Planet earth is a wet and salty place. Oceans cover 127 million square miles, seventy-one percent of the earth's surface. They contain ninety-seven percent of all the water on the globe.
Because water doesn't heat up or cool down as fast as land, the earth's vast oceans have a moderating influence on atmospheric temperatures, making many areas on land more habitable than they would otherwise be. When ocean currents draw water from tropical seas to higher latitudes, these uncharacteristically temperate areas occur with even greater frequency.
Sea water itself is highly habitable, containing much more than just water and salt. It has a number of dissolved minerals including calcium, sulfur, magnesium, and potassium. That special blend is part of a complex environment that sustains a staggering variety of plants and animals, much more diverse than on land, and found from the surface all the way down to depths of ten thousand feet and even deeper. In fact, new forms of oceanic life╤some receiving energy not from the sun, but from chemicals spewed by thermal vents in the ocean floor╤continue to be discovered, particularly in the dramatic depths along the mid-ocean ridges.
But the richness of the oceanic biosphere is being threatened by humankind... not just from giant oil spills, but from overfishing and air pollution, agricultural and industrial run-off, and the waste generated by growing urban populations. By the year 2000, a billion people worldwide will live in cities by the sea.
Still, some progress has been made. In recent years, fishing restrictions, including the banning of giant drift nets and ocean-dumping rules have helped. But the protection of the ocean as perhaps humankind's ultimate food source is far from assured.
