Would it make more sense to terraform a planet with a single climate or multiple varieties of climate?

Question

A human civilization in my story has terraformed hundreds, possibly thousands of planets across their galaxy to support life. They have done this by changing the atmospheres, adding minerals into the soil where needed, etc. Several other science fiction stories describe planets with basically one type of environment. For example, Tatooine in Star Wars is pretty much entirely desert.

If many of my story’s planets have been terraformed, would it make sense for the humans to make them with a singular environment (like a planet that’s all desert, all forest, etc.) or would planets with more diverse environments (such as deserts, forests, etc. on one planet) make more sense from a perspective of artificial terraforming? In other words, which result would be more likely from artificial terraforming?

Some details:

• The human terraformers are modifying existing planets within the habitable zones of their stars to make them habitable.
• The planets suns are similar to our own, though in at least one case, which I think is somewhat unique in my universe, one planet’s sun appears blue from the planet’s surface. This isn’t because the sun is blue star, but because of atmospheric filtration.
• The human terraformers have super advanced levels of technology. They can create traversable wormholes to travel across the galaxy. They’ve once in their past fled a galaxy to get away from a powerful enemy civilization. I hope this gives you an idea of the scope of their technology. They likely have the level of technology to achieve either a single-environment planet or a multi-environment one.
• They pass down in their traditions a story about their original homeworld, which was similar to Earth with bio-diversity and climate diversity. This homeworld is considered a paradise, similar to our story of the Garden of Eden.

Answer 1

It would make more sense to terraform a planet to have multiple climates. A single climate world is probably not actually possible because of axial tilt and distance from the star. The poles will always be cold and the equator always hot(unless it is a wonky planet). This will cause ice in the North and South and tropical conditions at the equator to the tropics. A single climate world would have to have a perfectly consistent rain cycle, sun exposure, and temperature to stay that climate type. The most likely single climate worlds would be desert planets(Tatooine) or ice planets(Hoth). This is because a completely dry planet could exist albiet the average temperature would be really hot. And an ice planet may exist because Earth may have experienced it before with the Snowball Earth during the Cryogenian Period

In the comments you said Mars is a single climate world and while you aren't entirely wrong, it doesn't work as justification for your argument. Mars is a single climate planet, but that is because it lost the majority of its atmosphere when its core cooled and it lost its magnetic field.

Answer 2

Ignore the planets of Star Wars. None of them have any association with reality. No matter how hard you try, you wouldn't get planets like dry Tatooine, the forest moons of Endor, or ice planet Hoth. Ok, maybe the ice planet, but the other two make no sense.

In order to cover an entire planet with forest, you would have to ring the planet with satellites that reflected sunlight to the poles, and massive machines on/under the surface to move air and water around. If you don't have enough water for an ocean, then all life on the planet would be on artificial life support.

Terraforming isn't like a cloning stamp, where you just overlay what is there with what you want. It's more like pushing sliders: more or less water, heat, and sunlight. Add new plants, adjust what's there, or destroy existing ecosystems. Most plans involve space-based resources to adjust light and huge atmospheric reactors to turn the gasses you don't want (CO2, H2SO4) into gasses you want. "Sufficiently advanced technology" involves nanotech or bioengineering, but light needs to be adjusted from the outside.

Answer 3

False premise

Noting that this question has been closed and reopened once already...

It is trivial for an uninhabitable planet or moon to have a single environment. Obvious examples in this solar system are Mercury and Venus (far too hot) and the moons of the outer gas giants (far too cold). Mars is also uninhabitable and is considered to all be "desert". However, note that this single-word classification covers a temperature range of up to 83C/150F between the equatorial summer and the poles. Which is greater than, but comparable to, the range of temperatures between the equator and poles on Earth. Just looking at summer temperatures on Earth, the south pole is more than 50C colder than the equator. In winter the difference in temperature between the equator and south pole is more like 80C.

Without any other considerations, this temperature range between the equator and the poles nixes the idea of a "single-environment planet". Water is only liquid between 0 and 100 Celsius, with significant limits on human survivability above 40C. With an 80C difference between parts of the planet (observed on both Earth and Mars), it is not possible for it all to be the same environment. If the poles are comfortable to live at then the equator will be unsurvivably hot. If the equator is comfortable to live at then the poles will be unsurvivably cold.

However, there are other considerations - to have widespread life there needs to be a water cycle. Plants on land cannot get water unless there are large bodies of water that allow evaporation to form rain clouds to allow rain to fall on high areas and trickle downhill back towards the sea. Which in turn means that there need to be sea environments and land environments. The far inland areas will be different to the coastal zones, and...

In the updated question, it is stated that the humans have the ability with technology to do practically anything. So, they possibly could focus giant lasers on the poles to heat them up to the same temperature as the equator and drop megatons of water into the atmosphere on demand to simulate rain etc etc. At this point, though, I suggest that it is not a terraformed single environment planet, it is a giant terrarium that is unsustainable without constant maintenance.

Answer 4

Multiple climates will be inevitable. Your planet will be hotter around the equator than the poles, unless it's tilted by roughly 90 degrees, or is tidally locked. Then, the side with perpetual day will be hotter than the side with perpetual night. Also, moist ocean air will be stopped by mountains, causing the side facing the sea to become damp and lush, while the opposite side will be dried up. For an idea of what a realistic map of another world would look like, here's one:

This map is of Odroia, an world my cousin created for the comic book the two of use are working on. As you can see, the biomes are realistic, with deserts being found on the western side of equatorial mountain ranges, places with lots of precipitation (especially around 45-degree latitudes) becoming lush and forested, and the polar regions being covered in snow and ice all year long. No matter how you slice it, a single-biome world is scientifically impossible.