How desolate can I make a habitable world?

Question

I want to center a fantasy-ish novel on a desolate world. I want barren land, rocks, and dust. No trees, grass, bushes, any vegetation of any kind. Heat would be good. I would like for there to be no water, but I know that without water you can't have life (at least as we know it), so I'm willing to allow sparse watering holes or perhaps underground springs. Basically I want death valley on a world-sized scale. Minus any cacti or bushes. And more rocks than sand.

So here's my question: How far can I go? How much vegetation and water can I remove before my world can't be lived on by humans?

Answer 1

You can't even go as far as to remove vegetation.

You said fantasy-ish, so I assume you mean that human life on the planet is not supported from space. If it is, we can allow some more "barren-ness", but without space support your humans need:

• Oxygen
• Food
• Water
• Shelter

Oxygen is produced by plants or algae. Since you don't want big bodies of water on your planet, you will need plants. Also, your humans will need water to drink, so there need to be fresh water sources. And they will need food. On a barren, desolate, desert world, you can't grow crops. So they need to hunt. So there need to be animals. Animals need to eat something. Animals can't all eat other animals, so there need to be plants.

And finally you need shelter. Shelter can be constructed out of many things, but without wood and in a barren world, if you don't want to live in caves, you are going to have a very bad time finding any shelter. No plants and no water means nothing to hold the ground together, so the whole freaking planet would be covered by dust and sand. It would be super hard to find clay or a cave entrance that is not buried under sand in the first place.

So I guess you need to tone it down a bit. Give your planet a sizable ocean - made out of salty, toxic, algae-ridden dirty water that kills you quicker than not drinking at all. That produces oxygen. Make some animals live at the shores, and some nasty creatures in the depths. Make all of them poisonous.

Then give your planet some plants. At least SOME. Some kind of grass, maybe even a few bushes and a few small trees. It will contrast the barrenness of your world better, and make a more believable environment. Give your planet some animals. Make most of them dangerous, poisonous or just super unfriendly, but make it in a way a lone traveller in the desert might just find those 3 scorpions that you can eat (if you know how to prepare them), make him find a few little trees to find a poor shelter for the day.

If your world is just a giant brick of rock and sand with an atmosphere that is for some strange reason breathable, it is not habitable by any standards. Mars sure isn't, and what you seem to want reminds me a lot of it.

Answer 2

You should check out the dune books

On the planet dune there is no rain. The only water comes from the polar ice caps or from under ground. Only a few desert plants grow on the planet and only in small numbers.

The giant sand worms produce oxygen so humans can live on dune.

Replace sand worms with something else. (Perhaps some kind of oxygen producing spell or maybe some spell that allows one plant to produce a large amount of oxygen.) And you have a system that fits your world perfectly.

Answer 3

Oxygen

You need some source of oxygen. On a grand scale if you want humans to be able to breath. Practically that means photosynthesis has to be taking place somewhere in a significant scale. That means green and water.

You can still however have you desolate wasteland, it just can't cover the whole world. Photosynthesis doesn't have to mean nice. You could have dank salt marshes.

Practically speaking you probably also need some oceans somewhere. You can even use them as a significant photosynthesis location with algae so you can avoid most trees.

You could have some gigantic continent with a huge central desert.

Poison the ocean

You can make the ocean hostile, poisonous to humans and storm-wracked. Just have the local algae producing some chemicals like botulinum on a grand scale while producing their oxygen.

Put something useful deep in the desert

Put all the useful resources like metals in the middle of the desert continent and you can have a situation where people have reason to live deep into the giant desert and less reason to stay near the poison coasts.

Answer 4

What about making it inhabitable with few spots that can support human population. Spots can be explained by some underground spring that is seeping into the above ground, making it fertile enough.

Oxygen could be handwaved by some kind of inorganic process.

Then, it becomes question of how big those spots need to be. This can be estimated by taking amount of humans you want at each spot and multiplying it by area person needs to survive.

Then, there is question how far away each of those spots can be so trade is complicated, but possible. Not such how to calculate this. Maybe take Sahara desert as an example.

Answer 5

So long as you are going on appearances I think you can make an extremely "desolate" world.

1) Water. Do we actually need standing water? No. The world is littered with volcanoes but they're pretty benign. At any one time the vast majority of them are doing nothing but powering geysers. There's a decent amount of water but it's buried deep where the volcanoes bring it up.

The result of this is you have humidity in the air but no bodies of water. The temperature is uniform enough that you do not get any appreciable rainfall.

2) Plants. Do we need them? No. We need things that photosynthesize but they need not be something we would remotely recognize as a plant. Look at Earth's oceans--there's an awful lot of phytoplankton. Technically plants but they're too small to be seen by the unaided eye. Lets make a land analogue--a "plant" that forms a very thin coating around grains of sand and grows as a patch on larger bits of rock. It's surface layer is airtight, O2, CO2 and H2O are transported by carrier molecules rather than directly. In the absence of sun they are very good at going dormant rather than dying--the wind blowing the sand doesn't kill them off. This "plant" forms the basis of our food chain. Note that we want a land that is mostly sand and rock, this will also make it seem more desolate.

3) Animals. We have a variety of small herbivores that "eat" the sand, digest the plant and excrete the now barren sand. (Think of the parrot fish that eats coral.) These creatures spend most of their life burrowed into the sand where they usually go unnoticed.

Next up we have small carnivores that hunt the plant-eaters. While these don't spend their life burrowed into the sand they hide out in the presence of larger creatures. Unless you disturb their hide they are very rarely seen. Think shy mice.

Above that we have larger carnivores that prey on the small carnivores. Again, they hide if they can. Think wild (not merely feral) cats.

Finally we have the apex natural predator. These are large enough to not be able to hide effectively. These, and the cat-analogues are the primary diet of humans although the sand-plants can also be processed into edible material.

To casual inspection you have a world containing nothing but predators.

Note that nothing beyond small bands of nomadic hunters can live in this world as no place supports enough life to sustain a population of humans.

Answer 6

tl;dr
If the vital resource can be replaced by synthetic one, you can spoil that resource.

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Long version:

Only thing you need is energy source. Anything else can be recycled.

Our Earth can be considered as closed system. No matter (significant) leaves the earth and no (significant) matter is gathered there. There is no source of water, no source of carbon, no source of any chemical (except ro radionuclides and izotopes in the decay, but they are not vital).

• By nuclear war you can vanish all animals. Their meat can be sythesized from carbon, nitrogen, hydrogen and essential elements mined on the surface.

• You can vanish all plants. The photosyntesis can be replaced by electrolysis of water. You can oxidize oxygen from any chemical, if you have enough energy.

• You can poison all the water on the surface. If your station is realy closed, filtering the dump water and the air moisture you have enough water to live.

100 % recyclation is vital. Garbage disposing, even burials are waste of resources.

If you want your community to grow and/or the system is not totaly closed, you have to replace the leaking material or the material needed for new citizen, you have to mine it on the surface.

Then you are limitted to technology:

• You can sythesize chemicals only.
  In that case you need planet that provides the resources of carbon, nitrogen, oxygen, etc.
• You can fuse lighter elements into heavier ones (2H->He,2Li->C,...) and break heavier elements to lighter ones (Fe->Cr+He). In that case you need only the source of matter. Nothing else.

Answer 7

Yes, easily. After all we are talking about a "fantasy-ish" world.

Simply include large ocean (as has been suggested) that is self sufficient in terms of photosynthesis, food chains, blah blah... With nothing on the land. Plonk your humans on the land, with the only available food source being the ocean then the land can be as barren as you like.

(Some of) the humans can then be the equivalent of fishermen, whale hunters, seaweed harvesters, etc. Anything else can be invented... Sea-wood from sea-trees, sea-bread made from sea-wheat in floating sea-farms havested by sea-farmers.

Put all that in the background of your story and that leaves plenty of room on land for the barren setting.

Why not have an ocean at each pole, containing different stuff where fortunes can be made by trading across ten thousand miles of barren desert to get from one to the other, provided you don't die or get killed first or someone else captures or poisons the rare and hidden vital watering holes in between and the cities that surround them.

(Ooh! I feel a book coming on...)

Answer 8

If it'll fit within your needs, have the planet be slowly dying. It was once lush with plenty of oxygen and at least adequate vegetation and water, until a catastrophe (gamma ray burst, near-miss from a rogue planet that threw off the orbit, etc.) cooked half of the life. Tidal stresses on the planet caused sulfur geysers that poisoned what was left.

Now things have settled, the planet is covered with ash, the "water" is mostly sludge and acid, but with a filter mask you can go topside. But the planet is eventually doomed. There's still plenty of oxygen in the atmosphere, but only because almost everything that breathes is dead. Almost no new oxygen is being produced, so the "lucky" visitors who arrived afterward represent the majority of the planet's oxygen demand.

Depending on how many people there are, it could take centuries before the rising CO2 and decreasing O2 levels make the planet uninhabitable once and for all.

This is somewhat off-topic, but I think it bears repeating often: having an entire planet be a single biome breaks believability. This happens all too often in sci-fi. This planet is all desert, that one is all snow, this entire moon is forest (I'm looking at you, Endor!). You can have a dead world be a single "ecosystem" (cold & dry, hot and acidic), but if it's going to have at least a region that's inhabitable then there's going to have to be some diversity. Different latitudes get different amounts of sunlight, which will greatly affect the climate even if the planet is otherwise uniform.

Answer 9

(can't make comments yet)
Some environments humans can adapt, faster or slower, but at some point it is not fitting for reproduction, or the environment causes severe body problems. Having minimal vegetation, animals and water will cause malnutrition in current surface-inhabiting population. They might adapt underground life, and that will transform their way of life, but still need to think it through, what their life would be (fitting your novel's goal)? Are they yet adapting to underground, or already adapted as much as possible, and is the existing sources support this staged human life or not.
If you are familiar with MadMax movies, maybe those are closest to your scenario.
Still it is possible to come up with a completely new life form, not based on water, but essentially it is not human
Answering in short your question "How much vegetation and water can I remove before my world can't be lived on by humans?": Depends on population count (as Euphoric pointed). If you can get information on astronaut supplies, it might help you more.

Answer 10

If there is no surface water on your world, then life could be heavily concentrated at oases. A great open landscape of blazing sun, scorching rock, burning sands, punctuated every few travel days by this.