The Ocean of Life
Page 17
a world free from moth and rust and full of color, a world largely made up of synthetic materials… a world in which man, like a magician, makes what he wants for almost every need out of what is around and beneath him.5
Actually, what is around and beneath us today is an endless vista of discarded plastic—a world full of color indeed. The wildflower-filled roadsides of old have for many of us been replaced by a near continuous succession of plastic food wrappers, bags, and lost or abandoned junk. By weight, about a tenth of our waste is plastic, and a much bigger proportion by volume. A third of all plastic is turned into disposable packaging, used once and thrown away. We pack our discarded plastic into landfills and recycle some, but a significant amount finds its way to the sea. There is a river at the bottom of my garden; when floods rush by I sometimes watch as a stream of rubbish bobs past. One fairly ordinary day I counted them: twenty-seven pieces of plastic in an hour. It is a story repeated in every one of the world’s streams and rivers that drains inhabited land. When it rains hard over the Caribbean island of St. Lucia, for instance, the sea turns brown with sediment washed from exposed soil, and the bays fill with bobbing plastic bottles and drifting shopping bags. I once opened my Sunday newspaper to a double-page photo that showed a solid mass of plastic bottles, bags, buckets, shoes, and other refuse. So choked was the scene that it was hard to tell whether this was land or water. Eventually I spotted the face of a little Filipino boy amid the rubbish, swimming in Manila Bay. I was stunned. Years later the image still haunts me.
Rivers launch their garbage into the sea, where some is picked up by offshore currents to join bath toys, sneakers, cans, and stuff lost from boats on transoceanic voyages. Curtis Ebbesmeyer called his book about this floating world Flotsametrics, but its subtitle, to paraphrase Daniel Defoe, might be “The Life and Strange Surprising Adventures of a Plastic Duck.” Actually, there is another book about these toys with the marvelous title Moby Duck!6 The great currents of the oceans move in counter-rotating circles that interlock with one another. Due to the Earth’s rotation, winds blow to the right in the northern hemisphere and the left in the southern, giving them an easterly or westerly heading (Coriolis again). The wind tends to come from the east near the equator in both hemispheres—these are called the trade winds—while at middle to high latitudes they blow from the west—the westerlies. Winds move the sea beneath, but again the Earth’s rotation gives them a twist, and continents block their movement. The result is that air movements spin up vast rotating currents known as gyres.
Sailors have recognized these winds and currents for thousands of years, but they weren’t mapped until the nineteenth century, when a United States naval captain, Matthew Maury, gathered together all of the oceanographic measurements available in a pioneering book, The Physical Geography of the Sea.7 Maury recognized at least three different gyres, a number that has increased to nine as modern oceanographers have added detail. Curtis Ebbesmeyer added two more small loop currents in the Arctic to bring the total to eleven.
Ocean gyres: Curtis Ebbesmeyer’s map of the world’s ocean gyres: giant surface loop currents. Gray spots inside the gyres show areas of trash accumulation, the so-called ocean garbage patches. Redrawn from Ebbesmeyer and Scigliano, 2010.
In general one finds two main gyres in each ocean, one to the north and another south of the equator. The Pacific Ocean is so vast that it has two in the north. The Indian Ocean has just one to the south, because monsoon winds dominate the north and India blocks water movement there. An unbroken loop of sea circles Antarctica, so the gyre flows all the way around this continent in an endless circle. If you have ever wondered why round-the-world yachtsmen often run into difficulties in the mountainous seas of the Southern Ocean, it’s because this is the shortest and fastest way to circumnavigate the world.
Thanks to the Earth’s rotation, revolving currents in the gyres push water toward the center, where it piles up into hills. You might have thought the sea was perfectly flat, but there are hills and valleys in the ocean just as on land. Where the crust is thin, such as over ocean trenches, the pull of gravity from the dense mantle beneath is strong and creates hollows in the sea. Admittedly, these are very gentle valleys and hills; the difference between a peak and a valley floor amounts to less than four feet of height over hundreds or thousands of miles. The piled-up water in the middle of each gyre is pulled down by gravity, and there is a downwelling to the deep sea like water flowing down a gigantic bath drain. A nautical almanac published in 1845 described these currents thus:
It has been observed that the waters of the Atlantic have a greater tendency toward the middle of the ocean than otherwise, and this seems to indicate a reduced level, forming a kind of hollow space or depressed surface… in the middle part, although within the region of the Trade-wind, the currents are not regular, but indicate a kind of vortex.8
This author mistakenly believed the currents flowed into a hollow in the ocean, when in fact they were pushed uphill by the combined force of the gyre and the Coriolis effect. But he rightly spotted the vortex. The central parts of some gyres—those with high atmospheric pressure air cells above them—gather everything that floats into enormous rafts, which are held there by the unseen hand of downwelling water. In the Atlantic gyre there is a place so distinctive it has a name of its own, the Sargasso Sea. Maury called all of the central regions of the world’s gyres Sargasso Seas due to their accumulation of the seaweed Sargassum, a floating weed buoyed up by shiny green clusters of floats that to early Portuguese navigators looked like grapes. But the name has stuck only in the Atlantic. Maury wrote:
Columbus passed through [the Sargasso Sea] on his first voyage of discovery to America. His crew were alarmed at it, for in places it is so thickly matted over with brownish weeds, as to hide the face of the sea, presenting somewhat the appearance of a drowned meadow, and looking as though you might walk on it, without sinking more than shoe deep in water. The sargassos of the southern hemisphere are not so well marked as this, nor are they as rich in drift or floating matter.
You observe that in both the North Atlantic and the North Pacific, the sargasso is in the middle of the pool as it were, or between the warmer current to the west, that flows north, and the cooler one to the east, which returns south. Into this sargasso of the Atlantic are carried the trees and plants and creepers that are brought down from the Andes by the Amazon, and from the Rocky Mountains by the Mississippi and its tributaries. These, with the wrecks of steam-boats that are blown up or snagged, sunk and lost on the Western waters of America, are all drifted out to the sea, and placed within the influence of the Gulf-stream. In the course of time they find their way into this sargasso. On their voyage to it,—their sea of rest,—they become loaded with barnacles and shellfish; arrived there, these die, or, loading their floating domicile too heavily, with increase of inhabitants, it finally sinks, conveying them down with it into the depths below.9
When Curtis Ebbesmeyer visited the Sargasso Sea in 1977 he was taken aback not so much by the rafts of weed, but by the number of Styrofoam cups that blossomed from it like water lilies.10 His meticulous tracking of ocean garbage has revealed the oceans’ remarkable interconnectedness. The great current that circles the planet, the global ocean conveyor, is powered at the surface by many gyres that act together, like the cogs in a clock. Those cogs are of different sizes and spin at different speeds. Slowest of all are the Arctic gyres that rotate about once in thirteen years. The vast gyres of the Pacific Ocean—Ebbesmeyer calls them the Turtle and Heyerdahl gyres, the latter after Thor Heyerdahl, who used it to cross from South America to the Marquesas on a balsa raft—turn once every six and a half years. The loop that circles Antarctica is driven faster by ferocious winds and turns once in three and a third years.
At each cycle some of the floating garbage escapes from the outside edge of the gyre and finds its way to the coast, where it is tossed up onto beaches. Once again, Ebbesmeyer’s extraordinary obsession with flotsam giv
es us a number: About half of the garbage carried is freed at every turn. There are still bath toys out there from the 1992 spill, but not many. At the time of writing, millions of tons of junk that were washed offshore by the devastating Japanese tsunami of 2011 are headed toward Hawaii and North America. The first wave is expected to make landfall by 2012, but as the bath toys show, beaches will continue to receive debris from this disaster for years to come.
For the last several decades, beach cleanups have been a regular activity for marine conservation groups, and an essential task for resort towns. The majority of that junk is plastic. Beach surveys from America to the Southern Ocean, and from the coast of China to remote islands of the central Pacific, show that the ratio of plastics to other trash typically lies in the range of 2:1 to 9:1. Averaged across the European Union there are approximately five hundred to six hundred pieces of litter per 110 yards of beach. This only includes pieces large enough to bother picking up. A survey of Orange County beaches in California that included all visible plastic produced a figure of over 100 million items of trash for the whole county, most of it tiny pieces of plastic.11 This is equivalent to more than 150,000 items per 110 yards of beach!
Despite the oceans’ capacity to carry garbage halfway around the world, plastic is most abundant in populous places, and close to cities. The northern hemisphere is affected much worse than the south, although right now rates of accumulation of beach trash are increasing faster in south polar latitudes than anywhere else.12 Each year about two thousand items of human-generated trash (most of it plastic) washes ashore in the northern hemisphere, compared to about five hundred in the southern, for every kilometer (0.63 miles) of beach.13 Enclosed seas like the Mediterranean are affected worse than open ocean coasts. There junk can wash in at eighteen hundred pieces per 110 yards of shore per year.
Most plastic is easily overlooked, too small to be seen by a casual glance, and much too small to be included in these surveys. Next time you are at the seaside draw a square about the length of your forearm on the beach near the strandline. Then pick from inside it every fragment of plastic you can find. You will need to look very closely, since much of it will be less than a quarter-inch across. Many of the pieces will be rounded drops of white or yellowed plastic known as nurdles, or mermaid’s tears. They are the raw material of the plastics industry—pellets ready to be molded into finished products. Vast quantities have been lost at sea and in spills on land over the years. Give yourself plenty of time, because you will probably find hundreds, perhaps thousands of them. A survey of some New Zealand beaches found up to three hundred thousand per linear meter (thirty-nine inches) of shore! Of the plastic found in the Orange County beach survey 98.5 percent were nurdles.
Plastic stuff gets thrown away in such abundance partly because it doesn’t last very long. I am often annoyed at how something made out of decent materials like wood or metal has to be junked because some critical bit of plastic in it has broken. But that fragility belies an incredible durability in the substance itself. Plastics break down very slowly, but over time they fragment into ever-smaller pieces. When you get bored picking them from your plot of beach, why not relax with a swim? As you enjoy the caress of waves, consider this: The water around you probably contains a multicolored soup of tiny plastic fragments. While there is plenty of the stuff near coasts, it has built up in offshore waters, and spectacularly so in the Kuroshio Current that flows past Japan and East Asia. There densities of plastics were reported up to nine million per square mile of sea.14
Not all plastic floats. Roughly half is denser than water and sinks at various rates, while the other half is what we are familiar with from ocean garbage patches, as Curtis Ebbesmeyer dubbed the middle regions of the gyres. Few surveys have been made of seabed litter, so there is little to go on, but it is clear that there is another hidden problem that we will soon have to reckon with. Contamination in some parts of Europe can reach levels of a piece of plastic for every square yard of bottom.15 Plastics and other rubbish have made it to the deep sea as well. Scientists who deploy instruments on the deep sea bed often return to find them clogged with drifting plastic bags. One submersible pilot reported that plastic bags passed him by like a succession of ghosts. Heavier rubbish thrown from boats reaches the bottom of the sea quickly. The deep sea is not so remote in distance, even if to us it is a profoundly alien environment.
I mentioned that ocean gyres lose about half of their flotsam at every cycle. Some of it comes off the outer edges and escapes toward the coast, but the rest goes inward. Just like the mats of floating seaweed that so amazed the sailors of old, great rafts of plastic, fishing line, nets, ropes, and a thousand and one other bits of junk have accumulated within the gyres. In a story often retold, a yacht captain, Charles Moore, took a different route from usual between Hawaii and Long Beach, California, in 1997 and crossed through the center of the gyre in the northeast Pacific. He was so stunned by the amount of garbage he found there that it changed the course of his life. Since then he has dedicated his life to the study of plastics at sea, and he is now a relentless campaigner for something to be done about them. One of his most famous findings was that there were six times more floating plastic fragments in the surface water by the turn of the millennium by weight than zooplankton.16 The gyre Captain Moore traversed has gained notoriety as the Great Eastern Garbage Patch, at about the size of Texas one of the world’s largest. Surveys across the Sargasso Sea show the scale of contamination. On average, plankton tows there revealed densities of floating plastic fragments in the order of hundreds of thousands of pieces per square mile.17
Plastics are completely foreign to life, so animals have been unable to mount any evolutionary defense against them. The Laysan Albatross, which nest on Kure Atoll in the central Pacific Ocean, have the misfortune to live close to the Great Western Garbage Patch, as the center of the gyre on the western side of the Pacific is called. Albatross feed by picking live and dead prey from the sea surface. Unfortunately, they can’t distinguish between plastic and flesh. Researchers recently found that adults returning from long-distance foraging trips fed their chicks an average of seventy pieces of plastic per meal!18 After the chicks starved to death and their flesh rotted, they left piles of fishing line, golf balls,19 pens, bottle caps, and sundry other fragments, each framed by a mute halo of feathers. Some chicks contained more than five hundred plastic items. The plastic content of chicks has increased tenfold in the last forty years, presumably in line with increases in the mass of trash circling the Pacific. As early as 1965, three quarters of Laysan chicks found dead had plastics in them.20 There is a heartrending possibility that albatross deliberately fly to areas of garbage concentration for the rich “feeding” opportunities they provide.
Autopsies of leatherback turtles in the Atlantic Ocean show that this beast has similar difficulties telling food from plastic. Leatherbacks eat jellyfish and other gelatinous zooplankton. To a dewy-eyed leatherback, plastic bags and balloons look much the same as prey. A study of dead leatherbacks washed ashore since the 1880s found plastics present from 1968 onward.21 Some contained lumps of tangled plastic bags and Mylar balloons (the helium-filled variety we give to kids) the size of a football. Today over a third of dead animals examined have plastic in their guts. The strain of hauling itself ashore to nest obviously got to one leatherback in French Guiana. It pooped a huge plug of plastic bags and sacks that weighed over five pounds.22 Normally turtles fast during the breeding season and don’t shit on the beach. How many other bags, I wonder, have been recycled through the guts of turtles far out to sea, and how many turtles’ lives are threatened by the plastics packed in their bellies? As jellyfish are 95 percent water, they make a pretty meager meal. Adult leatherbacks must consume hundreds of pounds of jellyfish every day to break even, over half their bodyweight. Even if plastics don’t kill outright by blocking the gut, they could interfere with digestion and cause animals to starve by tipping their caloric balance into the red.
/> Hundreds of other species ingest plastics, either deliberately or by eating something else that has. In the North Sea, nineteen out of every twenty fulmars—a smaller relative of albatrosses—that washed up dead on beaches contained plastic. On the Dutch coast, four out of five plastic fragments had peck marks from birds.23 Plastics have reached some of the remotest places on the planet. Fur seal scats at subantarctic Macquarie Island contain many plastic fragments that were eaten by the deepwater fish they prey on.24 Even whales have eaten plastics. A pygmy sperm whale stranded on a New Jersey beach in 1993 had its stomach blocked by fragments of plastic bags. The whale recovered after they were removed, and it was released into the Gulf Stream.25 Others have been less fortunate. A dead pygmy sperm whale stranded in Texas had a plastic garbage-can liner, a bread wrapper, a corn chip bag, and two other pieces of plastic sheeting choking off its stomach.26
These whales may have taken in plastics accidentally while feeding, but there are signs that whales target pieces of plastic junk deliberately. Two sperm whales that died on the California coast between them contained over two hundred pounds of net fragments, line, and plastic bags.27 The pieces packed into their stomachs came from all kinds of nets that may have been up to twenty years old and seem to have been tossed overboard by fishermen mending their gear.
I once came across a photograph taken far out at sea in one of the oceans’ garbage patches. A huge ball of fishing net suspended by a couple of hundred floats stretched across the frame for at least ten yards. At one end, a sad looking and exhausted turtle stared at the camera, helplessly entangled. This poor beast had dragged the net with it across how many miles of ocean nobody could tell. Like Sisyphus in Greek mythology, it was condemned to a life of immense hardship undertaking a task that could never be completed. Some of the most disturbing images of the harm done by human detritus are of sea lions that have put their heads through loops of plastic or net as pups. The loops tighten as they grow and cut a deep, bloody slash into their necks. When the sea lion finally dies from this slow-motion throat cut, it decomposes and leaves the loop of plastic to be picked up by another. The number of seals entangled in plastic and fishing line on California’s Farallon Islands rose from a handful in the 1970s to more than sixty a year by 2000.28