What makes something alive? Well, it depends on your perspective, since there is no standard definition of life. Despite this, most people are comfortable with the idea that life is an organism’s path through time, beginning with birth, experiencing changes such as various growth and reproduction, and ending in death.¹

As manned exploration of the solar system comes ever-closer to becoming an everyday reality rather than a science fiction device, speculative fiction writers have the opportunity to imagine new possibilities and niches without the overheads of running an expensive laboratory. We also have the opportunity to consider pitfalls, drawbacks, and impacts long before they happen. Or maybe we’re just a bunch of daydreamers, which is where I come in.

Imagine you’ve been asked to design a self-sustaining human habitation on a lifeless world, using only the genetic blueprints you’ve found on Earth. It needs to provide food, shelter, waste recycling, and some means of air purification. It also has to play a role in the long-term terraforming of your world. You start with a traditional biodome structure, but soon run into problems. Waste decays too slowly. Greenhouse gases build up too fast. Plants die, and the soil won’t sustain new life. Where to go from here?

Of course, there’s no shortage of science fiction exploring this topic. In the Monk & Robot books, Becky Chambers re-examines our hypothetical relationship with nature. In Aurora, Kim Stanley Robinson explores planetary inhospitability and closed-system collapse. Tade Thompson’s Wormwood trilogy asks us to radically reconsider our views of symbiosis and its influence on human society. There are dozens, if not hundreds, of similar examples.

While we’re brainstorming solutions to future problems, let me introduce you to the biogenic city. This improvement on the standard SFF staple biodome comes with numerous free upgrades, such as radiation shielding, advanced nutrient cycling, cheap protein, and living shelter. The drawbacks? You might end up with killer mushrooms. Read on!

About Fungi

As a phylogenetic kingdom, fungi are neither plants nor animals, but have a distinct existence all on their own. They exist from the microscopic to the macrocellular and can be found in almost every environment on earth, including in the air and under the sea. While some form the heaviest, densest, and most complex organisms ever discovered, others can travel thousands of kilometres unassisted through the atmosphere, reaching heights of several kilometres.

Of course, this is no different to the diversity of life found in animals or plants. And yet it is this very sense of separation from the more recognisable realms of plants and animals that gives it so much potential as a tool for science or the imagination.

Fungi’s Role in the Ecosystem

Before moving on to the task of designing living cities, it is worth recapping the role of fungi and what they provide. This gives a baseline with which to design new systems and structures later.

Fungi play a major role in soil building and substrate integrity. Hyphae, the long filaments that make up the bulk of fungal growth, function as a binding agent in soil. They hold particles together, form aggregate materials, and help create proper draining and pH levels. This is crucial in allowing for the long-term stability of a habitat and maintaining requirements for other species that live there.

But they are also often early colonisers, changing and modifying their environment to create new niches and different habitat structures. Without fungi, it would be much harder for other life to adapt and evolve. Indeed, there could be up to around four million different species of fungi, up to 90 percent of which are likely to still be unknown to science. The roles, function, and existence of these are likely to be deeply embedded into their environments, since this is certainly true for the known species.

It is precisely for this reason that designing novel habitats for fungi first, rather than introducing a few key species later as an afterthought, has so much potential. In the classic non-fiction work Entangled Life, Merlin Sheldrake argues that fungi are “infrastructure engineers” that can find design solutions to even the most complex problems.²

Symbiosis and Convergent Evolution

A lichen is a symbiotic organism formed between a fungus and an alga (and sometimes a cyanobacteria). The fungus provides shelter, stability, and protection, while the alga photosynthesises and produces much-needed sugars. Together, they form a single symbiotic organism for the benefit of both.

Lichens are by far the most successful form of symbiosis on Earth. The strategy of combining fungi and algae is so beneficial to both that it has evolved independently no less than ten times throughout history (other underappreciated examples include corals and mangroves). The power of this combination allows lichen to survive in some of the most extreme environments on Earth—already providing potential for science fiction worldbuilding!

In this context, fungi acts as a container, providing a stable substrate in environments where there may be no soil, or indeed any organic material at all, for traditional plants to grow in. As a symbiotic organism, they occupy an ecological niche that allows other plants and animals to move into an area by providing food and shelter where there was otherwise none.

There is an extra benefit, too. Lichens don’t just convert sunlight to sugars through photosynthesis. They absorb heat and store it, radiating it back out into the environment later once the sun has gone down. Their rough surfaces can trap moisture, creating tiny oases in otherwise barren environments. They break down rocks, form natural barriers, and add structure in barren wastelands. As pioneer species, they alter the chemical and physical environment, providing habitable focal points for plants, animals, bacteria, and indeed other fungi. From the first nucleation of a microhabitat in an otherwise inhospitable environment, this symbiotic relationship between algae and fungi creates a space where water, soil, vegetation, and animals can exist.

Finally, more lichens can grow in more extreme parts of that environment—such as the tops of trees—creating a patchwork, fractal-like pattern of life. The larger macroscopic life can become, the more sprawling, complex networks they can support, right down to microscopic levels.

This happens over and over again in the global ecosystem, but even more interestingly, current research is looking into the potential of creating synthetic lichens and deliberate symbionts, to create targeted, specific compounds and novel species for bioengineering.³ Since the component species remain separate, and it is only the relationship between them that is being artificially constructed, such research has wide applications.

Fungi’s role as a symbiont doesn’t end with lichen. It can form essential bonds with every other phylogenetic kingdom. Fungal relationships with bacteria would form a research paper of its own, and its role in animal digestion is fundamental to the evolution of certain kinds of vertebrates. Fungi fix nutrients into plants, provide shelter and protection, and reduce the risk of dangerous disease by breaking down waste materials more rapidly. In some cases—such as that of Monotropa uniflora, the surreal ghost pipe plant—a plant cannot photosynthesise, and survives by consuming sugars produced directly from mycorrhizal fungi within tree roots. Perhaps unsurprisingly, the species is also known for its ethnobotanical uses.⁴ Certainly, it is not difficult to see the possibilities for such interactions to form the basis of new life on alien worlds, particularly if subterranean or with varying access to sunlight.

Indeed, the role of fungi on Earth is so central that any consideration of a human-viable offworld environment should place them at the centre too.

The ghost pipe plant

Fungi and Biogenic Materials

What factors must you consider when growing a city from scratch? There’s more than you might think. For a start, there are all the services that humans need and expect, including recreation, justice, transport, education, third spaces, and a sense of identity, to begin with. But imagine a city on a secondary world: are there additional structures that need to be built in? Food generation, air recycling, a water cycle? As secondary world architects, we are responsible for building in all the services that nature creates for free.

Moreover, we might be comfortable enough designing for other people, since if we know a city, we know what it does or doesn’t need to provide. But what if we’re designing for species other than us? For radically different needs and scales, whether physical or temporal? How do we plan for a multiscale, multi-use, multi-species environment? Part of the problem comes from knowing where to start, and there are two options for doing this. We can start with the anthropocentric view: what does a human being need to survive? What plants, animals, and habitats do we need to bring with us in order to feel at home?

In this framework, we need ways to capture, sanitise, and transport water. We need space for food growth, waste recapture and purification, and places for nature to exist on its own terms. We need homes, workplaces, communication networks, and the ability to stay fit and healthy. We may want safe environments for pets and families in time (standard requirements for distant world habitations in space operas).

Of course, not everyone is going to be comfortable with this purely anthropocentric (and, often, culturally biased) perception of “human” need, and with good reason. There’s no rule to stop us designing a city from absolute scratch: if we are designing for biogenics, what do those species need—not just to perform a function, but to thrive? What symbiotic relationships can they form with what novel species? How do they prefer to optimally store and transport water and nutrients? What are their preferred parameters for growth and repair? Can we, as human beings, fit our lives into that? The answers to these questions are, unfortunately, still largely the domain of science fiction writers rather than grounded in academic research.

Thankfully, biogenic design gives us the opportunity to focus on any or all of these things. But for the sake of this article, I will reluctantly focus on anthropocentric architecture in the standard context of post-terrestrial settlement. First of all, let’s take a step back and start with the very basic building blocks for our offworld setting.

Ecosystem Services and Natural Capital

The two most obvious uses for fungal species in a city design is through bioremediation—breaking down waste materials and eliminating toxins—and food production, whether through direct use of high-nutrient mushrooms or through the fermentation and preservation of less digestible foodstuffs. These basic ecosystem services are “built in” to city design, but a truly biogenic city has benefits that far transcend what can be imagined by policy and economics.

The most powerful benefit for an offworld city comes in the form of radiation shielding. Many fungal species, particularly those that are incorporated into lichen, offer high amounts of protection against ultraviolet radiation, making them perfect superstructures in environments without atmospheric protection, reducing the specifications required for more traditionally imagined domes and, in some circumstances, providing temperature regulation and heat stores for colder times. Many species also produce bioluminescence, giving free light in environments (such as the moon) where access to daylight may be out of sync with the natural cycles expected by life on Earth.

When your city is grown, not made, you can adjust conditions to suit all those that live there. A lichen city can grow along a wide Martian plain, allowing sprawling single-storey protection, food production, and moisture gathering while still offering protection from violent sandstorms. If you focus only on sealing internal areas and living spaces, the amount of energy and resources needed to create a breathable habitat are markedly reduced.

At the same time, if you find yourself on a craggy rock world, with steep but otherwise protected cliffs, a city grown from a modified bracket fungi allows you to maximise the vertical space available. Indeed, whatever circumstances happen to arise, there is likely to already be an exact or approximate solution contained already within Earth’s genetic playbook.

Clearly, this is yet another area that is already rich with examples from SFF. If our physical environment shapes the ecological niches that evolve to make use of them, then it can be argued that social structures evolve as an additional layer on top of that. There are plenty of possibilities for egalitarian, anarcho-syndicalist, socialist, permacultural, or any other form of post-capitalist or uncapitalist ecologically driven society. Indeed, almost the entirety of the cli-fi subgenre explores alternative economies and ecological realities. A fungal city—fundamentally symbiotic, genetically cooperative, and designed around long-term circularity and habitat creation for future generations—reduces the need for product-driven societies, and thus reduces or removes economic hierarchies and all of the social and planetary harm that comes with it.

Biomaterials

The role of fungi, and in particular its subterranean mycelium, is already being explored for its potential in biomaterials and biostructures. The benefits of biomaterials include easy custom shaping, strengthening and self-repair, sustainability and circular economy, and negative carbon footprints plus a variety of secondary and tertiary downstream benefits. Let’s take a deeper look at each in turn.

One of the main benefits of a biomaterial comes in its capacity for modification. In recent years, there has been a considerable resurgence in interest in the different uses for fungi across different industries. Many of these applications focus on creating a substrate and then injecting mycelium into it to create a strong and living structure. While many start-ups focus on creating versions of traditional building materials such as bricks, in some cases the focus is more on developing a kind of fungal papier-mâché that can be used for furniture, household items, and even buildings.

In the most sustainable cases, the substrate itself comes from waste materials from another industry, and some of the most common examples are sawdust, pulp and paper, or agricultural waste. When combined with frames of wire, timber, or other materials, the endless capacity for customisation becomes clear.

Of course, when we imagine a fungal city, what comes to mind probably isn’t paper pulp held together with mycelium, but the vast fruiting bodies we are used to seeing in woodlands when temperatures fall. For those who are drawn to what could be rather than what is, it’s rather more romantic to imagine falling asleep below vast lamellae stretching overhead like rafters.

So how feasible is something like that? Well, of course, it depends on what you’re asking.

Photo: Alan Rockefeller, CC

Fungi, largely through mycelium, can grow horizontally for vast distances. The famous Honey Mushroom, or Humongous Fungus, in Oregon is considered one of the largest organisms on Earth. It extends around 3.5 square miles underground (estimates vary), weighs up to 35,000 tons and may be up to 8,700 years old. The species, Armillaria ostoyae, is also responsible for forming several other giant fungal colonies.

But how tall can it grow? Well, on average, its fruiting bodies extend around 15cm above ground.

Of course, there are other taxa with fruit bodies that are much more suited to our speculative purposes. Some of the largest include Phellinus ellipsoideus, with a fruit body of more than half a ton, and Rigidoporus ulmarius, which can grow to over four metres.

By far the largest known fungi, and one of the first known giant organisms to have evolved on Earth, was the enormous Prototaxites which grew up to eight metres tall and is dated back to the Early Devonian. While research increasingly casts doubt over whether it was a fungus at all or a member of an entirely separate lineage, what is known about its novel composition and structure can serve as another source of inspiration about what can theoretically be grown. Prototaxites had a unique columnar shape, held together with a tubular structure, which would have provided it with extra stability at perhaps a lower metabolic cost compared to more solid structures.

One of the biggest downsides of a fungal city is its lack of strength, particularly when considering fungal fruit bodies compared to mycelium or even lichens. Fungi really comes into its own when combined with other species or natural substrates.

A major concern about the use of mycelium as a building material is that it has a lower compressive strength compared to other materials such as concrete, making it less suitable as a building material. However, this concern can be waived, or at least reconsidered, in a speculative setting.

Let’s take the example of a lunar city. One of the best ways to strengthen our hypothetical structures is by enriching them, and there are many species of fungi and lichen that naturally incorporate rock and dust into their own structures, creating structures that are stronger and more resilient as a consequence.

Recently, a team of researchers successfully grew chickpeas in simulated lunar regolith, using a fungal complex very commonly found in terrestrial agriculture. They achieved some manner of successful growth in all mixtures, including pure regolith. Other studies have shown that the extremophile Cryomyces antarcticus can survive on both lunar and Martian rock, and can handle exposure to hostile conditions in space.

Moreover, when we think of a city structure, we tend to think of our needs on Earth. Vast skyscrapers, steel and concrete, and the ability to withstand all conditions. This is not the case elsewhere in the solar system. While the exact composition would depend on the needs of a city—grown within a safe and carefully controlled biodome, or left to fend for itself on an exposed surface—our role as writers is to account for any possibility. So let us return to our moon base and see whether fungi can meet some or all of our building needs.

In lower lunar gravity, the need for materials with a high compressive strength is reduced. Materials need to withstand less compression for the same height of structure due to the reduced gravity, and additionally, there is no atmospheric pressure to contend with, nor the kinds of strong weather conditions that a traditional building would have to withstand. You still have to protect against the impact of falling or stumbling objects, but a whole range of defences against this have evolved throughout the fungal kingdom. The imagination can run wild in trying to predict ways that a living city might defend itself against drunken wanderers stopping for a late-night snack.

One serious potential impact on the moon is that of micrometeorites. These small, sharp, piercing impacts can cause severe harm to traditional building materials, resulting in the risk of lost oxygen and decompression. And yet, fungal species are notoriously self-healing, with many species exhibiting mycelia which rapidly respond to impacts by repairing the gaps. Indeed, the communicative networks that facilitate this could well be utilised for early detection of structural failures, allowing for much faster detection of problems without running the risk of microscopic tears being left undetected, as in traditional materials.

Finally, while lunar regolith itself is relatively stable once you deal with the problem of direct sunlight, the problem of encountering radioactive material on other planets is reasonably high through natural radiation found in rocks. Direct radiation removal through Cladosporium species that may help human beings colonise areas with more active, and dangerous, forms of geological radiation, allowing a first-pass of clean-up that makes way for further waves of bioremediation.

All raw materials come from somewhere, and the recycling of previously living material into substrate for future life is fundamental. Without decomposition from bacteria and fungi, among other processes, mass and nutrients cannot be recycled back into the ecosystem. Life is fundamentally circular in a way that development and technology is struggling to catch up with.

Designing for circularity is one of the biggest benefits of a grown city. Early iterations create the raw materials that will be used later, rather than having to destructively mine for them. Inhabitants of a city can design and grow their own homes without requiring huge capital. Repairs and redesign can be personally driven and tailored to individual circumstances and cultures, reducing dependence on socioeconomics. While no development can ever keep its environment pristine—I will assume strict controls on introducing biological agents onto another world—there is a big difference between building from the surface of a world, rather than eating into it to build around it. The more material that can be grown—particularly from the waste of other industries – the less needs to come from destructive, single-use manufacturing. Since the latter is the main current model of development, even moderate reductions in raw material use allows for increased longevity.

Indeed, mycelium and fungi come into their own in offworld settings. Extremophiles can function in low, indeed very low, temperature environments, reducing or even removing the requirement for energy-intensive manufacturing that requires high temperatures to operate. This leads to much lower initial startup and manufacturing costs, as well as lower initial waste and pollution.

Some fungal species produce calcium oxalate crystals as a natural byproduct of their metabolic process. These sharp spikes or crystals can act as a carbon sink, but also have the potential to be collected and used for other domestic or industrial uses: they can be made into ceramic glazes for creativity and durability, used in the production of cleaning agents, made into a waterproof sealant, or used in manufacturing and pyrotechnology, among others. The more byproducts can be utilised, the more sustainable the city as a whole becomes.

Over time, mycelium has the opportunity to produce negative carbon through its role in sequestration. In terrestrial environments, this has the potential to “lock up” a third of global carbon dioxide uses. In an offworld habitat designed for long-term sustainability, designing for net productivity and habitat stability can be managed from the outset.

The humble fungal city has the potential to create a lot of other benefits that come for free. It has often been said that cities are in a constant state of improvement, but with biogenic architecture the move away from construction to growth creates a fundamental change in how space is used, designed, and respected.

In many ways, this is part of the appeal: traditional construction produces waste, displaces natural ecosystems, and in the worst cases can create areas where it is difficult to survive. Biogenic architecture puts life at the forefront of all design. Moreover, not just human life, but a thriving sustainable ecosystem where other plants and animals exist too.

Time and time again, research has shown that access to nature is an essential part of a thriving neighbourhood. Crime rates go down, house prices go up, and people are more able to reach their potential. In a purely imaginary city, where every structure has a living form, it is easy to imagine that the design itself has a social or reparative role.

Perhaps this is particularly true on bleak, lifeless moons or asteroids. Again and again, science fiction authors have explored the social and psychological consequences of living without access to green spaces, open water, or the blue sky. Perhaps we can only speculate whether a biogenic, but ultimately artificial, environment with no direct Earth comparison would have a similar effect or not.

Novel Relationships and Symbionts

So far, everything we have covered is already theoretically possible with known species and existing technologies, alongside a fair amount of experimentation and imaginary funding. But no speculative non-fiction article would be complete without some forays into the realms of what is conceptually possible but highly unlikely, as well as what is almost certainly impossible but could at least be imagined. These are not limited to fungi, but might include areas with the potential for deep symbiosis.

Electrochemical communication and the “feeling city”: although not strictly a fungus, slime molds can famously navigate mazes, using a novel form of externalised memory.⁵ This is a major growth area of research to potentially provide a novel framework for electrochemical and biogenic circuitry, often termed the “slime mold algorithm.”

Bioinformation storage and bioengineering are of course major areas of growth and development. Researchers at Cornell University developed a biohybrid robot controlled by mycelial electrical impulses.⁶ While there are clear benefits in terms of reduced need for electrical power (living organisms are their own power generators), it also allows for a far more sensitive machine that is more connected, and responsive, to its surroundings. This reduces the need for messy infrastructure and complex code and provides endless possibilities for novel interfaces and unimaginable applications.

Finally, of course, there is the science fiction staple of fungal telepathy. In Brian Aldiss’s classic Hothouse, the symbiotic and telepathic morel attaches itself to remaining humans and controls them for its own purposes. It is not impossible to imagine fungi evolving in such capacity: filamentous hyphae have long been conceptualised as nerve cells, and some species of fungi such as the Split Gill (Schizophyllum commune) exhibit patterns of electrical activity which are even reminiscent of speech and language.⁷

Conclusions

When it comes to the innovative possibilities of growing a city—particularly one on a distant world where we have total freedom to construct every aspect ourselves—perhaps the greatest gain of biogenic architecture comes not from trying to imagine a single species that does everything we might want, but from thinking of how to layer different organisms together to create something multi-symbiotic. This might include growing mycelium in soil held in vertical gables, strengthened by rock and ash, and then havinge larger fruiting bodies extending outwards from these walls for added shelter and growth.

There are endless possibilities.

¹ Viorica Corbu et al. (2023), Current Insights in Fungal Importance – A Comprehensive Review, Microorganisms, 11(6), https://doi.org/ 10.3390/microorganisms11061384.

² Merlin Sheldrake (2020), Entangled Life: How Fungi Make Our Worlds, Change Our Minds, and Shape Our Futures, Bodley Head.

³ Arjun Khakkar (2023), A roadmap for the creation of synthetic lichen, Biochemical and Biophysical Research Communications, 654,  https://doi.org/10.1016/j.bbrc.2023.02.079.

⁴ Savannah Anez et al. (2026), Ghost Pipe Then and Now: the Influence of Digital Media on the Medicinal Use of Monotropa uniflora in the United States, Ethnobotany and Economic Botany, 79(4), https://doi.org/10.1007/s12231-025-09637-1.

⁵ Chris Reid et al. (2012), Slime mold uses an externalized spatial “memory” to navigate in complex environments, Proceedings of the National Academy of Sciences of the United States of America, 109(43), https://doi.org/10.1073/pnas.1215037109.

⁶ Anand Mishra et al (2024), Sensorimotor control of robots mediated by electrophysiological measurements of fungal mycelia, Science Robotics, 9(93), https://doi.org/10.1126/scirobotics.adk8019.

⁷ Andrew Adamatzky (2022), Language of fungi derived from their electrical spiking activity, Royal Society Open Science, 9(4), https://doi.org/10.1098/rsos.211926.

Editor: Gautam Bhatia.

Copy Editors: Copy Editing Department.