The devolution of the seas

A visitor to the oceans at the dawn of time would have found an underwater world that was mostly lifeless. Eventually, around 3.5 billion years ago, basic organisms began to emerge from the primordial ooze. This microbial soup of algae and bacteria needed little oxygen to survive. Worms, jellyfish, and toxic fireweed ruled the deep. In time, these simple organisms began to evolve into higher life forms, resulting in the wondrously rich diversity of fish, corals, whales, and other sea life one associates with the oceans today.

Yet that sea life is now in peril. Over the last 50 years – a mere blink in geologic time – humanity has come perilously close to reversing the almost miraculous biological abundance of the deep. Pollution, over-fishing, the destruction of habitats, and climate change are emptying the oceans and enabling the lowest forms of life to regain their dominance. The oceanographer Jeremy Jackson calls it “the rise of slime”: In effect, humans are eliminating the lions and tigers of the seas to make room for the cockroaches and rats.

Destruction on this level will cost humans dearly in terms of food, jobs, health and quality of life. It also violates the unspoken promise passed from one generation to the next of a better future.

 

The Great Pacific Garbage Patch

The oceans’ problems start with pollution, the most visible forms of which are the catastrophic spills from offshore oil and gas drilling or from tanker accidents. Yet as devastating as these events can be, especially locally, their overall contribution to marine pollution pales in comparison to the much less spectacular waste that finds its way to the seas through rivers, pipes, runoff, and the air. For example, trash – plastic bags, bottles, cans, tiny plastic pellets used in manufacturing – washes into coastal waters or gets discarded by ships large and small. This debris drifts out to sea, where it forms epic gyres of floating waste, such as the infamous Great Pacific Garbage Patch, which spans hundreds of kilometres across the North Pacific Ocean.

The most dangerous pollutants are chemicals. The seas are being poisoned by substances that are toxic, remain in the environment for a long time, travel great distances, accumulate in marine life and move up the food chain. Among the worst culprits are heavy metals such as mercury, which is released into the atmosphere by the burning of coal and then rains down on the oceans, rivers, and lakes; mercury can also be found in medical waste.

Of special concern are those known as persistent organic pollutants. Studies by the US Environmental Protection Agency have linked exposure to persistent organic pollutants to death, disease, and abnormalities in fish and other wildlife. These pervasive chemicals can also adversely affect the development of the brain, the neurologic system, and the reproductive system in humans.

Then there are the nutrients, which increasingly show up in coastal waters after being used as chemical fertilisers on farms, often far inland. Fertiliser that makes its way into the water causes the explosive growth of algae. When these algae die and sink to the sea floor, their decomposition robs the water of the oxygen needed to support complex marine life. Some algal blooms also produce toxins that can kill fish and poison humans who consume seafood.

The result has been the emergence of what marine scientists call “dead zones” – areas devoid of the ocean life people value most. The high concentration of nutrients flowing down the Mississippi River and emptying into the Gulf of Mexico has created a seasonal offshore dead zone larger than the state of New Jersey. An even larger dead zone – the world’s biggest – can be found in the Baltic Sea, which is comparable in size to California. The estuaries of China’s two greatest rivers, the Yangtze and the Yellow, have similarly lost their complex marine life. Since 2004, the total number of such aquatic wastelands worldwide has more than quadrupled, from 146 to over 600 today.

 

Teach a man to fish – then what?

Another cause of the oceans’ decline is that humans are simply killing and eating too many fish. A frequently cited 2003 study in the journal Nature by marine biologists Ransom Myers and Boris Worm found that the number of large fish – both open-ocean species, such as tuna, swordfish, and marlin, and large ground-fish, such as cod, halibut, and flounder – had declined by 90 per cent since 1950. The finding provoked controversy among some scientists and fishery managers. But subsequent studies have confirmed that fish populations have indeed fallen dramatically.

In fact, if one looks back further than 1950, the 90 per cent figure turns out to be conservative. As historical ecologists have shown, we are far removed from the days when Christopher Columbus reported seeing large numbers of sea turtles migrating off the coast of the New World, when 3-metre sturgeon bursting with caviar leaped from the waters of the Chesapeake Bay, when George Washington’s Continental army could avoid starvation by feasting on swarms of shad swimming upriver to spawn, when dense oyster beds nearly blocked the mouth of the Hudson River, and when the early-20th-century American adventure writer Zane Grey marvelled at the enormous swordfish, tuna, wahoo, and grouper he found in the Gulf of California.

Today, the human appetite has nearly wiped those populations out. It’s no wonder that stocks of large predator fish are rapidly dwindling when one considers the fact that one bluefin tuna can go for hundreds of thousands of dollars at market in Japan. High prices make it profitable to employ planes and helicopters to scan the ocean for the fish that remain; marine animals don’t stand a chance.

Nor are big fish the only ones that are threatened. In area after area, once the long-lived predatory species, such as tuna and swordfish, disappear, fishing fleets move on to smaller, plankton-eating fish, such as sardines, anchovy and herring. The overexploitation of smaller fish deprives the larger wild fish that remain of their food; aquatic mammals and sea birds, such as ospreys and eagles, also go hungry. Marine scientists refer to this sequential process as fishing down the food chain.

The problem is not just that we eat too much seafood; it’s also how we catch it. Modern industrial fishing fleets drag lines with thousands of hooks miles behind a vessel, and industrial trawlers on the high seas drop nets thousands of metres below the sea’s surface. In the process, many untargeted species, including sea turtles, dolphins, whales, and large sea birds (such as albatross) get accidentally captured or entangled. Millions of tonnes of unwanted sea life is killed or injured in commercial fishing operations each year; indeed, as much as a third of what fishermen pull out of the waters was never meant to be harvested. Some of the most destructive fisheries discard 80 to 90 per cent of what they bring in. In the Gulf of Mexico, for example, for every kilo of shrimp caught by a trawler, over three kilos of marine life is thrown away.

 

Destroying the Earth’s final frontier

Hidden from view but no less worrying is the wholesale destruction of deep-ocean habitats. For fishermen seeking ever more elusive prey, the depths of the seas have become the earth’s final frontier. There, submerged mountain chains called seamounts – numbering in the tens of thousands and mostly uncharted – have proved especially desirable targets. The steep slopes, ridges, and tops of seamounts in the South Pacific and elsewhere are home to a rich variety of marine life, including large pools of undiscovered species.

Today, fishing vessels drag huge nets outfitted with steel plates and heavy rollers across the sea floor and over underwater mountains, more than a kilometre deep, destroying everything in their path. As industrial trawlers bulldoze their way along, the surfaces of seamounts are reduced to sand, bare rock, and rubble. Deep cold-water corals, some older than the California redwoods, are being obliterated. In the process, an unknown number of species from these unique islands of biological diversity – which might harbour new medicines or other important information – are being driven extinct before humans even get a chance to study them.

 

In hot water

As if all this were not enough, scientists estimate that man-made climate change will drive the planet’s temperature up by between four and seven degrees Fahrenheit over the course of this century, making the oceans hotter. Sea levels are rising, storms are getting stronger, and the life cycles of plants and animals are being upended, changing migration patterns and causing other serious disruptions.

Global warming has already devastated coral reefs, and marine scientists now foresee the collapse of entire reef systems in the next few decades. Warmer waters drive out the tiny plants that corals feed on and depend on for their vivid coloration. Deprived of food, the corals starve to death, a process known as bleaching. At the same time, rising ocean temperatures promote disease in corals and other marine life. Nowhere are these complex interrelationships contributing to dying seas more than in fragile coral ecosystems.

On top of all these problems, the most severe impact of the damage being done to the oceans by climate change and ocean acidification may be impossible to predict. 

 

A way forward

Many solutions exist, and some are relatively simple. For example, governments could create and expand protected marine areas, adopt and enforce stronger international rules to conserve biological diversity in the open ocean, and place a moratorium on the fishing of dwindling fish species, such as Pacific bluefin tuna. But solutions will also require broader changes in how societies approach energy, agriculture, and the management of natural resources. Countries will have to make substantial reductions in greenhouse gas emissions, transition to clean energy, eliminate the worst toxic chemicals, and end the massive nutrient pollution.

So long as pollution, overfishing and ocean acidification remain concerns only for scientists, however, little will change for the good. Diplomats and national security experts, who understand the potential for conflict in an overheated world, should realise that climate change might soon become a matter of war and peace. Business leaders should understand better than most the direct links between healthy seas and healthy economies. And government officials, who are entrusted with the public’s well-being, must surely see the importance of clean air, land, and water.

The world faces a choice. We do not have to return to an oceanic Stone Age. Whether we can summon the political will and moral courage to restore the seas to health before it is too late is an open question. The challenge and the opportunity are there.