Oceans

Oceans cover 71 percent of the earth's surface and contain 97 percent of the planet's water. Over 20 percent of the world's petroleum is derived from offshore sources, and 95 percent of world trade by weight—or two-thirds by value—is carried by ship. Eighty percent of the world's fish catch comes from the ocean, supporting the livelihoods of 140 million people. Economists have calculated that the world's oceans provide services to humanity valued at 21 trillion dollars, as opposed to only 12 trillion dollars provided by land.

Yet the ocean has emerged as an area of environmental concern only recently. In the European tradition of marine management, it was long believed that the ocean's resources were inexhaustible and that its environment was invulnerable to damage from human ...