Dying seas.

• Author: Platt, Anne E.

THERE ARE ONLY A FEW OF THEM ON THE PLANET. YET, THE CIVILIZATIONS THAT HAVE ALWAYS DEPENDED ON THEM FOR SUSTENANCE AND SECURITY ARE NOW SLOWLY KILLING THEM.

During the last four thousand years, the part of our past that we think of as the history of civilization, human settlements have tended to cluster around land-enclosed seas, rivers, and lakes. People in these settlements have been able to supply themselves with food, security, and community to a degree that would have been far more difficult in the vast inland territories--drylands, mountains, scrub forests, deserts, and steppes--that make up the bulk of the terrestrial world.

Whether it was the ancient Aegeans on the Mediterranean, the Persians on the Caspian, or the Chinese on the Yellow Sea, civilizations rose in places where small boats could exchange knowledge and goods, trade was easily conducted, fish were abundant, and the land was rich with the topsoil carried downstream by rivers.

For these reasons, the basins of the great seas were also more highly valued than other landforms, and controlling them became central to human notions of security. Security meant military control of homelands and trade routes. It has also meant, increasingly in the past few centuries, control of the water itself--by damming tributaries, digging irrigation ditches, dredging shipping channels and harbors, and constructing breakwaters.

In just the last few decades, however, a new kind of stress has crept into the historic relationship between humans and the seas. While civilizations have continued to develop most rapidly around the coasts and rivers that feed the seas, that growth has accelerated to a point that is now dangerously unstable. Various side effects of human activity that passed unnoticed until this century have begun to ravage the very qualities that make the seas valuable--depleting both sea-based and land-based food production, fouling the human nest, and evidently even beginning to alter weather patterns for the worse.

Today, most of the world's seas are suffering from a wide range of human-caused assaults, in various lethal combinations: their ecological links to the land blocked by dams; their bottoms punctured and contaminated by oil drilling; their wildlife habitats wiped out by coastal development; and their water contaminated--or turned anoxic--by farm and factory waste. And what fish remain after these assaults are being decimated by overfishing. In the world's most biologically productive and diverse bodies of water, ecosystems are on the verge of collapse--and in some cases have already collapsed. The levels of damage and progress toward protection vary from sea to sea. But in general, compared to the open oceans, semi-enclosed seas tend to be damaged more severely and quickly because water circulation is limited and there is less dilution of pollutants.

Today, the seas are as strategically important as they ever were in the days of Kublai Khan's armada or the Greek trading ships, but for new reasons. The old preoccupation with controlling key military positions, ports, and trade routes is now rivaled by a more urgent priority: to rescue and protect the more fundamental assets that made the seas worth living near in the first place, but which are now being dangerously damaged.

To set up this protection means establishing a new paradigm for security, in which shared responsibility for sustaining the vitality of these seas becomes the basis for a mutual, rather than competitive, effort. This is something that national governments may find difficult, since it necessarily overrides traditional concepts of sovereignty and control. But most of the great seas are shared in too many ways for anything but a mutual vigilance--and coordinated defense against our own human excesses--to work. Cooperative solutions have begun to emerge in a few regions, such as the Mediterranean and the Baltic. But on other seas, conflicts arc escalating--suggesting that cooperation is not likely to prevail without a fuller understanding of just what is at stake.

There are about 35 major seas in the world, some coastal and some enclosed by land. Of these, seven--the Baltic, Mediterranean, Black, Caspian, Bering, Yellow, and South China Seas--illustrate the panoply of ills that now afflict, in varying degrees, all 35. Each of these seven carries different wounds. One, the Black, is a microcosm of them all.

1. BLACK SEA: A SEA OF TROUBLES

   In ancient times, it was valued for its abundance of fish, its relatively temperate climate, and its strategic location: the city of Constantinople was the gateway between East and West, capital of the Byzantine Empire, and one of the great hubs of human civilization. During the past century, the Black sea became famous for its beach resorts where wealthy Russians and Ukranians built their dachas. But in recent decades, this beautiful place has been ravaged. First, and most tragically, there has been the onset of a disease that is now endemic to enclosed or semi-enclosed bodies of water worldwide: an immense excess of marine nutrients. Like a compulsive eater who becomes increasingly obese, immobile, and finally moribund, the Black Sea has been overloaded with nutrients--fertilizer washing downstream from farms, human waste from the cities. The result has been massive eutrophication--a burgeoning growth of algae and bacteria, creating thick floating mats so dense that they block sunlight and destroy the natural ecological balance.

   To this cancer-like process, other complications have been added. While the Black Sea was serving as a playground for elite Soviets during the Cold War, it was also being used as a convenient sink for all sorts of industrial activity--in an era when Soviet industries were driven by production quotas with little concern for their environmental impact. Toxic pollutants from plants ran uncontrolled down the three main tributary rivers, and growing quantities of municipal waste mingled with industrial and agricultural waste. The contaminated waters weakened the fish populations, which were further destroyed by heavy overfishing.

   In this morass of biological decline, the most visible blight is the vast greenish mass that now lies over much of the water. What was once a rich, diverse ecosystem has been replaced by a monoculture of opportunistic weeds and algae. Gradually, as the dissolved oxygen supply is depleted by the algae and bacteria, the water becomes anoxic--incapable of supporting oxygen-dependent plants or animals. When the algae dies, it settles to the sea bottom, releasing hydrogen sulfide, which is poisonous to animals.

   A key source of the trouble can be found along a 350 kilometer stretch of northwestern shoreline where three major rivers, the Danube, the Dniester and the Dnieper, drain into the sea. The Danube delivers much of the fertilizer runoff, detergent waste, and human sewage produced by the 81 million people in the Central and Eastern European drainage basin. Each year, it dumps an estimated 60,000 tons of phosphorus and 340,000 tons of inorganic nitrogen on the shallow waters of the Black Sea shelf, which is approximately one-fourth of the sea's entire area.

   In the past 25 years, the Danube's concentrations of nitrate and phosphate (stable compounds that form when nitrogen and phosphorus react with oxygen) have increased six-fold and four-fold respectively. Concentrations from the Dniester, which flows across the Ukrainian breadbasket region, have increased three-fold for nitrate and seven-fold for phosphate since the 1950s. The Dniester has also brought heavy loads of pesticides, after flowing through the...