Apocalypse How/Class 4

Planetary-scale Species Extinction of most complex multi-cellular organisms. Not only are humans gone, but most critters with them, leaving only a select few to evolve and refill the biosphere (or, as the name suggests, what's left of it).

Examples of Apocalypse How/Class 4 include:

Anime and Manga

• The anime Wolf's Rain, in which the Earth's crumbling biosphere is for all appearances dying of old age, has this as a comparatively optimistic outcome. No wonder the wolves want to leave.
• Mewtwo attempts this in Pokémon the First Movie via a self-produced global hurricane with the eye around his island. He creates a few dozen clones of the strongest Pokemon he could get, intending to repopulate the world with human-free Pokemon. Eventually he changes his mind.
  • In the following movie, the disruption of the harmony of fire, ice and lightning starts similar world-threatening storms.
• Second Impact in Rebuild of Evangelion and Neon Genesis Evangelion melted the Antarctic icecap and generated tidal waves that inundated coastal regions, wiping out cities and large tracts of arable land. Simultaneously, the oceans were poisoned and left barren and the axis of the Earth shifted. What species survived only endured due to humanity's intervention to maintain the terrestrial ecosystems. Third Impact is expected to escalate the situation to Class 5.

Comic Books

• In a three-part story arc at the beginning of John Byrne's post-Crisis Superman, (issues #20-22, 1988) three renegade Kryptonians from an Alternate Universe do this to their dimension's Earth. The enormity of their crime drove Supes to break his non-killing oath and give them a Kryptonite shower. Much controversy ensued.

Films -- Animated

• WALL-E: While (an unknown percentage of) humanity escapes into outer space, the biosphere of Earth completely collapses, with only two living species seen in the film proper: the cockroach, and a small plant (and both seem to be very rare). It appears that no humans survive on Earth itself. The fact that human civilization does survive (in a way) aboard the starliners makes this a bit of a toss-up between Class 4 and Class 1 -- but really, it's simply a case of humans fleeing from a Class 4 event.

Films -- Live-Action

• The cheesy sci-fi classic Robot Monster had the title baddie wiping out all life on Earth above insect level, save for a family of humans who took a serum to counteract the invader's Applied Phlebotinum. (The family lived a short walk away from the cave the alien was living in.)
• This is the effect of the Doomsday Machine from Dr. Strangelove. We'll...meet again...
  • Of course, the entire purpose of a Doomsday Device is lost... if you keep it a secret.
  • It's implied that life may survive in mine shafts, where animals will be "bred and slaughtered" and there will be "ten women to every man".
• The final prediction in Knowing. A massive solar flare incinerates the planet, instantly vaporizing everybody on it to a crisp, evaporating the oceans, reducing the surface to lava, and basically just ending all life on Earth, and ensuring it will never rise again for a few million years. Good thing the Sufficiently Advanced Aliens had spares.
• The Quiet Earth, film version. The vast majority of the Earth's animals were affected by the Event and disappeared, up to and including most humans. The cause of it was human-engineered, but the fact that animals were also affected pushed it from Class 3b to Class 4. Plants were completely untouched, however.

Literature

• In The Mote in God's Eye by Larry Niven and Jerry Pournelle, the Earth is a radioactive wasteland kept as a military training preserve by the Empire of Man, as a lesson to all young officers in the Imperial Fleet "to show them what the Empire exists to prevent." The only places on Earth that can support life are the high mountaintops (ironically, some Jamaican Blue Mountain coffee plants have survived the Apocalypse, and they've all been declared the private property of the Emperor for his exclusive use. Smart Emperor...)
• Clarke and Baxter's book The Light of Other Days describes an enormous asteroid that's going to collide with the Earth; large enough that the heat released will more or less sterilize the face of the Earth, such that only the most basic bacteria can survive. It eventually transpires that this had already happened once, billions of years ago, and the civilization that existed then hid away the life that would eventually evolve into us.
  • At the end of the book, this is averted, as society is able to deal with the asteroid by some unspecified means.
• Isaac Asimov's Foundation series has a galactic empire that has lost knowledge of where Earth is, although it is alluded to several times that it has been rendered fatally radioactive through nuclear war. The protagonists eventually find it.
  • In the Robot series R. Daneel Olivaw and R. Giskard discover that a spacer plot leads to the Spacers deliberately making the Earth grow radioactive to destroy the Settler society, and the robots refused to prevent the process, believing it will be better for the humanity, since it will force the Earthers to spread out.
  • In the opening chapters of The Stars Like Dust, the Earth has large areas of nuclear wasteland, and everyone is forced to wear film badges to measure their exposure to radiation, while in an early Imperial-era novel, the Earth is revealed to be almost completely uninhabitable.
• According to The Bible, a class 4 catastrophe occurred some 5000 or so years ago, with a global flood wiping out nearly everything except for a wooden supertanker-sized boat filled with animals and a human family.
• The conclusion of Dougal Dixon's Man After Man finds the Earth almost totally stripped of life by the evolved, no-longer-recognizable descendents of human space colonists. Its contaminated atmosphere no longer supports any organisms, such that only a handful of native species survive, clinging to deep-sea hydrothermal vents.
• David Gerrold's The War Against the Chtorr series is either Class 4 or Class 5. The Chtorr are gradually but inexorably replacing Earth's biome with Chtorr. The apparently inevitable result is the replacement of all life forms on Earth with Chtorr. The invasion started at the microbe level, with plagues that devastated the majority of human population. As the invasion continues, more and higher level positions in the food chain are being replaced with Chtorr, with the possible exception of the worms, who appear to be top-tier predators. But since nobody knows exactly what the Chtorr is, it's hard to say for certain.
• In Down To A Sunless Sea, the last nuclear war wipes out almost everyone, except two planeloads of people, who have to run to Antarctica to start over, then they discover that the nuclear weapons have knocked the planet off its axis, meaning that Antarctica is soon going to be in the tropics. Depending on which ending your copy has, either it's the end of the world, or they will go out to rebuild the world.
  • Mao Zedong apparently gave serious thought to having a few 747s full of Chinese citizens in the air at all times, to provide for just this situation. (In practice, the shockwaves from a global thermonuclear war would likely knock these aircraft out of the air, so it probably wouldn't work.)
• On the Beach showed humanity completely dying out after a large-scale nuclear war; in the book, just about every animal in the world is dead by the end.
  • This one is doubly engineered. The last of the human race is guaranteed to go extinct because of spreading radiation, but this death is so terrible that the Australian government has been issuing cyanide pills to everyone. Many of the last of the last people go ahead and take the cyanide.
• Scenario #8 in John Scalzi's Alternate History Search Results studies what would happen if Hitler had been killed in 1908...by hitting him with a meteor. Humanity and 93% of all species on Earth are killed off as collateral damage.
• In Alastair Reynolds' Century Rain the Earth has been taken over by nanotechnology gone amok, and the remaining humans live in space.
• In the Riftwar Cycle by Raymond E. Feist, Kelewan gets this, not once, but twice. In the same book. First it starts getting swallowed by an ever-expanding portal to what amounts to the second circle of hell, powered by the deaths of the army trying to stop it. Then, to put an end to that threat, Pug created a gigantic rift portal that basically slammed a large part of Kelewan's moon into its surface at extreme speed. Luckily, a good part of the population escaped to another world.
• The Fimbulwinter Game, played out at Dream Park in The Barsoom Project, depicts the near-total freezing of the planet by a crazed Cabal of Inuit sorcerers. Only Arctic natives and organisms have any hope of surviving, and it's hinted that the Cabal's rituals may have overdone it, potentially pushing even these into extinction (and this example into Class 5).
• Sergej Luk'yanenko's Линия Грёз, set in the Master of Orion universe, describes the destruction of the Sakras: the human Empire went for planet-wide meson bombardments on all planets that belonged to the Sakras race or were about to be conquered by them. Technically a class 6 for those Sakras on the receiving end, the bombardment burns the atmosphere and boils the oceans. Several decades later a human refugee remarks that there is hope for her homeworld - the oceans are about to stop boiling and the planet might be repopulated. The genocide of an entire race is unique in the books, and frowned upon by other races in the games, but repopulating and terraforming planets which were previously rendered sterile is par for the course. It is possible to win the game by becoming the only remaining sentient species.
• Roger Zelazny's Damnation Alley is set post-nuclear apocalypse. Most of the surviving population are in coastal cities, while those remaining in the Midwest blame scientists for the catastrophe, and crucify any they catch. There is animal life, but not as we know it.
• The Killing Star begins with an interstellar bombardment of relativisitic bombs pointed directly at Earth. The energy of the collisions causes so much devastation that almost all multi-cellular life is immediately annihilated.

Live-Action TV

• Power Rangers RPM starts with at least a 1.5, but by the end of Ziggy's first scene, it's clear that it's really a 4. Yes, this takes place on Earth. In PowerRangers. Its strongly implied that the means by which the Venjix Virus razed the planet was nuclear carpet-bombing.
• On Buffy the Vampire Slayer, the opening of the Hellmouth is a 4.5. This would release demon hordes onto the Earth, resulting in the extinction of not only the human race, but every other native critter. The natural biosphere would be replaced with a demonic one. This is averted four times, in the episodes "The Harvest", "Prophecy Girl", "The Zeppo", and "Doomed". The release of the First's army of Turok-Han, as averted in the series finale, would apparently have a similar effect.
• The Doctor Who stories The Ark in Space and "The Beast Below" disasters where enormous solar flares roasted the Earth, which are probably the same event. Humanity may well recover (they had warning and were able to evacuate), but the biosphere is implied to be long gone.
• The final episode of Dinosaurs.

Tabletop Games

• The Exterminatus operation in Warhammer 40,000 is an attempt to destroy a planet as an economic or military asset. Depending on how thoroughly it's carried out, it usually ranges from Class 4 to Class 5, but can go all the way to X if they really try. If the bombardees have particularly deep bunkers or the bombardiers get sloppy, this can be as low as class 2, as in the case of Tallarn (Single Biome Planet turned from lush vegetation to desert Death World, but still inhabited).
• The "Destinations" setting in "Post-Apocalypse Hero" takes place after a solar flare sterilized the Earth. PCs are among the few people who were far enough below ground to not be vaporized. Oh, yes, the total absence of plant life not only cuts down on food options but could thoroughly hose oxygen levels if you can't find a way to fix matters.
• Tech Infantry has a meteor impact do this to the planet Earth, although it is eventually resettled by humans and other life from colony worlds. Then it later gets destroyed in even more spectacular fashion.
• In the Dungeons & Dragons Splat book Elder Evils, this is the most likely worst case for four scenarios:
  • For the Sertrous scenario; should the heroes fail, the game world's ecosystem would remain unharmed, but most humanoid races would be rendered extinct and replaced by Sertrous' reptilian and demonic followers.
  • For the Hulks of Zoretha scenario, failure will mean the awakened Hulks beginning a campaign of extermination against all sentient beings on the game world who could possibly compete with their horrific offspring; the Blood Moon sign throughout the whole campaign might result in a Class 1 anyway, given the Hate Plague it causes.
  • Leviathan's scenario would cause whole continents to sink into the sea, destroying civilized areas; the ecosystem would mostly survive, but not much else. In fact, by the time its Sign reaches Overwhelming (right before the Final Battle) a Class 1 has already occurred, but hope for recovery remains should the heroes defeat the beast.
  • Worst case scenario for the Ragnora would make the world better suited to support life in general, but the corrupted positive energy caused by the abomination would be "too much of a good thing", causing most species who didn't die from it outright to mutate into horrid, mindless, pseudonatural beings.

Video Games

• The plot of the entire Halo series is a fight to prevent this from happening on a galactic scale.
• What happens to planets in "Spore" if you don't kill infected creatures in time in some some space stage missions. Biosphere Collapse. Everything, except your colonies, dies.
• In Xenoblade Chronicles, Zanza, the soul of Bionis, causes this whenever his civilization grows advanced enough to leave his body as without ether (i.e. life energy) from living organisms, he would die.

Web Comics

• In White Noise, the invading aliens temporarily halted the Earth's rotation, which caused everything to be thrown into the atmosphere and immolated. They then tried to Terraform the planet to suit their needs, but this didn't take. Life was only able to return to the planet because humans had three orbital space colonies to repopulate from. The Earth is presently habitable, but only by a very generous application of the word habitable.
• Homestuck: Every planet that starts a session of Sburb ends up with asteroids killing everyone who didn't escape.

Western Animation

• In the fourth season of Teen Titans, Trigon arrives and turns every organism on the planet into stone. Until the heroes hit the Reset Button.
• The pre-series apocalypse in Adventure Time seems to have been partially this, and partially version 3A: "Mushroom War" (name of the war that destroyed all humans but one...maybe) suggests that humans blew each other to bits, but there is also a distinct lack of normal wildlife in Ooo (about the only exception is Jake's family (dogs); everything else is anthropomorphic candy, part-rainbow, etc.) which sends it up to this class.
  • Actually, normal wildlife is also shown to still be around in the land of Ooo.
• Nightmare Moon attempted to do this twice in My Little Pony Friendship Is Magic, since nothing can live without the sun. She was stopped both times, however.

Real Life

• The great Cretaceous extinction event, which caused the end of dinosaur dominance on Earth's surface, falls here. Practically all large land animals went extinct, leaving small birds and mammals to take their place.
• The Permian extinction, 250 million years ago (and 185 million years before the Cretaceous extinction), killed off 95% of all species on Earth, putting it close to a Class 5. Thankfully for life on Earth, it didn't cross that line. Even jaded paleontologists not given to sensationalist names have nicknamed it "The Great Dying". In contrast, all the other mass extinctions, including the one that killed the dinosaurs, are only named after their geologic period.
• This is the outcome of a large (once every 50 million years or so) asteroid strike: most are not large enough to destroy all life, merely cause drastic climate change.
• Happened at the end of the Archean, when a nasty horrible toxic-waste-spewing ecosystem-destroyer evolved, and gradually poisoned the atmosphere for almost every other life form of its day. The culprit? Cyanobacteria. The toxic waste? Oxygen. Humans may manage to do the same thing over a period of thousands of years by replacing the biosphere and lithosphere with artificial structures while living on without a biosphere to support them, because that's how we roll.
• At the end of the Ordivician, Devonian and Triassic, a large number of animal species were wiped out.
• We're currently in the middle of a mass extinction surpassed by only "The Great Dying" in terms of species extinction (yes, we've surpassed the K-T extinction). Worse, it's caused by us.