Single biome planets are something of a staple in science fiction set in space. Dry desert worlds, lush forested planets, and icy moons all evoke a powerful sense of place. The landscapes of Tattooine, Endor, and Hoth resonated with Star Wars fans, which is presumably why a planet with a similarly consistent ecosystem will feature prominently in Rogue One: A Star Wars Story when the film debuts in December. Though the name of the planet remains unknown, the movie’s trailer and shooting schedule indicate that it will be a tropical paradise in the mold of the Maldives.
It’s hard to argue with the aesthetic choice; Imperial Walkers look very cool next to palm trees. But could a habitable single biome planet really exist? The science is complicated. Though there are plenty of extremely hot worlds and plenty of icy planets in outer orbit, whether or not a planet capable of sustaining life could have a truly homogenous ecosystem is largely dependent on the ecosystem in question.
So let’s consider the ecosystems here on Earth. Our planet, where the Star Wars movies have traditionally been shot, is extremely diverse, consisting of six major biomes: freshwater, marine, tundra, grassland, desert, and forest. These biomes are wildly different from one another, consisting of different climates and weather patterns, different species of plants and animals, and different geological features. What they all have in common, though, is that everything in the biome is instrumental to the health of that biome and of the planet as a whole.
All of the ecosystems on the planet work together, creating a global ecosystem that supports life. Energy flows through biomes as chemical and biological processes work together to create planet-wide balance and keep the air in our atmosphere breathable.
So, that’s how our planet works. But could other planets be different?: For the purposes of this extremely hypothetical discussion, lets establish two things.
1) We don’t know everything there is to know about how life might exist off-world. We know what some life forms need to live, but if theres life on other planets, there’s a better than good chance that it doesn’t abide by the same rules as life on Earth. For our purposes — talking about Star Wars planets — we’ll have to assume “livable” means capable of sustaining human life.
2) Ecosystems are all about balance. Predator-prey relationships, solar energy, climate and chemical processes are all a part of the system, and if anything within an ecosystem changes, there will likely be domino effect that leads to a bunch of other changes. Knowing that balance is important gives us a handy framework with which to consider the worlds of Star Wars one by one….
The best-known Star Wars planet, Tatooine is a desert planet that’s home to Luke Skywalker, Jawas, and whatever scum is hanging out at the Mos Eisley Cantina. Of course, there’s no way that we see all of Tatooine in the films, but from what we do see, it’s uniformly sandy, dry and arid. That’s problematic because water is critical to sustaining life. It’s important for agriculture and for basic hydration needs, but water also plays a vital role in sustaining plant life and the oceans that keep our atmosphere thick with oxygen. Because breathing’s pretty important, a way to maintain the chemical balance in the air is essential.
That said, Andrew Johnston of the National Air and Space Museum has pointed out that Tatooine, while inhospitable, bears some resemblance to Mars, meaning that its existence is totally plausible. We also know that Luke’s uncle Owen Lars is a moisture farmer, who uses vaporators to turn humidity into H20, which means that there must be a source of evaporating water somewhere on the planet. We just don’t see any evidence of it and it is never referenced. The Dune Sea is, as far as fans know, the only sea on the planet.
The takeaway is that Tattooine could exist — the landscape is plausible — if there were significant reservoirs of liquid water supporting significant plant life in a specific spot on the planet. No one talked about this and little flora is seen besides lichen, which couldn’t realistically bring oxygen levels up to a livable level. We must conclude that the planet is either totally implausible or hiding its most critical features.
Home to Maz Kanata’s Castle, Takodana appears in Star Wars: The Force Awakens and is described as lush and green. We catch glimpses of its trees and vegetation, as well as the lake near Maz’s Castle. This is sort of cheating because were talking about freshwater and forests, but the funny thing about trees is that they need water to survive.
A true single biome would be something like Endor, which is a no-go, but Takodana’s a little different story. Because there appears to be some variation, with water sources and vegetation, we’ve got some of the key ingredients of life. The problem here, though, might be oxygen levels. Too much oxygen can affect the species that roam the planet and even be harmful. Again, ecosystems are all about balance, so there needs to be something consuming and regulating oxygen, as well as creating it. We’d also need methods for expelling and regulating the other components of breathable air — things like nitrogen, carbon dioxide, and argon.
Beyond that, its imperative that Takodana encountered some variation in the way it’s heated by its sun. Uneven heating of the planet is what creates weather patterns, and things like storms and the redistribution of water are vital to its survival and habitability. It would appear on first blush, that this is a planet with a perfectly circular orbit, which would make it a rarity indeed.
Then, of course, this uneven heating begets the question of sameness in the ecosystem. To what degree will that uneven heating create changes in the ecosystem? Is there a sweet spot where the distribution of solar radiation and heat is uneven enough that it creates low pressure fronts and weather systems, but not so extreme that it fundamentally changes the ecosystem in a given place? Thats the million dollar question.
Coruscant is hard to assess because it is completely covered by a city, which would be impossible on Earth because of our rudimentary energy technology, but might be possible with more advanced systems and a way of recycling air. The problem presented by Coruscant isn’t ecological inaccuracy, but technological superiority: It’s hard to get a sense in the Star Wars movies of just how advanced tools have become.
If one believes strongly in the Republic’s culture of innovation and entrepreneurship, one can think that Coruscant could exist.
Endor is a pretty simple no-go. The forested moon that serves as home to the Ewoks faces pretty much all the same problems as Takodana — plus it has coniferous trees so the oxygen levels would be off the charts year round — and no water features. Can a forest exist without a lake or a sea? The simple answer is no. Zero-loss cycles don’t work in nature.
Swamp-covered Dagobah is a wetland ecosystem that, like Endor, doesn’t make a tons of sense. The problem with a swamp-covered planet is that, as we know, ecosystems are about balance and the role of a wetland ecosystem is to balance and regulating the way in which water moves through the global water cycle. If there isn’t a water cycle beyond the wetlands, then the water just steeps and becomes poisonous.
Wetlands also play a vital role in chemical regulation and play host to all kinds of chemicals, nutrients, and gases, perhaps most notably methane. Without a balancing force, the methane emissions from a swamp world would probably be so significant that they’d run the risk of making the planet unlivable. And then there’s the fact that without high and low points, swamps really aren’t possible: They always exists within a topographic context.
Just no. If all the water is frozen, there will be no water cycle and therefore no life. Sure, even the Earth had ice ages, but we never see a liquid sea on Hoth so we’re not talking about a cold snap so much as we’re talking about global stasis. That’s bad news for Tauntauns….
Overall, the case for single biome planets doesn’t look great. Planets depend on the balancing forces of interacting biomes and ecosystems, and the ability of a single biome to create a livable environment is doubtful.
Even so, were a long ways from understanding the finer points of life in the universe. Theres every possibility that the carbon-based lifeforms we know and understand are extremely fussy. There’s even evidence that species capable of surviving in relatively inhospitable single ecosystems exist, and theres a possibility well-known fixtures in our solar system (like Europa) might just fit the single ecosystem bill. Whether or not single ecosystems are capable of supporting life as we understand it is another matter entirely.