Cities of the Sea

Who are the world’s greatest living architects? Ask a marine biologist, and they will likely point you towards Scleractinia, the stony corals. It’s an initially unprepossessing set of candidates: animals never more than a few millimetres in length, lacking brains, eyes or a heart and, for most of their lives, even the ability to move independently. And yet they might just be some of the most important construction workers on the planet.

Corals start their lives as tiny larvae, floating in among the flotsam and jetsam of zooplankton, until they find a suitable site: a rocky outcrop on a ridge or seamount, exposed to sea currents, in warm, sun-drenched, nutrient-poor waters. When found, the coral stays there forever, becoming sessile (fixed) and their construction project begins. Fed with a steady supply of energy by photosynthesising algae in their cells, the corals collectively build from their rocky bases, fusing their living tissues with minerals extracted from the ocean’s water to form limestone exoskeletons. As each coral generation builds upon their forebears, these ancient animal architects gradually assemble the largest structures of biological origin on earth. 1 1 Source

These structures are not just large but also teeming with life. Despite covering less than 1 per cent of the ocean floor, they are home to over a quarter of marine species. 2 2 Census of Marine Life (2010). The unique complexity of reef architecture provides for countless nurseries, safehouses and other habitats for fish, other marine animals and even humans. Thousands of islands and atolls, including the entire land areas of the Maldives, the Marshall Islands, Kiribati, Nauru, Tuvalu and Tokelau, are formed from reefs whose built-up silt and sand breached the ocean surface many years ago. What’s more, corals provide food, livelihoods and essential protection from storm surges and tsunamis for over one billion coastal peoples. Whether corals’ value should be encapsulated in economic terms is debatable, but a study in 2020 totalled their annual contributions through ecosystem services at $11 trillion, 3 3 Hanny E. Rivera, Andrea N. Chan and Victoria Luu, ‘Coral reefs are critical for our food supply tourism, and ocean health’, Science Policy Review. Source dwarfing the economic output of all but two nations, 4 4 US and China. as well as the entire human design and construction sectors. 5 5 The global creative industries sector was estimated at 2$ trillion and the global construction sector at $9.7 trillion in 2022. Source

They have supported more-than-human life on our planet for over 450 million years and yet, within the coming decade, coral reefs could all but disappear. Reefs have already declined by over half since the 1950s, with many reefs irrecoverably damaged by extractive fishing practices, wayward ships, ports and seaway constructions, algal blooms induced by sewage and fertiliser run-off and tropical storms, which are becoming increasingly violent in a hotter atmosphere. Indeed, the impacts of global heating could soon sound the death knell for corals. Marine heatwaves cause them to ‘bleach’ a ghostly white, expelling their colourful cohabiting algae. Without a food source, they die soon afterwards. Uniquely vulnerable as sessile and extremely slow-growing animals, corals cannot move to avoid human activities or rapidly poleward-shifting isotherms. When inevitable disasters hit, regeneration takes decades or more. If corals are the ‘cities of the sea’, 6 6 As described by the Natural History Museum exhibition, Coral Reefs: Secret Cities of the Sea (2015). then we are taking a bulldozer to them faster than they can rebuild.

What if, rather than reef destruction, we could utilise human intervention to instead catalyse processes of repair? This is the idea behind a range of restorative practices which have emerged over the last few years. These range from ‘coral gardening’, whereby coral larvae or cuttings are grown in labs or underwater nurseries for planting out in reef restoration projects, to ecosystem engineering in the form of artificial reefs. The latter – human-designed interventions which restore or extend the physical infrastructure of damaged reefs – provide a robust substrate for the growth of corals and secure refuges for some of the countless animals displaced by the loss of natural reefs.

Humans, perhaps surprisingly, have a long history of intervention in reef ecosystems. “Artificial” reefs have been built since ancient times for fishing and aquaculture in places such as Japan and the Philippines. 7 7 Shinya Otake, ‘Design and Creation of Fishing Grounds in Japan with Artificial Reefs’, Modern Fisheries Engineering. Boca Raton: CRC Press, 2020. They have been employed, in a less sustainable fashion, in the US and Europe in commercial and recreational fisheries since the 1950s, in the form of concrete and steel megastructures, before being re-deployed in conservation projects including reef restoration to replace natural reefs damaged by human activities. 8 8 Initially off the coasts of Monaco in the 1970s. Source The design of the artificial reefs typically used in restoration projects betrays this extractive ancestry, typically consisting of concrete forms or stacked blocks, or, less frequently, steel cages. While cheap and freely available, these materials are high in embodied carbon, corrosive, and heavy and cumbersome to install, requiring large ships and machinery, leading many to question their overall benefit to marine ecosystems.

Fortunately, in the last few years, a number of design practices, focused on what they can do for corals and reef ecosystems, have taken a deep dive into this design problem. Reef Design Lab, a multidisciplinary studio in Melbourne led by industrial designer Alex Goad, created MARS – the Marine Artificial Reef System – in 2018. It’s a lightweight and more sustainable artificial reef composed of small interconnecting modules, which ‘click together just like Lego’. 9 9 Alex Goad, interview with Questacon – National Science and Technology Centre, Canberra (2017). Source As such, MARS can be installed on the seafloor by local divers from small fishing boats, expanding the possible locations of intervention. In turn, this fosters a sense of stewardship and care among the human communities who depend on reefs, as Alex explains, ‘because they’ve physically installed it themselves. 10 10 Ibid.

MARS responds with equal sensitivity to the more-than-human reef ecology. The system has been carefully and beautifully designed to re-create the complex ‘cellular structure’ 11 11 Ibid. of a reef’s bedrock, while remaining a flexible modular system that can adjust in overall height or width to provide a diversity of reef topographies to suit different species and sites. The modules are slip-cast in ceramic using a 3D-printed mould, creating a product with a complex topography of niches and cavities at multiple scales. The forms are beguiling, but they have an ecological function, helping young corals to get a foothold and providing myriad concavities as havens for small marine animals. MARS has been deployed in test sites including on a sandy seabed with no existing reef in the Maldives, which represented the largest artificial reef of its kind. Six years since installation, the structure has been transformed by a profusion of coral growth and new resident fish, creating a flourishing ecosystem from almost nothing.

MARS is an inspiring case of how the involvement of more-than-human designers – by thinking through forms, materials and systems – can contribute to more agile, responsive and ecological modes of intervention. Today, such designers’ specialisms are being relied upon and tested ever more, as reef restoration faces an increasingly severe problem of scale. Where bespoke artificial reef products like MARS remain relatively costly, and are thus mostly appropriate for piecemeal intervention, the latest reef restoration programmes are more strategic, focused on the adaptation of entire reefs. Australia’s Reef Restoration and Adaptation Programme is a paradigmatic example. The Great Barrier Reef – at 2300 kilometres long, the world’s largest – has experienced dramatic 97 per cent declines in 2024 due to mass bleaching. 12 12 Adam Morton and Lisa Cox, ‘“Devastating”: 91% of reefs surveyed on Great Barrier Reef affected by coral bleaching in 2022’, The Guardian, 10 May 2022. Source In an effort to help the reef adapt to hotter temperatures, the Programme’s team of over 360 researchers have identified specific coral varieties from around the world that appear to have survived heatwaves, and are using them to propagate new heat-tolerant corals through species hybridisation and genetic modification. The goal is to deploy millions of these resilient corals every year, from the aquaculture labs on land to the homes on the Great Barrier Reef, all with minimal human intervention and cost. It represents the world’s largest ever project to protect an ecosystem from climate change.

The designer Pirjo Haikola has been key to unlocking the scale, speed and effectiveness required by this challenge. Collaborating closely with the multidisciplinary team, she has created ‘coral seeding devices’. These three-armed modules, appearing as angular starfish in size and shape, will deliver young corals to the reef and shelter them in the early stages of life. Iterative testing of different designs pointed towards the star-shaped module with a side-facing refuge for the coral larva, which dramatically improved the corals’ chance of survival by protecting it from the activities of grazing fish and the accumulation of algae and sediments. 13 13 Whitman TN, Hoogenboom MO, Negri AP and Randall CJ, ‘Coral-seeding devices with fish-exclusion features reduce mortality on the Great Barrier Reef’, Nature, Sci Rep. 2024 Jun 10;14(1):13332. doi: 10.1038/s41598-024-64294-z. PMID: 38858572; PMCID: PMC11165004.

The devices are designed to be simply dropped down onto the reef from the sea surface by drones, removing the time and cost involved with human crews and divers. Modules can be arranged in various configurations that help them to securely nestle themselves in among the variable reef topography. Over time, the corals’ growth incorporates the modules into an indistinguishable part of the reef, helped by their construction from calcium carbonate, the same primary mineral ingredient as the reef. By designing out human involvement and imprint as far as possible, the system perhaps loses the affective possibilities of human stewardship championed by Alex Goad, but it gains in possibly being able to economically address the enormous scales of intervention required for reef adaptation.

These projects represent fascinating expansions of what design can do. Humans have long created tools, shelters and infrastructures to extend the habitable regions of the planet for the benefit of ourselves and a small range of companion animals but rarely for wild ecosystems as complex as reefs, or for animals with life-worlds as alien to ours as a coral’s. It is, however, a role that is approached with some caution by those already working closely with the more-than-human world. The proposals to transplant and genetically modify corals, for instance, are highly controversial among reef ecologists, who are concerned about the unknowns of such interventionist approaches. 14 14 Graham Readfearn, ‘As record heat risks bleaching 73% of the world’s coral reefs, scientists ask “what do we do now?”’, The Guardian, 29 July 2024. Source

Similarly, the act of installing a prefabricated artificial reef is radically different to the iterative growth of a natural reef, which is shaped by a dizzying diversity of ecological relationships forged over centuries. As necessary as these designed interventions might be for a rapid response, is the result truly a reef? And how resilient might these human–coral collaborations prove in the long run? Ultimately, we don’t have the luxury of time to find out: with human intervention already happening everywhere through habitat disruption and climate change, reparative acts are required before the true consequences can be understood.

Navigating these unknown, treacherous waters requires the development of more radical forms of collaboration, not just in multi-disciplinary but in multispecies terms, and a re-positioning of the human designer within an expanded assemblage of more-than-human expertise. As Haikola describes:

‘This more-than-human design is systemic, not centred, and has to take into account many species and ecosystems, requiring… different methods of working from those typically used by designers.’ 15 15 Pirjo Haikola: Urchin Corals, presentation at the World Around 2023. Source

Iterative processes and a continual to-and-fro between disciplines, from the design studio to the laboratory to the field and back, are critical to a more-than-human design process. Frequently, the preferences of non-humans can completely upturn the initial narratives set up by humans. For instance, Haikola initially set out to investigate the re-use of the calcium carbonate shells of sea anemones in biopolymers for artificial reef structures, but the corals didn’t take to the substrate. ‘We don’t really know why,’ Haikola admits, ‘but we let the corals choose their materials.’ 16 16 Ibid. Successful more-than-human design, therefore, is necessarily an act of collaboration between human and more-than-human designers, but communication is still a challenge.

Danish artist collective Superflex has gone further than many along the path of inter-species collaboration. Founded thirty years ago by Jakob Fenger, Bjørnstjerne Christiansen and Rasmus Rosengren Nielsen in Copenhagen, it has since expanded its network of collaborators to include musicians, scientists and even fish. The inception of an inter-species expansion to their collective was on a visit to the islands and atolls of the South Pacific. As Neilsen described, ‘we were visiting islands and atolls where climate change was happening in a radical way… you read about it, but seeing it for real is a different thing.’ 17 17 Author’s interview with Rasmus Nielsen, 17 October 2024. The trip begun an extended collaborative art research project, undertaken as part of a team which includes Anja Wegner and Alex Jordan at the Max Planck Institute for Animal Behaviour in Berlin, corals and another reef resident, the damselfish.

Superflex, Wegner and Jordan assessed how the damselfish reacted to various interventions. ‘It was like an Ikea for fish,’ says Nielsen, describing the process of installing different structures into their underwater showroom. 18 18 Ibid. They then used their findings to develop a series of artificial reef sculptures in response to the fishes’ preferences. The sculptures that result from this process are largely simple cubic forms, but they are composed of chaotic folds of pink material, providing the characteristic porosity and complexity of a reef. This vibrant colour, a preference of the fish and the coral alike, is an exaggeration of the pigmentation of many coral algae and is also understood to promote coral growth. It’s a marked contrast with the naturalistic aesthetics of the MARS system or the refined, ecological functionalism of Haikola’s seeding devices, and yet the team found that the damselfish preferred these clearly artificial reefs to their natural, rocky alternatives.

These experiments suggest that a restored reef might not necessarily need to look like a reef for it to work ecologically. More-than-human designers might find enough openness within animals’ preferences to find a productive space between naturalism and economies of material and scale. At the same time, it raises the importance of responsibility in all acts of more-than-human design: namely, how do we know that our intervention is a genuine contribution to an ecology, or whether we are merely creating a trap, attracting certain species away from more suitable sites, like moths to a lamp? 19 19 Author’s interview with Anja Wegner, 17 October 2024.

Superflex, for their part, are as interested in the designed objects as the wider narratives that might emerge from more-than-human design. This is exemplified by DiveIn, an early exposition of their reef investigations, in which a multispecies stage modelled on the first drive-in cinema in the United States was constructed from the vibrant reef material that the more-than-human team had developed. The structure was placed in the reefs off the Pacific coast and then replicated as a cinema in the arid valley of Coachella, California, where the fish’s inhabitation of the sister structure was screened to a drive-in audience. In this way, the project forged an unlikely but pertinent connection between American car culture and the precarity of the reef.

Superflex’s playful work communicates a sobering reality: that all efforts to save coral reefs will ultimately be futile unless wider design cultures can be challenged and overturned. Global temperatures have already breached the UN’s critical threshold of 1.5 degrees above pre-industrial levels for over a year. 20 20 ‘1.5°C: what it means and why it matters’, United Nations Climate Action resource. Source If sustained, this temperature rise is predicted to lead to a loss of 90 per cent of reefs worldwide. 21 21 ‘99% of coral reefs could disappear if we don’t slash emissions this decade, alarming new study shows’, World Economic Forum, Nature and Biodiversity, 4 February 2022. Source At two degrees rise – which, collectively, humans are still making precious few steps to avoid – the loss is practically total.

Artificial reefs may be temporary measures – reparative acts in an era of irresponsibility – but they prompt us to consider the obligations of all designers to the more-than-human world. As the destruction of the cities of the sea holds up a dark mirror image to human construction on land, we are invited to reflect upon how design practices, for all their humanist contributions, have been complicit in an unprecedented loss of diversity, structure and even basic functionality in the shared, more-than-human world. Even the urgent narratives around the renewable energy transition, filtered through existing extractive mindsets, are generating yet more new forms of marine disruption, as efforts to mine the seabed for rare earth metals for batteries threaten severe impacts on pelagic coral reefs. 22 22 The world’s largest cold water coral reef lies beside the first experimental deep-sea mining test site. Source How might we finally shine a light on these shadow places of design? 23 23 Val Plumwood, ‘Shadow Places and the Politics of Dwelling’, Australian Humanities Review. Source

Though corals lie below the ocean surface, they are not in the dark. Instead, they are colourful, charismatic and cherished, and their loss is a siren call for others hidden deep. By acting holistically, we might reflect their iridescence onto other, less spectacular environments. Alex Goad, working with Mariana Pinto and the Centre for Marine Science and Innovation at UNSW, has developed a range of new modular systems called Living Seawalls to transform human infrastructure on the shore, 24 24 https://www.reefdesignlab.com/living-seawalls while also trialling zero-carbon marine concrete made from mollusc shells. 25 25 Mariana Pinto, email exchange. Superflex, meanwhile, have brought their fishy design explorations back to the stone reefs of their native Denmark, announcing a plan to restore over 55 square kilometres of this disrupted temperate habitat, and helping to shape government policies towards marine restoration. 26 26 Super Reef: Source Stone reef restorations as part of the marine nature fund, 2023. Source Supported by interview with Rasmus Nielsen, 17 October 2024. Whether in the regeneration of aquatic or of built environments, in the drafting of policies or in the ongoing care for our local more-than-human communities, we might all benefit from a mental journey to a paradise not-yet-lost, to return to our collective work re-energised by the wonder and the precarity of our planet’s greatest living infrastructures.