The next step is to see whether these experimentally evolved algae can help corals survive the heat. Corals in the wild naturally shuffle and switch their algae, and they can be nudged to do the same in captivity. In one study, young corals were given heatproof zooxanthellae, and after ten months at 80.6 degrees Fahrenheit, they had grown to twice the size of other corals with the wild-type algae. Then the researchers simulated a heatwave, cranking up the temperature in the experimental aquariums to 87.8 degrees Fahrenheit for forty-one days, and watched as the corals with regular zooxanthellae bleached. The corals with the heat-evolved variety stayed colourful and survived.
Manipulating other parts of the corals’ microbiome can also help boost their health and resilience. Just as humans have communities of microbes living inside our bodies, without which we can’t live healthy lives, so do corals. A coral’s microbiome includes bacteria, viruses, and microscopic fungi, which protect them from stress and disease by providing vitamins, antioxidants, and antimicrobial compounds. This opens the possibility of performing the coral equivalent of faecal transplants in humans, a successful therapy that involves a healthy person donating samples of gut microbes, which are then used to inoculate people suffering from various gastrointestinal disorders. It is not yet a standard procedure for coral reefs, but there are signs that it could work, even with transplants conducted within the same reef.
Off the island of Phuket in Thailand, divers collected fragments of naturally heat-resistant corals that grow on reef flats where the shallow waters get periodically simmered by the sun at low tide. Scientists stripped off the living tissue from these coral samples and used the resulting slurry to inoculate other, more sensitive corals that had been growing in gentler conditions on the reef. These inoculations made the corals substantially more heat-resistant when researchers dialled up the temperature in their tanks. Genetic tests suggest that particular strains of bacteria were transferred and fortified the corals. A goal for this kind of research is to culture probiotic treatments that would give corals the right blend of bacteria in their microbiomes to help them survive at higher temperatures.
A new and no doubt tempting molecular tool already available to coral restorationists is gene editing. CRISPRe technology involves cutting and pasting specific sections of DNA code, making it possible to create designer organisms with desirable genes added in or unwanted genes cut out. Experts have not yet deployed this technology to engineer corals, but they are using it to better understand what makes some corals particularly tough.
A breakthrough came in 2020, when a team led by researchers at Stanford University used CRISPR to identify a gene that plays a critical part in corals’ resistance to heat stress. They cut out this gene, known as heat shock transcription factor 1 (HSF1), from coral larvae. Without HSF1, the larvae became much more susceptible to rising heat, indicating this gene does something important in protecting corals from heat stress, although at this stage no one knows exactly what. Pasting more copies of the HSF1 gene into coral genomes could potentially boost their resistance, although there are likely other genes involved, all interacting in ways that scientists have yet to untangle.
CRISPR could also be used to find genes involved in other aspects of coral health, including their tolerance to acidification, pollutants, and pathogens. A promising place to look for these is among the corals’ many highly usual genes, known as unigenes. These are so unlike all known gene sequences in other living organisms, it’s impossible to predict what they do.f Unigenes could potentially boost coral health via mechanisms that don’t exist in other organisms, and they could give researchers a whole new way of understanding what makes corals tick.
In the past few years, spurred on by the accelerating impacts of ocean warming, major research programmes have started exploring what technologies have to offer the future of reefs. An Australian initiative, with a budget of AUD$92 million, began in 2020 to investigate various options to help the Great Barrier Reef resist, adapt, and recover from the climate crisis. These tactics range from biologically engineering heatproof corals to geoengineering methods that would dim sunlight above reefs by creating mists or fogs of seawater or releasing blankets of bubbles.
Scientists will identify the most promising methods to save as many as possible of the thousands of reefs and islands that make up the Great Barrier Reef and then, it is hoped, apply them to reefs in other parts of the world. But there’s no guarantee any of these efforts will work, which is one reason a backup plan of sorts is running alongside these research programmes. For a site on the coast of northern Queensland, architects have designed an eye-catching circular building, inspired by Fungia corals, which look like upside-down mushrooms. The building will become a living coral biobank, filled with aquariums in which every one of the world’s eight hundred or so species of stony corals will be kept in safe isolation from the Anthropocene ocean.
Elsewhere, coral species are gathered up, and their cells, sperm, and eggs are frozen. It’s a similar scheme to seed banks, which aim to preserve all the world’s plants, so people in the future can use them to breed the crops they need or replant species that are lost from the wild. Coral DNA is also being sequenced and archived to preserve the genetic codes that would be lost forever if those species went extinct. And for a growing collection of species, extinction is becoming a distinct possibility. The last full assessment, in 2008, showed that one-third of all stony corals are threatened with extinction. In the Caribbean, twenty-six coral species are now placed in the Red List’s most high-risk category, Critically Endangered. This includes pillar coral, a species that used to grow in fingerlike colonies all along the Mesoamerican Reef, from Florida to Trinidad and Tobago, but it’s being wiped out, like many other Caribbean corals, by the newly arrived and catchily named stony coral tissue loss disease, which can infect hundreds of feet of reef in a single day.
Biobanking and cryopreservation are pragmatic options for corals. The information contained in preserved tissues and genetic codes could prove useful for future restoration in ways nobody has thought of yet. However, none of these projects are cure-alls for sick reefs, and crucially, efforts must continue to slash carbon emissions and prevent damage to and demolition of more ecosystems. While the belief that technology can fix the troubles of the living planet is alluring, the animals won’t come marching back, two by two, and the ocean isn’t going to simply bounce back to normal. It will take gargantuan endeavours to avoid a dystopian future where all that’s left of the wild ocean are genetic and digital memories locked away in archives on land of once diverse and complex ecosystems.
While scientists are busy engineering corals and testing other solutions to help ensure reef building continues into the Anthropocene, even greater technological challenges are still to come. To have any meaningful effect in the ocean, the scale of coral-reef restoration will need to massively expand. Reef restoration has so far typically been done on a microscale, with projects operating across hundreds of square yards of reef. The problem is that, just in the past decade, warming seas and bleaching have devastated thousands of square miles of reef.
Current methods of reef restoration are immensely labour-intensive. Most rely on scuba divers installing structures underwater and fixing onto them coral fragments and colonies. Entire armies of well-meaning scuba-diving tourists lending a hand wouldn’t be enough to scale up restoration efforts.
To go global, reef restoration will need a techno-centric transformation on par with the industrialisation of agriculture. Steps in the process would need to be mechanised and automated. Machinery could prepare the seabed—much as tractors prepare fields for planting crops—clearing away loose coral rubble or spraying bio-glues to bind up loose material that would otherwise abrade and smother small coral recruits. Other machinery could sense and forecast when remaining healthy coral reefs are spawning, then swoop in to scoop up floating slicks of coral larvae, including millions that wouldn’t survive anyway because they would drift into open seas, and deliver them to depleted reefs.
Coral factories on land, or perhaps floating out at sea, will need to churn out many varieties of heat-tolerant colonies. To maximise their chances of survival, the young corals will need to be carefully planted out, perhaps with the kinds of precision techniques that are now being introduced to agriculture. Rather than homogenising the landscape by planting endless acres of monoculture and spraying entire fields with fertilisers and pesticides, precision farming involves working at a much finer resolution—for example, autonomous robots deliver water and fertiliser to individual plants and, equipped with artificial intelligence, accurately determine whether a plant is diseased and needs dosing with pesticides.
It’s not beyond the bounds of reality to imagine fleets of underwater robots scanning the topography of an area of seabed and making decisions about the best places to plant corals. The robots could select a coral species from its onboard manifest, locate a spot with exactly the right light and angle for it to grow well, fix it in place with a squeeze of quick-setting eco-cement, give it a dab of probiotic treatment, and then move on to the next one. The underwater robots could work in synchrony with drones at the surface that spray fine mists of seawater into the skies to reflect the sun’s heat and cool the sea while the new corals are settling in below.
This would require bespoke technologies to be developed, because no existing devices are available to do the job. The remote-operated underwater vehicles in current use by ocean scientists were originally developed by the oil and gas industry to work on offshore drilling rigs in deep, calm waters. Scientists have also built autonomous vehicles that steer themselves through the deep ocean gathering data. These machines would likely struggle to navigate around the rugged topography and turbulent waters of shallow coral reefs just a few yards below the surface, let alone to be dexterous enough to manipulate individual coral colonies.
Given enough funding, teams of engineers and scientists could no doubt invent technologies to make large-scale coral restoration a reality, but financing will not be straightforward. Restoration projects for other habitats, such as mangroves and terrestrial forests, are commonly funded by carbon-trading and offsetting schemes. But coral reefs are not substantial enough carbon sinks to be traded on blue carbon markets.g An alternative for funding reef restoration is to tap into the value the reefs hold in protecting coastlines from storms and flooding. Globally, tropical storms are the most common and costliest natural disasters, and healthy coral reefs are one of the most effective natural barriers against storm impacts. Just in the United States and its territories, coral reefs fringe close to two thousand miles of at-risk, low-lying coasts, including in Florida, Hawai’i, American Samoa, Puerto Rico, and Guam. These reefs help protect tens of thousands of lives and save an estimated US$1.8 billion each year that would otherwise be needed to repair storm-damaged homes, commercial buildings, and infrastructure. A possibility that has yet to be fully explored would be to divert some of the billions spent on mitigating coastal hazards—building flood defences, for instance—towards coral restoration.
Money could be raised some other way, perhaps through a new mechanism to capture the economic value of the very existence of species and biodiversity, or by using the fund that richer nations are pledging to assist lower-income nations to adapt to climate change. However it’s done, a restoration economy for coral reefs would raise some deep ethical issues.
The damage to coral reefs lies front and centre among the global injustices of the changing ocean. Most people who depend on coral reefs for their food and livelihoods, and to protect their homes and coasts, live in countries that contribute the least to global carbon emissions. The climate crisis that’s killing corals and devastating reefs is caused by carbon emitted by nations that, for the most part, don’t have their own tropical reefs. There are a few exceptions, notably the United States with its Floridian and Hawai’ian reefs, and Australia with its Great Barrier Reef. Both nations are technological leaders in coral-reef restoration and are devoting considerable resources to research and development.h This means that if restoration is to be rolled out more widely, it will inevitably require a one-way flow of technological know-how, as well as financing and labour, from high-income nations where most research is happening, to low- and middle-income nations where most of the world’s coral reefs exist.
Reef restorationists will need to avoid unintentionally repeating mistakes made over the centuries by colonialists who imposed their ideas of how the natural world should be managed and used, and how it should look. Colonial powers dramatically transformed landscapes and rearranged the world’s biodiversity by introducing animals and plants to hunt, rear, and cultivate, or even simply to remind them of home. Reef restorationists aren’t proposing anything as preposterous as bringing rabbits and camels to Australia or English house sparrows to the United States, but they will make decisions about the future of reefs. And the outcome could look very different depending on who gets to make those decisions.
Governments in countries with lucrative tourism industries might decide to pay to install heatproof reefs of a type that overseas visitors consider to be beautiful and worth flying around the world to see. These sorts of decisions are already being made—for instance, in Raja Ampat, Indonesia, a programme is underway to reintroduce zebra sharks to reefs where many shark species have been overfished and depleted. The choice of the zebra shark is based on several practical matters, including the fact that they breed well in captivity, and that their living egg cases can be easily moved from the aquariums where they were born and flown internationally to coral reefs on the other side of the world. Zebra sharks also happen to be attractive, with their rounded snouts and speckled skin, and they are docile and easy to see lying on the seabed, making them a favourite species among scuba divers. There’s nothing inherently wrong with bringing back species that visitors want to see, and the approach can work. But these sorts of decisions will influence how reefs will be. It’s hard to imagine reintroduction programmes attempting to boost local populations of species that diving tourists are more fearful of, say, or that they deem too ugly or boring.
When coral reefs fade to white, they dramatically reveal how the ocean is changing. Climate impacts play out in front of people’s eyes from one day to the next, week to week. Bleaching reefs are impossible to ignore, and they deliver to us a sense of helplessness and desperation to do something, anything, to stop the damage from happening and go back to the way things were. Restoration fills that need to take action. What used to be a marginal patching-up of damaged parts of individual reefs is morphing into a global endeavour.
Not everybody agrees this is the best way forwards, and a battle for the soul of coral reefs is gathering pace. Some reef experts contend that it’s already too late for any form of restoration because conditions in the ocean can no longer support reef growth as it was known a decade or two ago. Focus instead, they urge, on helping reefs, with their novel mixes of species, find a place in the Anthropocene ocean. Instead of concentrating on coral cover, consider other measures of reef health, such as the number of fish and amount of food they support, and the ability of these ecosystems to keep on functioning.
Many still advocate for reef protection, campaigning for more marine reserves, to ease the threats their watery boundaries can hold back. Others argue for techno-centric approaches to restoration—from biobanking to engineering heatproof corals—which are often judged to be the extreme solutions necessary to grapple with the existential threats to reefs. And yet these steps are labelled as radical because they involve cutting-edge technologies and deliberately changing coral biology, which carry inherent risks and dangers that something unforeseen could go wrong. Restoration is not a radical method for saving coral reefs because it can go only as far as fixing some of the symptoms of the Anthropocene, while it does nothing to address the source of the problems. A perversely chilling vision of the future sees engineered, heatproof coral reefs growing in countries that can afford them, while the ocean continues to heat and carbon emissions continue unabated. Restoration of reefs could still be deemed a success even if nothing at all is done about the climate crisis.
Unhitching humanity from business as usual, shifting the underlying drivers that cause so many problems, and finding new ways of living with the changing ocean is where truly radical views of the future lie.
a Pronounced zoo-zan-thellee.
b The global area of tropical corals is approximately 110,000 square miles.
c Cirrhilabrus finifenmaa. Finifenmaa means “rose” in the Maldivian Dhivehi language. This was one of the first species found and described in the Maldives by a Maldivian researcher.
d These are only the corals that normally have algae symbionts; azooxanthellate corals can’t bleach.
e CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats.
f Many genes are similar enough among different organisms that, from the DNA sequence alone, geneticists can tell if it’s a gene for, say, light receptors in a retina or a skin pigment cell. But this is not the case with unigenes.
g Following the example of terrestrial carbon offsetting schemes, blue carbon is a term applied to the carbon sequestered by marine ecosystems, such as mangrove forests and seagrass meadows. Blue carbon credits can be created when areas of habitat are protected or restored, and the credits traded by greenhouse gas offsetting programmes. Major forest carbon offsets on land have come under heavy criticism for being largely worthless for the environment and potentially making global heating worse.
h While at the same time not devoting nearly enough resources, many critics say, to reducing the nations’ carbon emissions.
Chapter 10
Living in the Future Ocean
The future of the ocean is not yet determined. What lies ahead will depend on how exactly the most critical changes in the climate play out—how hot the seas become, how fast and high they rise, how quickly oxygen ebbs and carbon climbs, how storms are stirred and where they strike. And it will depend on how humanity responds to the changes that are well underway, and the choices people make from this point forwards. A range of possibilities could still unfold, but plans are being laid down by entrepreneurs and industrialists, who are assembling their vision for the future and steering the ways people will live with and use the Anthropocene ocean.
Cities set adrift at sea or built underwater are science-fiction staples. Today architects are putting these imaginings into practice (although for now chiefly above the waterline) in places that could otherwise become unlivable. The construction of the world’s first truly floating city is slated for the Maldives archipelago in the northern reaches of the Indian Ocean, a cluster of low-lying islands mostly standing less than three feet above current sea level. Candy-coloured houses will have picture windows overlooking a sparkling turquoise lagoon. People will stroll and cycle along sandy paths and over bridges connecting the city’s hexagonal segments, which will link together like the honeycomb patterns of brain corals. The modular units are to be fixed to a massive underwater concrete structure screwed to the seabed with telescopic steel stilts, allowing the buildings to gently rise and fall with the waves. The city will float inside a five-hundred-acre lagoon bordered by sand barrier islands. For added protection, foam-glass structures will be fixed beneath the city for new corals to settle and grow on, perhaps transplanted from other reefs around the islands. Solar power for twenty thousand people will be harnessed within the city; sewage will be treated locally and used as compost for the displays of tropical flowers; instead of air conditioning, cool water will be pumped up from the deep sea into the lagoon.a
The Maldives’ floating city could lead the way for more of this new kind of urban ocean living. This venture is a private-public partnership between a Dutch architectural firm and the Maldivian government, championed by former president and committed climate campaigner Mohamed Nasheed. In 2009, President Nasheed held an underwater cabinet meeting; he and his ministers, wearing scuba gear, knelt on the seabed writing on waterproof slates. They called on the rest of the world to help fight against climate change and save their vulnerable nation from drowning. Nasheed had also raised the possibility of purchasing land elsewhere to relocate the entire population, which has grown to more than a half million people. Now the focus is on finding ways to keep the Maldivian homeland, and if the building schedule goes according to plan, this first floating city will be up and running by 2027. Designers don’t intend this to be a luxury tourist resort but a practical solution for living above rising seas. With a reported starting price of $150,000 for a studio apartment, international investors will no doubt snap up their slice of tropical paradise and the residence permit that will be thrown in with it. Whether an average Maldivian fishing family will be able to raise enough capital is another matter.b
On the opposite side of the globe, efforts are already underway to clean up the plastic debris floating in the ocean. The Ocean Cleanup, a nonprofit organisation, was founded in 2013 by a then-teenage entrepreneur, Boylan Slat, from the Netherlands. Outraged by disastrous plastic pollution, Slat raised millions of dollars and began sending out ships towing U-shaped barriers to skim floating plastic from the infamous Great Pacific Garbage Patch. In April 2023, the Ocean Cleanup announced the removal of its two hundredth metric ton of plastic from this slowly spinning gyre. It’s estimated that at least fourteen million metric tons of plastics enter the ocean every year. For that reason alone, we need to focus on reducing the production of plastics.
When it comes to cleaning up existing plastic pollution, many scientists and conservationists are worried about the method used to skim off floating plastics. The surface of the sea is a wide, flat ecosystem, home to a mix of delicate organisms that float and drift with the winds and currents. Many of these animals evolved to match the colour of their surroundings and are various shades of indigo and cobalt blue. Velella is a jelly-like creature with a little sail sticking up to catch the breeze; Porpita looks like a round blue button edged with a fringe of stinging tentacles; Janthina janthina are deep purple snails that hang down from the surface on frothy rafts of bubbles. On an eighty-day survey undertaken while sailing across the Pacific from Hawai’i to San Francisco, scientists found that these three blue animals live in the garbage patch. The same currents that sweep up the floating plastics also gather these animals together, and they occupy the same regions of the sea surface. It follows that scooping up plastics will likely scoop up these and other animals, threatening the survival of species—a form of unintentional bycatch equivalent to oceanic sharks getting snagged on longlines. These blue-tinted surface dwellers are important food for predators such as sea turtles and seabirds and form critical links to other ecosystems, which could be broken by plastic clean-up efforts. Experts caution that the impacts of plastic collectors on these living communities haven’t been taken seriously enough or properly assessed. Meanwhile, investors are pouring money into this method that picks out only the big bits of floating trash and creates little incentive to stop making so much plastic in the first place.
While some initiatives currently in development, including those exploring ways to clean up plastics, aim to reduce humanity’s impact on the ocean, others are aggressively ramping up exploitation. In shipyards in China, new vessels are being built that will hasten the practice of super-intensive industrial fishing. Their target will be the shoals of krill swimming in the icy seas surrounding the Antarctic Peninsula. Most of these ships are so huge they wouldn’t fit diagonally across a football field. Among them, a 460-foot-long krill trawler will be the biggest, most advanced of its kind, capable of sucking more krill out of the ocean than any vessel before it. Russia also plans to re-enter the Antarctic krill-fishing business, having exited in 2010, and India may soon join the fray in the Southern Ocean.
