Now I love huge living creatures and fantasy settings, this just might be reflected in my questions, so I had the idea to make a massive living island. I saw a similar question, but unfortunately it asked not how it would work, but how it would evolve and play out, so I still need an answer.

Now to start I said plant, so its flight will have to be passive, so lighter than air gases are needed. My ideas both include giant gas bladders so will that work and how? For my idea the roots would hang down all the way into the ocean, the plant would grow up from the ocean floor. Eventually forming an island which as the bladders are made and start to fill up with the lighter than air gases slowly lifts off. Will this work and if no, how else? PS: For size something massive like the isle of Wight.

  • 2
    $\begingroup$ Maybe something like kelp as it has an anchor at the bottom and many sacs of air across it? Just an idea $\endgroup$ Feb 16, 2017 at 0:10
  • $\begingroup$ Just a hunch but something tells me that size is way too large for a living organism; it won't be able to coordinate itself effectively. $\endgroup$
    – Zxyrra
    Feb 16, 2017 at 0:29
  • $\begingroup$ @Zxyrra This is a problem commonly found in my questions and I am aware of it but it can be bypassed, and has solutions I just don't know exactly how it could work. $\endgroup$
    – Mendeleev
    Feb 16, 2017 at 10:31
  • $\begingroup$ How much weight does this thing have to support? Are you planning an island people living on with houses and etc or just a few hand full of people who pass through from time to time? $\endgroup$
    – cybernard
    Feb 17, 2017 at 2:48
  • $\begingroup$ It would definitely have trouble coordinating itself, but who says it has to? A clonal colony which is all physically interlinked can be considered one organism by some definitions, but all the parts are basically 'independently' living. No example on current Earth is as big as the Isle of Wight (although the fungus Armillaria ostoyae and probably the seagrass Posidonia oceanica can cover multiple square kilometers) -- but given sufficient time and an ideal environment without effective competitors, the 'network' structure of these things means there's no real maximum size. $\endgroup$ Feb 17, 2017 at 4:59

4 Answers 4


Air bladders (as found in sargassum weed) plus methane-producing bacteria.

The plant or alga grows in shallow seas (shallow enough that the light that reaches the bottom is sufficient for photosynthesis), and spreads largely by budding from its 'root' or holdfast. It grows into a kelp-like frond which reaches the surface. The frond's tip is an air bladder, holding it at the surface (for maximum photosynthesis).

Most of these plants (due to budding) have identical DNA, and as their fronds make contact, sometimes they grow into one another. In some cases the air bladders merge, while in others they remain separated by a wall of tissue. Eventually, a giant, convoluted mass of photosynthesizing air bladders floats at the surface.

Some such colonies develop a symbiotic relationship with methanogenic bacteria which live inside the air bladders. They eat nutrients provided by the plant colony, and in return, excrete methane gas which makes the bladder float higher in the water - allowing it to shade out & outcompete neighboring surface flora.

As this process continues, the (now gigantic) colony eventually becomes buoyant enough to rise out of the water entirely. It is still linked to the bottom of the sea by its stems, and the result resembles a giant green brain (the surface is crenelated & convoluted due to all the separate air bladders) linked to the water by thousands of green nerves.


Having it be ONE plant, or one single gas bag, connected by one single line, seems limiting for the organism. It's not very easy for them to propagate or evolve or anything. Therefore, I am going to go with a model that features lots and lots of these plants.

So, let's say helium is the element you'll be using to float your plants. In this case, you'll have to find a way to have your plants manufacture helium.

Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei. (source)

Since it comes from radioactive materials, these will have to be present in abundance for the plant to process. This may change the entire ecology, and so should be approached with caution.

Helium might not be the way you'll go. There are other options, such as:

  • methane, which is far easier to produce, although more often for animals than plants
  • hot air, which will need a mechanism for heating, and thus will be difficult for a plant to achieve.
  • Hydrogen, which is present in water, and is perhaps the easiest, but your plants will need a mechanism to separate the oxygen from the hydrogen. They will be very flammable. EDIT: This may be a problem, because if there is any kind of fire on this island, many will explode, causing the island to dip lower or fall into the ocean. In fact, this could be part of the natural life cycle, and the island needs to fall in so that the process can begin again. Like pine cones You could also have it so that sections of the island can break off and fall away resulting in holes in the middle of your island or breakaways at the edges. This will depend on growth pattern. (They can grow in rings so that the edges are stronger and the center is empty, filling in as they go, or randomly, or out from a center point).

First, you must decide the mechanism and type of gas you want to use. That determines a lot of other things and factors.

Next, let's look at how the ground will be built.

Are people meant to walk across the top of the plants and that forms the ground of your island? Or are you looking at having the plants grow up THROUGH this "ground" basically as balloons over the ground? If it's the second one, that means the plants have to have a way to form the ground, and once it is formed, a way to poke through it. Forming the ground is a matter of lattice work between plants, and falling leaves from the plant, which will create soil. How stable it will be will depend on how it's built. Once a lattice work of plants is formed, and the ground is too solid, I would expect that it would be difficult for the ones underneath the island to be be able to get above this newly created ground.

So you'd have to find a mechanism for that, and you'd likely have immature ones beneath, that are gas filled but haven't come out yet. EDIT: You could have any mechanism to get this done, but if parts of the plants burn if it's hydrogen, you can have these searching for the "holes" or weak spots created by this.

There's other ways to do this too--the gas bag plants have phases, in which they can grow directly on the created soil (and don't have to have a line down to the ocean).

I would have them start in clusters, over miles of ocean, for sure, so that there's multiple lines down to the ocean.

Edit: Even better, they start as one or a cluster with the line to the ocean, but eventually that falls away and it just floats free in a particular stage of development, such as when the island reaches a certain size. Then, all the plants on it grow from the "soil" produced by the main plants. Additions to the soil will come from birds (their poo, nests, and carcasses) and other plants which grow on that soil. It eventually won't be tethered to the ocean, but the weight will keep it from floating into the atmosphere.

  • $\begingroup$ Nice answer but couldn't it be a single more complex organism? $\endgroup$
    – Mendeleev
    Feb 16, 2017 at 22:10
  • $\begingroup$ @Mendeleev why are you insisting on a single organism instead of an ecology. Forests aren't comprised of single organisms, and what you're protesting is far more complex... at a certain point you're blurring the lines between "single complex organism" and "aggregate of simpler organisms." There are people who philosophically address the earth as a single, complex floating organism... ;) $\endgroup$ Feb 17, 2017 at 1:54
  • $\begingroup$ @Mendeleev If you like it, upvote it. :) Sure. It could be a single complex organism, set up in exactly the same way as I have outlined. The effect would be the same, it's just semantics. But ONE gas bag for it, I have problems with. $\endgroup$ Feb 17, 2017 at 2:31
  • $\begingroup$ @ErinThursby I never said one gas bag at least I don't remember. $\endgroup$
    – Mendeleev
    Feb 17, 2017 at 16:34

Entry eighteen, day 52

"Being low on supplies, Faraday called the suggestion that we make anchor on a nearby island to collect water and food. It was on gathering from a selection of fruiting trees that we detected a foul odour on the breeze - something akin to sulphur or decay. On checking our baskets, we found none of the fruit to be bad, nor could a place be found for the smell's origin.

"As the weather closed in and took a turn for the worse, we gathered underneath a branching tree. Overhead, a large, dense cloud drew in, carried on the breeze.

"It soon became apparent, however, that it was not a cloud, but a continent-sized growth of lichen - wiry as beard-hair and as light as spider webbing - which descended upon us like a snow. Light wisps at first, followed by large clippings. It soon threatened to engulf us, and we had to make a concerted effort to prevent it from compromising our shelter. On attempting to shift it with our bare hands, we found our skin to become rashed and chemical-bitten.

"As the wind picked up again, the lichen was blown away in large patches - the hairy barbs caused it to clump together and take with it patches of fruit and bark from the nearby trees. It would appear that this is how the colony of lichen fed and received moisture, moving across the land like a travelling blight or cloud of locusts.

"Large patches were left like carpet in the aftermath of a barber's shop, where the dry lichen had become too damp or laden to be carried by the wind. On the return journey to the ship, we were careful to avoid contact. Indeed, we saw some creatures which had not been as lucky as we had been to find shelter, and they had died of their afflictions."

TL;DR: a lichen which, when dry, can be borne on the wind in large quantities resembling a mobile island without need for a root system


Entry 22, day 102

"We were travelling the gulf when we came across a rather quaint thing. We could neither decide on plant or creature - but from here on we shall describe it as a plant. Details on this shortly.

"As we had encountered it, the plant was floating above the water at a degrading altitude. We caught it before it had become submerged and thoroughly inspected it.

"Its stems were knotted and bulky, yet tubular and empty like plumbing pipe, perhaps like a succulent bamboo - which made capturing it with the barge hook from the port side of our boat an easy task. On its apex, a single, withered grapevine split like hollow veins to encapsulate a partially filled ballooning membrane. On the dexter side of these veins, small holes with wrinkled grape-like valves which must have, in a previous evolution, been stomata.

"After our analysis and samples were taken, Charles released the plant into the water - at which point this seemingly dead plant sprung back into life.

"The roots and stems began to swell (you could see the water being drawn up through the pipe-like stems) and the outsize plant stomata began viciously gulping air by action of their fluctuating turgidity. The weather-balloon at its topmost point began to inflate and it was not long before (now laden with water) the plant began to ascend into the firmament.

"It was only later on this trip that we discovered this plant to be a juvenile, as indicated by its nut-hatchings and partially discarded shell. Fully grown plants, in our experience, might reach the size of a small continent - given that it does not drown itself under its own weight first."

TL;DR: Strange mechanical action is sometimes stumbled upon in nature - the valves of the heart, the undulations of jellyfish or, even in the plant world, the exploding cucumber or the sensitive plants.

exploding cucumber sensitive plants

While most plants have 'nervous systems' which trigger in one direction only (Venus fly traps close, sundew plants curl up etc) - it's not impossible to imagine a mechanism where the Bernoulli principle causes a fluctuation of parts, which in turn, through another development of kelp-like gas sacs - allows a mechanical suction and storage of air.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .