Another approach, which is popular in Europe, is to protect parts of the sea to safeguard particular vulnerable habitats or species and to prohibit only the specific activities that impact them. For instance, in parts of Scotland, maerl beds are protected from trawling and dredging. However, if the protections safeguard a species that lives up in the water column, such as the bottlenose dolphin or basking shark, then trawling is often allowed in the protected area, under the misguided assumption that the seabed and the water column above it are ecologically separate, when in fact everything is connected.

All these various protected areas share a similar ethos of trying to help ocean life to be generally healthier and more abundant. Protecting the seabed from physical damage, most importantly by heavy fishing gear such as trawlers and dredgers, can keep habitats in good condition and stop more from being destroyed. And parts of the ocean that are already degraded and depleted can be safeguarded to give sea life a chance to recover, as is happening in Lamlash Bay.

In some cases, the same protected area encompasses both healthy and degraded habitats, with the aim that local regeneration will occur. A hundred miles off Cape Wrath, the most northwesterly point of the United Kingdom, and around three thousand feet down, lie hundreds of thickets of cold-water corals that have been growing there since the end of the last ice age, around ten thousand years ago. Individual corals are estimated to be at least forty-five hundred years old, and unusually for deep-water corals, they’re growing not on firm, rocky ground but on soft humps, known as sand volcanoes, where seawater bubbles up through the seabed. First discovered by scientists in 1998 and named the Darwin Mounds after their research vessel, the RRS Charles Darwin, these coral ecosystems are also rich in many other life forms, including fish, crabs, sea urchins, and single-celled organisms called xenophyophores, which look like basketball-size chunks of honeycomb.

By the time scientists knew about the Darwin Mounds, parts of them had been damaged already by trawling nets dragged over the seabed to catch fish such as orange roughy. A protected area prohibiting trawling was set up in 2003. In 2019, scientists sent an autonomous underwater robot to survey the mounds and found that areas that had been heavily trawled were not yet showing any obvious signs of recovery after sixteen years of protection. The good news is that parts of the Darwin Mounds that weren’t too badly trawled are looking healthy. Coral larvae have settled and are growing into new colonies. For long-lived, slow-growing species such as deep-sea corals, recovery is obviously going to take a long time—all the more reason to protect them before damage occurs.

Regulations are gradually being put in place to protect the most vulnerable parts of the deep ocean. Bottom trawling on seabed deeper than a half mile has been banned in European Union waters of the northeast Atlantic since 2016 to safeguard fragile coral and sponge reefs growing on underwater mountains. An additional six thousand square miles of habitat was protected in 2022, when that lower limit for trawling was raised up to thirteen hundred feet. Much damage has already been done by decades of unrestricted deep-sea trawling, but these measures should begin to turn things around.

Elsewhere, pre-emptive steps are being taken to protect parts of the ocean from future impacts. Among the biggest marine protected areas is the Ross Sea in Antarctica, one of the most significant areas of largely intact ocean ecosystems left on the planet. Despite being incredibly remote, more than two thousand miles south of Aotearoa and reaching within two hundred miles of the geographical South Pole, this sea has faced growing pressure from industrial fishing fleets pushing into its icy waters to catch krill and Antarctic toothfish. Between them, krill and toothfish are staple foods for many other Ross Sea animals, including emperor penguins, Antarctic petrels, and Weddell seals. The Ross Sea is also the exclusive home to the world’s smallest orcas, known as type C, which grow to only twenty feet long. Until recently, scientists weren’t sure what this population of orcas feeds on. Then, when marine-mammal expert Regina Eisert was working at the ice edge in the Ross Sea, an orca swam right up and head-butted the waterproof camera she had lowered into the water on a pole. The orca opened its mouth and revealed a large, chewed tail of an Antarctic toothfish. Eisert was convinced the orca had done this on purpose, like a cat presenting a dead mouse to their owner. It proved that type C orcas eat toothfish, and further studies have shown these fish constitute more than a third of their diet. This means the Ross Sea region Marine Protected Area is critical for protecting the food source of this unique population of marine mammals.

Setting up the protected area in 2017 had taken years of difficult negotiations among all the nations that are part of the Antarctic Treaty, since no single nation can lay claim to Antarctica and its surrounding seas, and all members must agree on regulations. Several countries with major fishing interests supported the protected area only when the original plans were reduced in size by almost half, down to 420,000 square miles, and when concessions were made to allow fishing in some areas. Holding out until the end were Russian officials, who agreed to the plans after a sunset clause was introduced. The Ross Sea was given an initial period of thirty-five years of protection.

The boundaries of marine protected areas drawn on maps are chiefly there to show the people running fisheries where they can and can’t legally operate, but obviously those lines don’t exist out in the ocean, and marine organisms are oblivious to the designations. This leads to another of the potential benefits of ocean protection. Within protected waters, animals have a chance to live longer, grow bigger, and produce more offspring, as is happening among the scallops and lobsters of Lamlash Bay. But they don’t all stay inside the no-fishing zone. Mature animals may have home ranges bigger than or straddling boundaries of protected areas, or they may embark on seasonal migrations that lead them into more distant waters. What’s more, their young likely drift and swim away to start their own lives elsewhere, replenishing surrounding seas.

Conservationists and fisheries scientists refer to this as spillover^b and generally see it as a good thing, using it as a major argument for protecting more of the ocean. Stop fishing in some places, and catches overall should improve because fish populations will be healthier and more productive. Even if fishers lose out in the short term when they’re denied access to parts of their normal fishing grounds, the theory suggests that catches in nearby areas could soon outweigh the losses. Several studies confirm that protected areas work beautifully within their boundaries, boosting the abundance and diversity of species inside compared to outside. It’s much trickier to detect the spillover effect, in part because the ocean is so endlessly complex and dynamic. It also takes time for depleted populations to recover enough for spillover to be noticeable, and many parts of the sea haven’t been protected for long enough. In the United States, for instance, most marine protected areas are less than twenty years old.

While scientists are still busy debating whether spillover is a general effect that will occur more widely in the coming years as protected areas mature, some hints of it are occurring. In the northern Channel Islands off the California coast, there are now more spiny lobsters hunkered on the seabed both inside and a short distance outside a series of ten-year-old no-take zones. In Aotearoa, the effect of one small no-take zone was measurable much farther away. One in every ten juvenile sea bream occurring in waters up to thirty-five miles away is born within the protected waters of the reserve.

Even highly mobile species that head off on long migrations across ocean basins are beginning to show signs that marine reserves can work for them too, although the areas they need to cover are truly vast. In 2016, US president Barack Obama expanded the Papahānaumokuākea Marine National Monument^c to encompass all the waters surrounding the northwestern Hawai’ian Islands, so that it now covers an area almost half as big again as the Ross Sea region Marine Protected Area in the Antarctic. To determine whether this enormous no-take zone is having any effect on tuna populations, scientists analysed catch data from the Hawai’ian longline fishery going back to 2010. Since the reserve was expanded, longliners have seen the catch rates of yellowfin and bigeye tuna increase up to a hundred nautical miles outside the boundaries.

Details within the data suggest this is a genuine spillover effect. Longliners working closest to reserve boundaries have seen their catches increase the most, suggesting they’re snagging the tuna as they swim out of the protected waters where their spawning grounds lie. The apparent spillover is, as expected, gradually building over time as more tuna mature. And the species that had been hardest hit by overfishing, the yellowfin tuna, has shown the most pronounced increase. Its catches have seen a dramatic uptick, with the number on each longline increasing by over half compared to earlier catches. It makes sense that the depleted yellowfins are benefiting most, and the reserve is helping their population recover.

Papahānaumokuākea is a phenomenally large marine reserve, quite likely still the world’s largest by the time you read this, and it seems to be of the necessary magnitude to help protect these fish that swim so fast and far. Still, it may not be big enough or in the right place to continue safeguarding tuna as the ocean around them changes. Tuna will keep responding to the shifting conditions as their seas warm and lose oxygen and their prey moves too. Where tuna spawn and feed today will likely not be where they do so in ten, twenty, or fifty years.

The same fluidity that helps marine reserves to restore ocean life beyond their boundaries may also be their undoing. Their watery borders can’t hold back warming, acidifying waters any more than they can hold back the climate migrants that swim through them. Conservationists are grappling with the difficult, unanswered question of how the ocean’s protected areas will fare in the climate crisis.

Species are moving, habitats are shifting, and new ecosystems are assembling, and soon it will no longer be enough to decide where to install a marine reserve and then step back and leave that part of the sea alone. As the ocean changes, ideas of what protected areas can be, how they are run, and what they can do will have to change.

There’s an inherent contradiction in trying to establish reserve boundaries around species and ecosystems that are responding and shifting with the changing climate. The way reserves are set up will have to become a lot more responsive, with plans and regulations that can change and adapt as the environment changes. For that to happen, necessary legislation will need to be already in place. Our intentions won’t be of any use if it takes years or decades of legal wrangling for new types of reserves to be established.

Uncertainty of what exactly lies ahead is no excuse to do nothing but sit back and watch as the present generation of marine reserves gradually stops working. Pre-emptive actions will be critical. One idea is to create stepping stones through the seas and protect areas not only where species exist now but where they will likely move to in the future as the ocean continues to warm. Another approach involves combining the fixed reserve approach with more dynamic measures. Methods exist now for tracking vulnerable species and diverting threats away from them in near real time, as has happened with North Atlantic right whales. Fewer than three hundred and fifty of these docile giants are left, and many of them recently moved into the Gulf of Saint Lawrence in Canada, the body of water through which the North American Great Lakes drain into the Atlantic. The whales followed the climate migration of their staple food, small swimming crustaceans called copepods. This brought the whales into the busy waters of the gulf, where many of them were killed when ships ran into them or they got tangled in fishing gear and drowned. In 2017 alone, thirty-one right whales were found dead, and likely twice that number died and were never found. In response to this crisis, the Canadian government introduced a system to track the right whales based on reported sightings as well as detection of their underwater calls through hydrophones. Daily updates then determine, depending on the whales’ whereabouts, where fisheries need to be closed and ships told to slow down. This kind of effort requires considerable expense and coordination, but it’s helping to save more of these critically endangered animals.

A paradigm ingrained in marine science is that marine protected areas could boost the ocean’s resilience to climate change. If this turns out to be true, they could simultaneously protect against local and global threats.

The idea behind this concept is that protecting species and habitats helps them to be more resistant to change and better able to recover from crisis. Protected areas should contain more biodiversity, which acts as insurance against disaster; if some species are lost, others are available to take their place and keep the ecosystem functioning. There may also be greater genetic diversity, making populations more likely to adapt to changes in the environment. Protected areas should also contain bigger animals with more substantial food reserves in their bodies, which can help them survive tough times.

Though not enough evidence exists to show these things happening inside marine reserves and confidently turn this concept into reality, there are some hints. Wild winter storms in 2013 and 2014 pummelled the rocky reefs in a protected area off Britain’s south coast, which is home to lacy, bubblegum-pink sea fan corals. The seabed in Lyme Bay was scoured by waves and sediments, and habitats inside and outside the reserve ended up in a similar state of devastation. And yet, by 2016, the pink corals were growing again inside the reserve. The corals were recovering much faster than they had when the reserve was originally set up and scallop dredging was first banned, suggesting that protection is boosting the ecosystem’s resilience.

Evidence is also emerging that marine reserves have a role to play in helping ecosystems mitigate climate change. A 2022 review of more than twenty thousand studies found that where protected areas keep habitats such as mangroves and tidal marshes intact, they can help protect coastlines from sea-level rise. Protected areas help lock up more carbon from the atmosphere in green habitats like seagrass meadows. Seabed sediments also sequester more carbon when they’re not being dragged over by trawl nets and dredges.

The big picture from across all these studies backs up the theory that protected areas can boost biodiversity and increase food security and income for people living along coastlines. At a broad scale, increased fish catches from areas adjacent to protected areas can more than offset the losses when fishers are excluded from fishing grounds.

Even so, protected areas are not always welcome. In 2022, plans were scrapped for a no-take zone around Lindisfarne, a tiny tidal island off the northeast coast of England that’s home to an ancient monastery and a small fishing community. Fishers were up in arms over the potential loss of their livelihoods. The vicar of Lindisfarne warned that the fishing ban would rip the heart out of the community. In 2023, marine protection became a hot-button topic in Scotland as rows broke out in fishing communities over the government’s plans to introduce more no-take zones. Fishers in various parts of the country feel these measures are being imposed on them, and they’re convinced the zones would ruin their industry. The response is a far cry from that of the Isle of Arran community, which worked towards safeguarding its waters for everyone’s benefit, showing why successful planning for the future ocean must involve everybody who has a major stake, right from the start.

Making certain parts of the ocean off-limits to exploitation comes with other potential drawbacks and can lead to a false sense of security and risky decisions about how the rest of the ocean is used. Plans are accelerating to open the world’s first deep-sea mines and extract metal-rich rocks from the seabed several miles underwater. Fevered mining interest is gathering pace in the Clarion Clipperton Zone (CCZ), a twenty-five-hundred-mile-wide tract of the central Pacific Ocean between Mexico and Hawai’i, where the undulating abyssal seascape is covered in fine sediments and rocks. Since 2001, more than a dozen mining companies have been buying up prospecting permits for plots of seabed in the CCZ, each one around thirty thousand square miles in area, which is slightly larger than the island of Sri Lanka. The companies are eager to get their hands on black, potato-size rocks scattered across the seabed, generally referred to as polymetallic nodules, which contain valuable elements like cobalt, nickel, and rare-earth metals. The nodules also create vital habitat for a diverse ecosystem, which scientists are only just beginning to know and understand. Biological surveys of the CCZ so far have found more than five thousand species, including delicate sponges made of glass, intricate brittle stars and feather stars, octopuses, corals, and worms. Nine out of ten of these species haven’t been seen anywhere else, and scientists haven’t yet had a chance to name them. It’s likely that at least eight thousand unique species live in the CCZ, making it a critical hot spot of the earth’s biodiversity.

Some parts of the CCZ have not been sold off to prospective miners but instead have been designated as no-mining zones, to try to limit the impacts of the industry. The problem is, those protected zones were selected after mining companies had first pick of the seabed. The protected areas were pushed to the periphery of the CCZ, in places that mining companies weren’t interested in mining anyway because the nodules there are far less abundant. And where there are fewer nodules, fewer species exist because the rocks themselves are the basis for the ecosystem. Nodules provide the solid foundation for corals and sponges to grow on and habitats for all sorts of tiny creatures that live on and inside them. The protected zones in the CCZ are not ecologically equivalent to the areas that may be mined. It’s like protecting only the edges of a forest and not its dense heart. Parts of the seabed with greater abundance and diversity of life undoubtedly will be damaged and destroyed if mining of the CCZ goes ahead.

As part of their licensing deal, mining companies would also be required to leave some portions of their leased CCZ plots unmined. However, the environmental gains this could have are based on some dubious assumptions. A study modelling the impacts of noise pollution from seabed mining has indicated that nowhere within an entire thirty-thousand-square-mile plot will be left in peace. Massive, remotely operated mining machinery would thunder across the seabed, scooping up rocks and shooting them, clattering along riser pipes, to the surface, sending waves of sound for hundreds of miles through the ocean. This would interfere with the richly acoustic lives of the whales that migrate through the CCZ. Very little is understood about how important sound is for many of the delicate organisms of the deep, but some are thought to use subtle vibrations in the water to find their way around and detect prey. This means that even the animals that aren’t directly killed by mining or choked in sediment plumes would still have their lives transformed if their quiet world is turned into a noisy industrial zone. The so-called protected areas in the CCZ will not protect the overall ecosystem.

There are plans to mine deep-sea metals from other parts of the deep ocean, including the tall chimney stacks of hydrothermal vents known as black smokers. These ecosystems, some of the most extreme and diverse in the deep sea, flourish in the dark by tapping into the energy of toxic chemicals pouring out of the seabed. Black smokers are home to their own entourage of phenomenal organisms, the likes of which are seen nowhere else on earth. There are Yeti crabs that farm bacteria in their fur, golden-coloured snails with their shell made partly from iron (no other animals we know of do that), and worms clad in glittering sequin-like scales that protect them during fearsome worm-on-worm battles.^d All these creatures have the misfortune of living on and around hydrothermal-vent chimneys that mining companies are hankering to exploit.

Along parts of the ten-thousand-mile north–south underwater mountain chain of the Mid-Atlantic Ridge, mining companies from Russia, Poland, and France have bought licences to prospect hydrothermal vents. Just as parts of the CCZ would be off-limits, the vent mines could be interspersed with strips of no-mining zones that, theoretically, could help the mined sites regenerate once the machinery has moved on. Regeneration would depend on those protected areas remaining intact and healthy, but they could easily be harmed by the noise and toxic sediment clouds generated by mines on either side. What’s more, any recovery of mined sites will require animal larvae to drift in, something they naturally do, riding currents and colonising vent fields that are dotted along the linear mountain chain. For now, it’s not at all well understood how far different species can disperse or how well they would cope with crossing over mined sites and passing through contaminated seawater. Mining might well leave behind nothing but a series of dissected, diminished patches of vent habitat that stand little chance of persisting in the long term.

A far safer option would be to protect whole hydrothermal vent systems from mining, a preventative measure that has already been achieved in a few parts of the ocean. In Antarctic waters, a protected area surrounding the South Georgia and South Sandwich Islands prohibits any future mining activities on the entire deep hydrothermal vent fields there and safeguards their inhabitants, including Yeti crabs with chests covered in auburn hairs.

Many hydrothermal vents elsewhere in the ocean remain unprotected. Iron-shelled, scaly-foot snails live on only three remote black smokers in the Indian Ocean; prospecting permits for two of those sites have already been sold to German and Chinese mining companies. Because of the future threat of deep-sea mining, scientists have listed this snail species as Endangered on the IUCN’s Red List. A full survey of all the snails, clams, and other molluscs living on deep-sea vents reveals the peril facing the entire group. Out of 189 species of vent molluscs worldwide, only 25 are considered safe from deep-sea mining. All these nonthreatened species live inside protected areas where mining won’t be allowed. They include Gigantopelta snails with smoothly spiralling, golf ball–size shells, and Provanna snails with delicately ridged, turret-shaped shells, both of which live alongside the hairy-chested Yeti crabs on the protected vents of Antarctica. All the other vent-living mollusc species face varying degrees of extinction risk, their Red List rankings ranging from Vulnerable to Critically Endangered. When a similar analysis for other animals living on vents is produced, no doubt the same story will emerge of species endangerment driven by the threat of mining.

Done well, ocean protection holds great promise for helping sea life and people thrive together, although what protection actually means remains alarmingly ambiguous. Numerous studies have shown that ocean protection is most effective in no-take zones, where no fishing or any other extractive activities are allowed, at least when regulations are properly enforced. The reality is that today, many so-called protected areas are only partially protected—if at all.

France, for instance, has declared that, as of 2022, it has exceeded its target of protecting 30 per cent of its seas. Second only to the United States, France has a vast oceanic territory covering almost four million square miles. Most of it is made up of overseas territories, holdovers from the colonial era, including French Polynesia and New Caledonia in the Pacific, French Guiana in the Atlantic, and a collection of obscure islands in the southern Indian Ocean. Across all the ocean that France claims, less than 2 per cent lie in highly protected no-take zones, and most of those strictly protected areas lie around the uninhabited subantarctic Crozet, Kerguelen, and Saint Paul and Amsterdam Islands. In contrast, only a minute fraction of the waters around Metropolitan France are well protected. Similar numbers play out elsewhere. In the Mediterranean, 0.06 per cent of the ocean basin is highly protected. Across the northeast Atlantic, the figure is half that.

What is actually happening inside many of these designated protected areas is even more alarming. In waters of the European Union, more than half of all so-called protected areas are commercially trawled. Data from tracking systems on vessels operating in Europe indicate that the intensity of trawling is higher inside protected areas than outside. Some is illegal fishing, which obviously needs dealing with, but much of it is fishing activity that is perfectly legal; often regulations allow fishing within protected areas. Consequently, ocean life is often worse off inside than outside reserves. European protected areas are home to smaller populations of endangered species of sharks and rays than occur elsewhere, even though they’re precisely the kinds of animals these areas are supposed to safeguard.

The situation is barely any better in Britain following its departure from the European Union. Despite the chanted chorus of taking back control and pledges to protect British seas, the UK government is still making feeble progress. Proud announcements have been made that nearly a quarter of British territorial waters are already protected, and yet almost all the protected areas are being legally dredged and bottom-trawled. In the years after Brexit, the already-absurd levels of trawling inside protected areas tripled in some places, rather than being reduced, and there have been only tentative steps towards establishing more no-take zones.

In the scramble to meet international targets, political expediency is taking precedence over the real needs of the environment. Quantity is coming before quality. The more of the ocean that is declared protected and then is left unguarded or is assigned regulations that are so weak as to be meaningless, the greater the risk that global leaders will lose sight of what actually matters in the ocean. The more ocean protection is pushed to the distant, unseen, and largely unfished parts of the ocean, the less relevant it will become. And when these marine unprotected areas fail to deliver the benefits that were promised—of better fishing, improved livelihoods, and greater abundance and diversity of ocean life—then it’s possible those in charge will give up entirely on protection.

Instead, we must embrace and celebrate the incredible power of ocean life to regenerate, and thoughtfully and effectively push for more. Wherever possible, the protections need to be driven by the people who live and work in and around the affected areas. Plans will need to adapt to the changing climate, and efforts to enforce protections will need to be coordinated internationally, between nations across whose jurisdictions the same wild species roam.

In 2015, the year he died, Bill Ballantine wrote that “conservation needs places where nature is left wild.” The pioneer of marine protection remained a lifelong advocate for identifying significant parts of the ocean where no fishing of any kind should be allowed. He never argued that these highly protected areas were all that ocean life needs in order to survive or even thrive in the Anthropocene. Ballantine always made it clear that no-take zones should be additional to other established means of managing human activities and impacts in the ocean, such as regulating fishing gear and controlling pollution.

a Maerl is one of Scotland’s eighty-one Priority Marine Features, a list of habitats and species that legally need protecting in Scottish seas. Other listed habitats are seagrass meadows, oyster reefs, and cold-water coral reefs.

b Bob Ballantine called it “the thistledown effect.”

c The name combines Papahānaumoku, a mother figure in Hawai’ian tradition who is personified by the earth, and Wākea, a father figure personified by the sky. Native Hawai’ian people recognise these figures as their ancestors, whose union resulted in the creation of the entire Hawai’ian archipelago.

d These are the Elvis worms, named after the King of Rock and Roll and the sparkling costumes he wore later in his singing career.

Chapter 8 Future Forests

In the ocean there are forests—great, verdant, important places—that mirror their counterparts on land. Pay a visit to an underwater forest with a mask, snorkel, and thick wet suit (underwater forests grow only in cold places), and this version of a sylvan stroll will take you drifting through the canopy. Watch out, though. These aquatic realms are constantly in motion in ways that can be disorienting. Many times, a switch has flipped in my mind, and all at once the undulating foliage fixes in place, and the rocks beneath begin sliding to and fro. I’ve learned to relish the dizzy feeling, knowing that it won’t last long before my mind reorients, the world once more behaves as expected, and the seabed holds still.

The wildlife of underwater forests is unlike that anywhere else. Within one, I’ve watched minute white sea slugs stream gently by, like horizontal snowflakes, and had one land on my fingertip and explore my hand. I’ve seen tall piles of red-mottled, mouse-size sea hares stacked one on top of another, each of these shell-less hermaphrodite molluscs mating with the one below it; the lowest in the pile acts solely as a female, the topmost as a male, and all the others in between as both male and female, a highly efficient way to go about things when you’re a sea hare. Countless endemic species are found only in underwater forests. This is where sea dragons, giant cuttlefish, and whiskery flat sharks called wobbegongs live, as well as fish that walk on the seabed on fins like splayed-out fingers—fish that are so rare now and difficult to spot in the forest shadows that nobody is quite sure they still exist at all.

At least a quarter of the world’s coasts are fringed in underwater forests, which collectively occupy more than five hundred thousand square miles of the ocean, five times the area occupied by the world’s tropical coral reefs. The forests grow in regions bathed in waters rich in dissolved nutrients often delivered from below by deep, upwelling currents. Their foundations are not ocean-growing trees but varieties of large brown seaweeds known as kelp, which belong to an entirely separate assemblage of living things to other algae and plants.^a

More than 140 kelp species inhabit different coasts. Offshore from California’s coastal redwood forests, the Pacific Ocean grows its own giants—the biggest kelp of all, Macrocystis pyrifera. These tangled towers can reach well over 150 feet, not quite as tall as the tallest redwoods but much faster growing. Given enough food and light, giant kelp can put on two feet a day, or around an inch an hour, placing them among the fastest-growing organisms on earth. Giant kelp hold themselves upright, oriented skywards, with gas-filled orbs and form a floating canopy at the surface.

Bullwhip kelp (Nereocystis luetkeana) is another imposing species at up to 115 feet long, with a slender stipe (the equivalent of a tree’s trunk) and a lollipop mop of fronds on top.^b Other kelp species are not quite as huge, five or ten feet tall, but are no less intricate. There are forests of golden kelp (species of Ecklonia) with ragged-edged fronds that look as if they’ve been torn from larger sheets of kelp. Undaria species resemble ferns with deeply divided blades. Across the Northern Hemisphere grow feathery Alaria; huge, hand-shaped Laminaria; and long, crinkled strands of Saccharina.

It’s possible to explore the life of kelp forests without getting wet. After storms off temperate and cold coastlines, beaches are often strewn in pieces of kelp that were torn away and expelled from the sea. Hold a kelp blade up and see if it’s taller than you are (quite possibly). Feel the smooth and pliable material, slippery but not slimy, which may feel like manufactured plastic but is entirely natural. Kelp stipes lie like fallen sapling trunks or twisted ochre bones poking through the sand. Other seaweeds, many of them red and wispy,^c use the stipes as a firm habitat to settle on, a miniature forest within the forest. Look for holdfasts, like balled-up fists, that grow at the base of kelp. These aren’t roots, and don’t absorb water or nutrients as roots of land plants do, but are simply there for holding tightly to rocks. They serve the incidental purpose of creating habitat for the many other small creatures that burrow among their fingers—sponges, bryozoans, bivalves, gastropods, amphipods, copepods, and worms, all adding to the biodiversity of a kelp forest.

Piles of storm-stirred kelp on the beach make up only a small portion of the organic matter lost from underwater forests. As it grows, kelp absorbs carbon dioxide that has dissolved in seawater from the atmosphere above. Fragments of kelp that break off and drift away from the forest end up sinking, taking that harnessed carbon with them, sometimes into the deep ocean, where it can no longer act as a greenhouse gas. Calculating exactly how much carbon kelp forests sequester in the deep is not easy, certainly compared to terrestrial forests, in which carbon is stored within the standing biomass of trees, the roots, and the surrounding soil, making it relatively straightforward to measure. Underwater, carbon is not locked up within forests themselves, and so it’s much harder to gauge the magnitude of the long-distance carbon highways streaming from kelp, especially because this varies greatly depending on ocean currents and storms. The latest estimates suggest kelp forests globally remove eighteen megatons of carbon dioxide from the atmosphere each year, thereby soaking up the equivalent of the emissions from approximately one million North Americans.

The value of kelp forests goes far beyond the carbon they can banish from the atmosphere. They generate at least $500 billion yearly, mostly from fisheries. Kelp forests create important habitat for many commercial species, such as lobsters, abalone, and the kelp itself. In Australia, kelp forests are the summertime home for young bluefin tuna, which later in life are caught and sold for huge sums.