Our global ocean will change dramatically over the next few decades. What might it look like, and how will humans adapt?
Estimated reading time: 20 minutes
Peering out over the blue-green surf of the Atlantic Ocean is like catching a glimpse of infinite time. From our vantage point on land, its monumental scale makes it look immutable, eternal; a bottomless resource. For most of our short existence as a species, that has been the case. Ever since our ancestors first pulled food and other resources from beneath its surface, the sea has been essential to our growth and survival. In the next century, its waters will take a remarkable turn. The ocean itself and the ways we use it are poised to change dramatically, making it a very different place from the one we know today.
By 2100, the global population will reach some 11 billion—almost a third larger than today. As climate change alters weather patterns, we’ll experience more droughts, mega-storms, and heat waves, making sustainable food and energy production on land even more difficult. As a result, we’ll need to turn to the sea for our livelihood. Over the next ten years—a period that the United Nations has already deemed the “Decade of Ocean Science for Sustainable Development”—we’re almost certain to see growth in ocean-based technologies, aquaculture, and offshore energy, be it wind, oil, gas, or biofuels. Fifty years out, that growth could expand exponentially.
But exactly how will the future play out? How will we help shape a changing ocean? And how might new practices, policies, and technologies help preserve it as one of the world’s greatest shared resources? These are questions that WHOI scientists are actively studying in a collaborative and interdisciplinary way.
“The way we’ll be using the oceans in 50 years will be unrecognizable—we’ll almost certainly be leveraging them for energy and aquaculture far more than today.”
—Hauke Kite-Powell, WHOI’s Marine Policy Center
Future fisheries: a shift from capture to culture
Joel Llopiz, who studies fisheries oceanography and ecology at WHOI, says that the most direct impact on humans may be widespread changes in areas we commonly fish. At the moment, the world gets 17% of its protein from the sea, a number that will increase as cities grow and viable farmland shrinks. Yet, it’s unlikely that the massive commercial fishing operations, standard practice in the 20th century, will be sustainable deep into the 21st.
“We want to understand the processes at work that allow some coral reefs to survive despite conditions that should kill them.”
—Anne Cohen, WHOI scientist
According to the United Nation’s Food and Agriculture Organization, 60% of fisheries are already fully exploited and another 30% are badly overused. The coasts of New England and Nova Scotia provide an ominous example: in the early 1980s, the annual haul of cod in the region was more than 50,000 metric tons per year, but today, it’s 2% of that figure. While overfishing has played a major role in that reduction, the added pressures of warming seas and a changing food web haven’t helped matters, says Llopiz.
In the sands of Stellwagen Bank, a shallow area roughly 20 miles from the Massachusetts Coast, the plight of one tiny species—the sand lance—reveals how fisheries may change in the future. These miniscule silver fish are a direct link in the food web between plankton (their food of choice), and animals like cod, seals, seabirds, sharks, and even whales that feed on sand lances. Yet as warming seas reduce the amount of plankton in the water, sand lances have also dropped in number.
“We’ve already seen sand lance vanishing to the south, off the coast of New Jersey and Virginia, where the waters are getting warmer,” says Llopiz. “They can’t easily move away from their habitats like herring and other species, so they’re likely just dying off,” robbing commercial species of a major food source.
“I think we’ll see regions pre-permitting certain areas for specific uses and restricting activity in others, similar to zoning on land.”
—Hauke Kite-Powell, WHOI’s Marine Policy Center
As fish like these disappear due to warming, it could push some large commercial fish species, like hake and flounder, to migrate into cooler waters in search of food, he notes. Other species like pollock and halibut may be going deeper for the same reason. And yet, even as some populations shrink, others may expand—which might mean the overall number of commercial fish remains relatively steady, but the variety of species could change.
“Cold water species like cod are just not going to come back in great productivity,” says Steve Murawski, a biological oceanographer at the University of South Florida and former Chief Scientist of the U.S. National Marine Fisheries Service. “We see the same thing with northern shrimp on coast of Maine. They haven’t had a season in five years, so they could be a goner as well.”
Scientists around the globe are already trying to understand how global fisheries will respond to a changing ocean, and hope to reveal how those changes will affect key food sources for humans, says Di Jin, senior scientist at WHOI’s Marine Policy Center. Despite the growing concern about fisheries’ health, Jin thinks open-ocean fishing will continue to play a major role as a global food source. “I’m very optimistic that we’ll still see capture fisheries 100 years from now, but it’s likely that they’ll need to be integrated into aquaculture systems to meet our needs,” he says.
Sustainable aquaculture: food security for the future
“The way we’ll be using the oceans in 50 years will be unrecognizable,” says Hauke Kite-Powell, a research specialist at WHOI’s Marine Policy Center. “We’ll almost certainly be leveraging them for energy and aquaculture far more than today.”
As land-based resources are stretched thin due to increased population and changing climate, the oceans are the only real growth area for farming, he says. Aquaculture will continue to expand and is poised to become a massive industry, bypassing capture fisheries in the near future.
This is already happening. Since 1990, the amount of wild-caught fish has hovered around 80 million metric tons, while aquaculture has more than quintupled, from less than 15 million tons to roughly 80 million in the same time. Today, aquaculture provides almost the same amount of fish and shellfish globally as commercial fishing.
At the moment, Kite-Powell says, the vast majority of aquaculture takes place off the coasts of southeast Asia, China, and Japan, where fish, oyster, and seaweed farms are common. He thinks farms like these may soon appear off Europe and North America.
While a shift to ocean-grown proteins would cut down on greenhouse gas emissions from livestock farming, he notes, it’s unclear whether aquaculture can provide all the food our growing population will need. Only a few species of finfish can be successfully farmed, so the variety of available seafood will go down—and food for all those fish will still have to come from somewhere. Right now, it’s mostly provided by turning huge numbers of forage fishes, like anchovies, into fish meal, says Llopiz.
“A lot of commercial fishing today exists just to catch protein to feed farmed species,” he says. “You can’t grow fish like salmon without marine-derived proteins.”
That poses a bit of a conundrum: even with more offshore farms, we’ll still need to fish the open ocean to feed those farmed species. That, alone, may mean that aquaculture won’t be enough to meet society’s food needs sustainably.
Farming shellfish, however, could be a different story. Mussels, oysters, and clams don’t need special foods to survive: as filter feeders, they pull nutrients directly from the waters around them. Compared to fish, they grow far more densely in the same amount of space, and also improve water quality. One nonprofit organization (aptly called the Billion Oyster Project) is working to restore oyster reefs in New York’s harbor and bring them back to once-massive levels by 2035. In the process, they hope to revive a major source of seafood in the region while removing waterborne pollutants like nitrogen.
Mussels are another good choice for seafood farming, adds Scott Lindell, a research specialist at WHOI who studies marine aquaculture. “Mussels in particular have a great attribute of sticking to things, so they can be applied to ropes and hung in the water up to 60 feet below the surface,” he says. “In a very small footprint, you can produce tons of high-quality protein that’s better for the environment than beef, and has heart-healthy oils.”
Lindell isn’t exaggerating. A ton of cultured mussels emits less than a tenth of the amount of greenhouse gas caused by farming beef, and roughly half that of poultry or pork.
Aquaculture won’t be limited to growing animal proteins, he notes. Seaweed, too, could become a viable ocean-farmed crop on a large scale. Lindell envisions extensive offshore kelp farms, creating artificial seaweed beds that could be harvested sustainably for food and biofuels. If large enough, those farms could also cool certain areas of water by providing shade and increase oxygen in the water even as they absorb CO₂. That could improve the health of local fish populations attracted to the kelp habitats, creating artificial fishing grounds. With the right infrastructure, kelp and wind farms could even exist in tandem, creating two sources of renewable marine energy, Lindell says.
For these farms to be sustainable and cost-effective, however, we’ll need to develop new ways of monitoring huge areas of aquacultured kelp, he notes. Kite-Powell agrees.
“In order to provide biofuels on a commercial scale, we’ll need seaweed farms on scale of land-based farms in the Midwest,” Kite-Powell says. “Building and operating farms of that size in open water will require new technologies—not just to maintain the crops, but also to harvest them. They’ll have to handle an enormous amount of material.”
Saving our coral reefs: lessons on resilience and recovery
Coral reefs, which support fisheries and act as a barrier against storms, are also being deeply affected by a changing ocean. Over the next 50 years, reefs worldwide will continue to erode from sedimentation, nutrient runoff, bleaching, and extreme weather events. Shellfish and other fisheries that depend on coral reefs will certainly be affected, and vulnerable coastlines will be exposed to storm surges and high surf.
As reef waters become too hot for coral polyps, they expel the symbiotic algae that give them essential nutrients—and their trademark colors—leaving them ghostly white. A growing number of coral species are dying off after bleaching, says WHOI geochemist Amy Apprill, while others are proving surprisingly resilient. In 2016, the Great Barrier reef in Australia experienced widespread bleaching from a massive heat wave that killed off almost 30% of its shallow-water corals, but in other areas, like Turks and Caicos, reefs have bounced back unexpectedly after multi-year bleaching events. To save corals worldwide, Apprill notes, it will be important to figure out what exactly makes the surviving reefs resilient.
In some areas of the world’s ocean, coral reefs are protected from extreme heat by features called internal waves. According to Anne Cohen, who studies coral reef ecosystems at WHOI, these natural subsurface waves bring cooler water from the deep ocean up near the surface and within reach of the coral reef and its inhabitants. During extreme heat events that cause widespread bleaching and coral death across ocean basins, those reefs lucky enough to be situated in the path of internal waves continue to benefit from this natural air conditioning. A study led by Cohen’s graduate student Tom DeCarlo showed that as ocean warming continues, enhanced stratification will strengthen internal waves in some regions, increasing the chances of those reefs surviving 21st-century warming.
The Asian shore crab was first introduced in the northeast in the 1980s. Between it and the green crab, these invasive species are almost the only crabs found among the rocks on many New England beaches.
To understand and predict coral resiliency, Cohen is looking to “Super Reefs” that have demonstrated capacity to survive ocean warming. Some Super Reef communities are genetically adapted to higher temperatures, like corals in Palau, whereas others seem able to recover quickly, like some reefs she and her team have studied in the central Pacific. Reefs protected by internal waves are also considered Super Reefs because they have the greatest potential to survive into the next century despite climate change. Cohen is working closely with conservation organizations and governments of coral reef nations to find and protect Super Reefs from other human activities that can harm them.
“As technology improves, we’ll see not only better autonomous sensors and drones, but more powerful computers and tools to crunch that data, giving us even more insight into how the oceans work.”
—Admiral John Richardson, WHOI Board of Trustees
“We want to understand the processes at work that allow coral reefs to survive despite conditions that should kill them, so we can come up with plans to ensure that they still exist in the future,” she says.
It’s also possible that corals could migrate—albeit slowly—into cooler waters, says Apprill. Their microscopic larvae can drift hundreds of miles through the ocean, and could settle down to form reefs in areas with more comfortable temperatures.
“That could be a lifesaver for reefs,” she says. “The best example we have at the moment are reefs near Bermuda—they’re at higher latitudes compared to tropical and subtropical reefs, but they have lots of really old, healthy, vibrant corals. Not all coral species can survive that far north, but we know it’s certainly possible for some.”
Aliens of the ocean
Changing ocean habitats and increased human impacts may allow not only novel pathogens to thrive, but new invasive species as well, by creating opportunities for them to settle in, grow, and take over existing ecosystems. In addition, ships traversing the globe unintentionally spread the larvae of marine species picked up in water for ballast from one port to another when their tanks are flushed.
In the U.S. Great Lakes, zebra mussels have been devouring key plankton sources and clogging infrastructure since the late 1990s. In New England, green crabs—which were accidentally introduced in the ballast of European ships more than a century ago—have begun to edge out species that are fished for food, says Carolyn Tepolt, a biologist at WHOI who studies invasive species.
“The green crab is not picky; it just eats everything it can get, especially young shellfish, so it’s been pretty devastating for the soft-shell clam population in New England. When it expanded into the Canadian Maritimes, it started destroying important habitats for scallops and lobsters. It has created a real problem for those fisheries,” she says.
Sea lice—a type of copepod that causes lesions and ulcers on fish—is an invasive species of great concern, and a growing nuisance to farmed seafood. Other invasive species, like a sea squirt informally called “rock vomit,” can smother mussels and other shellfish beds, and even kill off worms, snails, and other species in marine sediments that provide food for larger organisms.
“There’s going to be major changes in ecological communities as ranges shift,” Tepolt says. “We’ll probably see species not traditionally considered invasive taking advantage of new conditions. In that way, there may be more homogenization of communities—if you have two different places in the world with a similar environment, it’ll be more likely that you’ll see similar species,” she says.
While this sort of redistribution of species may cause major disruptions in certain ecological niches, it may be barely discernable in others. In some cases, Tepolt points out, invasive species can actually serve the same ecological functions as native species, letting them settle smoothly into a new area. On the west coast of the U.S., researchers discovered in the 1980s that the native blue mussel is being widely replaced by an invasive species of Mediterranean blue mussel—yet most fishermen hadn’t noticed.
“They just don’t look different enough from the native species,” she says. “It took genetic testing to tell them apart. It’ll take a lot more study to know if they’re actually doing different things in the marine environment.”
Informing future policy
As humans continue to expand our reach offshore, we’ll likely see more development in wind energy, oil and gas infrastructure, telecommunications, mineral extraction, and more, as hundreds of new and existing industries combine to create a “blue economy” in the future. To get there, however, we’ll need to improve our scientific understanding of the oceans and develop innovative new policies for managing coastal and offshore waters. In order for human populations to grow sustainably, Kite-Powell thinks we’ll see a shift away from existing systems of oversight—where towns, counties, and states share jurisdiction—to a more regional approach that creates dedicated zones for offshore farming, fishing, and other activities.
“I think we’ll see regions pre-permitting certain areas for specific uses in a proactive approach. It’ll be similar to zoning on land. Look at national parks that are off-limits for development or industrial use, with a planned balance of public use and ecological conservation. We’ll need to move to something like that for oceans as demands for resources rise sharply over the next century,” he says.
Creating more marine protected areas could also help preserve sensitive ecosystems. The Tubbataha reef system, a wild area 90 miles off the coast of the Philippines, offers a prime example: Fished to dangerously low levels in the 1980s when local fishermen used extreme measures like dynamite and cyanide to bring in their catch, it was declared a marine protected area in 1988 by the Philippine government, and eight years later the military enforced a ban on fishing. Since then, Tubbataha has recovered dramatically, and has even been designated a UNESCO World Heritage site for its outstanding diversity and density of marine species. Its return to near-pristine condition offers a promising model for creating protected areas to restore marine health.
Surprisingly, stricter land-based zoning will also become a critical component to how we adapt to a changing ocean. As sea levels rise, municipalities may rethink how they manage resources. Some cities, for example, may choose not to maintain roadways that are regularly swamped by high tides and storm surge to discourage development in regions likely to flood, says Kite-Powell.
New risk management approaches by insurance companies might play a role, as well. AxaXL, a major reinsurance firm, is in the process of developing an “ocean risk index”—a way of quantifying the impacts of storm surge, sea-level rise, and the changing marine ecosystem. The company plans to share this index openly to governments and industry when it’s complete.
“Most of the regions that are at the highest risk for sea-level rise or storm surge are located in small, underdeveloped areas,” says Chip Cunliffe, director of sustainable development at AxaXL. “They’re the least able to help themselves or to cope with the impacts of higher storm intensity or flooding. The index helps regions know where the risks are most acute so they can plan appropriately.”
New Tools for Ocean Management
Whether on or off shore, however, decision-making and marine policy will be increasingly shaped by technology in the future. As new autonomous sensors are deployed and marine observing arrays spread, we’ll have real-time information on the ocean and its ecosystems. Combined with new artificial intelligence and modeling software, that data could be a boon for both science and national security, says Admiral John Richardson, former chief of naval operations during the Obama administration.
“[Growth in technology] is a tide that’s going to be impossible to stop,” he says. “As technology improves, we’ll see not only better autonomous sensors and drones, but more powerful computers and tools to crunch that data, giving us even more insight into how the oceans work.”
“With new ocean observing data accumulation and prediction systems, we’ll be able to quickly integrate a huge amount of information about the oceans,” adds Jin.
That may open up new possibilities for ocean management. New sensing and computing technology could map out where species are in real time and predict future movements. In doing so, Jin suggests, it would allow governments to better manage ecosystems and determine where new marine protected areas should be.
“I think we’ll need to move toward seeing ocean management as something far more dynamic,” he says. “In the past, the strategy was, ‘let’s impose a rule against harvesting certain species in a certain location,’ but now, we recognize that the ocean is transient. Species are mobile. Having real-time data from ocean observatories will let us incorporate a tailored approach to marine management, like opening one spot to fishing or resource extraction in the spring, but not the fall, for instance, to protect those ecosystems in sensitive seasons.”
Hope for the Future
Even today, when the future of the world’s ocean looks uncertain, Jin notes there’s reason to be hopeful about our ability to cope with changing seas. For the first time in its history, the United Nations has included oceans as part of its sustainable development goals, making “Life Below Water” one of its focal points for 2020, and declaring a Decade of Ocean Science for Sustainable Development (2021-2030).
Public schools are increasingly incorporating ocean literacy into their curriculums, educating young students about the role the seas play in the planet’s health. And young activists like Greta Thunberg are injecting new passion for environmental causes into a growing generation.
No matter what recommendations we make today about the best use of our ocean in the years to come, the people who will actually make those decisions are likely sitting in an elementary school classroom right now. Educating them about the critical importance of the seas in their own future—and in the future of the planet—will be essential to creating an informed, passionate group of leaders.
“We’re seeing ocean science being written into K-12 textbooks,” Jin says. “That’s a very positive sign that students are targeted to become more ocean literate, and so hopefully more open to sustainability. Children are starting to really understand that although they may be in Kansas, the ocean is affecting their life through climate, through biodiversity, through available seafood.” They’re also realizing that they, in turn, affect the ocean through their lifestyle habits and choices, he adds.
The ocean may be a vastly different place in 50 years, but there is hope that we can still thrive. Researchers are breaking new ground in ocean science and technology every day, policy-makers are preparing for new levels of diplomacy and collaboration, and educators are striving to equip students with knowledge to face new challenges, says Kite-Powell.
“My hope for the future is that we will use the ocean to produce food and energy in ways that are both good for people and safeguard the integrity of marine ecosystems. If that happens in a way that is sensible and scientifically informed, it will help us through global climate change and a century of population growth ahead of us,” he says. “Over the next 50-100 years, it will be crucial for us to get those things right.”