More abused than used - A special report on the sea

But the sea can be harnessed for energy, and to store carbon

The Economist print edition, Dec 30th 2008

Sad were my thoughts that anchor'd silently

Of the dead waters of that passionless sea

Unstirr'd by any touch of living breath:

Silence hung over it, and drowsy Death,

Like a gorged seabird, slept with folded wings

On crowded carcasses—sad passive things

Thomas Hood

OF ALL the blights afflicting the sea, carbon dioxide is just one. Man has used the oceans as a dustbin for far too long.

The bin would be even fuller and fouler had the London dumping convention not been signed in 1972, but the sea is still hideously polluted. Over 60m litres of oil run off America’s streets and via rivers and drains find their way into the oceans each year. Through sewage and medical waste, antibiotics and hormones enter the systems of seabirds and marine mammals. Mercury and other metals turn up in tuna, orange roughy, seals, polar bears and other long-lived animals.

So does radioactive effluent, whether from Sellafield, a nuclear reprocessing plant on the west coast of England, or the scrapyards of Russia: between 1958 and 1992, the Arctic Ocean was used by the Soviet Union, or its Russian successor, as the resting-place for 18 unwanted nuclear reactors, several still containing their nuclear fuel. All over the world, oil spills regularly contaminate coasts.

More alarming still is the plague of plastic. The UN Environment Programme reckoned in 2006 that every square kilometre of sea held nearly 18,000 pieces of floating plastic. Much of it was, and is, in the central Pacific, where scientists believe as much as 100m tonnes of plastic jetsam are suspended in two separate gyres of garbage over an area twice the size of the United States.

About 90% of the plastic in the sea has been carried there by wind or water from land. It takes decades to decompose or sink. Turtles, seals and birds inadvertently eat the stuff, and not just in the Pacific. A Dutch study of 560 fulmars picked up dead in countries around the North Sea found 19 out of 20 had plastic in their stomachs—an average of 44 pieces in each. Moreover, when plastic breaks up it attracts toxins, which become concentrated in barnacles and other tiny organisms and thus enter the marine food chain.

Some action is being taken. Volunteers work to catch at least some of the plastic pellets—hundreds of millions each week—that are washed out to sea by the Los Angeles river. Oil spills should become rarer after next year, when all single-hulled ships will be banned.

Efforts are also being made to prevent the spread of invasive species through the taking on and discharging of ships’ ballast water. The worry is that creatures like the Chinese mitten crabs that have been introduced to San Francisco Bay (along with 175 other alien species), for instance, may spread to other places, overwhelming the native varieties. A “global ballast partnership” hopes to reduce this risk. Similarly, a UN convention may soon ban the use of tributyltin, a highly toxic chemical once added to the paint used on almost all ships’ hulls, in order to kill algae and barnacles.

Shipping itself is a huge cause of pollution. The International Maritime Organisation said last year that sea transport accounted for only 2.7% of total emissions in 2007. But leaks last year from an unpublished report by the Intergovernmental Panel on Climate Change put the figure at nearly 4.5%, about twice as much as the share of aviation. And, though shipping is now in decline, by 2020 emissions are expected to rise by 30%. Since ships burn bunker oil, the dirtiest of fuels, that means not just more CO₂ but also more “particulate matter”, which, according to a controversial paper published in 2007, is already responsible each year for about 60,000 deaths from chest and lung diseases, including cancer. Most of these occur near coastlines in Europe, East and South Asia.

Various measures could reduce this pollution. Some ships are already going slower, to save fuel; some are also burning cleaner, low-sulphur oil; some journeys are becoming unnecessary, as rising costs make it unprofitable to send food, for instance, from America to be processed in Asia and then carried back to where it came from. And shipping could, and should, be included in all carbon-trading schemes, notably the EU’s.

In principle, it should also be possible with concerted action to arrest, if not reverse, another growing problem, the rise of slime. This is a term coined by Jeremy Jackson of the Scripps Institution of Oceanography at the University of California in San Diego, here used as shorthand for the increasingly frequent appearance of dead zones, red tides and jellyfish. All these seem to have occurred naturally for centuries, and still do. Red tides, for example, regularly form off the Cape coast of South Africa, fed by nutrients brought up from the deep, and off Kerguelen island in the Southern Ocean. Nowadays, though, most are associated with a combination of phenomena including overfishing, warmer waters and, often, the washing into the sea of farm fertilisers and sewage.

Floundering towards the primeval ooze (Bluegreen)

In shallow coastal waters, most of the fish tend nowadays to have been caught. As the larger species disappear, so the smaller ones thrive. These smaller organisms are also stimulated by nitrogen and phosphorous nutrients running off the land. The upshot is an explosion of growth among phytoplankton and other algae, some of which die, sink to the bottom and decompose, combining with dissolved oxygen as they rot. Warmer conditions, and sometimes the loss of mangroves and marshes, which once acted as filters, encourage the growth of bacteria in these oxygen-depleted waters.

The result may be a sludge-like soup, apparently lifeless—hence the name dead zones—but in truth teeming with simple, and often toxic, organisms. These may be primitive bacteria whose close relations are known to have thrived billions of years ago. Or they may be algae which colour the sea green, like the carpet of weed in Qingdao that nearly brought the sailing to a halt in last year’s Olympic games. Sometimes they colour it red, but this is less the wine-dark sea of Homeric fame than the red-brown waters of Florida’s Gulf coast—or Chesapeake Bay, or the Adriatic, or Hiroshima Bay, or the inlets of New South Wales. In such places red tides tend to form, some producing toxins that get into the food chain through shellfish and rise up to kill bigger fish (if there are any left), birds and even seals and manatees. Occasionally, the poisons waft ashore to fill clinics with coughing patients.

In other places, such as Australia, Spain and Namibia, the plague brings a different form of simple, invertebrate life, the jellyfish. As other fish disappear, these plankton-eating organisms move in, to the despair of swimmers and the consternation of fishermen. Some trawlermen, however, have adapted, abandoning more conventional catches in favour of jellies. Nearly 500,000 tonnes of these creatures were caught in 2006, most of them in Asia and destined to be eaten in soup or salads by Chinese or Japanese.

Red tides and similar blights do not necessarily last long, nor do they cover much of the surface of the sea. But they are increasing in both size and number: dead zones have now been reported in more than 400 areas. And increasingly they affect not only estuaries and inlets, but also continental seas such as the Baltic, the Kattegat, the Black and East China Seas and the Gulf of Mexico. All of these, point out Robert Diaz and Rutger Rosenberg, authors of a report last August inScience, are traditional fishing grounds.

The spread is exponential, they say. The direction is just as worrying. The winners in these newly polluted, over-exploited, oxygen-starved seas are simple, primitive forms of life, whereas the losers are the ones that have taken aeons to develop. Algae, bacteria and jellyfish thrive while fish, coral and sea lions die. It is, wrote Kenneth Weiss of the Los Angeles Times in 2006, as if “evolution is running in reverse”. And though a few ideas have been put forward to reduce fertiliser runoffs—a cap-and-trade system for nitrogen polluters, similar to those for European carbon polluters, for instance—it is hard to see a solution. Not enough is known about the causes of the problems, and too many of the agents are far removed from the scene of the event.

Realms of ocean, fields of air

Have all marine resources been abused or exploited to the point where the sea can do nothing more for man? No. It still has much to offer, especially in helping to solve one of the very problems from which it suffers itself, CO₂-induced global warming.

The most beguiling idea is to speed up the rate at which carbon is taken out of the atmosphere and into the sea: increase the concentration of CO₂ in the oceans by 0.5% and the concentration in the atmosphere returns to pre-industrial levels. The trouble is the sea then becomes an acid bath. Even so, some people think it can still help.

Not quite what Homer meant

One popular idea is to use iron to fertilise the sea, causing the same explosions of phytoplankton that often precede dead zones and red tides. If this were to happen in the deep sea, the carbon absorbed by the plankton through photosynthesis would descend to Davy Jones’s locker for several hundred years. It was this thought that caused John Martin, once head of the Moss Landing Marine Laboratories in California, to declare, “Give me half a tanker of iron, and I’ll give you an ice age.” Laboratory experiments suggested that every tonne of iron sprinkled on the sea would remove 30,000-110,000 tonnes of CO₂ from the air.

Several companies are now trying to put this into practice and thus make money by selling carbon credits. One trouble, though, is that very little of the carbon drawn into the sea by plankton sinks far enough down before it is eaten by other plankton and recycled into the atmosphere. Another drawback is that the side-effects are largely unknown and potentially horrible if, for example, a “weed” species were to take advantage of a changed ecosystem. At best this scheme offers a small and temporary benefit.

Two other ideas are more promising. One is to capture CO₂ and store it under the seabed. David Goldberg and Taro Takahashi of Lamont-Doherty believe that nearly 150 years’ worth of the United States’ CO₂ production could be injected into 78,000 sq km of subsea rock off western North America. The basalt and the CO₂would react with each other, reducing the scope for leaks, which would be further diminished by the blanket of sediment that covers the ocean floor in that area.

Though it is harder to pump CO₂ into saline aquifers or disused oil wells in the sea than on land, the idea is still attractive, and certainly less risky than another proposal, which is simply to dump the captured CO₂ on the floor of the deep ocean, where pressure and temperature would keep it liquid and well away from the atmosphere. Currents, however, might stir it more than expected, and it would react with the water above it. This might lead to the formation of hydrates, which could be unstable if disturbed, and it might also lead to a lake of CO₂ on the ocean floor which would be acidic at the margins.

An altogether different, and better, idea is to use the sea to generate green, CO₂-free energy. The sea offers three ways of doing this. The winds—whose energy derives from the sun, via the convection of air currents—are increasingly harnessed by windmills both on- and offshore. The advantage of having them at sea is that they can occupy unused open space and ruin fewer views than on land. But wind power is uncertain, sometimes providing too much electricity and sometimes too little.

That is true of wave power, too, which also gets it energy from the sun, in this instance via the winds. The first commercial wave-power farm started producing electricity last year off Aguçadoura in northern Portugal, using one of several available designs, this one developed in Scotland. Its first aim is to provide enough power for 1,500 homes, and ultimately nine or ten times as many. Rival technologies are being developed in Canada, the United States and elsewhere, and some are operating, for example, off Hawaii and the west of Scotland.

A better bet, at least in terms of continuity of production, is tidal power, whose energy comes from the gravitational pull of the sun and moon. A few tidal projects, such as the 42-year-old barrage at Rance in France, operate like traditional hydro schemes, in which tidal water simply rushes through turbines. Most others use the principle of an underwater windmill whose rotors are turned by the tide. The leading test centre is in Orkney, off north-east Scotland, where the winds blow and the tides race as in few other places.

One trouble with tidal power is the difficulty of servicing underwater installations. Another is ensuring that they do not get carried away in storms: Orkney’s climate may yet prove too wild. And, like all marine energy, tidal power may be easiest to produce in places where it is least needed—far away from centres of population, where connections to the national grid would be expensive. New York, though, could be an exception: a tidal scheme is now being tested in the East River. South Korea’s Sihwa Lake tidal plant, planned to open this year, will also serve a neighbouring city, Ansan, with 690,000 people.

Copyright © The Economist Newspaper Limited 2008. All rights reserved

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