It is reasonable to conclude (even if fisheries managers have not normally done so) that industrial fishing has caused a progressive loss of overall living marine biomass. And the time scale and pattern of expansion of commercial fishing and whaling offers a closer parallel to the recent CO2 rise than does the pattern of fossil fuel burning. This is an important observation. This is not to say that fossil fuel emissions are having zero impact on the atmosphere, but it suggests that the impact of missing sea life might be greater. 

Records of the recent CO2 rise and the acceleration of fuel burning present a surprisingly poor correlation. Prior to 1800, CO2 levels in the Earth’s atmosphere had stabilized at approximately 280 ppm for a period of at least 10,000 years. The recent rising trend in CO2, which has climbed steadily, began at the turn of the nineteenth century, 60 years before the beginning of the industrial revolution (1860). Scientific research indicates that a substantial CO2 rise occurred before 1860.

This clue was not missed by the scientists. But it presents a perplexing question, because a suspected cause clearly must precede its presumed effect. Therefore, there must have been another human-induced source of CO2 to the atmosphere prior to 1860. In the search for the source of excess CO2 pre-1860, scientists have concluded that it must have been the result of land-clearing practices and wood burning at the time. Therefore, at some point, the official explanation for the rise in atmospheric CO2 changed from “fossil fuel emissions” to “fossil fuel emissions plus land clearing.”

But the absolute effect of land-clearing on CO2 levels remains difficult to pinpoint, since areas where trees re-grow and wood accumulates act as carbon sinks, as opposed to “old growth” forests which seem to exist in an approximate carbon balance with the atmosphere. Some of our changes in land use, for example the culture and artificial fertilization of certain crops, have resulted in faster carbon uptake than the natural undisturbed vegetation would have accomplished. Scientists have increasingly discovered that terrestrial ecosystems, even greatly human-altered ones like North America, work surprisingly well as carbon sinks. Many trees now grow more quickly and reach larger sizes than they did in the past. As atmospheric CO2 has risen, the rate of carbon uptake by land plants has tended to increase too.

If the land acts as a net carbon sink now, might it not also have worked this way between 1800 and 1860? If so, we can no longer be certain that changes in land use between 1800 and 1860 were capable of causing the CO2 rise during that time. Historical records of land use are being studied to try and answer this question, but this seems unlikely to reveal anything that convincingly implicates changing land-use practices as the source of excess CO2 early in the nineteenth century. If not, then another CO2 source must be found. Something else must have happened between 1800 and 1860 that caused CO2 to accumulate in the atmosphere.

Commercial fishing* flourished greatly between 1800 and 1860, and it was well established before that time. As I have argued, our understanding of the workings of natural systems should now allow us to realize that the massive bulk extraction of sea life had the potential to induce a rising trend in atmospheric CO2. (*In this discussion, “fishing” means all sea life extraction; besides catching fish it includes whaling, sealing and the killing of seabirds.)

Unsuspected for centuries, it now seems certain that prolonged, large scale fishing has always had the potential to gradually sap the strength of sea life at all levels. We have tended to consider the effects of fishing only very superficially, measuring nothing beyond the immediately observable effects on our target species. A subtle “biological forcing” or active control of plankton growth by larger animals, and the effects of eroding this, has never been considered. But major resistance to this concept can be expected, regardless of how well the case is argued, because it explodes our most cherished myth about the ocean: that we can have our fish and eat them too…in perpetuity.

Sea life today is a mere shadow of what existed 500 - 1000 years ago, and the animal-enhanced strength of the “biological carbon pump” has been reduced accordingly. But underlying ocean currents have remained steady. Therefore it becomes plausible that the amount of CO2 exhaled by the sea has surpassed the amount inhaled for at least the past two centuries.

Any human activity that could have a measurable impact on global atmospheric CO2 levels must have been well established before 1800. Considerable time would be needed for the global system to be pushed off-balance, since many buffering components are built into all living systems that tend to maintain stability. Therefore, the force that caused the global CO2 rise had gathered enough strength to overwhelm built-in stabilizing features of the biosphere by the year 1800, since that is when the balance first started to tip. Commercial fishing was well developed before 1800. Many populations of marine animals had been severely depleted, some to extinction, before that date. The largest creatures were severely affected: lost were the great auk, Steller's sea cow, and the Atlantic gray whale, and driven to near oblivion were the walrus and all other “great” whales. The systematic human slaughter of sea life had been under way for centuries when CO2 first began to inch upwards, and even then, at the beginning of the nineteenth century, fishermen were voicing concerns about the declining numbers of fish in the sea.

The timing of the development of the fishing industry is therefore better correlated to the record of the recent CO2 rise, than is the industrial revolution and subsequent fossil fuel burning patterns. I have described the human extraction of sea life as “relentless,” but while studying the details of the CO2 record, I realized that for a short period of time during this “experiment,” humans did relent, and fishing pressure was released to a significant degree. There is an unexpected “glitch” in the CO2 record for the 20th century, a hesitation in the steady steeply rising curve. At one point, for a few years, even a small downturn was recorded. The timing of this unexpected reversal of the pattern coincides with World War II, a time of increased fossil fuel emissions, but, interestingly, also a time of markedly reduced fishing activity. Fishing, whaling and sealing in the North Atlantic Ocean came to a virtual halt during the war. (Was the “biological carbon pump” in the sea therefore able to recoup a bit of its former strength and momentum while the fishermen were otherwise engaged, fighting the war?)

“Between 1935 and 1945 the atmospheric CO2 concentration was constant, or even declined slightly. The reason for this is unknown.” ₃

Large increases in fish numbers were apparent in the North Sea and elsewhere by the end of the war. The biological activity that built those larger fish stocks seems possibly to have been the same activity that briefly drew down more CO2 from the atmosphere, and caused the “glitch” in the graph. Enough life remained in the sea in 1939 to rally and realize a noticeable gain in a few years. Like a “new growth forest,” re-growing what was cut down, a fish population recovering from a depleted state can act as a carbon sink, and also as a catalyst for faster plant growth. During the wartime break from fishing, marine life in the Atlantic Ocean “inhaled” CO2 deeply, rapidly rebuilding fish stocks, and it seems from the atmospheric record that marine CO2 uptake briefly equalled CO2 exhaled by the ocean in those years.

Things are different now. Sixty fishing years later the ocean is in much weaker condition. We have recently tried easing the pressure on individual fish stocks only to find that they are extremely slow to “recover.” To allow the ocean dwellers to realize a gain, we will need to relieve all fishing pressure, not just shift our demands from one species to another.

Humans are brainy, a powerful, egotistical, and self-assured species, but how profoundly mistaken might we yet be about the subtle nature of the damage our actions are inflicting on the biosphere? Despite the current dogma about fossil fuel emissions causing CO2 to rise, scientific understanding of global carbon cycling remains very crude and sketchy, a most imprecise art. Do we stand any real chance of preserving health and long-term stability for ourselves if we only reduce fuel-burning, while doggedly continuing to consume great quantities of “sustainably-caught” ocean fish?
 
The growth of sea life is unarguably the largest force capable of removing CO2 from the air, and the ocean is also the largest global source of carbon dioxide. Over 90G (“gigatons” = billions of tons) of carbon have been estimated to be released to the air annually by the ocean, in comparison to about 6 G released by all fuel-burning. The 90G released by the ocean is always assumed to be balanced by 90G (or more) absorbed into the surface water. The key word is “assumed.” However, if the active carbon-uptake capacity of sea life were lowered to a point where net ocean carbon intake was reduced by even 10%, then the ocean would tend to make an annual net deposit of 9G of carbon into the atmosphere, outweighing the total contribution from fuel emissions.

How much has been lost? Consider marine life a few centuries ago:

“It is probably impossible for anyone now alive to comprehend the magnitude of fish life in the waters of the New World when the European invasion began. It may have been almost equally difficult for the early voyagers. According to the record they have left for us, they seem to have been overwhelmed by the glut of fishes.

In 1497, John Cabot set the tone by describing the Grand Banks as so ‘swarming with fish [that they] could be taken not only with a net but in baskets let down [and weighted] with a stone.’ On the lower St. Lawrence in 1535 Jacques Cartier reported that ‘This river...is the richest in every kind of fish that anyone remembers ever having seen or heard of; for from its mouth to its head you will find in their season the majority of the varieties of salt- and fresh-water fish...great numbers of mackerel, mullet, sea bass, tunnies, large eels...quantities of lampreys and salmon...[in the uper River] are many pike, trout, carp, bream and other fresh-water fish.’” (Farley Mowat, in “Sea of Slaughter,” 1984)₄

People may never grasp the scale of destruction we have wrought upon sea life. But a prominent marine scientist recently described what he has seen during his career:

“Essentially, if we compare the amount of fish, the biomass of fish before the introduction of industrial fishing in various parts of the world, what is left, the relationship is about 1 to 10 roughly; that is you go into the Gulf of Thailand, you catch if you’re 20 kilograms per hour with a standard trawl. Then in the 60s you would catch 200, 300 kilogram per hour with a standard trawl so you have a fact of 10. And this fact of 10, that’s what you find in a lot of fisheries...For things like seabirds and sea turtles and large marine mammals, we probably have much less than 10%, perhaps 1%, perhaps even less. Turtles, it’s a disaster. Some species of marine mammals are extinct.” (Daniel Pauly, 1998)

Fish and larger sea animals have undeniably been decimated, but has the growth of ocean plankton actually slowed too, as a result of some degree of lost animal-forced fertilization? If so, there should be direct evidence of this. As stated earlier, however, an accurate estimation of the growth rate of the tiny floating plant cells cannot be made by simply counting them, because dramatic shifts have occurred in the small animals (zooplankton) that feed on the plants. Zooplankton abundance off California has shown a stunning 70% decline since the 1950’s. Dramatic declines in zooplankton numbers have also been witnessed in the North Atlantic Ocean, but, unfortunately, for most of the world ocean this type of data does not even exist.

The plankton question can be studied in other ways. Scientists can use “proxy” records to study the past. For example, inferences are made about such things as past climate conditions by studying old growth rings in trees. Humans with plankton nets are not the only ones who keep ocean records, because the natural predators of plankton keep them too. Bowhead whales in the Bering Sea, massive plankton-feeding mammals that can live 200 years, have recently been discovered to be keeping records of ocean fertility (primary productivity) in the growth pattern of their baleen.

"We've actually looked at bowhead whales to learn how ocean productivity has changed over the past 50 years. It turns out that whales are a unique window into the past. Bowhead whales overwinter in the Bering Sea, where they feed on zooplankton. Zooplankton are the first consumers of phytoplankton, the small plants that are the first rung of the ocean food chain and an important indicator of productivity in the ocean. These whales consume vast amounts of zooplankton. And also because they eat the zooplankton in the fall of the year, the zooplankton have themselves consumed and stored the energy of a large percentage of the ocean's phytoplankton productivity. This productivity can be measured by using isotope ratios in the baleen of whales. Without getting too scientific, I measured the type of carbon in whale baleen. Since you are what you eat, the carbon in this case is from the consumption of plankton. The changes in carbon type in whale baleen reflects the abundance of plankton in any given year and can be used as an index to changes in ocean primary productivity…

We've studied baleen taken from recently harvested whales and from whales harvested in the 1960s and the 1970s. And by using the animals from the 1960s we can look all the way back to 1946. From this we have developed a record of phytoplankon productivity in the Bering Sea all the way back to 1946. The story it tells is amazing because the whale baleen reflects phytoplankton productivity quite well. The record shows that from 1946 to 1963 everything went along fairly smoothly at a relatively high rate of productivity. And then in the mid-1960s it increased and peaked at around 1965. Then ocean plankton productivity began to decline, and since the mid-1970s it has gone down and down and down. The last samples we have from 1994, 1995 and 1996 show the lowest primary productivity in the Bering Sea over this 50-year period.

The implication is that the Bering Sea has decreased in productivity by 35 to 40 percent since its peak in 1965 or so. Now a 40 percent decline in the carrying capacity of the ecosystem is going to have profound effects on the top consumers, and I think that is in part what we are seeing now. Salmon are near the top of the consumer chain. Steller sea lions are at the top and they eat salmon and other fish. It implies that there is indeed a bottom-up change that is occurring, and it may have contributed to the decline of these mammals and other Bering Sea species."₅

A large decrease in ocean productivity, having “profound effects” on top consumers? Why would this change not be expected to also have a “profound effect” on the ocean-atmospheric CO2 balance?

The productivity decline in the Bering Sea is usually attributed to a slackening of ocean currents and of “physically forced” fertilizer mixing patterns. However, a similar pattern of decline extends far beyond the Bering Sea. The growth of marine animals has also slowed in ocean areas where water is constantly, reliably, mixed by tidal action. This is clearly seen off the east coast of North America, where the Bay of Fundy and Georges Bank, once exceptionally rich and productive fishing grounds, are showing the same patterns of declining food production.

Reflections of oceanic primary productivity embodied in live animals go beyond whales. Shorter-lived, but more common, fish record the same essential information in their bodies. As plankton productivity and food availability have declined, ocean fish in general are growing more slowly and becoming thinner. Long-term changes recorded in fish stocks world-wide agree with the evidence discovered in the baleen of the bowhead whales: plankton production, and overall “marine productivity,” has been gradually slipping.

From an ocean that once produced cod of six feet in length and weighing 200 pounds, one small, emaciated codfish (since she now typifies her kind) may hold more useful information about trends in marine “primary productivity” than all the mathematical models developed by fisheries scientists. (Accepted models have failed to explain and to predict many recent changes, I suspect, because the biological control of plankton growth has never been included. Why not? Because this is unthinkable: if true, it discredits the very foundation of the “science of sustainable fisheries.” But…fish eggs do float…and whales do defecate at the surface…and…)
 
If we continue fishing, now our cherished tradition, humans will eventually transform the sea into a closer approximation of Kenneth Hsu’s “Strangelove Ocean” than the one we have today. Accelerating instability in natural systems is predictable, and rapid, unpleasant changes will be widespread. Scientists warn that “mass extinctions” are already occurring, but the majority still seems oblivious to this reality, and to the basic principles that apply to sustaining living systems.

Millions of years from now, perhaps a core sample of marine sediment will be studied. In a deep layer, the remains of the original “Strangelove Ocean” will still be preserved, a thin band of evidence attesting to the massive loss of animal life during the dinosaur extinction. Somewhat closer to the surface, the core sample will reveal what happened in another blink of time, say from 1500 to 2500 A. D. The signature will be there of the current mass extinction and of the formation of a second “Strangelove Ocean,” characterized, like the first, by unusually low marine primary productivity. Coincident with each mass extinction will be a time of unusual plankton blooms, plus unusually high atmospheric CO2. Similar to the earlier pattern, settled above the second “Strangelove Ocean” band of sediment will be a reflection of the ensuing millenia, in which the core sample will contain evidence of a gradually renewed abundance and diversity of large sea animals. Within this, the character of both ocean plankton and the atmosphere will regain qualities that have always been associated with a strong fish presence in the sea, and that once moderated a pleasant climate for humans. Fertility and stability will both be seen to rise with the resurgence of the living biomass of fish. The most unlikely element in this scenario, of course, is that there will be any humans alive at that future time to study the ocean’s fossil record.
 
References
1. Michael Fasham. 1993. Modelling the Marine Biota. In Heimann, Martin (ed). The Global Carbon Cycle. NATO Advanced Science Institiutes Series. Springer-Verlag
2. Gary Shaffer. 1993. Effects of the Marine Biota on Global Carbon Cycling. (also in Heimann, 1993.)
3. Vincent R. Gray. 1999. Atmospheric Carbon Dioxide. Greenhouse Bulletin No. 120 ( http://www.microtech.com.au/daly/bull120.htm )
4. Farley Mowat. 1984. Sea of Slaughter. Bantam Books.
5. Donald Schell, quoted from “Oral History...Straight From the Whale’s Mouth” ( www.discovery.com 2001) 

(Posted October 13, 2004, this is a revised version of the original "Strangelove Ocean" article by Debbie MacKenzie, which was published here in 2001 and included more details of the carbon science.)

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