Natalie Jing Ma, PhD

Ecosystem in miniature: A mushroom grows among moss and decaying pine needles on the forest floor. (Lahemaa National Park, Estonia)

Life on Earth is complex and if we want to live out in space, it’s unlikely that we can take every species with us. Our ventures off-planet have carried only the bare necessities and due space constraints (pun intended), that’s unlikely to change in the near future. But constraints breed creativity, so to honor that spirit let’s look at what we small groups of species we can send off into space that would continue to survive without the umbilical cord of earthly supplies. Specifically, our question is:

“What is the smallest self-sustaining ecosystem that we could send to space?”

That’s a tough one, so we’ll start by defining what we mean in this question. First, let’s tackle the meaning of ‘ecosystem’. This is the word we use to encompass many different species living and interacting with each other and the nonliving components of their environment. This is the mix of all the microbes and trees and animals in a rainforest, combined with who eats who and conditions like the amount of rainfall or sunlight available. It is the tiger that eats the deer that eats the leaves, who dies to be eaten by the worms and microbes, who make the dirt to feed the leaves to feed the deer to feed the tiger. This isn’t merely poetic, it’s the literal passing of matter and energy, physical stuff and the power to move it, between individual parts that comprise the ecosystem.

Simple Ecosystem: dead plant matter (a log) feeds moss and fungi, which in turn feed a fly that will die to become food for more plants. (Bialowieza Forest, Poland)

Now, let’s move on to ‘self-sustaining’, the hardest part of our question. We want our ecosystem to continue without supplies from Earth. Is that even possible? Hypothetically yes, but it depends what you mean. Earth itself survives without supplies from elsewhere, passing matter between the living and nonliving in ecosystems – in this sense, Earth is a closed-loop system, moving physical stuff, matter around without gaining or losing matter from an outside supply*. But that’s just matter. Energy is a different story; the sun constantly supplies Earth with energy that flows through ecosystems and eventually dissipates back out to space, mostly as heat. So if we’re talking energy, Earth is an open-loop system, constantly being supplied more energy.

While it would be amazing to make an ecosystem that is both closed-loop for matter and energy, the problem with energy is that it decays into ‘useless’ energy like heat that cannot be used by life. Yes, I feel that irony writing from -10C temperatures in Boston, but it’s scientifically true. So for our question, we’ll aim to find an ecosystem that’s closed-loop for matter, but gets an energy supply from elsewhere. Even this is a hard problem; Earth is huge and while individual ecosystems are mostly ‘closed-loop’ for matter, they’ll shunt waste products off to other ecosystems to use. In space, we won’t have that luxury. Any waste made in an isolated, spacebound ecosystem must be used by something else in that same ecosystem.

Stuck in the bucket: matter usage in a spacebound ecosystem would have to be almost entirely, if not totally closed-loop. (Banks of the Danube in Budapest, Hungary)

And lastly, what do we mean by ‘simplest’? We could say that ‘simplest’ just refers to the fewest number of different species in our ecosystem. After all, fewer moving parts that can have something go wrong is better, right? Or we could say that ‘simplest’ refers to how complex the species in our ecosystem are, meaning we’re looking to work with the simplest parts we can get. This would be microscopic life like bacteria, amoebas, fungal yeasts, cyanobacteria, and single-celled algae, which have the benefit of being small as well as ‘simple’.

Finally, we could take a step back and erase species from the equation and instead say the ‘simplest ecosystem’ is just the fewest number of chemical reactions to keep matter moving through the environment when you add energy. This is like cutting away all of the walls and membranes on cells and just looking at their metabolism, what chemical reactions they are running to convert starting reactant A into finished product B. Another reaction then need to take B and make C, and a third reaction then takes C and makes A. For now, we won’t settle on a specific definition of ‘simplest’, but will keep all of these in mind as we look for the simplest self-sustaining ecosystem.

A “simple” ecosystem with only a few visible species may have thousands more unseen microbes carrying out complex chemical reactions. (Bialowieza Forsest, Poland)

Speaking of, where are we going to look?

Good question! Stay tuned for Part II, in which we’ll speculate on where to start looking for the simplest self-sustaining ecosystem.

I start my first consulting job this Monday, working with a healthcare consulting firm to help companies solve real-world problems. Before this, I was PhD student working in a research lab and my consulting experience was only pro-bono projects with a graduate consulting club. Nor was I terribly close to the healthcare field—my lab doesn’t do research on anything directly related to healthcare of pharmaceuticals. Given this background, you might be asking how I can possibly work in healthcare consulting. There’s so much I don’t know, how can I possibly succeed? Where do I possibly start learning?

When faced with a huge field containing a lot of information, I’ve found the best way to start learning is to build stories. The human brain is wired for stories because it naturally creates or attributes agency to things. It finds causes and effects. So we can use this innate understanding of stories to go into a field and build a narrative that helps us understand. Think of the story of Newton and the apple during discovery of gravity. Whether or not it’s true, we remember that an apple fell onto Newton’s head and he realized gravity exists. There’s a cause – the apple – and effect – Newton suddenly ‘getting’ gravity as a force that pulls things toward the Earth. In learning this story, we remember more than if someone had simply told us “Gravity pulls things toward the Earth.”

But in a new field, it’s not enough to simply hear the story. It’s the act of making that makes you remember. To truly understand something, build the story yourself. As an example, this isn’t my first field switch; before my PhD in synthetic biology, I got a B.S. in Environmental Science. But the those two fields are far apart, so I built stories that covered the major breakthroughs in synthetic biology. I looked at who had done what and when and who built on that research afterward. It helped me rapidly catch up and graduate on time with my peers. Science also backs me up on this one: writing, or more broadly just interacting with information beyond reading it silently helps you remember it (Sources: PopSci article, Hardcore paper source from recent literature).

Fullscreen capture 1162018 85057 PM.bmp — An example of a timeline made in Sutori (link below) to help understand companies in the healthcare industry.

So if you’re jumping into a new field or subject, don’t just passively read stories, make them. How? There’s always pencil and paper, where you can draw a timeline or write a paragraph-long story summarizing what you’ve learned. But if you want something searchable, try making your story digitally. I’m currently using Sutori, which lets you create timelines for free using any kind of mixed media (text, image, video). There are also several other timeline builders listed here, and you can even organize information beyond the timeline and make a flowchart or sketch on Google Docs, Microsoft Office, or wherever else you can find the tools to sketch and write. Get creative, because the more you create, the more you’ll remember.

So feeling lost in a new field? Start making a story out of it.

The smallest self-sustaining ecosystem: Part I

Making sense of the mess: creating stories to understand