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underwater photo of oil rig encrusted with sea life
Marine life thrives as an “accidental reef” on the Eureka oil platform off Long Beach, California. Photo by Mark Strickland/Blue Planet Archive

Oil Rigs Are a Refuge in a Dying Sea

Our reliance on fossil fuels is harming marine ecosystems—but the platforms we use to extract oil are giving marine life new homes.

Authored by

by Sasha Chapman

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First, let me tell you how the accidental reef came to be.

In the beginning, there was mostly mud below the shallow waters off California. And beneath the mud lay something the two leggeds considered very valuable: billions of barrels of oil. The two leggeds had always known there was oil in the Santa Barbara Channel. Natural fractures in the Monterey Formation had allowed the oil to bubble and seep to the surface for as long as anyone could remember; Chumash people living along the coast for millennia may have used natural asphalt to seal their boats. In 1792, an English naval officer surveying the area described the rainbow slicks that formed on the water’s surface and how the smell of tar wafted on the offshore breeze.

Where there was only mud on the ocean’s bottom, there was no obvious place for sessiles to congregate. No hard surface where these invertebrates could fix themselves into place. And because there were no colorful sponges or corals or tunicates (or shapely scallops or gleaming mussels), there was little reason for hungry crabs, shrimp, and brittle stars to congregate. There weren’t many places for little fish to hide or things for them to nibble, either—which meant there wasn’t much to attract the larger fish that ate them.

Of course, the two leggeds weren’t thinking of the sessiles, or the other creatures these invertebrates might sustain, when executives from the Atlantic Richfield Company (ARCO) and Mobil signed an offshore lease with the State of California in 1965. They were only thinking of the tiny creatures—mostly diatoms—that had lived and died millions of years ago, now transformed into oil-rich Miocene shale.

The oil and gas lease allowed ARCO to build a large platform, like a stationary ship, three kilometers offshore. The platform itself would rest on top of the water, and a rectangular web of steel—called the jacket—would support it underneath, reaching 64 meters down to the mud bottom.

This was a major undertaking for the two leggeds, and an amazing feat of engineering. The steel itself—all 5,200 tonnes of it, or about three-quarters of the weight of the Eiffel Tower—was welded and assembled in Louisiana. A barge then towed the structure in two large pieces down the Atlantic coast, through the Panama Canal, up the Pacific coast. There it was reassembled in San Francisco Bay and then towed into the Santa Barbara Channel, where engineers and their machines fastened the platform and its drilling rig to the wrinkled folds of the ancient seafloor.

The oil drilling platform Holly, in the Santa Barbara Channel, California

The oil drilling platform Holly, sits in the Santa Barbara Channel, California. Photo by Maureen Sullivan/Getty Images

Once everything was in order, the people who worked on the platform in 12-hour shifts around the clock began operating the rig itself—the machinery that would drill 30 wells into the seabed and pump out the ancient hydrocarbons trapped inside it. The two leggeds drilled wells deeper than 1,000 meters. Some of the wells lay as far as 3,000 meters beyond the platform.

The two leggeds named the platform Holly. It was, for a blink in Earth time, one of the deepest oil platforms in the world.


Today, there are more than 10,000 installations fixed or floating in the Earth’s oceans. Many of them are far larger and extend deeper than Holly. Perdido, now the world’s deepest, reaches down 2,400 meters to the bottom of the Gulf of Mexico. Made in Finland, it took three months to reach its resting place.

Only the oil industry has the ambition and funds to build such elaborate structures in our oceans. And because the oil industry has a lot of ambition and a lot of funds, it has built a lot of structures like Holly over the last 80 years or so: in the Gulf of Mexico, where the platforms are most numerous, an archipelago of about 6,000 of these artificial islands runs the length of the coast from Alabama all the way to the US-Mexico border.

The oil companies that underwrote the platforms and the engineers who designed them did not set out to create new habitat for wildlife underneath the massive structures, but that’s exactly what they did. What makes Holly a good design for oil extraction—four massive steel legs that run the depth of the water column, braced by beams that run horizontally, vertically, and diagonally to make an open weave that quickly dissipates ocean energy—is also what makes it an excellent habitat for sheltering an amazing diversity of sea creatures from sharks, turtles, and dolphins to the tiny hard and soft coral polyps that crust over the metal legs and transform them into a riot of color and texture, attracting hundreds of thousands of fish into their midst.

So, the ocean is not as untouched as we two leggeds like to think.

Offshore Oil Drilling Rigs at Sunset

There are about 6,000 oil rigs in the Gulf of Mexico, from Alabama to the US-Mexico border. Photo by Unlisted Images, Inc./Alamy Stock Photo

Since the 1940s, the world’s oil companies have been conducting a large-scale (if unintentional) geoengineering project in the oceans, creating new habitats and new ecosystems that would not otherwise exist. These artificial reefs have become so complex and dynamic that one University of Edinburgh project has concluded that “platform ecosystems are evolving to mimic those in the wild.” Scientists estimate that artificial reefs in the Gulf of Mexico may provide as much as 30 percent of its reef habitat. In California, the marine biologists who study oil platforms have declared them the most “productive” marine habitats in the world. (They sustain a lot of fish.) Some of these artificial ecosystems closely resemble the natural ones; others are different enough to suggest something entirely new: novel ecosystems that manifest entirely novel qualities.

This grand (and complicated and problematic) experiment could soon drag to a halt. Most of the world’s platforms are now reaching the end of their “useful” lives. In other words, the oil platforms aren’t as profitable as they once were—either because the wells are running dry or the price of oil is often not high enough to warrant such a costly and potentially dangerous extraction process.

Market analysts tend to use active oil rigs as a gauge for how optimistic the market is feeling. When the oil market is bearish, offshore production plummets. Then offshore oil is deemed too costly and too risky to extract.

The challenge is that we two leggeds don’t know how to agree on what happens after they stop pumping oil from these platforms. Do we pull out the structures and consign hundreds of thousands of kilograms of steel—and hundreds of thousands of creatures—to landfill? Or do we simply cap the wells and let the artificial reefs remain mostly intact, to protect the creatures that depend on them for habitat?


When ARCO first signed its oil and gas lease with the State of California, Holly’s future seemed pretty straightforward. After the rig was done pumping oil, the lessee—like all offshore lessees in California waters—promised to cap the wells and dismantle its entire steel structure. (Federal regulations require all offshore platforms to be removed within one year of terminating an outer continental shelf lease.) At the time, this made sense: citizens would be assured that oil companies were not going to junk up the ocean with their trash, leaving old platforms to rust and rot.

But these promises were made before climate change became a mainstream discussion, before so many coral reefs began whitening and dying in waters that are becoming too hot and too acidic for survival. Back then, nobody was thinking of these large steel structures as artificial reefs, or that they might provide important habitat for creatures under threat—often as a consequence of the very activities that oil had fueled.

surfers with oil rig in background

An oil platform looms over surfers and a kayaker in the Santa Barbara Channel. Photo by Greg Lawler/Alamy Stock Photo

For nearly 50 years, Holly pumped oil for its operators and lined the pockets of executives at ARCO and Mobil and finally Venoco as the platform kept changing hands. Production peaked in 1984. Then, in 2015, Holly stopped pumping, when the Plains All American pipeline that carried its crude to shore broke open and spilled about 3,000 barrels of oil into the ocean. In the history of oil spills, it was a fairly minor one, but it was enough to shutter the platform. Holly’s operator at the time, Venoco, quitclaimed the lease two years later and abandoned the stationary ship.

Since then, the platform has stood rusting at the edge of Santa Barbara’s horizon as a ward of the state, while different factions argue about its future and who will ultimately pay the cost of dismantling or keeping the structure. Exactly who’s on the hook for what is now a question for the courts to decide.

Decommissioning a platform can mean many things: put simply, it’s the process of ending operations at an offshore platform. Most often, the process means totally removing the steel structure and capping the wells, so that the seafloor is returned to something resembling its prelease condition, as ARCO originally promised in the 1960s. It usually involves the use of explosives or divers with diamond saws to sever the structure from its base. The structure is then taken to shore for limited recycling; the rest ends up in landfill. So do the hundreds of thousands of creatures that are clinging to it. “The smell was beyond anything,” recalled one observer, after watching a reef-encrusted platform get pulled from California waters in the 1990s. “You gotta bury it quick.”

But there is another option. At least part of the structure can be “reefed”—left in the ocean to continue providing habitat for the creatures that call it home. (How much of the structure is left in place is decided on a case-by-case basis; usually, the actual platform and a portion of the jacket near the surface of the water are removed so that the structure will not pose a navigational hazard for boats.)

Reefing is an established practice in the Gulf of Mexico, where platforms are more numerous and public sentiment toward oil companies is generally less antagonistic. There, five states have incorporated decommissioned platforms into their artificial reef plans, and more than 500 platforms have been reefed since 1984, when a National Artificial Reef Plan was first introduced. “It’s a win-win,” says Dale Shively, who coordinated Texas’s artificial reef program until he retired in December 2020. He says a typical four-legged structure can provide several acres of important habitat for tens of thousands of fish. Platform operators like the arrangement because they can save money: reefing costs may be half as much as the cost of removing the whole thing. In Texas, operators donate half of their estimated savings to the state’s artificial reef program. Title and liability of the platform are then transferred from the operator to the state, and the state keeps a slush fund to pay for any future expenses related to maintenance or liability issues. But reefing remains voluntary, and it’s not always desirable or economically or ecologically feasible. Some reefs require more physical modifications to be left in place than others; some are less ecologically productive or poorly situated. (A reefed platform can also be towed to a “better” location.) This may account for the fact that only 11 percent of decommissioned platforms in the Gulf were reefed before 2016. The other 89 percent were all removed and towed to land.

Schooling jacks under an oil rig in the Gulf of Mexico

The steel frames of oil platforms provide food and refuge for a variety of animals, such as this school of jacks under an oil rig in the Gulf of Mexico. Photo by Kip Evans/Alamy Stock Photo

The rigs-to-reef arrangement is really just the continuation of a century-old American tradition of building reefs out of all kinds of scrap: toilets, tires, cars, trains, and even battle tanks and fighter planes. If it’s cheaper and easier to sink these objects than dispose of them onshore, owners will do it, and US legislation will generally allow it. This, however, “gives rise to the complaint that reef creation is just a legalized method of dumping waste at sea” as one 1997 industry white paper out of Norway and the United Kingdom observed. This makes the artificial reef itself no less valuable to the inhabitants that depend on it, or to the sport fishers who wish to catch them, but it does make many environmentalists uncomfortable—especially in Europe, where historically there has been greater resistance to repurposing platforms or “recycling” other materials in the ocean.

No oil platform off California has ever been left in place as an artificial reef at the end of its life, and the size and depth of the platforms make removal far more costly and complicated than for the shallower water platforms in the Gulf of Mexico. A specialized vessel must be brought in from Asia or the Gulf of Mexico just to begin the work. Complete removal of California’s 27 platforms could cost more than US $1-billion.

In 2010, California passed a rigs-to-reef bill, making it theoretically possible to preserve at least part of the underwater structure to sustain wildlife. Marine biologist and ocean activist Sylvia Earle has spoken out in support of the bill, and a growing number of people and organizations in California now favor reefing, as evidenced by the concerned citizens and organizations who stand up to speak at the town halls that are periodically held to update the public and discuss platform Holly’s future. They see Holly as a test case: a chance to show that reefing can actually benefit wildlife—if someone is willing to let the structure remain. Holly is also the only platform within state waters (as opposed to federal waters) that is deep enough to be considered for reefing.

Decommissioning Holly will take years to complete, even if it is not reefed. This in itself is a massive undertaking—nearly as massive as building and fastening the rig to the ocean floor in the first place. The same equipment used to begin the life of a well is also used to end it, notes Jeff Planck, one of the overseers of Holly’s decommissioning for the California State Lands Commission (SLC), the agency now in charge of the platform. Making the abandoned platform safe enough to begin capping its 30 wells requires more than 115,000 hours of labor. They are almost rebuilding the whole thing just to remove it.

But Venoco has left the state a mere $22-million bond for Holly’s decommissioning. Already, the state legislature has had to appropriate $110-million just to complete phase one. The SLC expects that Exxon Mobil, which is deemed partially responsible, will in the end bear the vast majority of the final facility decommissioning costs, about $125-million to plug and abandon the oil wells and another $175-million to dispose of the platform itself.

When Venoco filed for bankruptcy, Exxon Mobil, the SLC, and other state agencies and creditors began submitting claims. “It is unknown how much the commission and Exxon will receive from the bankruptcy estate, but it will be a small fraction of the amounts actually expended on plug and abandonment and decommissioning,” says Sheri Pemberton, chief of external affairs and legislative liaison for the SLC, in an email.

Meanwhile, the SLC estimates that the platform is costing the state as much as $1-million each month, just to sit in the water. The platform and attendant facilities must be continuously staffed, because hydrogen sulfide will continue to emanate from the wells until they are plugged and abandoned. And that’s without taking into account any of the actual costs associated with decommissioning.

“It has been quite litigious,” says Seth Blackmon, chief counsel for the SLC, at one of the town halls, “and I assume it will continue to be so.”

At bottom, the argument over the future of Holly—the largest platform in the Pacific to be considered for decommissioning—is an argument over what happens after the oil boom. It’s an argument that will repeat itself often in the coming years, as more and more platforms reach the end of their useful life. And it’s an argument that is especially fractious here, in Santa Barbara—the site of the world’s first offshore oil drilling and also the world’s first major oil spill—where America’s environmental movement began.


Tunicates and bryozoans were probably the first animals to attach themselves to Holly’s steel jacket in 1966. Next came the amphipods and barnacles. Within two years, barnacles, mussels, and sponges had overtaken the structure. A thick reef crust began to form—as thick as 10 centimeters in places—as more and more invertebrates fixed themselves to the growing artificial reef. Anemones and sea stars arrived. Rock scallops. Limpets and jingle shells. Crabs and more crabs. And because the structure itself casts long shadows in the water column, the way a kelp forest does, it attracted juvenile fish and other prey looking for somewhere to hide.

Each structure has its own type of life, says Bob Evans, when we spoke by phone. The Santa Barbara photographer began diving in the 1960s. Since then, he has logged more than 5,000 hours underwater, and more than 850 dives on Holly and other nearby Channel Island platforms. He and his fellow divers—often biologists surveying the wildlife beneath the platforms—were amazed by the diversity and size of wildlife they found there. In a single photograph, says Evans, he has counted more than 30 crabs. Mussels, in particular, grow unusually deep and large under Holly. Evans surmises that the larvae, which are usually found drifting in shallower waters, might have attached themselves to Holly’s steel legs when the structure first arrived in the Santa Barbara Channel, floating at the surface for several days before the engineers flipped the jacket and drove the legs into the pilings in the seafloor.

Below the jacket, mussel shells and other invertebrates accumulated on the seafloor, dislodged from the reef above by routine platform cleaning or heavy swells. (Oil companies typically “clean” the biofouling every six months or so from the top portion of the jacket.) The shell mounds that form below platforms can grow to several meters thick, creating more habitat for octopuses and shrimp, rock crabs and king crabs, and many, many fishes: rockfish, lingcod, poachers, painted greenling, and other benthic species. These mounds also carpet the mud and broken bits of rock brought up from below when the wells were first drilled. It is possible, say scientists, that toxicants could be released into the ocean if the shell mounds are disturbed or dismantled.

Brittle stars covering beams of Oil Rig Elly

The beams and girders of oil platforms provide a place for marine invertebrates to settle and thrive, resulting in a conundrum for biologists and conservationists: leave decommissioned platforms in place as artificial reefs, or remove these “novel ecosystems” and the habitats they provide? Photo by Phillip Colla/Blue Planet Archive

Holly became known as a hangout for juvenile bocaccio rockfish. This caught the attention of Milton Love, a marine biologist at the University of California, Santa Barbara, who began studying platform wildlife in 1995. Bocaccio were of particular interest to him, because they were overfished. Before he’d become a biologist, Love had had a job collecting local species for an aquarium, and he’d noticed an abundance of fish near the platforms. “I thought that was interesting,” he says.

It’s worth noting that oil platforms also function as mini sanctuaries. Operators in California generally discourage boats from tying up, and some of the platforms are also hard for fishers to get to: they are located in rough waters or too far from shore. Safety regulations may even limit fishing vessel access altogether. Love wondered whether these facts alone were enough to explain the abundance he saw.

Biologists in general, and the people who study platform wildlife in particular, often argue over whether a specific habitat feature (in this case an oil platform) actually increases the population of a species or whether it simply acts as a meeting place for creatures that would otherwise gather somewhere else.

Love began to think of ways to investigate whether platforms were aggregating or actually producing more fish. “When you see 150,000 baby bocaccio rockfish at a platform, it looks like a good nursery ground. But if you pull out the platform, would the drifting larvae find another reef to shelter in?”

If yes, then the platform would be superfluous as far as the rockfish are concerned.

Love and his team began looking at ocean currents. A collaborator created a computer model that could reflect prevailing weather patterns and added in the drifting bocaccio larvae. A lot of them hit the platform. Then Love’s team removed the platform from the model and watched the rockfish drift again. They assumed that bocaccio carried inshore would find their usual nursery sites and survive, while those that drifted out to sea—where there are few natural surfaces to provide shelter and food—would die. Over a three-year period, Love’s team concluded that 70 percent of the juveniles would die if the platform were removed.

“This doesn’t mean it’s true for all platforms, all species,” he cautions. “But it lends credence that maybe these platforms are pretty good nursery grounds. And if that’s true, then it’s very hard to argue that platforms are not helping to produce fish.”

Love emphasizes that there is nothing magical about platforms. They are large and span the entire water column, which makes it more likely for larvae to hit a platform than a natural reef. Fish can also migrate down the structure and into deeper water as they grow. In a shallower, natural reef habitat, they would have to leave the safety of their nursery grounds and strike out into the open water in search of a deeper reef as they mature. The structures are also complex, and complexity of a hard substrate is “associated with marine habitats that have high abundance and diversity of fishes,” as a 2014 research article noted in the Proceedings of the National Academy of Sciences.

fish swim under an oil rig

Whether you remove an oil platform or leave it in place, the oil from the original wells or the pipelines used to transport the oil can still leak. In 2021, oil from a pipeline between platform Elly, shown here, and the Port of Long Beach, California, leaked, fouling the life living on and near this artificial reef. Photo by Phillip Colla/Blue Planet Archive

The article (which Love contributed to) makes a compelling case for the productivity of California’s oil platforms—measured not in the number of barrels pumped but the number of fish a platform might sustain. When the authors compared square meter to square meter, a platform could be as much as 27.4 times more productive than a natural rocky reef located at a similar depth in the same area. The oil platforms reviewed in the paper are, they conclude, among the most productive fish habitats in the world.

The fact that these platforms were never intended to be biologically productive seems irrelevant. Their success, argue the authors, provides us with “insight into what drives high rates of fish production for both natural and artificial habitats.” Surely this seems especially pertinent now, they say, in an era when “human activities are threatening fish populations on natural reefs globally.” Understanding how these artificial reefs work could be “critical,” say the scientists, “in terms of conservation of marine resources.”


One of the ironies in the debate over the future of oil platforms in general, and Holly in particular, is that self-described environmentalists may find themselves arguing for the destruction of wildlife—because that wildlife was underwritten by an oil company. This is especially true in Santa Barbara, where antipathy to oil interests runs high.

Santa Barbara has a complicated relationship with oil. This part of California was the site of the world’s first offshore oil exploration—the first wildcatters drilled oil wells off wooden piers just east of the town in the 1890s. The oil boom drove up real estate prices and trains stopped here to refuel, laying the groundwork for the burgeoning tourist industry. The oil and gas industry remains a significant contributor to the local GDP: in 2017, it generated more than $60-billion in Southern California.

But Santa Barbara was also the site of the world’s original catastrophic oil spill in 1969, just three years after Holly began its operations. The spill happened a few kilometers from Holly, when Union Oil workers tried to cap a well and the gas bubbled up anyway, leaking hundreds of thousands of barrels of oil over 10 days. The oil slick that formed off the coast stretched hundreds of kilometers. People who were there still remember how the ocean went eerily quiet, the sound of the waves dampened by the heavy slick. Oil-smothered waves don’t crash against the beach: they slop.

1969 oil spill off Santa Barbara

An oil spill off Santa Barbara in 1969 alerted the world to the potentially catastrophic consequences of offshore oil wells. For 10 days, oil leaked from a well and formed a slick that stretched hundreds of kilometers. Photo by Santa Barbara News-Press/Zuma Press/Alamy Stock Photo

It was a world-changing event. Photographers came from all over the world to document the carnage: seabirds, fish, seals, and porpoises washed up dead or struggling against the shore, slicked in heavy black crude. The Santa Barbara News-Press ran a photo of a mother holding a toddler in her arms, looking out her living room window toward the ocean. The window was spattered black. “Oil on beaches, birds and boats,” read the caption, “but on picture windows?”

Fourteen new federal environmental laws were written after the spill. Local and state laws were also passed. A year later, the Environmental Protection Agency was formed and the first Earth Day was celebrated in 12,000 separate events. One impassioned Earth Day speaker, Harriet Miller, went on to become one of Santa Barbara’s longest-serving mayors.

After the 1969 spill, California stopped issuing offshore drilling leases.

Many people in Santa Barbara want the oil companies gone, full stop. “When you have come to the ocean, it should be the ocean,” Carla Frisk said on a 99% Invisible podcast in 2019. Frisk is a regular at SLC’s town hall meetings and speaks for a Santa Barbara advocacy group called Get Oil Out! (GOO!), which was formed after the oil spill. GOO! wants the Santa Barbara Channel returned to its “natural,” pre-exploration state and wants the oil companies who built these large steel structures that interrupt the horizon to be held to the promises they made so many years ago. GOO! sees platforms as trash that is junking up the view of the horizon, and the oil that leaks from their wells as an environmental hazard. (A recent study suggests that abandoned oil wells in the United States and Canada are the 10th and 11th leading causes of methane emissions and have been significantly underestimated until now.)


The desire to return the ocean to a pristine, natural state and to go back to the way things were before the oil companies arrived, before human beings began engineering the ocean, seems hopelessly naive. The serpent is already in the garden, and everything has already changed: there is no way to pretend that we have not been here and that we have not already engineered a new environment. The ecosystem that develops under a platform—or a wind turbine, or any other structure we put into the ocean—is modified by technology and possibly amplified by it, but it is still a system that supports reef life. In this sense, it is what ecologist Richard Hobbs referred to in a 2006 paper as a “novel ecosystem” and later defined as “a system of abiotic, biotic and social components that, by virtue of human influence, differ from those that prevailed historically, having a tendency to self-organize and manifest novel qualities without intensive human management.” But the term remains politically charged and subject to interpretation. Aren’t ecosystems always changing? And in the Anthropocene, can we say that anything on this planet has escaped human influence?

In 2015, writing in Ensia, biologists Daniel Simberloff and Carolina Murcia cautioned that calling an ecosystem “novel” could be used as a kind of “Get Out of Jail Free card for companies or individuals trying to avoid investing in research, mitigation or restoration by claiming they are producing novel ecosystems that will provide ecosystem services.” Those who see the value in and wish to work with novel ecosystems tend to find themselves at odds with restoration ecologists and conservationists who say that things should go back to the way they were before human beings began to meddle with them. Some are accused of being apologists for the oil companies; some are funded by them.

In 2019, Australian researcher Marie-Lise Schläppy, together with Hobbs, observed in Global Change Biology that “when an altered system cannot be restored to a chosen historical baseline, the value of the novelty needs to be the focus of research.” Novel ecosystems, they suggest, might be a form of triage for ecosystems and species that are under threat. But they also acknowledge that our understanding of novel ecosystems is not purely biological—there is always a social component that informs our view.

Anemones coat the girders of platform Elly, near Long Beach, California

Anemones coat the girders of platform Elly, near Long Beach. Photo by Phillip Colla/Blue Planet Archive

Why wouldn’t we want to preserve the life that platforms have made possible, except because of some deep-rooted sense of payback, of wanting to hold the platform operators to account? Of course, oil companies should be held to account. But removing an artificial reef is no guarantee that the wells below them won’t leak. The wells will be there whether or not the structure that looms above them is consigned to landfill or preserved as an artificial reef.


When I first asked Love about his views on whether or not platform Holly should be fully removed, he demurred, saying he didn’t have an opinion as a biologist. He was only interested in facts.

We both fell silent.

“But I do get to have a view as a citizen.”

Forget the fish, he said, now warming to his subject. You’re dealing with hundreds of millions of animals on a platform, if you include all the tiny creatures that fasten themselves to the steel legs. “If you remove the platform,” he said, “you’re killing them all. I just don’t think that’s moral. Why are you killing them because they had the misfortune of landing on a piece of steel rather than a rock?”

We two leggeds move easily across land and water: we build new houses in new places whenever and wherever we wish to set ourselves down, no matter what the climate. We migrate easily when local conditions no longer serve us, in search of more hospitable environments. It is part of what makes our species so successful. Many of our fellow creatures don’t have the same luxury of movement, or the ability to engineer better conditions for themselves. Once sessiles fix themselves into place—on a rock or a metal leg—they will live there until they die, or until someone or something tears them down.


In the end, there was still a lot of mud below the shallow waters off California. There were also wells drilled into the mud—some of them already capped, some of them still pumping out the ancient diatoms that had long ago fossilized into fuel. And looming over them stood the accidental reefs the two leggeds had built—accidental reefs that were still teeming with life, even as the natural reefs around the world were beginning to whiten and die.