Thoughts on Biosphere 2 and the gardens of space ships

by Roger Bourke White Jr., copyright December 2005

Biosphere 2 was a high-profile project set up in the Arizona desert in the late 1980's to simulate traveling a garden through space on a long space journey. (Biosphere 1 is the Earth itself.) The original goal was to establish a garden with a variety of ecosystems in it, then hermetically seal it off, and see if the garden and its attendees could survive a year, as if they were on their way to a nearby star.
The project failed in the sense that additional supplies -- in particular oxygen -- had to be added to the Biosphere before the year was up. But as is usual with any such failure, much was learned.
The principle lesson learned at Biosphere 2 was that self-contained gardens are tricky to maintain. The gardens will "snap" -- become self-sustaining -- but rarely with the mix of plants and animals that their human tenders intended. In the case of Biosphere, some desired species died off, cockroaches were overrunning all the ecosystems, and soil bacteria were thriving surprisingly well. It was their success that was leaching so much oxygen out of the air and the primary cause of failure.
The main lesson learned from Biosphere 2: We don't know enough yet about garden ecosystems to count on them as sustenance for long space voyages.
If we want to use garden ecosystems on space ships, what steps can we take to improve their usefulness?
Two steps come to mind.
First, plan on a long shakeout before the ship actually starts its journey. If we build a ship for travel to Alpha Centauri, then we should build it, populate the garden, then let the ship sit in Earth orbit for a year while the garden sorts itself out. If after a year in space orbiting around Earth, the garden is stable, then the garden is ready to travel.
Second, plan on multiple gardens rather than a single garden, and each of those gardens should be "resettable" -- capable of being sterilized completely and repopulated. I would recommend ten gardens, of which only two are required to sustain the space ship. Using this technique says that trouble is to be expected and can't be prevented, and that the trouble will come up at random times and from random causes. In such a case, what can be done is to have sufficient spare resource that the tenders can periodically clean the slate and start over.
With these solutions in mind, the gardens of space ships are likely to be massive affairs. They are also going to be compartmentalized, and there will be security measures in place to keep the gardens isolated from one another.

Beyond Biosphere 2
It’s been twenty years since Biosphere 2 launched, and much has been learned about genetics and growing things in the meantime. One big change coming is that open-spaced gardens as we now envision them will be ornamental on a starship, not functional. They will be there for humans to walk through and admire. The functional gardens – the ones that supply food and oxygen -- will be more compact and composed of engineered plant and animal species, and those species will be more like algae and bacteria mats in vats than waving fields of grain. What these high tech gardens will have in common with the Biosphere gardens is the ability to surprise – there will be cockroach equivalents that thrive in the vats and elsewhere on the ships even though humans don’t want them to. Redundancy and the ability to start over will still be vital.
The advancements in biology also mean that gardens won’t be used to move species from one system to another. It will be a lot more effective to engineer new life forms at the destination after the characteristics of the planetary environments there have been studied on-site for a while.
In sum, Biosphere 2 was an interesting experiment for its time, but it’s now a horse-and-buggy solution to the challenge of moving self-sustaining life between the stars.

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