For centuries, humanity has viewed the ocean as a metaphor for infinity. The assumption was — and frankly still is for many people — that the enormity of the sea comes with a limitless ability to absorb and metabolize all. This vastness is what lends the ocean deity-like potential. And more dangerously, it is what has given humans the license to dump virtually anything offshore. Oil, sewage, corpses, chemical effluvium, garbage, military ordnance, and even at-sea superstructures like oil rigs disappear into the oceans, as if swallowed up by a black hole, never to be seen again.
Ships knowingly release more engine oil and sludge into the oceans in the span of three years than that spilled in the Deepwater Horizon and Exxon Valdez accidents combined. They emit huge amounts of certain air pollutants, far more than all the world’s cars. Commercial fishing, much of it illegal, has so efficiently plundered marine stocks that the world’s population of predatory fish has declined by two thirds. At the same time, since the Industrial Revolution, companies on land have been allowed to dump carbon into the air for free, and roughly a quarter of that carbon is absorbed by the oceans. The hidden cost to that dumping is what we now call the climate crisis.
As the lungs of the globe, the oceans produce and filter half of the oxygen we breathe. But our “smoking habit” has caught up with us and those lungs are failing. In ways big, small and surprising, overfishing is a driver of climate change. For example, since whales are enormous carbon sinks, the past century of whaling equates to the burning of seventy million acres of forest.
With rising global temperatures, the ocean’s levels of dissolved oxygen have plummeted. As rainfall crosses land, it picks up sewage, fertilizers, detergents, and microplastics and carries them straight into the world’s oceans. This nutrient runoff feeds excessive algal and microbial growth worsening the 500 or so coastal water sites classified as “dead zones” — areas with so little oxygen that most marine life cannot survive. The largest of these is bigger than Scotland.
The current outlook on the climate crisis barely even considers the oceans, even though it covers two thirds of the earth’s surface. For instance, climate change agreements, such as the Paris Accord, have embraced the goal of restricting global temperatures to within 2 °C above pre-industrial levels. But what does that ambitious goal mean for marine life? If global temperatures rise by 1.5 °C, only about 10 to 30 percent of coral reefs will survive, diminishing the habitat of roughly one-quarter of all ocean species, not to mention the impact on coastal storm protection, food and job security, and our marine prospects for biomedical research.
But the biggest problem is this: while most of the climate crisis attention is focused on land, many of the best fixes are offshore. A growing chorus of marine researchers is calling for governments to “rewild” the world’s coastlines, a conservation tactic that involves restoring habitats so nature can eventually revive itself. The oceans host three types of coastal ecosystems — mangroves, salt marshes, and seagrasses — that collectively absorb more carbon than all the planet’s forests. If bolstered, these ocean biosystems could drastically slow the climate crisis.
Of course, this approach only works if protecting these habitats in one region doesn’t give tacit permission for them to be destroyed faster elsewhere. The gravest risk with any approach aimed at ameliorating climate change is that, if successful, it might equip fossil fuel and other carbon-intensive industries with an excuse to dodge their emission-cutting commitments and maintain business as usual. Rewilding the oceans will require stricter controls on destructive activities like bottom trawling, dredging, and offshore mining and drilling, which decimate the seabed and release stored carbon into the water column.
The oceans have also become a laboratory for some of the most promising and risky forms of geo-engineering. One group of scientists hope to lock away atmospheric carbon using a specially designed type of sand made of an abundant volcanic rock, known to jewellers as peridot. Depositing it offshore on 2 percent of the world’s coastlines would capture 100 percent of total global annual carbon emissions. Another set of engineers has developed a machine called a flow reactor that pulls in seawater, and using an electrical charge makes it alkaline, triggering — not unlike the forming of seashells — the carbon dioxide to react with the seawater’s magnesium and calcium, producing limestone and magnesite. The water then flows out, cleaned of its carbon dioxide and capable of absorbing more.
Among the more daring but controversial ideas are ocean fertilization. This involves dumping large amounts of iron pellets into the oceans to foster carbon-capturing algal blooms or marine cloud-brightening which entails spraying a fine mist of seawater into clouds so that the salt makes them brighter, and more reflective of the sun’s heat.
Offshore wind energy can produce more than 7,000 terawatt hours per year of clean energy in the United States alone. This is roughly double the amount of electricity used in the United States in 2014. Cargo vessels and passenger ferries emit nearly 3 percent of global greenhouse gas emissions, including black carbon. Decarbonizing the global shipping fleet would be roughly equivalent to cutting all of Germany’s carbon emissions.
The oceans are a bustling workplace where more than 50 million people earn their livelihoods. Fully half of the world’s population now lives within a hundred miles of the sea. And yet, most people, with sedentary occupations and land-locked lifestyles, conceive of this space as a liquid desert that they occasionally fly over, a canvas of lighter and darker blues. Meanwhile, a woeful lack of governance offshore has given rise to a dystopian hinterland where a rogues gallery of sea slavers, fish pirates, repo men, arms traffickers, oil dumpers, and conservationist vigilantes operate with impunity. Countries do have vast and untapped jurisdiction to act in this relatively ignored realm. Half of the territory belonging to the US, for instance, is underwater. But the same out-of-sight-out-of-mind perspective that makes the ocean outlaw has created our worst blind spot on the climate crisis.
Perhaps it’s time to think of the oceans in a radically new way. Surely, they are no longer a thing we take for granted, a bottomless trash can, a forever self-replenishing resource that we use to fill our stomachs or line our wallets. Maybe the oceans instead are a vast habitat that we should leave alone. Better still, what if the oceans are our 11th-hour saving grace, or a place to find answers, less a grocery store than a library? Perhaps in helping them to flourish, we will see that the oceans are not just a victim of the climate crisis but a big part of its solution.
CORRECTION (08/30/21): The original version of this article stated that the ocean’s dissolved oxygen levels were skyrocketing. That has been corrected.