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The Scenario

After an apocalyptic events my world was permanently covered in dark clouds. They seem to have unique property of absorbing most of all light. Even worse is that these clouds stick around permanently.

I am well aware of all the secondary consequences of such an scenario like freezing temperatures. Though because I want to focus only on the darkness aspect I will assume that only visible organisms are affected.

I also know of the various ecosystems that survive with out light. Though my question is what would survive in a normal European ecosystem if we drastically reduce it's available light? Or if any flora could even survive.

Assumptions:

  1. Assume an European ecosystems
  2. 90% to 98% of sunlight is blocked
  3. Higher frequency = higher block %
  4. Lower frequency = lower block %
  5. The conditions are PERMANENT

Ignore the following:

  1. Temperatures differences
  2. Changes to wind and rain
  3. Microbes and ocean life

Structure of the solution

By many solutions

Name what can survive in broad categories and don't focus on individual species.

By a few solutions

Name the individual species that could survive.

By no solution

Just say so, having no possible surviving species is also a valid solution.


Related questions:

Part 2: What fauna can survive a permanently dark sky?

Part 3: Living under a permanent dark

Related: Highly resistant House Plant

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    $\begingroup$ Don't answer in comments $\endgroup$
    – L.Dutch
    Commented Apr 9 at 2:30
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    $\begingroup$ Have you done any research into what lives in caves or deep sea vents? Starting with known solutions will help narrow questions and make them more profitable. $\endgroup$
    – JBH
    Commented Apr 9 at 3:10
  • $\begingroup$ @JBH i know about them that is why i excluded them from the scenario. I particularly wanted to know what would survive when we take a normal European Land environment. I was also well awere of the possibility of everything dying. Though there are particular organisms like molds of which i am unaware of if they might survive even in my hellish scenario as they grow seemingly every where. Though i will make my question more clear. $\endgroup$ Commented Apr 9 at 4:57
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    $\begingroup$ If your clouds absorb all light, your planet would be cooking - not freezing. If you want your planet to be cold, your clouds need to reflect away solar light instead. Please check Cloud Feedback for details - it is a fascinating topic and seldom explored properly in sci-fi. $\endgroup$
    – Mermaker
    Commented Apr 9 at 14:33
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    $\begingroup$ @Fallenspacerock Thus I offered a comment to point out something you may have missed on your works, not an answer. Those details are often make or break on fiction. $\endgroup$
    – Mermaker
    Commented Apr 9 at 16:38

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Shade-growing plants - typically found in nature on forest floors (up to about 5 meters), or the understory layer of rainforests (about 5 to 20 meters) - can do fine in sunlight levels that range from 2% to 10%. They tend have high ratio of leaf mass to total mass and to grow slowly.

Keep in mind that even a few percent of daylight is still daylight. 10% sunlight is a typical cloudy day. 2% is a sunset on a clear day or bright interior lighting.

Keep in mind that holding temperature and rainfall the same is definitely magic (or Sufficiently Advanced Science). This isn't a bad thing, but it is what it is.

I am not a botanist, but here are some semi-educated guesses:

Ecosystems are complex and interlinked, and any drastic change of environment will result in mass extinctions, even of species that are superficially well adapted to the new environment. But there's more than enough biodiversity in shade-growing plants that the surviving species will expand into a thriving and varied ecosystem with plants covering most of the non-desert, non-permafrost land in the world.

Most of the plants living in forests will die at first. The underlayer will die first, leaving the light-loving trees that form the canopy layer alive. Some forests will burn as the dead undergrowth plants turn into dry kindling.

Light-loving plants will not all die off suddenly. A few especially delicate species will die, and many species will never sprout again after the first winter, going extinct. However, the species that survive through the winter, like trees, shrubs, and grasses, will continue living a diminished life. They will disappear gradually because other, shade-loving plants will beat them in reproduction. Starved of energy, the sun-loving plants will reproduce less, grow less, and gradually give way to shade-loving plants, going extinct many years after the apocalypse. They will be perhaps helped along, and then followed into oblivion, by increasingly desperate herbivores that depend on having them in their diet.

Where the forests don't burn, the underlayer will remain a dark nightmare world where no plants grow, only fungi, microbes, and spooky animals living and preying on one another in twilit darkness. Over a long period of time, the tall trees will slowly be replaced by lower-light species that survived at the perimeter of the forests, while other low-light species like ivies colonize the standing trunks of the dormant, slowly starving pre-apocalypse trees.

Fields will be home to low-growing plants that used to characterize forest floors, as they become able to outcompete the light-loving plants at the edges of the forests. Wintergreen, mosses, small shrubs, and hardy ferns might cover the places now characterized by fields of grasses in North America, for instance.

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  • $\begingroup$ @g s like this awnser though when is the limit where even these plants will die? How much % of light can be blocked for them to still stay alive? $\endgroup$ Commented Apr 10 at 5:04
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    $\begingroup$ @Fallenspacerock 2% is probably close to the limit. That's about the brightness at the forest floor of a rainforest. If you want plants that grow and spooky light levels at midday, I'd suggest just going full magic. Again, not a botanist. $\endgroup$
    – g s
    Commented Apr 10 at 5:31
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    $\begingroup$ @Fallenspacerock alternately you could have the magic clouds reflect visible and UV, but transparent to IR. Plants photosynthesize IR pretty well, and about half of the sun's brightness is in the IR bands. For extra spooky, let a little bit of red visible light through, too. Dim blood red sky at midday, perfect for vampire attacks. $\endgroup$
    – g s
    Commented Apr 10 at 5:38
  • $\begingroup$ @g s i will think of it. Si sorry to ask again but how do you think animals and such could be effected? $\endgroup$ Commented Apr 10 at 5:44
  • $\begingroup$ @Fallenspacerock That sounds like a second question, once you make up your mind exactly how plants and light levels have been affected. $\endgroup$
    – g s
    Commented Apr 10 at 6:01
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Many forest floor species should be able to survive with 10% light levels. And a few such as liverworts and some mosses should be able to survive 2% light levels.

Below that things get difficult although some species like red algae can tolerate exceptionally low light levels and there is a chinese nettle that can survive in 0.04%: https://phys.org/news/2012-12-cave-nettle-china.html

A lot would depend on the quality of the light such as the amount of different parts of the spectrum available. The duration of interest would also be important as fungi could live off of rotting remains for a very long time. Given sufficient time plants like the nettle mentioned above could spread and evolve into a range of different species.

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  • $\begingroup$ thank you for your input. Though the duration of darkness is only about 200 years so not enough time to have different species evolve. $\endgroup$ Commented Apr 10 at 7:31
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The key is this:

  1. 90% to 98% of sunlight is blocked

that is not so bad. That is roughly an early nightfall. Many plants on the tundra can survive this and near-zero temperature months long, then hibernate for the winter and then be happy.

Now life would survive around the equator in these circumstances.

What would happen:

  • There are multiple types of photosynthesis, among them C4 carbon fixation tolerates the best the low-light environment. Thus, the likely rulers of the future Earth would be probably C4 plants migrating from the near arctic (antarctic) world to the equator.
  • There would be a strong extinction event, dependending on the circumstances, 10-90% of the species would be lost.
  • Humanity would probably survive, but surely none of us would want this.
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Wipeout

It is difficult to guess to the full ramifications, but you can expect everything to die.

It is true that some plant species might be hardened enough to survive, but there’s many other effects that effectively kill everything.

Erosion

The moment a certain amount of an ecosystem dies, there will be a battle against erosion. Without plants and trees the fertile ground will be washed away by rain or blown away by wind. We can see in real world projects that only a relatively few healthy plants planted in grids can be enough to stop and reverse erosion. The problem is that nothing will be healthy, or will replace the dying vegetation on time to halt erosion. In the months and years following the fertile ground will wash away, leaving a barren wasteland with only a few tiny pockets of life where erosion doesn't happen.

Dinnertime

Unfortunately any pockets of life will have a hard time as well. Though many life cycles use the sun, there's plenty that use temperature as they start underground for example. Microbes, insects and larger life still need to eat. For most of them their preferred food will be gone and many will die. In desperation some will try the remaining plant life that hasn't been killed by erosion. There is so little plants to support anything that it is likely any plant will be eaten to death. Some of this life might grow temporarily to epic unsustainable proportions by the initial death, and might be numerous enough to attack the living plant life as well.

Wasteland

In the end there might be a few miniscule pockets of life where an equilibrium will be reached. Think a part where a few rocks are together, keeping in water and fertile ground, or close to rivers that temporarily deposit fertile ground. In general even at these places there will be a barren land, empty of the life it once held, mercilessly battered by rain and wind. It'll not be a happy place.

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  • $\begingroup$ really like the idea of a few remaining pockets of life. This is very thematically appropriate with what i actually planned in my world and i am glad i can minimize the use of magic for it now so thank you for your input. $\endgroup$ Commented Apr 10 at 7:42
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You created a dark, relatively warm, and relatively moist environment filled with dead plant-matter. What thrives perfectly in such environment?

The answer is, FUNGI.

You created a dark, relatively warm, and relatively moist environment.

The Darkness would kill the vast majority of the biosphere, leaving incredible amount of rotting biomass for bacteria and fungi to consume and convert. This would simply replace plant-based environment with fungi-based environment + the few species of algae, lichen and low-light plants that can closely cooperate with fungi, or which utilize the resources from the extra-rich soil to overcome sunlight deficiency.

With no competition from true plants, and not even enough animals to feed on them, mushrooms and lichens will spread all over the land, only locally out-competed by things like slime-mold.

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  • $\begingroup$ would they not eventually consume all plant life? So wouldn't they too eventually die out over 200 years? $\endgroup$ Commented Apr 10 at 8:31
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    $\begingroup$ @Fallenspacerock, the fungi would just consume the already dead plants and recycle biomatter, not kill living plants. Since by the prompt, the landmass affected does not lack for energy from heat, just from sunlight, the fungi will have enough energy input to last for millennia, possibly indefinitely thanks to the 2% sunlight available for the rare plants and lichen, as well as energy that flows from continents not affected by the darkness. Since the land is covered in dark, light-absorbing clouds, it would soon become very hot due to reverse albedo effect. Basically, hot, humid, dark basement $\endgroup$ Commented Apr 10 at 12:22
  • $\begingroup$ while i am not 100% set on having a warm apocalypse it does sound indeed very interesting. $\endgroup$ Commented Apr 10 at 12:36
  • $\begingroup$ @Fallenspacerock, take note, that plenty of fungi, their myceliums and many types of mold growths are poisonous or strongly hallucinogenic. A continent covered in shrooms will be an interesting place for humans to live on. It would be Apocalypse on LSD. $\endgroup$ Commented Apr 10 at 14:00
  • $\begingroup$ that would seem very interesting. $\endgroup$ Commented Apr 10 at 14:36
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You would get a eco-system over time that is based on https://en.wikipedia.org/wiki/Aeroplankton and ever larger airborne community, with the resource starved ground dwellers that eat the survival plants (moss/ djungle groundfloor plants), waiting for whale-falls from beyond the clouds.

With all the symptoms of life in the deep sea- brittle bones and strange stalkers wandering the dark dessert.

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    $\begingroup$ sounds interesting but what do you mean with "whale-falls" and "strange stalkers"? @Pica $\endgroup$ Commented Apr 10 at 9:08
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    $\begingroup$ A whalefall would be anything that evolves to filterfeed on the aero-plankton. up in the sky and falls down, bringing its nutrients into the dark lightless dessert. Life in the deep sea regions is quite the guidance to what to expect. en.wikipedia.org/wiki/Anglerfish and there are tons of creatures preying upon the mating signals in the dessert. Thus strange stalkers. $\endgroup$
    – Pica
    Commented Apr 10 at 9:18
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    $\begingroup$ thanks for clarifying though while the conditions are only in place for 200 years some of what you suggested might indeed be useful. Besides that i can always speed stuff up with magic and i really like the concept of fallen mega fauna. @Pica $\endgroup$ Commented Apr 10 at 9:22

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