Intestinal Micro-flora.
By the time you’ve done this, you have already imported or developed a whole ecosystem. Beyond that, I think you just need whatever food crops and livestock you need to satisfy the nutritional and caloric requirements of the settlers.
We will need a ton of inter-related microbial life in thye soil. Just adding fertilizer won’t work-an ecosystem depends upon bacteria, fungi, and microscopic insects to recycle nutients and condition the sooil. Growing potatoes on Mars is a big fantasy-true terra forming will take thousands of years.
Per The Martian: You could start with human shit and potatoes.
Lots and lots of trees. Fungi. Likely thousands of species of arthropods, worms, sponges, corals. A lot of this should probably also be done before humans get there.
Why would you need any of these things?
Trees are great at cycling carbon dioxide. They regulate weather patterns and their roots hold soil which can prevent mudslides and soil depletion. They’re a backup measure. If your world is trying to be self sufficient, it’s important to have a stable ecosystem. Imagine a world without wood or trees and there’s a power outage during the winter. What would you do for warmth? A society that’s trying to live on it’s own needs to be entirely self sufficient.
Fungi play an important role in breaking down organic material for new organisms to grow. The diversity of insects and other creatures are to ensure a sustainable and strong ecosystem. A system with few parts has low redundancy and is prone to failure. Not to mention trees look nice and state of mind is as important as anything else to long term survival. (and this is supposed to be the longest survival possible)
No, they aren’t. And they are totally unnecessary in a world where “You’ve added enough microbes, algae, and whatnot to get yield an Earth-like atmosphere and fertile soils”
No, by definition they do not in a world where you’ve added enough microbes, algae, and whatnot to get yield an Earth-like atmosphere and fertile soils.
For which you need none of those things.
Exactly what >95% of the population of this planet do. Hint, it has nothing to do with "trees, fungi, arthropods, worms, sponges or corals. It’s called clothing.
By definition, yes. And none of the things you mentioned seem at all necessary for that.
Why do you need more than the number required for to get yield an Earth-like atmosphere and fertile soils?
You have totally failed to ecplain how or why.
No really, no.
Gee, I guess Eskimos must not have survived for very long. Oh, hang on…
Apparently, all we’ll need is bees and 8 different plant varieties. Of course, we’ll resort tocannibalism and plural marriages but hey…
Serious answer - in the OP’s casual “microbes, algae, and whatnot to get yield an Earth-like atmosphere and fertile soils”, there’s a lot of complexity hidden in that “whatnot” - an Earthlike atmosphere (assuming modern O[sub]2[/sub] levels) is going to require quite a lot of algae, as much as in our own oceans, at least. And the “whatnot” has to include fungi and other saprophytes to get your fertile soil.
I’m with Blake on there being no real need for trees - they’re a fairly late addition to the game - but you’re going to need some land plants to provide the biomass to generate that “fertile soil” and some of that O[sub]2[/sub]- since it’s a condition of the OP that the planet has to be self-sustaining, so you can’t keep adding imported fertilizer, and the geochemistry of the various mineral sources of nutrients are complex - much easier to let plants and microbes do a lot of the work of fixing and concentrating N and P for you than go mining primary sources.
My gut feel is to say that a whole ecosystem will be necessary, if only to ensure self-sustainability without constant human input of energy and direction. But that it can be a simplified one.
I think it would probably help if the OP can define the technological capabilities of the people in the question. Since the criteria is to be able to survive without any outside supplies, the requirements from the environment will depend more on their tech than on local plants and animals.
If we’re talking about a penal colony where criminals are dropped off to scrabble out a stone age existence on their own, then they’ll need to acquire everything from nature and they’ll need a full ecosystem.
If we’re talking advanced space-farers making interstellar trips, they ought to already have machines capable of recycling and reproducing everything they need. Otherwise, they wouldn’t have managed the space-faring part. It might even be that archaic practices like growing food and building with lumber are so inefficient that they’re a waste of time to these folks. These guys don’t need a planet at all.
I bet you felt really clever typing that. I will oblige your request for an explanation. Trees are in fact very useful to humans. As timber, trees provide a simple material for building, and in times where heat is needed they can be burnt as a fuel. Contrary to what you seem to think, having enough microbes on a planet to create modern oxygen levels is quite difficult. The oxygen content of our atmosphere was well below it’s current levels for much of the early history of the earth. The value that trees provide to soil is not for nutrition or anything chemical, it is for structure. The root systems of trees hold dirt together and help prevent mudslides and landslides during extreme rain. Trees also have a direct effect on the climate through the transpiration of water out of their leaves. Up to half of the rain that falls in a rain forest is sourced from the forest itself through transpiration. Trees act as a windbreak on otherwise flat terrain, where strong winds could build.
Fungi are a useful organism to break down organic material like cellulose, leaves and other organisms.
We have one model to show us how a stable and strong ecosystem functions, one that DOES function and has functioned well for us for thousands of years. We study this ecosystem and explore extinction events and die-offs in our planets past and we find that largely, extinction events are preceded by a shrinking ecosystem. As the diversity of species drops, each species becomes more heavily dependent on the other species in the ecosystem, and if one of those species is compromised, it can cause an environmental collapse.
Simply planting crops and having bacteria and algae around won’t oxygenate the air as well as forests could. In the event of a power outage, sources of fuel would be unavailable to sustain ourselves. You mention the Eskimos, a people that do not use (much) wood or fire, yet that is as flawed a response as any other- the Inuit use heavy furs, fats and meats to sustain themselves. They fish in the ocean, hunt whales and seals and caribou and use the furs and fats as both clothing and insulation. This crop-and-algae world has no caribou or fish or whales, and if you wanted any of these animals, you’d have to provide an environment conducive not only for their existence and survival but for the strength to withstand environmental changes. A weak ecosystem doesn’t last very long, and when we’re creating an ecosystem from scratch, that leaves us with many issues. I have only barely mentioned, but the Inuit DO use wood, in the form of drift wood to fashion harpoons and spears for fish hunting. In reality, trying to argue that humans could subsist indefinitely on a dirt world with a few grasses, some bacteria and some algae is laughably ridiculous. You could compare that to a boat not packing life jackets because “the people won’t be in the water, they’ll be on the boat”. It takes no account of the risks associated with the weather patterns and natural events an entire planet can produce.
If the planet has a magnetic field (and can repel its stars solar wind) it is likely volcanically active. If it has wind, it will likely develop massive tornadoes in the flat plains that the treeless terrain produces. All in all, trying to survive without these things is difficult, dangerous, and foolhardy.
Sorry if this comes off a bit aggressive, I don’t mean to attack you directly, only defend my position.
Yeah, the bit about “You’ve added enough microbes, algae, and whatnot to get yield an Earth-like atmosphere and fertile soils.” is masking the real question: It’s like asking “After you have everything you need, what else do you need?”.
I haven’t read the entire thread yet, but has anyone made a Dune reference yet?
It’s not enough to create an oxygen rich atmosphere; the top layer of the crust would be unoxidised, so it would suck oxygen out of the atmosphere as fast as you could make it. I think the Earth’s crust has soaked up more than 10 atmosphere’s worth of oxygen before the present day. So you need to keep a healthy stock of photosynthetic organisms on your terraformed planet, in case the crust is too hungry.
Terraforming would be a nightmare to get right- I doubt we could get it right the first, or even the second time we do it. Luckily we’ve got Mars and Venus to play with.
I thought the reason most planets don’t have an oxygen-rich atmosphere is because the oxygen reacts with the rock and gets chemically bound. For example, the surface of Mars is heavily oxidized, isn’t it?
Oh, yes. But there is room for a lot more oxidation in the average planetary crust.
Presumably the original atmosphere would be CO2 and methane (and less reactive nitrogen) and free-flowing water. It would take a significant amount of runaway processes using sequences of steadily more oxygen-tolerant organisms to convert the result to oceans full of life poisoning their own nest with free oxygen. On earth, that presumably took more than millions of years. It would be an interesting feat to do it in anyone’s lifetime or even over several generations.
I hope not too long.
Start with denitrifying bacteria, all the way to the horse and all other kinds of livestock.
It wasn’t trees that got them up to liveable levels, though. And it’s not trees that contribute most of it today.
I think you’re mistaken as to the percentage contribution of trees to the oxygen budget - it’s only 20-5 %, depending on various factors.