In addition to this, I’ll need the hand-eye coordination of a middling video game player, a stack of petri dishes and an insulated box that can keep my edited embryos in the Goldilocks temperature zone of around 28.5 degrees Celsius. In fact, the most difficult part is getting a reliable supply of freshly fertilized zebrafish embryos for my experiments. Fortunately, at the Marine Biological Laboratory in Woods Hole, Massachusetts, where I spent 10 days in May learning how to do genetic editing, it’s not a problem. The lab can produce a new batch every hour, so I have plenty to work with.

I line up dozens of single-cell embryos along the edge of a glass slide. Under the microscope, they look like a string of yellowed pearls. When I prod them with an ultra-fine glass syringe, they squish like tapioca balls in a boba tea. But if I get the angle right, I can inject them with a carefully calibrated dose of CRISPR-Cas9 designed to disable a gene associated with eye development. When they hatch into larvae a few days later, they will have no eyes. If I were to allow them to reach adulthood, which I won’t, they could theoretically breed with other similarly blinded adults to create a population of eyeless fish for an aquarium exhibit of unnatural wonders.

The process is deceptively simple; the implications are anything but.

Breaking The (Genetic) Code

In the 13 years since biochemist Jennifer Doudna, Emmanuelle Charpentier and their fellow collaborators harnessed an ancient mechanism of bacterial immunity to develop a genome-editing technology, CRISPR-Cas9 has become a powerful and infinitely customizable tool that allows humans to rewrite the language of life. It can target plant and animal genes, and promises a cure for any disease with a genetic component. It can alter heritable traits like eye color, size, strength and cognitive performance. It has already been used to make crops more productive, fruit sweeter and rice cultivation less water-intensive. 

The tool allows humans to genetically edit sterility into pests, like the New World screwworm — a flesh-eating maggot that preys on both cattle and humans — and the mosquito that carries malaria, potentially driving them to extinction. 

We can also edit animals out of extinction by using the same process to insert DNA derived from ancient forebears into their modern descendants. In April, the venture-backed biotech firm Colossal Biosciences introduced to the world a litter of what they said were “de-extincted” dire wolves brought back into existence after disappearing from the world for more than 10,000 years. Critics dubbed the wolves “dire-ish,” noting that only a few genes in the modern gray wolf — those that dictate coat color, size, musculature and jaw shape — had been altered, not the whole genome. Still, the technological advance offers a tantalizing glimpse of what else can be achieved with genetic editing.

It may also promise us the ability to prevent extinction in the first place, starting with one of the most threatened ecosystems on the planet: coral reefs.

Fixing Failure Through Genetic Editing

Coral reefs are fundamental to the health of our oceans. They cover less than 1% of the Earth’s ocean, but are home to a quarter of the ocean’s fish. They protect our coastlines from storm surges and rising sea levels and bring in hundreds of billions of dollars a year in tourism and fishing revenues. Without them, we would lose a major carbon sink. And they are on the brink of extinction, threatened by ocean acidification and rising temperatures that are outpacing their ability to adapt. The millions of tiny polyps that make up a reef rely on a symbiotic relationship with algae, which photosynthesize sunlight into food for both organisms. When stressed by high heat, coral expel their colorful symbionts, leaving behind a bleached white reef. Recovery is possible, but when bleaching events repeat in quick succession, the coral usually dies.

A recently published study in Nature finds that 70% of Atlantic coral reefs will be dead or dying by 2040 under current warming conditions. If warming exceeds 2°C degrees Celsius beyond pre-industrial levels, nearly all reef systems — at least 99% — will stop growing by 2100. We are already averaging 1.3°C, and could hit 1.7 °C as soon as 2027, according to the World Meteorological Organization.

If scientists could use CRISPR to engineer a more heat-tolerant coral, it would give coral a better chance of surviving a marine environment made warmer by climate change. It would also keep the human industries that rely on reefs afloat. But should we edit nature to fix our failures? And if we do, is it still natural?

Using the new field of biotech to save the natural world from the fallout of a previous technological romance has gained traction among scientists and conservationists who worry we have no time to waste. However, it remains a hotly debated topic, pitting those who say, “we can” against those who say, “we shouldn’t.” At the core is a fundamental divide over what makes nature natural, the risks of unintended consequences and the responsibility that comes with using a technology once relegated to the realm of a divine creator. 

“CRISPR presents us with new options,” Christopher Preston, an environmental philosopher from the University of Montana, told me. His book, “The Synthetic Age,” explores how humans are poised to radically reshape the natural world using CRISPR editing, de-extinction and climate engineering. “So the million-dollar question is, how do you decide? Which parts of the world should we leave to natural evolutionary processes, and which parts of the world should we grab hold of and design so that they work better?”

Evolution is not keeping pace with climate change, so it is up to us to give it an assist, he said. In some cases, the urgency is so great that we may not have time to waste. “There’s no doubt there are times when you have to act,” Preston continued. “Corals are a case where the benefits of reefs are just so enormous that keeping some alive, even if they’re genetically altered, makes the risks worth it.” 

Not all genetic interventions are feasible for now. But eventually, say scientists, they will be, and it is better to start studying the implications before they are regularly deployed by citizens, scientists and venture capitalists trying to fix the mistakes of the past, at the risk of inadvertently making new ones. This is precisely why I ended up hunched over a petri dish, examining the results of my first experiment: rewriting the code of life for approximately 150 zebrafish embryos. 

CRISPR stands for clustered regularly interspaced short palindromic repeats, and it is an ancient bacterial defense system that identifies and fends off viral attacks. When bacteria are attacked, the survivors embed a snippet of the invading virus’s DNA into their own genome, which then serves as an internal mug shot that is passed down through generations. The next time the bacteria encounter that specific DNA sequence in an invading virus, they will cut it out by using an enzyme that works like a molecular scalpel, called Cas, which stands for CRISPR-associated protein, neutralizing the threat. It is this seek-and-destroy mechanism that Doudna and Charpentier repurposed into an elegant tool for manipulating DNA sequences. They published their breakthrough in 2012 and received the Nobel Prize in Chemistry for their work in 2020. 

CRISPR can be programmed to target specific patterns of genetic code, and once found, the Cas9 will cut it out. In most cases, this disables the gene’s function entirely; however, the same system can be used to replace a gene segment to purposely alter its function, or to repair a gene’s faulty mutation, much like a spell-check for DNA.

A day after the injections, I could see my zebrafish embryos starting to develop inside their eggs. The ones that had been successfully injected had no eyes. The un-injected embryos — my control group — did. This was to be expected. The zebrafish’s genome, like that of fruit flies and lab mice, is well understood, and I was working with a version of CRISPR-Cas9 designed to target the Rx3 gene, which governs eye development in most vertebrates. For a less-studied species, like coral, there is no map of what each gene does. To figure that out, scientists must knock out specific genes one by one, observe the impact and then deduce their role. Before CRISPR, this would have been near impossible. Even with CRISPR, it’s not exactly easy. 

Climate Proofing Coral

Unlike zebrafish, a freshwater species from Asia that spawns whenever the lights go on, coral only spawns at the beginning of the summer, in the middle of the night, for just a few evenings following a full moon. For Phillip Cleves, a principal investigator at the Carnegie Institute for Science’s embryology department who has dedicated his career to studying coral genetics, that meant packing up his lab and decamping to Queensland, Australia, while he waited for the Acropora millepora corals of the Great Barrier Reef to get it on.

Once they did, the process of injection was pretty much the same as with my zebrafish embryos: He collected the newly fertilized eggs, lined them up in petri dishes and then spent the next several hours injecting the embryos with a solution containing CRISPR-Cas9. Back in 2020, he was working on a hunch that disabling the HSF1 gene would decrease coral’s heat tolerance even further. HSF1, or Heat Stress Factor 1, is a gene that can be found in almost every species from yeast to humans, and is believed to influence how organisms respond to heat. Cleves’ hunch proved right.

Once his coral larvae hatched, Cleves exposed them to moderately high temperatures. Those whose HSF1 gene had been disabled via the CRISPR solution injection died. The others survived. Cleves’ identification of the gene in coral responsible for controlling thermal tolerance brings scientists one step closer to using genetically assisted evolution to engineer a more heat-resistant organism. Now that they know what HSF1 does, they could, theoretically, replace it or manipulate it to encode a higher heat tolerance. Cleves’ findings are among the first non-commercial applications of CRISPR-Cas9 for conservation purposes.

It’s one thing to disrupt a gene, and something else entirely to replace it with a different one, so this approach to climate-proof coral is still tantalizingly out of reach. “We know that knocking out one gene causes a decrease in tolerance, but it’s unclear what types of genetic changes we could make to increase it,” Cleves told me. “Finding genes that can enhance heat tolerance in corals is an essential research topic.”

He suspects that heat tolerance is polygenic, meaning that it is influenced by multiple genes. These genes may vary between species. And even different populations of the same species may express their genes differently, turning them off or on, depending on the environment. Targeting only one gene would be like genetically engineering a gray wolf to have white fur and calling it a dire wolf.

In the meantime, Cleves is optimistic that his quest will eventually bear fruit. “We’re seeing massive death of corals, and then, in some cases, recovery,” he says. “CRISPR helps us understand how this is happening. Because it’s an open question as to how coral will survive climate change. They need to adapt. We must find out how we can facilitate that.”

Cleves’ lab now has a domesticated coral farm that can produce embryos several times a year, so he no longer needs to wait for the first full moon of summer over the Great Barrier Reef to continue with his experiments. The accelerated pace couldn’t come at a better time: The past three years have seen back-to-back bleaching events that have all but wiped out coral in the Caribbean, and nearly half the species in the Indo-Pacific.

“Catastrophic is not a word I use lightly, but that is exactly what 2025 is shaping up to be,” Kate Quigley, a molecular ecologist and a principal research scientist at Australia’s Minderoo Foundation, told me. “There are only a few species left in the Caribbean, and my colleagues there are now saying words like functionally extinct, which means there are not enough individuals to have successful breeding. That is terrifying.”

Scientists still don’t understand why, exactly, coral expel their algae symbionts when the water heats up, but Quigley, who replicates bleaching events in a tank to test coral heat tolerance in her lab in Western Australia, can tell you what it smells like. “It’s awful, like rotting fish. You walk into the lab, and you know you have dead coral even before you look in the tank.”

In Quigley’s lab, scientists take coral to the extreme limits of heat tolerance to identify those that survive. Then they crossbreed the survivors to see if they can produce a more resilient organism. She feeds details of those findings into an AI model that helps identify parts of the reef most likely to produce hardier corals that could bolster any future breeding program. 

For all the research Quigley and Cleves have dedicated to climate-proofing coral, neither wants to see the results of their work move from experimentation in the lab to actual use in the open ocean. Needing to do so would represent an even greater failure by humankind to protect the environment that we already have. And while genetic editing and selective breeding offer concrete solutions for helping some organisms adapt, they will never be powerful enough to replace everything lost to rising water temperatures.

“I will try to prepare for it, but the most important thing we can do to save coral is take strong action on climate change,” Quigley told me. “We could pour billions and billions of dollars — in fact, we already have — into restoration, and even if, by some miracle, we manage to recreate the reef, there’d be other ecosystems that would need the same thing. So why can’t we just get at the root issue?”

Given the persistent failure of governments to act with the urgency necessary to stem the burning of fossil fuels that are driving climate change, it is easier to look with hope towards techno-optimist solutions that promise to fix what society has already broken. Colossal Biosciences’ dire-ish wolf program aside, genetic editing is already offering concrete advantages in a conservation context.

A Genetically Edited American Chestnut Grows Roots

The American chestnut — a vital source of timber, food and shade for early Americans that once blanketed the eastern half of the United States with billions of trees — was nearly wiped out by a deadly invasive fungus in the early 1900s. The few remaining examples rarely reach maturity, and plant biologists consider the chestnut to be functionally extinct.

But over the past three decades, The American Chestnut Foundation, a non-profit hub for research and conservation efforts, has supported genetic editing to create a blight-resistant strain of this once keystone species. “The dire wolf is cool, but ecologically it’s not important,” Gregory Kaebnick, a senior research scholar at New York’s Hastings Center for Bioethics, told me. “The American chestnut, though, if you replanted those across Eastern forests, that could make a difference. And so it strikes me as worth the investment.”

Other programs are looking to use CRISPR not to save a specific species, but to save ourselves from our excesses. RemePhy, a company built by bioengineers from Imperial College London, has genetically modified plants to enhance their ability to draw waste metals and toxins from polluted soil, providing a cleanup service around mining sites. 

George Church, the Harvard Medical School professor of genetics behind Colossal’s dire wolf project, was part of a team that successfully used CRISPR to change the genome of blue-green algae so that it could absorb up to 20% more carbon dioxide via photosynthesis. Silicon Valley tech incubator Y Combinator seized on the advance to call for scaled-up proposals, estimating that seeding less than 1% of the ocean’s surface with genetically engineered phytoplankton would sequester approximately 47 gigatons of CO₂ a year, more than enough to reverse all of last year’s worldwide emissions. 

But moving from deploying CRISPR for species protection to providing a planetary service flips the ethical calculus. Restoring a chestnut forest or a coral reef preserves nature, or at least something close to it. Genetically manipulating phytoplankton and plants to clean up after our mistakes raises the risk of a moral hazard. Do we have the right to rewrite nature so we can perpetuate our nature-killing ways?

“We’ve gone from talking about how to let nature carry on as best it can, to ‘How can we engineer it to provide this vital service?’” Preston, the environmental philosopher, told me. “We’re not trying to preserve a natural system. We’re just trying to find the best way to pull carbon out of the atmosphere. That requires a little bit more humility.”

It also requires caution. 

CRISPR-Cas9 enables us to hack the genetic code. But we still can’t build a reef from scratch. We have vague ideas about how the ocean works, and we don’t know how to replicate what does work. The possibilities of genetically editing a more resilient ecosystem are endless. But so too are the risks.

When my RX3-injected zebrafish embryos hatched, I noticed that many of them were stunted. A few had deformed flippers, and some could only swim in circles. It was unclear if the stunting was a result of injection trauma, a side effect of the CRISPR-Cas9 editing process, or if the gene that I had disabled would have otherwise contributed in some way to normal growth.

Amateur geneticists like me have probably done the zebrafish RX3 experiment thousands of times. The results are usually predictable, but the unexpected stunting side effect illustrates the need to allow for unintended consequences, either within the organism or the ecosystem it occupies. We don’t want to save one species only to ruin another part of the environment that we don’t quite understand yet.

The CRISPR-edited American Chestnut trees demonstrated blight resistance, but a few of them appeared to be shrubbier than their unedited forebears, and many died from other diseases. A lab mix-up early on in the breeding process didn’t help. It led to the misidentification of several trees, accusations of a possible cover-up and commercial interference, and the withdrawal of support from the American Chestnut Foundation — an arboreal drama tailor-made for a true crime podcast. Researchers still don’t know why, exactly, the CRISPR’d trees are not flourishing, but they suspect that the editing process encoded a defect on a critical gene. The project continues.

CRISPR-Cas9 editing is not immune to human error, and it is never 100% accurate, noted Josh Rosenthal, a biologist at the Woods Hole Marine Biology Lab who taught me and other journalists how to use the technology. As with my stunted zebra fish, or the shrubby, disease-prone chestnuts, “There could be off-target changes,” he said. Most of them won’t appear as problematic, “But every once in a while, they’re going to change something in a detrimental way.” That’s acceptable in a lab. It could be hazardous in the environment.

My blind, stunted zebrafish probably wouldn’t survive in the wild, but escaped novelty zebrafish genetically altered to glow red or green for aquarium hobbyists are now flourishing in Brazilian rivers. The blacklight glow probably doesn’t give them a competitive advantage, but it does show that CRISPR-edited organisms can reproduce in natural environments, passing their altered genes down through generations.

Even a successful intervention could inadvertently set off a chain reaction. It could, for example, give the new organism a competitive advantage, depriving others of food, space and an opportunity to evolve climate resilience unassisted. A super coral might thrive in a warming ocean, but if there is only one species, the reef becomes a monocrop, devoid of biodiversity and vulnerable to disease. At a minimum, successfully climate-proofing a reef would require editing heat tolerance into hundreds, if not thousands, of coral species.

But then there is the complex interplay of growing acidity caused by excess CO₂ in the water, and other organisms essential to reef function. A sense of humility is essential, Quigley told me, echoing Preston. “Engineering the ocean, or the atmosphere, or coral is not something to be taken lightly. Science is incredible. But that doesn’t mean we know everything and what the unintended consequences might be.” 

It is too late to put the genetic genie back in the bottle. The technology to alter organisms is not only widely available — you can buy a frog genome editing kit for the cost of a nice terrarium — its power is now amplified by AI. ChatGPT will, with the right prompts, suggest edits to render a virus more virulent. A quick Google search can take you to biotech companies willing to sell the basic components. Using CRISPR-Cas9 to manipulate heritable traits in humans is still frowned upon. But nothing really governs its application in other organisms other than one’s personal ethics or those of the lab sponsoring the science.

As knowledge of the technology spreads beyond the lab, anyone with a hand steady enough to inject an embryo can start knocking out genes. Knocking them in is still difficult, but that, too, will change. “We are as gods, and might as well get good at it,” wrote pioneering environmentalist Stewart Brand in 1968, describing humanity’s technological impact as a “force of nature” in his inaugural issue of the Whole Earth Catalogue magazine.

As with all powerful technologies, getting good at it means balancing the benefits of using it against the consequences. When it comes to preserving the planetary environment in the face of an all-but-certain climate-driven catastrophe, that also means weighing the cost of inaction. “Maybe gene editing isn’t appropriate for reefs that are still relatively healthy,” Quigley told me.

But in places like the Caribbean, where many reefs have already bleached into rubble-filled wastelands, it could be, she added. “I think people’s tolerance for risky endeavors will change relatively quickly once things start to rapidly decline.” As much as Quigley loathes the idea now, she doesn’t hold herself exempt. “It’s a terrible thing to imagine a world without coral.”

The post Editing Nature To Fix Our Failures appeared first on NOEMA.

In a way, he had. His hometown of La Spezia, on Italy’s Ligurian coast, is famous for mussel cultivation. But around two decades ago, Varrella broke with tradition to try his hand at oyster farming, resurrecting an industry that had been dormant for around a century. For years, Varrella’s quixotic sideline in oysters was a source of good-natured ribbing among La Spezia’s mussel farmers — why compete with France’s dominance in the oyster market when Italian mussels already offered a solid business model?

But when water temperatures spiked in the early 2020s due to climate change, the population of a local fish that preys on mussels exploded, wiping out 95% of the mussel harvest. The oysters were left unscathed. His colleague’s oyster jibes evolved into heartfelt appreciation for Varrella’s prescient bet. Without the oysters, the La Spezia shellfish cooperative would not have survived, Varella said.

These days, mussels are back in La Spezia, but oysters are also now a key pillar of the local aquaculture economy, a necessary diversification for an industry made increasingly unpredictable by climate change.

Varrella’s oysters, with their deeply cupped shells and blue-green gills prized by Michelin-starred chefs, aren’t just a culinary product that could put La Spezia on the map; they are one of the rare, farmed products that contribute more to nature than they detract. One oyster can filter up to 50 gallons of ocean water a day, removing pollution and debris. Oysters naturally build reefs that foster biodiversity and protect surrounding habitats from erosion. Farming them requires no fertilizers, feed or antibiotics; they sequester carbon as they grow. For those keeping an eye on their carbon footprint, they are a tasty, guilt-free source of protein and nutrients. “Oysters are the perfect food,” Varrella told me, with the zeal of a new convert. “Everyone should be growing oysters. Or at least eating them.”

If they did, oyster farming could help communities adapt to some of the worst impacts of climate change on our planet while cleaning up oceans and contributing a vital food source for a growing global population. But they, too, are threatened by the combination of warming waters, opportunistic disease and ocean acidification that also threaten La Spezia’s mussels. Varrella’s oysters may have withstood La Spezia’s most recent marine heat wave, but they may not survive the next. Scientists are now in a race against time to develop so-called “climate-proof” oysters that can withstand the multiple threats compounded by global warming. Oysters could help humans better adapt to climate change, but only if humans help them adapt first.

The Sea Made Solid

Like sharks and nautiluses, oysters are living fossils, their anatomy relatively unchanged in their 190 to 250 million years on this planet. When dinosaurs walked the earth, oysters dominated the oceans, sculpting the marine environment with massive reefs built on the remains of their predecessors. Excavations of ancient settlements indicate that Stone Age humans relied on oysters and other shellfish for survival, and some scientists postulate that this increase of omega-3 fatty acids in their diet helped with brain growth and the development of tools, culture and religion.

Some archaeologists hypothesize that the abundance of shellfish along the coast helped guide human migration over the North American land bridge and into the Americas. That bounty sustained human populations for millennia. In the mid-1800s, New Yorkers ate an average of 600 oysters a year, dredged from reefs so big they appeared on nautical charts. European appetites were equally voracious — and destructive. By the end of the century, wild oyster reefs had all but disappeared from the globe, having fallen victim to over-harvesting and industrial pollution. Scientists now estimate that today’s global oyster population is a mere fraction of historic numbers.

Our hunger for oysters has changed the geography of our coasts, denuding them of natural wave breaks and making them more vulnerable to sea level rise, storm surges and erosion. Had the great expanse of oyster reefs that historically protected New York Harbor south of Staten Island remained in place, instead of dredged to feed a growing population throughout the 1800s, damage from 2012’s Hurricane Sandy wouldn’t have been nearly as bad, said Sally McGee, who manages the Shellfish Growers Climate Coalition within the environmental nonprofit, The Nature Conservancy.

Groups like The Nature Conservancy are working to restore oyster reefs worldwide, from New York to Louisiana, Australia and the United Kingdom. Not for food — that would defeat the purpose — but for their other, more environmental, services. In New York City, the Billion Oyster Project has set a goal to restore 100 acres of oyster reefs by 2035.

In most cases, “restoring” means starting over. The Billion Oyster Project uses a small structure made of oyster-friendly substrate, “seeding” it with oyster larvae. The spat — young oysters — excrete a concrete-like substance to anchor themselves to the structure for life. Once mature, an oyster spawns every summer, releasing millions of gametes into surrounding waters and producing the next generation of larvae that will, in turn, settle on other shells, eventually building into house-sized reefs.

Oysters are so prolific, estimated one researcher, that if half of a female oyster’s offspring were to develop into female oysters, it would take less than five generations to repopulate the world’s oyster beds. However, rising water temperatures and increasing ocean acidity caused by climate change mean that few larvae survive in the wild, and the nascent reefs set up by oyster restoration efforts must be reseeded annually with hatchery spat to continue growing — a kind of IVF for the bivalve set. 

Since its founding in 2014, the Billion Oyster Project has midwifed 150 million oysters into existence, creating a total of 19 acres of new reef across multiple locations in New York Harbor. New advances in oyster propagation are speeding up the process, and Carolyn Khoury, the program’s director of restoration, told me she is confident they will reach their goal. She said the cost of restoring the reefs is not much different from installing sea walls or other protective measures. However, as living, self-repairing systems, they are a more robust alternative to traditional construction. 

“Oyster reefs are what we refer to as a nature-based solution for climate resilience,” Khoury told me. “When paired with wetland restoration, they can improve shoreline resilience to wave energy, increased storm frequency and erosion caused by climate change.” 

They also provide more ecosystem services than a concrete wave barrier. Oyster reefs may not be as pretty as their coral cousins, but they are a vital habitat for spawning fish and other marine organisms. As they grow, they convert the water’s dissolved calcium and carbon into their shells, which sequester about 12 grams of carbon per oyster. The larvae that don’t survive end up as a meal for everyone else.

An oyster reef is like a giant Brita filter for the ocean, removing pollutants and purifying the water around them. They are “The Giving Tree” of the underwater world. “Everybody wants the pill for fixing climate change. Oysters are probably as close as you are going to get,” said Dan Martino, who wrote “The Oyster Book,” a history of the bivalve. “I can’t think of a single drawback to growing them.”

Martino is another recent convert to the oyster cult. Like Varrella, he started farming oysters relatively recently, around a decade ago in Martha’s Vineyard. He saw them as a solution to a looming global food crisis. Conventional land-based agriculture will not be able to meet the needs of a growing global population, he said, especially as droughts, heat and extreme weather push crops to their limits, while intensive animal farming adds to the carbon emissions causing climate change. The ocean provides an alternative. But farming fish, like farming beef and chicken, requires vast amounts of feed — usually other fish — also creates pollution, and typically requires antibiotics and other medicines to treat outbreaks of parasites and disease. 

Bivalves don’t need anything. They feed on plankton filtered from the water. Fertilizers are unnecessary, and they don’t contribute significantly more carbon into the atmosphere. “They’re the most sustainable species we could farm on Earth,” Martino said. Marine conservation societies agree, rating farmed shellfish as the best choice for consumers, noting that they encourage marine biodiversity. 

And they are much healthier to eat. Most bivalves have more protein than beef and are rich in omega-3 fatty acids, iron, zinc, iodine, magnesium, calcium and phosphorous. Oyster aficionados describe them as “the sea made solid.” Martino told me they are more like superfoods on the half shell: Just six oysters a day provide 100% of many of a person’s major nutritional requirements. “Farming oysters can meet our growing food demands while bettering our ecosystem, our environment, and our health,” Martino said.

Ernest Hemingway sought out oysters to help assuage his depression, writing in “A Moveable Feast” that when he was eating oysters, “with their strong taste of the sea and their faint metallic taste that the cold white wine washed away, leaving only the sea taste and the succulent texture … I lost the empty feeling and began to be happy and to make plans.”

These days, they are one of the rare treats that are both good for you and the planet. That double halo of nutrition and sustainability is driving sales: Global oyster production increased from 1.3 million tons in 1990 to 7.5 million tons in 2024 and is expected to reach 8.9 million tons by 2033, according to industry analysts. Demand continues to outpace supply. Martino said he could double production at his oyster ranch and still sell out. Rising water temperatures and increased ocean acidity caused by climate change are most likely the largest threat to the $8.5 billion-a-year industry, marine biologists who specialize in oyster aquaculture told me.

Sand In The Oyster Shell

Tim Green, a professor of fisheries and aquaculture at Vancouver Island University in Canada, has been studying oysters since 2008, when a mysterious disease all but decimated France’s oyster crop. From France, Ostreid herpesvirus 1 (OsHV-1), or oyster herpes, hitchhiked across the world’s shipping lanes on cargo carriers, ravaging New Zealand’s oyster farms, then Australia’s. In 2018, it led to mass die-offs in San Diego. “It doesn’t affect humans, but for oyster farmers, it’s devastating,” Green told me. “Ostreid herpesvirus can wipe out a farm in four days. We are talking 90% mortality.”

Meanwhile, something else is stalking oysters in the Pacific Northwest, which produces more than a quarter of America’s oysters. Farmers have reported mass die-offs for several years, usually just before the summer harvest. Summer oyster mortality, as Green and other scientists call it, could be caused by a virus similar to oyster herpes or an as-of-yet-unidentified bacteria. What Green does know is that marine heat waves — a period of unusually high ocean temperatures that can be caused by changes in ocean currents, weather events or climate patterns — trigger outbreaks of both diseases. “An elevated temperature is key,” he said. “Maybe the virus was always there, ticking along quietly, killing an oyster every once in a while, and then all of a sudden, boom, it gets hot, the oysters are stressed, and the virus kicks into overdrive.”

Scientists at the United Nations’ Intergovernmental Panel on Climate Change found that the number of marine heatwave events — in which temperatures increase 2 degrees Celsius to 5 degrees Celsius (3.6 to 9 degrees Fahrenheit) relative to historic temperatures — have doubled around the world since the 1980s, and predict that the frequency, duration, scale and intensity of future marine heatwaves will continue to increase with global warming.

Green isn’t sure if warmer waters help the pathogens proliferate or if the heat waves stress the oysters, making them more vulnerable to disease. Either way, heat can be deadly, and it’s getting worse. Heat waves in the Pacific Northwest used to be rare. Now, they sometimes happen several times a year. “It’s a ticking time bomb,” Green said.

Detonation isn’t far off, Green and other ocean scientists believe. A new study published by the United Kingdom’s University of Reading found that the world’s oceans are warming more than four times faster than they were 40 years ago. In the late 1980s, ocean warming was akin to adding a trickle of hot water to a full bathtub. Now it’s more like opening the hot water tap on full blast, Christopher Merchant, the study’s lead author, explained in a briefing for journalists. That already has enormous ramifications for ocean health — impacting everything from coral reefs to storm severity — but the study’s prediction that rising temperatures will continue to accelerate “by a significant margin,” over the next 20 years, as Merchant wrote in the study’s introduction, will fundamentally alter life underwater. The Reading professor of ocean and Earth observation elaborated in the university’s briefing: “The way to slow down that warming is to start closing off the hot tap, by cutting global carbon emissions and moving towards net-zero.”

Those carbon emissions don’t just drive up temperatures; they also increase ocean acidity. If you’ve ever dropped an egg in vinegar, you know what happens next. Oyster shells are made mostly of calcium carbonate, which starts to dissolve in an acidic environment. Mature oysters with thick shells can tolerate — to a certain extent — increased acidity, but in such an environment, juvenile larvae can’t grow strong shells fast enough (or in extremely acidic environments, any shells at all), making them vulnerable to predators and disease. “We’re getting to the point where, throughout the entire summer, it’s no longer favorable for a little oyster to make its shell,” in certain parts of the Pacific Northwest, Green told me.

The hatcheries that provide larvae to oyster farmers found a workaround by keeping their juveniles in tanks of specially buffered water until they could grow thick enough shells to survive in the wild. Harvests improved in some cases, at least for a while. However, Green and other researchers have documented another alarming die-off among this new, coddled generation. Green suspects that raising the larvae in temperature and pH-controlled tanks reduces their resilience in other ways. “You can protect against one stress,” he said. “But how does that influence them down the line when this oyster suddenly gets exposed to elevated temperature and a disease at the same time?”

Green and his team are working on future-proofing the industry by selectively breeding to create stronger oysters. So far, he told me, they have developed a more heat-tolerant strain and another resistant to ocean acidification. They are now working on disease resistance against oyster herpes, norovirus and vibrio, he said. Unlike oyster herpes, which is harmless to humans, eating oysters infected with norovirus or some kinds of vibrio bacteria can make humans sick. Strict regulations on water testing in commercial fisheries mean such infections are rare, he noted. “The big trick now is combining all that to make a super oyster,” Green said.

It’s not the first time scientists have intervened to make a more resilient oyster. In the late 1970s, researchers selectively bred a strain of oysters that, like seedless watermelons, had three sets of chromosomes instead of two. The triploid mutation made the oyster sterile. Researchers found that when oysters spend all their energy on growth and repair instead of reproduction, the result is a tastier, faster-growing and more resilient product. “This is what’s called triploid vigor,” said Matt George, a marine biologist specializing in bivalves and now the coastal shellfish manager for the Washington Department of Fish and Wildlife.

Sterility has a market advantage. The old exhortation to only eat oysters during months with an “r” in their name — September through April — derives from the fact that oysters spawn in the summer. Just before spawning, they are gamey with gametes. Just after, they are flaccid and watery. Triploid oysters are meaty and sweet all year round. They can also be harvested sooner — after a year or two (or sometimes even sooner) instead of the three years or so needed for diploids to grow to market size — reducing the chance they will be felled by disease.

By the 2010s, the market advantages of triploid oysters had converted half of the West Coast’s commercial farmers, most of the East Coast’s, and nearly all of Europe’s. Demand for oysters on the half shell now peaks in summer, when they are best appreciated on a bed of ice served alongside a chilled rosé.

But a funny thing happened on the way to the raw bar. In 2021, an unprecedented heatwave hit the Pacific Northwest, killing at least 619 people and cooking some billion bivalves — oysters, mussels and clams — in their shells. George, the oyster specialist, had been researching triploid vigor at the time and seized the opportunity to conduct a study on heat tolerance. “Our original hypothesis was that triploidy would make oysters more climate-proof, that sterility would boost their available energy and ability to deal with large-scale climate events like this,” he said.

The hypothesis was wrong. George and his team found that triploid oysters were nearly 2.5 times more likely to die than diploids when exposed to heat stress. That’s terrible news for an industry that has grown accustomed to year-round sales as global temperatures climb. It’s also an opportunity. George suspects that the extra set of chromosomes in triploids may play a role in their stress response, even if it helps save on reproductive energy.

If scientists can figure out what causes triploids to succumb to heat stress, they can start engineering their way around it, just like they figured out how to breed sterile oysters in the first place. (To do so commercially, researchers first bred a male tetraploid — with four sets of chromosomes — and a female diploid.) “The technology is really promising,” George noted. “If we can engineer these animals to have the benefits of triploidy without the possible drawbacks of an extra separate set of chromosomes, then we are getting closer to a truly climate resilient oyster.”

Technological advances in breeding sterile, climate-resistant oysters for market may help feed a growing population on a warming planet, but they won’t do much for the wild oysters whose reefs protect our shorelines, clean our oceans and promote biodiversity.

For them, it may already be too late, concedes Green. “The oyster industry will be just fine. But for wild populations that deliver those ecosystem services, it’s a major crisis,” he told me. Groups like the Billion Oyster Project will have to augment their reefs with larvae from commercial hatcheries well into the future instead of relying on self-sustaining wild spawning, especially as temperatures and ocean acidity increase with climate change. “Without human intervention, wild oysters will start disappearing,” Green said. 

For Varrella, the Italian oyster farmer, that would be a travesty. He fell in love with oysters while studying for a degree in marine biology, attracted by their ability to improve local biodiversity and clean the water around them. “We work on the ocean 365 days a year, with our hands in the water. So we can directly see the impacts of climate change. Oysters are a solution for that. With my farm, I’m doing my part. But wild oysters are just as important.”

Varrella favors triploids because the economics of a year-round product makes more sense. Martino, the oyster evangelist from Martha’s Vineyard, prefers diploids for their ability to benefit the wider ecosystem. Triploids may be better for the market, but Martino contributes to the local food chain by allowing his oysters — he buys around a million babies every year — to spawn. “I want to be the Johnny Appleseed of oysters,” he told me. “I want my oysters to make babies. It would probably destroy my farm-to-market model, but I would love to see oysters everywhere.”

And maybe, just maybe, those babies will join others in the wild, evolving into something more resilient on their own. After all, oysters survived the Ice Age, the last greenhouse era and the asteroid that killed the dinosaurs. If there are enough of them in the wild, they might just survive us humans, too.

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