Oceans if people disappeared

[Brigid Barry]

There's a great series on History Vault about what would happen if people disappeared called Life After People, unfortunately none of the episodes have what I'm looking for and internet searches were less than helpful. Trying to figure out what might happen to the world's oceans and seas for my post-apocalyptic fantasy. The human population is dramatically reduced, but for the sake of simplicity let's pretend people are gone.

Will there be any trace of shipwrecks? The Titanic is predicted to disintegrate entirely in about 30 years. Would there be any sign left of the metal ships currently on the world's oceans? Rust on the ocean floor? Anything that someone can look and say "a ship was once here"?

Would endangered marine life recover if the threats posed by shipping, fishing, and other human activities ceased, or would they continue declining into extinction? Thinking mostly about whales and other sea life that can be viewed from the surface.

Thanks in advance!

 

[Maggie Maxwell]

Well, a quick google says that the oldest known shipwreck location dates back to somewhere between 2700 to 2200 BC. While the ship itself is gone, a cargo site with clay vessels and other ceramic piece remain. Four to five thousand years underwater and still traceable. It feels safe to assume that there will still be traces of seafaring life if you know where to look. You might also get coral reefs forming over the wreckage and holding things together longer. A lot is going to depend on just how far in the future this is. The closer to the societal collapse, the more likely there will be remnants. There's also cases of stone o concrete statues underwater that will be worn down with time, covered in barnacles, but still probably maintain a human shape for a long time.

Endangered marine life is going to entirely depend on the sustainability of the creatures in nature at the point of collapse. If the species is maintained by breeding and rescue facilities and hasn't reestablished a sizeable genetic biodiversity, they probably won't make it on their own. Things that lay clusters of eggs will have a better chance of recovery than mammals that birth one or two babies at a time. Or at least, they'll recover faster. I think in this circumstance, really anything could be believable. If you want something to be extinct or to survive, they probably can. I think recovery would be the most likely event for the majority of species, and we'd see a lot of coastal activity. Prey would increase as they lay more eggs, then the predators increase for having more food, and you'd end up seeing a lot of hunting whales nearer the shores. Just theorizing from basic biology, I'm far from an expert on any of this.

 

[Unimportant]

My vague understanding, echoing the above commenter, is that some things like stone and clay and glass last a long time, particularly underwater. Metal and wood, far less. Styrofoam and plastic and disposable nappies -- dunno, but probably forever

 

[CMBright]

If you are projecting from Earth today, how warm are the oceans going to get? Will algae be able to adapt to temperatures or die off? If algae dies off, that is a major source of oxygen for marine life. It is also a major source of oxygen for air breathers as well. Expect a lot of marine and terrestrial die offs.

If algae adapts and survives, there is a lot of overfishing right now.

Best guess, given too many variables, is that most endangered species would recover with bottleneck effects as long as viable breeding populations remain in the wild.

On the land side of the artic, we are seeing increasing overlap in polar bear and grizzly bear territories resulting in hybrid cubs. This might occur in marine species as well. While it is rare, a small percentage of hybrids are naturally fertile. Imagine what might result from a fertile cross between a beluga whale and a narwhale after a number of generations.

 

[Helix]

Sea defences will get eroded without constant maintenance, so you'll get collapse of sea walls and dykes resulting in the flooding of low-lying areas, beaches being swept away by storms and longshore drift, and cliff collapses. Rivers and ports kept open by dredging will silt up.

 

[neandermagnon]

I think without humans all the ecosystems would recover, but won't necessarily be the same as before and how long it takes would vary wildly from place to place and depending on the extent of the damage. There will be species that go extinct, both because humans pushed the population to critical levels but they never recovered, and because the post-human ecosystems adapt in a way that doesn't enable certain species to survive any more.

Look at how the Earth recovered from previous mass extinction events. Ones that wiped nearly all life on Earth, where only a few things survived, but those things evolved into new species, including completely new megafauna. Life finds a way and as destructive as humans are, we aren't close to wiping out every last bit of life on the planet. Whatever's left will evolve to adapt to the way the planet is. It's helpful to think of ecosystems rather than individual species. Where species are lost, they will eventually be replaced by whatever evolves to fill those ecological niches. Past mass extinction events give us clues as to how long this would take, but the extent of the disruption is a factor. Humans not being there anymore isn't the same as a volcanic winter.

There will always be traces of humans, such that any alien species or newly evolved sapient species would be able to find traces of humans, including traces of shipwrecks. The question is what level of technology they would need to discover them. For example, Victorian scientists discovered Neandertal bones - you won't find them without digging. Modern scientists discovered Denisovans by analysing the human genome and sequencing the genome of a toe bone fragment in a cave in Siberia, and have discovered traces of Neandertal DNA in caves where no other Neandertal remains have been found. You need much more advanced technology than digging implements to discover this kind of thing. So it all depends on who's looking and if they are actively looking or just seeing what's there on the surface.

Also, there are still the remains of shipwrecks that are much older than the Titanic. The Mary Rose is the most famous British one. It was Henry VIII's ship which sank in the English Channel and it survived for centuries and was dredged up in the early 80s (I remember watching it being recovered on TV when I was in primary school) and is on display in Portsmouth (which is on the south coast of England) if you want to go and see it.

I've watched documentaries about even older shipwrecks - from ancient Roman/Greek times. The building materials were different to the titanic - mainly timber. Not only have the shipwrecks themselves survived but often some artefacts from trading ships survive also. One documentary, the ancient shipwreck site had lots of amphoras, which they could forensically analyse and find that they contained some kind of oil. (I forgot the exact details.) Even if iron/steel hulls may rust away given enough years, there will be other materials that don't decay so fast. Even the timbers of antiquity haven't all rotted away. There will be non-perishable materials left behind such as cargo.

There are various documentaries about old shipwrecks, what's left, how scientists have analysed them, etc - I don't know what streaming services outside the UK would have them, but on Disney Plus in the UK there's the National Geographic sub channel, there's the Drain the Oceans series which is about archaeology under the sea - I'm pretty sure the above examples that I remember (i.e. the non-Mary Rose ones) come from this series, but I'm not 100% sure because I watch a lot of these kinds of documentaries. It's fascinating and will probably help you find the answers to your questions about what evidence, if anything, your story's characters would be able to find of shipwrecks. If you look up about the Mary Rose you can find all kinds of info online, not just on the ship but also extensive archaeological studies done on the human remains and other artefacts found within the wreck.

 

[Friendly Frog]

What timeframe after the disaster do you want? Thirty years after an apocalypse is going to have more human remains than after a hundred.

The whale-hunting moratorium has shown many whale species can repair their numbers if human hunting is vasty reduced. And without direct human intererence the degradation of their habitat due to shipping (noise, pollution, collisions, overfishing of whale food) will allow them even to regain more of their habitats and bounce back even better.

Generally species can bounce back if the pressure is eased off. It mostly depend whether they have enough habitat left to thrive. Ocean dwellers should have it easier than landanimals. Endangered species, like say in Australia, may not make it without humans to keep the non-native predators at bay. If humans die out suddenly, the adandonned pets are going to wreak havoc. Take the kakapo for instance, the world's largest flightless parrot from New Zealand. Currently only survives through a rigorous breeding programmes that has taken every remaining bird to a set of predator-free islands off coast. If any stoat makes it to those islands, like they have in the past, and there are no humans to intercept them, the kakapo can go extinct in a matter of years. If they even survive without humans because they get fed and all wear tracking equipment.

Is the apocalypse very sudden or very gradual? This too will have an impact on what remains. If it's sudden, you can have a lot of ghost ships floating the ocean for years afters. If it is gradual, those ships will likely end up their lives as rust in harbours.

 

[Brigid Barry]

My vague understanding, echoing the above commenter, is that some things like stone and clay and glass last a long time, particularly underwater. Metal and wood, far less. Styrofoam and plastic and disposable nappies -- dunno, but probably forever

400-600 years. So the metric tons of plastic that go into the oceans (according to NOAA, China is by far the worst offender) will be gone by the time this takes place.

@neandermagnon I've seen several all the documentaries about the wooden ships. I think there was a viking ship that got returned for the sake of preserving it and the one you were discussing in the Mediterranean. I was this close to mentioning that in the original post but didn't. I'm more talking about the ships on the oceans today - the military and shipping vessels, aka, the steel-hulled giants.

Thank you all so much for your answers! My story is in one tiny fraction of the world but now I'm sad about the parrot in New Zealand.

 

[jclarkdawe]

Shipwrecks disappear at vastly different rates. RMS Titanic is disappearing rather quickly. USS Midway is suffering very minimal damage from sitting on the bottom of the sea with most of the damage being caused by battle damage and the plunge to the bottom. Here's an article on Black Sea shipwrecks. https://en.wikipedia.org/wiki/Ancient_Black_Sea_shipwrecks. Some ships have sat on the bottom for centuries in incredible states of preservation.

So the question is what sort of time span are you talking about? Then you have to look at the environment in which the remains of a ship are sitting in, just like remains that are out of the oceans. Some places keep artifacts without damage for centuries, other places can cause things to disappear in a few years.

 

[Brigid Barry]

About 1000 years, in cold seawater up to a few hundred feet. Strong currents and moderate winters.

 

[Maryn]

400-600 years. So the metric tons of plastic that go into the oceans (according to NOAA, China is by far the worst offender) will be gone by the time this takes place.

I don't get it. Where is all this plastic going? My (shallow) understanding is that much of the plastic waste in the oceans is likely to take thousands of years to break down (except for newer plastics designed to break down more quickly--don't use grocery bags for long-term storage). Maybe when I learned this, the experts' understanding was incomplete?

 

[Brigid Barry]

This is the site that I used (very late at night when I was tired): https://www.weforum.org/agenda/2018...ong-everyday-plastic-items-last-in-the-ocean/

It was specific to plastics in the ocean, which might be different from plastics in landfills or other environments.

 

[Maryn]

Thank you. Looks like what I was taught long ago might not be right.

 

[dickson]

Would endangered marine life recover if the threats posed by shipping, fishing, and other human activities ceased, or would they continue declining into extinction? Thinking mostly about whales and other sea life that can be viewed from the surface.

That’s the $64,000 question of our present pass, innit?

 

[Brigid Barry]

Thank you. Looks like what I was taught long ago might not be right.

And this may just be one small piece of data. It also says that it breaks down into microplastics - maybe the microplastics take additional time to degrade and the entire time for plastic to degrade is thousands of years. I don't know. I was honestly surprised to see the time ranges in that article because I also believed 1000 years.

 

[Friendly Frog]

If you need a metal ship to survive, I think you could make it work, provided the ship has spent most of that millenium in good preservation conditions, like being buried under mud or without air or oxidising agents. Most of the shipwrecks that have survived under water have either been buried under sediment (until the weather, calamity or archaeologists uncover them again) or like in the Black Sea which has oxygen-starved depths.

There have been metal swords found that are at least that age that have been wel preserved. But the conditions are key. Anything exposed, like a wreck in a shallow sea or stuck into a beach will have weathered after so many centuries.

Climate change can play a factor. If the global climate shift and the accompanying acidification of the oceans continues, the world may lose much of the coral. But some scientists have argued that, in light of prehistoric records, it is possible that coral can reappear quite quickly after long period of acidification, so the post-apocalyptic world does not have to be coral-less.

Same with water levels. Global water levels are predicted to rise so the coastlines may become entirely redrawn. The past can serve as good inspiration. The forming of the Mediterrannean comes to mind. The inside of North America has long been an inland sea. Doggerland that once connected the UK with mainland Europe. etc...

Thank you all so much for your answers! My story is in one tiny fraction of the world but now I'm sad about the parrot in New Zealand.

For what's it's worth, the kakapo isn't doing so badly right now. The breeding programme is impressive in its achievements. They went from 50 something birds to a little under 250 since the start. It's slow-going but parrots are slow-growing animals and the dumbasses have tied their breeding to a plant that only fruits like once every four years or so. Who knows, maybe in your story, when the apocalypse comes, their numbers are vast enough to maintain the species without our help.

 

[ElaineB]

Re that WEF site. "Biodegrade" might need definition. That article's from 2018 and recently plastics from the ocean have been found in clouds over Mt. Fuji. What that means is still unclear.

 

[frimble3]

Interesting that killer whales (orcas) seem to be willing to test this hypothesis.
Their attacks on boats seem unprecedented (unless up 'til now they've been eating all the people on board) and, (this has got to mean something) they seem to be attacking yachts. Not small pleasure craft, not fishing boats, not swimmers. Just big, fancy, pointless yachts.

 

[tusenord]

I know that the wood ship of Vasa was preserved in water for quite some time, and that bringing her up to the surface after over 300 years actually started to degrade her. Huge museum in Sweden about her - https://www.vasamuseet.se/en/explore/vasa-history

Marine life should recover, but that's based on each species reproduction rate etc and other climate changes. If the amount of breeding pairs is too low, there could be a genetic drift that wipes them out though, especially with climate changes or sudden weird weather phenomenon. The fact that there is no more noise should make a difference in migration routes. Marine life that depends on fresh water migration (salmon etc) should keep having issues because dams should still keep them from their breeding grounds. Deltas might still not develop properly for the same reason. Beaches could be washed away where humans have kept replacing sand that would otherwise be brought to the sea by currents. Some marine life that has been able to use human activities (like feeding at fishing docks) could experience issues - but that's mostly birds I guess.

Plastic breaks down into smaller and smaller pieces like you discussed, and would probably be eaten and kill animals for a long time. Something you really should consider is the dangers of ghost nets - forgotten nets that will keep killing animals until the net degrades (and modern ones are often plastic).

I could probably come up with more stuff but got to run to work!

 

[Brigid Barry]

I decided that people had the common sense to shut down the nuclear plants and generally clean up what they could because it was pretty obvious that things were going to fall apart. They installed wells and made sure that there was basic infrastructure for when everything went dark.

How fun it is to build this entire world in my head where only I can see it.