.
  • Jackie Chan Adventures: In "Shanghai Moon", Tso Lan the Moon Demon plans to pull the moon out of its orbit with his gravity powers, which will wreck all of Earth's ecosystems, because he'll find the planet's landscape afterwards more to his liking. The show overall indicates this isn't in any way a necessity for him but is merely a matter of preference.
  • Solar Opposites: The Pupa is designed to eventually turn Earth into a duplicate of the planet Shlorp. "99 Ships" reveals that the Shlorp the main characters come from isn't the original one, not by a long shot. There have been thousands of Shlorps which repeatedly get destroyed, after which teams are sent out with Pupas to make a new Shlorp.
  • Star Trek: Lower Decks: In "Moist Vessel", the alien ship has an molecular fluid that converts inorganic matter to organic matter, which is why Starfleet wants to study it. Unfortunately, it does so indiscriminately and was meant for a different species, which causes problems when it infests the starships towing the derelict carrying it and starts turning them into alien plant life and coral.
  • Steven Universe:
    • It's revealed that had Earth become a Gem colony as planned, it would have been completely gutted to serve the Gem homeworld's purposes. The graphic simulation shows us a world that is nearly hollowed out, to the point that it can only charitably be called a planet at all, with Gem technology covering what's left. We don't know how many inhabited worlds have met this end. While the Crystal Gems managed to save the Earth, in-universe maps show that the Earth's geography was still drastically altered — most prominently, Siberia has largely sunk.
    • Lapis Lazulis have this job as a specific role in the Hive Caste System, using their immense control over water to reshape planets by slicing down the landscape with pillars of water.
  • Storm Hawks: In "Fire and Ice", the Blizzarians have used a blizzard crystal to turn a desert terra into something more suitable for themselves after their original terra was conquered by Cyclonia. The conversion was hostile two ways because, unbeknownst to the Blizzarians: (1) the terra was actually the Raptors' personal leisure retreat, and the lizards are none too happy at what the Blizzarians have done with the place; and (2) the Blizzarians didn't bother to properly check there weren't any heat-adapted animals living on the terra (which there are in the form of small, furry Leapers) before they froze over the environment. The terraforming apparently isn't permanent yet, as the Blizzarians still need to use the crystal (which is lost at the episode's end) to deal with geothermal geysers breaking through the ice.
  • Super Friends
    • 1973-74 season. The inhabitants of the planet Solar Terrarium are moving the Earth closer to the Sun so it will become hotter and more comfortable for them. They are too desperate for their own survival that they couldn't worry that the increased heat and resulting climate change will kill most of the humans living here. Being the benevolent heroes that they are, the Super Friends agreed to repair their planet if they stopped trying to mess with Earth's climate.
    • In an episode of Challenge of the Super Friends, beings from the planet Venus agree to help the Legion of Doom destroy the Super Friends in exchange for increasing the Greenhouse Effect on Earth so that the Venusians will be comfortable there.
  • Teenage Mutant Ninja Turtles (2012): Episode "TCRI". The Kraang plan to alter earth's atmosphere to one that they prefer, and that earth natives can't breathe in.
  • The Smogulans from Toxic Crusaders are trying to pollute Earth to make it more like the planet Smogula because their race need pollution to survive.
  • Young Samson and Goliath episode "Cold Wind From Venus". Two robots from Venus plan to impose "environmental control" over the entire Earth by reducing the temperature to -200 degrees Fahrenheit (turning it into an Ice Planet) so Venusians can settle here.

    Real Life 
  • Our Sun has done this a few times. When Venus was formed, it had water oceans as Earth has now but the Sun evaporated them, converting Venus into the Death World that is nownote . Conversely, as the Sun's luminosity is increasing as it ages, in around a billion years from now it's expected the Earth will be unhabitable too.
  • Invasive species: migrants introduce new species of plants or animals to an ecosystem for their own benefit, and the results on the native ecology are frequently disastrous.
  • The American Acclimatization Society's attempt to introduce European birds mentioned in the works of William Shakespeare to North America. Attempts to introduce rabbits to Australia for similar reasons didn't turn out so well either.
  • Going way back in time, the oxygen crisis definitely was an example of this. Free oxygen like we know today was not around much back in the early days when photosynthesis had just been invented and aerobic breathing was yet to be. Most early life was, in fact, unable to survive in the presence of oxygen. You can do the math on what happened next when primitive algae started pumping massive amounts of O2 into the environment.
  • The Atlantropa project, a proposal to build a series of massive dams at the Strait of Gibraltar between Spain and Morocco, the Straits of Sicily and Messina between Tunisia, Sicily, and mainland Italy, and at the Dardanelles to lower the Mediterranean Sea by up to 200 meters. Additional dams would've been created in the Congo basin to create a massive inland lake. In theory, this would've opened up massive new farmlands (especially in the Adriatic Sea), created an African reservoir to use for irrigation and shipping in the interior of the continent, generated tons of cheap, clean electricity with the mega-dams, and tied the Middle East and Africa closer to Europe, which Atlantropa's supporters felt was necessary for Europe to remain competitive with the rising America and the emerging "Pan-Asia". In practice, the new land created in the Mediterranean would've been salt flats useless for agriculture, the Mediterranean fishing industry would've been ruined, the African lakes created by the Congo River projects would've destroyed vast swaths of the Congo rainforest and displaced millions of people, and the climate change caused by shrinking the Mediterranean would've turned Southern Europe and North Africa into deserts and plunged Northern Europe into a new ice age.
  • During the age of American westward expansion, a number of high-ranking officials involved — most notably President Ulysses S. Grant, General William T. Sherman, and William "Buffalo Bill" Cody — set deliberate measures in place to kill as many American bison as they could, with the stated goal of making the Great Plains as inhospitable as they could to the traditional Native American way of life, which had relied heavily on bison hunting. One colonel reportedly encouraged a hunter that "Every buffalo dead is an Indian gone."
  • Global Warming / Climate Change, though not the goal of humanity's actions, is certainly an artificially induced process that is making the planet less hospitable to both human civilization and nature.

Alternative Title(s): De Terraforming, Hostile Xenoforming