Post Apocalyptic Decay
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Basic Information

This page describes the affects on our planet, it's environment, and human technology and endeavor in an After The End scenario. Assume mankind is wiped out by some contagious and lethal supergerm, or taken away in The Rapture. What happens to our planet, our cities, and any scattered pockets of survivors?

Cue the Apocalypse

Just how our world is altered will depend on what the nature of the Apocalypse is. The decisions you make for your campaign will color this information. If it's World War III, you'll have to worry about nuclear winter. If it's alien invasion, or a global pandemic, those will have consequences and aftershocks to affect this as well.
Just as important is on how long after the disappearance of man the campaign is set. The impact of time will be pretty radical, and is the bulk of what's detailed below.

Another important element is where the setting is on earth - coastal areas and rainforests will see the fastest degradation of man's monuments, and dry desert areas will preserve things the best. This is mostly addressed in the text that follows, but if setting a game in a very wet or very arid location, you'll want to adjust timeframes slightly.

The text below mentions survivors, since we're using this for gaming and at least the PCs are still alive. In order for these predictions to be accurate, though, far more than 99% of the population would have to be gone. Communities of even a few hundred survivors should have no trouble maintaining dwellings and with a bit of effort or luck retain some measure of technology. If more people survive in your world, then these descriptions may only apply to areas that are abandoned (for whatever reason).


A Few Hours Later

Psychological Trauma

This soon after the death or vanishing of humanity, the main focus is on the creepy ghost-town effect, and the mystery of what happened to the human race. PCs are probably among a scattered handful of those left on the earth, and they'll probably scramble to determine the fate of family and friends, scout for survivors, etc. Games with psychology and sanity rules should be smacking the players pretty hard.

Power Outages

Most Fossil-Fuel power plants shut down once their immediate supply of fuel is exhausted, within a few hours after mankind is gone. This causes local blackouts, which cascade across the power grid. Only places supplied by nuclear, hydroelectric, or wind power stay lit, and some of those blackout as power is drawn away from further down the wires.

Vehicular Dangers

If mankind left instantly, due to rapture or a disease that kills in minutes, then moving vehicles provide a challenge. Empty cars swerve and crash. They idle and pollute until their fuel supplies run out. Planes continue flying on autopilot until their jet fuel runs out, then they drop from the sky over a period of several hours. Trains collide or derail.


A Few Days Later

The ghost-town effect is still an omnipresent theme at this stage of the campaign. The initial shock may have passed, but survivors may still be facing denial, and are likely to seek out broadcasting towers and long-range radios to send messages that they hope will reach other survivors.

Vehicles are no longer a danger (or running), but the other issues that manifested within hours of mankind's fate grow more pronounced.

Blackouts spread further on the power grid.

Many subway systems and urban tunnels would flood as no one is around to activate the pumps that keep them dry.

Animals

House pets trapped in homes would begin to starve, though they'll have water leaking out of defrosting freezers. Pets capable of getting outside would escape and fend for themselves. Those bred for cute appearance, with short legs and small mouths, would face serious disadvantages. Given this situation most players will be likely to take pity on them and spend time opening doors or breaking windows so dogs and cats can escape.

Electric fences on zoo pens are no longer functional, and starving animals will eventually make a break for it. In the early stages they'll stay contained, or feast on each other, and not be a threat to PCs who don't actually go to the zoo.

Corpses

If mankind died, instead of disappeared, the bodies will begin to stink and rot. Scavengers will pick at the bodies, and most human corpses will be crawling with insects. These sights should lead to more psychological trauma in games that support such things.

In the big cities, there's just too many corpses for the PCs to bury them all. The stench of rotting meat will be awful. Smart survivors will grab supplies on day one, and drive to less densely populated areas for at least the first few weeks.

Toxins and Radiation

Nuclear reactors automatically enter safe mode and are rendered harmless. However, the on-site storage for spent power rods no longer has the water circulation needed to cool it. It boils away, and releases clouds of radioactive gas. This results in radioactive rain, and thus groundwater contamination downwind from power plants.

Similar problems happen within toxins (instead of radiation) at many factories. If the smelting furnaces, chemical extractors, etc were running when mankind vanished, safety measures and waste containment would likely fail, depending on the level of automation involved. The worst would be various industrial chemicals that are gaseous at room temperature, but stored in a chilled liquid state. Blackouts make the refrigeration shut down, and as the chemicals warm up they turn gaseous and expand. Pressure would build up, and without oversight (or power for automatic safety systems) many of the tanks would eventually burst, releasing clouds of chlorine or other toxic gases. Traveling through heavily industrial eras is akin to voluntarily subjecting yourself to a chemical warfare attack.


A Few Weeks Later

A strong element of any campaign set a few weeks after man is gone would be the interaction with animals left behind. Vermin will be everywhere.

Animals

Mice, rats, roaches and gulls will see a temporary upswell in population as food is briefly plentiful and easy to acquire. They take over the supermarkets and dumps.
Produce rots, followed by things that had been refrigerated or frozen. The insects and rodents eat into boxed and bagged foods.

If humans died, the insects that feed on them will also have population spikes, but eventually be forced to compete for dwindling resources as the corpses are cleaned. One exception to that crash cycle would be Mosquitoes. The vampire of the insect world would naturally exist in much higher numbers if not for the extreme efforts of mankind. Humans pour poisons into the environment, put layers of oil on top of lakes to asphyxiate mosquito larvae, and drain swamps all in an effort to battle skeeters. Without us around to contain and eliminate them, Mosquito populations will expand dramatically, and will feed off other animals. Mosquitos are also quite capable of supplementing their diets with plant nectar to get them through thin times. Survivors will need to contend with clouds of biting insects.

Those dogs that don't starve will begin to gather into packs, and a pecking order will develop.

Farms

Most of the cows will have died from starvation or udder infections. Only free range cattle will be likely to survive. In rural areas predators and scavengers (including domesticated dogs) will feed on dead penned up cattle.

Domesticated chickens probably won't survive either, as their survival skills have been bred out of them, and predators are many. Those kept in tiny cages in factory farms will starve or peck each other to death.

Supplies

At this point, PCs will be unlikely to have any guilt over raiding abandoned stores and houses for supplies.
Canned goods are still a plentiful source of food for PCs, but the trip to the grocery store to retrieve them will be a very unpleasant experience thanks to rotting food and vermin infestation.
Clothing, camping supplies, jewelry, firearms, etc, are also readily available. The buildings are still sound, and these sorts of stores probably won't feature nearly the level of infestation that plagues the supermarkets.


A Few Months Later

The survivors will have largely grown used to the ghost town effect by this point. Increased presence of animal life, however, remains one of the big themes of a campaign set in this timeframe.

Animals

Rats and mice start abandoning homes and supermarkets, and range further out for food. Hawks and coyotes come to prey on the tail end of the rodent explosion. Animals have definitely noticed the absence of man at this point, and wildlife will infiltrate the suburbs. Those housecats that didn't get trapped in a house and starve will have plenty to feed on, and will quickly adapt to the new conditions.

Cockroaches, having exhausted the actual food in our buildings, will eat paper, cardboard, and glue. PCs who realize this may struggle to protect libraries from insect invaders.

Large zoo predators will range further out, as the supply of their natural prey is exhausted. PCs may be prepared to deal with packs of dogs, swarms of insects, and rodent infestations, …but a tiger?

Supplies

Canned food is still good, and exists in sufficient quantities in large cities to sustain the PCs for some time. Accessing it is not nearly as much of a problem as it once was, as the supermarkets are no longer swarming with vermin.


A Few Years Later

The PCs are used to the ghost town affect by now. However, aging and disuse will cause buildings creak and groan, and that, plus animal intruders, may cause unstable NPC survivor to grow paranoid. The buildings themselves will remain stable for now. If you don't mind stairs, skyscrapers and other tall buildings are a good place to stay - the corpses are no longer fresh, the plants and animals haven't gotten very far up the buildings, and they provide shelter from the elements.

The last of the Hydroelectric Power Plants fail around the one year mark, and the nighttime world returns to a level of darkness the likes of which it hasn't seen in centuries.

Animals

Wild animals would move into the cities in large numbers. The PCs are probably used to this by now. Unless survivors are numerous or very active (or live in tall buildings), wild animals will never be far away. The migratory patterns of land animals may resume, as there are no more busy highways to interrupt them.

Most of the vermin who had major population spikes in mans immediate wake will now have reduced numbers, as food supplies have dwindled and predator populations increased.

Overgrowth

A new visual to spring on the players is how plantlife has expanded into urban terrain. Plants will sprout within the cracks in streets, sidewalks, and buildings. Within five years, most urban areas will be covered with grasses, vines and saplings. Ivy crawls up the walls unchecked. Roads will disappear beneath the clover. Non-native plants that were formerly tended by gardeners will have either died off or spread out of control, depending on how well they deal with the local climate.


A Few Decades Later

Former garden vegetables now resemble wild strains, and are less palatable. Survivors who've hunkered down and engaged in controlled agriculture as opposed to nomadic hunting and gathering won't face this particular problem.

Buildings

Predominantly wooden houses have burnt and rotted away, unless they are being actively maintained by PCs or NPCs. The roofs will collapse before the walls, and trees may grow within them after the roofs are gone. Unchecked by man, termites will prosper and consume residential areas, so even houses maintained by PCs might start to have issues.

Brick and masonry buildings are weakened by salts and plants, but many still stand, and any maintained by PCs should be fine.

Buildings in arid climates fare the best, those in coastal or rainforest areas deteriorate quickly. Lowland and coastal cities are swallowed up by (or washed out to) the sea as locks and dams fail due to disrepair.

As the window sealants succumb to the weather, windows in skyscrapers crack and fall to the ground far below. Walking between the skyscrapers is hazardous due to the falling glass, though the concrete and steel buildings themselves are still stable. Steel structures show stress and corrosion, but still stand.

Suspension bridges, however, will give out. It only takes a few corroded cables to start a chain reaction that collapses them.

Animals

Thanks to neutering practices while mankind was around, many of the large dog packs will fail to sustain their numbers. Larger domesticated dogs will likely be accepted into wolf packs, and may interbreed with wolves. Even if the crossbreeding doesn't happen, wolf territory and numbers will expand dramatically in the absence of humans.

As the windows of skyscrapers crack and fall, pigeons and other birds will nest within the building frames.

Whether animals that escaped the zoo will die off or adapt to their transplanted environment is not only a matter of the animals fortitude and survival skills, but also a matter of whether or not mating opportunities are available to continue the line. If the local zoo has just one big cat, it's only a threat for so long. But if it has mated pairs of lions and tigers, you could end up with generations of cubs and even a few ligers and tigons.

Vehicles

Most automobiles will have rusted out and been overgrown. Tires have deflated, but are still intact. Within 75 years most cars aren't even recognizable unless you dig through the overgrowth - only their tires and plastic components will be the least bit salvageable.

Coral reefs will form around abandoned ships in harbors and beaches. While ships washing up on individual beaches is rare when you look at the short term, after several decades they'll start to accumulate. There are still plenty of ghost ships adrift on the sea at this point.

Toxins and Radiation

Rains have dispersed the radioactive clouds the Nuclear Power Plants emitted, and buried or scattered the particles. Life will return to the areas around the powerplants and factories, and only the most concentrated pollutants will keep plants and animals away. By this point you might not realize there's something toxic nearby until you're almost standing in it.

Satellites fall from the sky over time, looking like shooting stars. Only a few reach the ground to start fires. Some will have nuclear reactors, and without anyone monitoring their safety failures, the debris may contaminate large areas.


A Century Later

Remains of Technology

Houses have vanished in areas at all prone to hurricanes or flooding. Wood support beams will have rotted, and the waters will wear away at bricks and mortar. The next big storm washes away even the bits that can't degrade.

Tin cans are corroding and degraded. Should you find a can that's appears to be intact, the food inside it is probably unsafe by now. Aluminum cans are faded, but not corroded.

Abandoned tires finally start to decompose. All that's left of cars is just the most durable plastic pieces, and corroded bits of metal. Even cars maintained by the initial survivors will be non-functional now. Unless enough people survived with the knowledge and resource to make new ones, they are lost.

Books that weren't personally saved by human Survivors are completely lost. Weather penetrated the library roofs, rain molded the books, and vermin ate the pages. Much of technology, science, and philosophy will have to be discovered all over again. PCs hoping to preserve the knowledge of man will need to gather the books in an arid climate, dry them out, and seal them in aluminum, plastic, or pottery.

Plants and Animals

Vines grow up into the steel and concrete skyscrapers, turning them into multistoried ecosystems. Rodents and birds move into them when the plants do. Feral cats become the ultimate predator in this environment, capable of climbing and skulking through the layers.

Most animal species reproduce quickly enough to have repopulated themselves to levels approaching those before the industrial revolution.

Human survivors have certainly reproduced, but mankind has longer gestation and slower onset of maturity than most of the animal kingdom, so it'll be a while before we hit our old levels again.

The sea is once again teeming with life as it did before commercial fishing. The oldest of individual fishes will reach sizes they rarely (or never) did when man was hunting them.


Another Century Or Two After That

Assuming the PCs didn't get themselves killed off before establishing a community of survivors and future generations, they could be the new founding fathers.

Plants and Animals

Elephant populations expand dramatically in regions where they'd previously been endangered by Ivory Poachers. They fear no predators now.

Winters are colder than they were when humans were around. There's less pollution, fewer fires, and no cities to hold in the warmth.

Rodents, birds and cats are displaced (or killed) as the skyscrapers collapse.

Buildings

All that remains of houses is the plastic, aluminum, and stainless steel items that were within them. Pots and pans, faded toys and utensils, parts of appliances can be found amid the undergrowth. Suburbs have reverted to forest.

Subways and tunnels in urban areas, which had flooded long ago, cave in. This collapses many skyscrapers before the time they would have normally become unstable on their own.

Other large steel structures collapse from corrosion and disuse over the centuries. Proximity to water is a large factor in how fast they degrade. When one of these buildings comes down, it'll be a sight to behold (and very dangerous to those near it). Concrete buildings slowly succumb to moisture as well, as the rusting rebar reinforcements breaks them from within.

Other Debris

The last of the ghost ships has washed ashore or sunk. Ocean beaches are littered with rusting hulls.

Metal casings on atomic bombs corrode away, leaving radioactive cores exposed.

Aluminum cans slowly degrade over the course of 200-500 years of exposure.
Plastic may photodegrade and break into smaller pieces as it weathers, but does not biodegrade into non-plastics.
Other substances likely to survive beyond this point are ceramics, bronze, and radioactive isotopes.


A Millenium Later

The survivors have had long enough to reproduce and relearn lost technologies, if they didn't learn their lessons they could rebuild quickly enough to do this all over again.

Modern cities disappear entirely, buildings having long ago collapsed. Their wreckage has now been been broken apart by the roots of the trees now growing atop their wreckage. Plastic items remain, but are broken by roots an buried under layers of new topsoil.

A new ice age likely expands, further obfuscating and damaging whatever stone walls and well-constructed artifacts may have miraculously survived to this point. Eventually, glaciers will bury Chicago, New York City, and Paris under tons of snow and ice. The southern US will also become cold desert. The Amazon rain forest will die off, and be replaced by a grassland.

Only a handful of man-made structures can still be detected: Hoover Dam, Mount Rushmore, The Great Pyramids, the Great Wall of China. The rock ones might stay recognizable for hundreds of thousands of years. Perfect for a Planet of the Apes Ending, though Lady Liberty herself has long since corroded and collapsed.


Much, Much Later

Chemical pollutants in the soil, present since the start of the industrial revolution, are finally cleansed away after tens of thousands of years.

Exposed nuclear bomb cores (remember that the metal casings corroded away) are far less dangerous, having met their half life several times over. Depleted Uranium has an insanely long half-life, though, and it's tough enough to survive the passage of ice ages.

Bits of plastic remain for millions of years - it doesn't biodegrade, it just breaks into smaller pieces. Styrofoam likewise has in indefinite lifespan, it might never break down. Individual styrofoam beads and tiny flakes of plastic will be found in the soil and on beaches for ages to come. Beyond what we see, microscopic flakes of plastic will litter the air, water, and ground for until something evolves to feed on it. Though portions of it will sink, shatter, or be eaten by animals, the bulk of the Plastic Continent will remain long after man is gone.

After several million years, Continental Drift will fill in or squish the Straight of Gibraltar and turn the Mediterranean Ocean into a land-locked sea. The next big ice age after that will drop sea level and turning it into a desert salt flat.


4 to 5 Billion Years Later

The sun swells as it nears death, raising the temperature of the planet beyond what multicellular life can endure. Microbial extremophiles survive for a million years beyond that. Eventually, though, the expansion of the sun sets the earth ablaze, and all is swallowed in fire.


Not On This Earth

It's possible the PCs aren't on the earth when the apocalypse happens. What evidence will be found as they approach and try to land?

Returning from Space

The final radio and television signals of Humanity degrade into the background radiation after they travel a light year or two, rather than the waves continuing across the cosmos infinitely as had once been thought. If the setting had manned deep space probes out before whatever calamity befell the earth, those missions might have expected there was a good chance they'd lose contact with earth during the voyage. Radio silence won't be disturbing to them until they get back within a light year of earth. They'll certainly be confused or scared when they return to find humanity mysteriously gone and their landing pads overgrown. Genre Savvy characters might hit on the planet of the apes angle pretty quickly.

If they approach on the night side of the planet, the lack of lights from cities will be very noticeable, and very disturbing. Radio break up could just be solar interference or equipment malfunction, but a dark planet means something really bad has happened back home.

Meanwhile, On The Moon

Items left on the Moon will stick around for millions of years, even those that would have been unrecognizable after a year on earth. There's no atmosphere, moisture, or bacteria on the moon to break them down. Long after man has passed, aliens exploring this region could learn of us by finding things left in our various lunar landings. Unless that changes somehow, things on the moon should be perfectly preserved until the Earth or the moon are destroyed.

See Also


Sources

Bibliography
1. Books: World Without Us by Alan Weisman
4. TV: Life After People on the History Channel
6. TV: Aftermath: Population Zero on the National Geographic Channel
8. TV: The Future Is Wild on Animal Planet

The wikipedia pages in particular have been most helpful in assembling the above timeline.

Game and Story Use

  • Hopefully very useful for an After The End campaign, where this information can add to campaign verisimilitude.
  • May be helpful for setting Alternate History or Lost Civilizations in your campaign setting. Turns out, as long as a civilization didn't develop plastics, aluminum, radioactive isotopes, or advanced chemistry, it can vanish without a trace a few hundred years after societal collapse. Atlantis, Hyborea, Mu, Pre-Desert Sahara, or some unknown culture in Antarctica could have hit an almost Wild West level of technology without leaving signs of it's passage. Much more advanced than that, though, and we'd be swimming in Out Of Place Artifacts.
  • You could give a Planet Of The Apes Ending to a fantasy setting. After several months of play with only very subtle hints the players are likely to miss (describing bits of broken plastic as gems or magic eggs or whatever), have the PCs pursue the orcish bandits (or whatever) back into their hills and find Mount Rushmore or the Hoover Dam or just a superdungeon, that turns out to be Site R. The players would get it, even if their characters didn't.
  • How about a sci-fi version of Roanoke Colony, where the PCs arrive to find a formerly-prosperous colony world empty? They have to figure out why it went dark, and how recently, so that they can know if this is a threat to other colonies.
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