Looking Into the Abyss - Part Two

6/3/21

Jun 04, 2021

As a reminder, last week I outlined some of the longstanding (and accelerating) harms an expanding human population has inflicted upon life in the oceans – pollution, overexploitation of fisheries, habitat destruction – and the long-term threats these harms pose. This week I’ll focus on the so-called “deadly trio” (a term from the 2013 IPSO State of the Ocean Report to describe ocean warming, deoxygenation, and acidification), and how this state of affairs seems to resemble the entry point for Earth’s five previous mass extinctions.

Last week’s focus was on the equivalent of conventional warfare – man v. fish, deploying bottom trawlers and ghost nets and single-use plastic and chemical pollutants – while this week’s focus might be compared to the threat of thermonuclear warfare: a complete and hostile transformation of the marine environment. My apologies for the extreme metaphor, but given the trend toward conditions in previous mass extinctions, it’s apt.

Simply put, a warming climate warms the ocean, disrupting all life living in it or relying upon it. The disruption occurs by changing the temperature regimes that have governed life underwater for untold millennia, by expanding oxygen-deprived dead zones, and by dramatically increasing acidity. I’ll take these one at a time.

The consequences of warming oceans are extraordinarily complex and consequential. As a 2019 Sustainable Ocean Alliance report put it, “Climate change will reorder the distribution of life in the ocean.” Species will attempt to shift habitats to find waters with the right temperatures, but the rate of change in the Anthropocene is so much faster than ordinary evolution that few species are likely to fully adapt. Some species are more mobile than others, of course, but moving is of little use if food and shelter don’t move too.

We think of climate change as an atmospheric phenomenon happening above and around us, but the oceans have absorbed more than 90% of the excess heat produced by greenhouse gas-associated warming since the 1850s. This affects not just the life undersea, but the very nature of the sea itself. For example, as the surface layer of the oceans warms, it becomes less dense and thus less likely to sink and be replaced by cooler, nutrient-rich water which pushes upward to feed phytoplankton, the tiny ocean plants that are the foundation of the ocean’s food web. Thus, phytoplankton-deprived “biological deserts” in the deep oceans have been expanding recently at a rate of 1 to 4 percent per year. Biological activity in the Atlantic has recently been declining by an estimated 4 to 8 percent per year. In some tropical oceans, oxygen-producing phytoplankton have declined by up to 40% since the 1950s.

Other large-scale ocean changes due to warming include the loss of Arctic sea ice, increased release of methane from the Arctic sea floor, and the slowing of ocean circulation. Each of these, in turn, will (if unchecked) significantly amplify the impacts of climate change. An ice-free Arctic reflects less sunlight and thus accelerates its own warming; methane is twenty times more powerful as a greenhouse gas than CO2; and already ocean circulation in the Atlantic is 15% slower than in the past, and could be reduced by around 40% by the end of the century, making Europe colder and stormier, and increasing sea-level rise in eastern North America.

Nearly everything I mentioned last week, from habitat loss and fisheries exploitation to the impact of pollution, will be worsened by warming waters. “We are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure,” according to the 2013 IPSO report. Factor in the predicted increase in acidity, decrease in oxygen, and the disappearance of coral reefs and other essential habitats, and you might as well yell “Fire!” in a crowded circus tent.

If we were slowly raising Earth’s temperature over a few million years rather than spiking it over a few centuries, then biodiversity would be reshaped rather than decimated as life adapted to new conditions. There’s nothing inherently inhospitable about the planet being several degrees warmer – crocodiles and lemurs can live in the high Arctic if conditions are right – but sudden change causes sudden death. The difference in impacts between gradual climate change and human climate change is like the difference between remodeling your house and razing it to the foundation before rebuilding.

One recent analysis of the end-Cretaceous (dinosaur-killing) mass extinction noted that it took about twelve million years for a full recovery back to normal extinction rates. The same analysis saidthat , incredibly, predicted extinction rates for the next century or so are a thousand times higher than the end-Cretaceous. (The study used freshwater gastropods for its data set, not marine species, but it’s a representative sample for a global phenomenon.) Assuming the analysis is valid and relevant, and assuming we don’t reverse our current trajectory, it will take many millions of years for life on Earth to correct for our shortsighted use of fossil fuels.

The 2018 Kiel Declaration on Ocean Deoxygenation – titled “The Ocean is Losing its Breath” – was written at a conference of three hundred scientists who implored “nations, societal actors, scientists and the United Nations” to see ocean deoxygenation as a critical global threat. In the last fifty years hypoxic (oxygen-depleted) waters have quadrupled, for two main reasons: expansion of dead zones from ocean warming and expansion of dead zones from nutrient-loading pollution.

Oxygen enters the ocean from the atmosphere, but a warming ocean, like a warming glass of soda, holds less gas. Imagine each disappearing bubble in your room-temperature drink as a disrupted species, and you get the picture. Fish are at least as sensitive to oxygen levels as we are, and prefer to live where they can breathe better. They will respond to hypoxic conditions as they will to warming temperatures, which means previously defined habitats and ecosystems will be in flux. And, as mentioned above, a warming ocean does not mix as much with deeper waters, and so does not bring as much oxygen into the depths. These deep hypoxic zones are expanding, in part because phytoplankton in nutrient-poor waters decline, which in turn reduces the oxygen they produce during photosynthesis. Another warming-related deoxygenation scenario unfolds wherever sea ice and glacial ice are melting at higher rates and creating a layer of less saline water on the ocean surface. That layer reduces oxygenation of the salt water by the wind.

Deoxygenated dead zones from excessive nutrients being washed out to sea are better known than warming-related ones. Many of us have heard of the massive dead zone in the Gulf of Mexico due to the agricultural and urban runoff (fertilizer, sewage, etc.) arriving in the outflow of the Mississippi River. (The 2020 dead zone was approximately 6,700 square miles.) These nutrient-loading dead zones exist in many places around the globe, particularly around dense human population centers (and their rivers), and have doubled in number every ten years since the 1960s. Nutrients are essential for life, but too much nutrient-loading in aquatic ecosystems leads to runaway growth of algae and phytoplankton. These massive blooms become massive death zones as most available oxygen is consumed by the bacteria consuming the dead phytoplankton. Sunlight is blocked, water quality is diminished, and any unfortunate marine species caught in the zone either flee or suffocate.

Gulf of Mexico dead zone - note the Mississippi outflow creeping along the LA and TX coastlines

Surface ocean waters are already 30% more acidic than they were in pre-industrial times. The rate of acidification, according to IPSO, is “unparalleled in at least the last 300 million years.” If left unchecked, by the end of this century this rapid acidification will turn the oceans 150% more acidic than they have ever been since humans first walked the Earth. Rising temperatures and expanding death zones are serious and pervasive threats to marine life, but acidification may be far more deadly.

Think of acidification as eroding the foundation of life in the oceans. Plankton, corals, and of course familiar shellfish like oysters and clams all rely on an abundance of calcium carbonate in the water to form their shells. Increasing acidification reduces calcium carbonate, making it harder and harder for these organisms to survive, and it corrodes the shells that are formed. Once the bottom of the food chain starts dying off, so does everything that relies on it. Already there have been die-offs of Pacific Northwest oyster larvae, while pteropods (tiny, beautiful plankton known as “sea angels” and “sea butterflies”) there and in Antarctic waters are struggling to form complete shells. Pteropods are essential for the food web in the Southern Ocean, but may be erased from Antarctic waters by 2050.

Healthy pteropod shell on left, acidified pteropod shell on right - source: (left) Bednaršek et al. 2012;16 (right) Nina Bednaršek

Atmospheric CO2 concentration is currently at 419 ppm. It first reached 400 in 2013. Once it reaches 450-500 ppm, according to some predictions, acidic erosion of coral reefs is expected to outpace the corals’ ability to build new reef. Perhaps as soon as 2050 or so, many of the last reefs that haven’t succumbed to overfishing and pollution and warm-water bleaching will, in increasingly acidic waters, quickly turn from wondrous technicolor nurseries into slime-covered rubble.

“The terrifying reality of ocean acidification has only fully dawned on the scientific community in the last decade or so,” writes Peter Brannen in The Ends of the World, his book on previous mass extinctions: “Even more so than global warming, ocean acidification is what people who understand the fossil record, and who think about the future of the oceans, are most distressed by.”

Previous mass extinctions: % of extinctions on the y-axis are of marine animal genera, not species (for example, in the end-Permian, over 50% of genera were lost but about 85% of species went extinct) - source: CNX OpenStax

Taken together, the “deadly trio” of warming, deoxygenation, and acidification are rapidly reducing the complexity and productivity of all the planet’s oceans. Temperature, chemistry, nutrient flow, circulation, and oxygen supply are all out of whack, at the same time that marine ecosystems are being destabilized by pollution, overfishing, and habitat destruction. Entire food webs are being stressed and dismantled. Very few places in all the world’s oceans resemble what they have been for countless millennia before modern human activity. It is hard to overstate the sudden shock the oceans are experiencing, and even harder to imagine the consequences.

Except that we can imagine the consequences by looking at the fossil record (which mostly consists of marine fossils). Where each of the five previous mass extinctions occurs, so do the trio of extreme warming, deoxygenation, and acidification. Or as the 2013 IPSO report put it, “It is notable that the occurrence of multiple high-intensity stressors has been a pre-requisite for all the five global extinction events of the past 600 million years.” To be clear, we’re not in a mass extinction – if we were, the tent would be on fire and very few circus animals and clowns would be getting out alive – but we’re creating the ingredients for one. The main ingredient is CO2. The Earth has a carbon cycle which, simply described, emits CO2 into the atmosphere through volcanic activity, and subtracts CO2 by mixing it with calcium in the oceans. Eventually that calcium carbonate which settled into the ocean floor becomes limestone which millions of years later might become molten lava spewed out by a volcano, and so the cycle continues.

But this carbon cycle is very, very slow by human standards. (This is how slow it is: the calcium in the oceans comes from the wearing down of mountains by rain…) Our CO2 production is moving way too fast for the Earth to catch up anytime soon. CO2 levels have hovered around 200 to 280 ppm for the last few million years. We’ve pushed it up to 419 ppm in just a century or so, a timespan so short it’s not really measurable in geological terms. We pump out a hundred times more carbon dioxide from our power plants and trucks than is emitted by the planet’s volcanoes. One estimate suggests we’re injecting CO2 into the atmosphere about ten times faster than the rate of the end-Permian event, the worst mass extinction in Earth history, when more than 85% of ocean species went extinct.

I have written in a previous post that we seem much like an asteroid, given our sudden destructive arrival on the planetary scene. Perhaps, though, it’s more accurate to say we resemble a supervolcano. Some mass extinctions were brought on by continental-scale volcanic activity, spewing such vast amounts of carbon dioxide that, in the worst case – the end-Permian extinction – writes Peter Brannen, “the planet was rendered a hellish, rotting sepulcher, with hot, acidifying oceans starved of oxygen.”

So, having looked into the abyss, what do we do about all this? First, we have to acknowledge two things: 1) We live in difficult times which will become worse for us and especially for the next generation, but 2) we absolutely have time and the capacity to avoid a mass extinction. (We need to develop the will to avoid it soon, though, so that we still have the time and capacity.) There will be plenty of grieving to do along the way, but as Elizabeth Rush says in a beautiful, sharp essay in the current issue of Orion, “the only way to survive grief is to care for what remains with even more heart than before.”

So, to improve the fate of the oceans (and us), we manage all fisheries across the globe thoroughly, and in the context of the additional pressures fish populations face from the deadly trio; we go upstream to stop unnecessary and harmful plastic production; we make immediate and large-scale reform of agriculture and industry to control runoff of nutrients and other pollution; and we initiate massive restoration projects of mangrove forests, kelp forests, and coral reefs wherever possible.

Mostly, though, we need an immediate drawdown of CO2 production to limit future warming and deoxygenation and acidification in the oceans, and we need a plan to reduce the impact of the ocean warming that’s already occurred. That last concern is where this week’s Good Idea comes in.

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A Good Idea: Marine Permaculture

What if one large-scale innovative solution worked to reduce all three of the deadly trio all at once? Imagine a simple technology that brings cooler, less acidic deep water to the surface. What if it also increased nutrient flow to feed plankton and thus the entire marine food web? What if it also provided crucial habitat for small fish, which provided food for larger fish and apex predators like tuna and sharks? What if it provided food and fertilizer for humans as well?

This is the dream of marine permaculture. Imagine offshore kelp farms – “floating ocean forests” – growing from frames sunk about 80 feet below the surface and connected to pumps a few hundred feet deep. The pumps, powered by wave action on buoys, pull cold deep waters up to replace warm waters above, essentially mimicking the natural upwelling process that has sustained ocean life for untold millions of years. In recent decades, upwelling has slowed as surface waters have warmed, making them less likely to sink CO2 and oxygen into the depths.

Imagine each these built arrays scaled up to nearly half a square mile. The result, if successful, would create novel marine ecosystems, kelp forests not anchored to the sea floor but farmed from these arrays, each providing a nursery for pelagic (open ocean) fish that feed on the plankton blooming in the nutrient-rich water brought up from the deeps. Enriching the bottom of the food chain quickly enriches the top too, which means these marine permaculture arrays (MPAs) could help restore some local fisheries. Meanwhile, the kelp forests, which are the planet’s most productive ecosystems – the kelp can grow up to a foot and a half per day – can be harvested to provide food supplements, fish food, fertilizer, and even biofuels.

Imagine a million of these MPAs scattered around the globe, drawing down oceanic CO2, building up fisheries, feeding people and sustaining an economy built on improving the world we’ve profoundly disturbed.

Most of the CO2 emitted by humans is sequestered in the top 500 feet of the oceans. That means first that the coral reefs and mangroves and natural kelp forests and all the near-shore fishing waters are taking the brunt of a warming, acidifying, deoxygenating ocean. But it also means that if we can accelerate the movement of CO2 from the upper layer down into the depths we’ll be on the way to rejuvenating the most vital part of the oceans, including the habitats that are crucial to biodiversity and our own needs. Cutting back on our emissions is vital, but the timeframe for the ocean to respond on its own to reduced emissions by improving upwelling is too long for our needs. We’ll need to speed things up.

There are plenty of caveats here. First, the technology is not a replacement for actual habitat restoration (mangroves, kelp forests, corals) in shallow waters. Nor is it a way to greenwash or justify status quo CO2 emissions. This is a tool to reduce the harm while we are simultaneously changing civilizational behavior. And though the force behind the technology, Dr. Brian Von Herzen and the Climate Foundation, has been working on the concept for many years, it’s still in small-scale demonstration mode (currently in the Philippines). It’s easy to imagine the technical difficulties of designing equipment required to last in the ocean for years at a time, for example, and then there’s always the problem of funding. And we still don’t know if artificial upwelling like this might actually work too well in some places and create algal blooms followed by deoxygenation.

I’m not a fan of geoengineering our way out of the Anthropocene. There are crazy ideas, like injecting aerosols into the atmosphere to block sunlight, and I often wonder why we would ask the kinds of people who pioneered the problems to pioneer the solutions… In many of these scenarios, mistakes will probably be incredibly difficult to fix, and will likely increase suffering for both humans and other species. Marine permaculture, if it can be made to work at scale, feels like an exception to the hubris of geoengineering, though. I don’t like that the idea isn’t the kind of solution that everyone can participate in, and that we’d have to rely on the often slow and inefficient powers-that-be to build and operate these solutions offshore, out of the public eye. But the promise of the concept is extraordinary, and deserves large-scale funding and experimentation.

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Looking Into the Abyss - Part Two

6/3/21

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