One day in the late 1970s, the ocean explorer Jacques Cousteau joined me at a Paris café, pulled a piece of paper from his jacket pocket, and pushed it across the table. On it, he'd listed two dozen words with tally marks beside each. "The winner is saccage," he said.

For weeks, Cousteau had been asking colleagues to help him choose a word that could focus public attention on the environmental threats posed by the mechanical destruction of coastlines and other natural habitats. After all, he reasoned, for centuries the word "pollution" had referred to the abominable sins of desecrating churches and defiling one's self. It was no coincidence, Cousteau thought, that the environmental movement took off just when the word "pollution" entered the popular lexicon as a grim description of poisons poured into air and water. For Cousteau, the French word saccage -- meaning plunder, pillage, looting -- described the sack of the coastlines as vividly as it did the sack of Rome. This became a second key word in his environmental lexicon.

The concept of saccage had not come to Cousteau as a flash of inspiration. In the 1940s, when he invented the Aqualung and began making undersea films, he descended daily into a Xanadu profuse with fish, corals, and plant life. As years passed, he found it progressively more difficult to find film locations. Finally, in the late 1970s, he returned to an area of the sea with a towering, craggy rock on the bottom -- the kind of habitat around which sea life proliferates -- that had once provided his most spectacular footage of colorful creatures and undersea gardens. He now found the waters barren and the bottom covered with a blanket of rot. Given the number of other desolate areas he'd seen, he realized that what a full dozen of his films had captured no longer existed.

Cousteau estimated that life in the Mare Nostrum (the Mediterranean) had diminished by some 40 percent. Blaming pollution, Cousteau obtained scientific assessments of water, sediment, and plankton samples. His measurements showed that toxic poisoning alone could not have caused the diminution of life that he had seen. If that pollution had not taken this toll, then what had? Cousteau pointed toward the Riviera, where beaches, landfills, and dozens of ports had been constructed on stretches that had once been marsh and wetland. Between the Alpes Maritimes and Monaco, more than 1,700 acres of the most fertile strip of shallow waters had been overwhelmed by saccage -- buried under dikes, landfills, and inside artificial harbors. He watched as workers sloppily built a landfill to extend a runway at the Nice airport. The structure collapsed, causing a tidal wave that smashed boats and houses, causing millions of dollars in damage. One woman was fatally swept out to sea, and at the airport six men were killed and three more vanished forever.

More than 30 years have passed, and saccage has taken on ever greater dimensions. The effects of global warming may well exact a payment from the sea, specifically regarding the force of severe storms that have recently hit American coastlines. James Elsner, professor of geography at Florida State University, led a team that this September published an elegant study in Nature magazine. The team found that global warming appears to increase the violence and deadliness of tropical storms. "Our results are qualitatively consistent with the hypothesis that as the seas warm, the ocean has more energy to convert to tropical cyclone wind," the researchers wrote. The study showed that as sea surface temperatures have risen, so have the duration and speeds of winds in the strongest tropical cyclones over each ocean basin, with the greatest increases over the north Atlantic. Other scientists have reported that the largest waves in violent storms have grown in height by 20 percent since the late 1970s.

Rising sea levels compound the threats posed by raging winds and waters. As the seas warm, water expands and sea levels rise. Arctic snow and ice melt, more sunlight is absorbed, and the seas grow warmer and higher still. In the past century, the seas have risen by 4 inches to 10 inches. The United Nations Intergovernmental Panel on Climate Change (IPCC) has warned that global warming may raise the sea by another 7 inches to 23 inches before the close of this century. Other studies call this a conservative estimate.

Higher seas and more violent storms pose ominous risks for coastal inhabitants. The Woods Hole Oceanographic Institute estimates that coastal storms cause 71 percent of annual U.S. disaster losses and that within 60 years, a full quarter of all structures within 492 feet of the ocean will be destroyed. The rising seas and the fury of storms also increase erosion: In the United States, we are annually losing more than a yard of shore along 60 percent of the Pacific coast and 35 percent of the Atlantic coast.

And what of the future losses, both in economic and human terms? Nearly two-thirds of our human population resides within 50 miles of a coastline. In just the next 20 years, that portion is expected to increase to three-quarters of all people. The IPCC warns that by 2080, about 100 million people could be threatened each year by floods. In a worst-case scenario, climate change could assault North America alone with a mega-flood every three to four years, instead of at nature's rate of once a century. According to a recent report from the Organization for Economic Cooperation and Development (OECD), the number of human beings threatened by flooding due to climate change could triple by 2070 and property losses could increase to $35 trillion. According to a 2007 study published by the journal Environment and Urbanization, more than 634 million inhabitants of 183 countries live in areas threatened by rising sea levels, defined as those below 33 feet above sea level. Poor nations face the greatest human losses.

Still, we continue to pressure our coastlines. In the United States alone, the coastal population rises by some 3,500 people a day. Wetlands, a first line of defense against storms, are estimated to reduce storm surges from 3 inches to 9 inches for every mile of marsh. Nevertheless, Americans have lost more than half of the wetlands that existed 200 years ago across what is now the Continental United States -- a loss exceeding 100 million acres of wetlands as humans dried, plowed, developed, subdivided, logged, and destroyed them by dikes, levees, and logging.

An example: In 1985, Cousteau filmed the U.S. Army Corps of Engineers using heavy-handed measures to alter the Mississippi River. In its efforts to shorten the river's path to the Gulf of Mexico by 200 miles, the Corps laid gargantuan sheaths of concrete mats to stabilize the banks, changing the Mississippi, in Cousteau's judgment, from a river to a paved waterway. Even at that time satellite pictures showed the great Louisiana delta shrinking as the river's faster currents no longer dropped their rich silts to extend the land but swept them out and dumped them over the edge of the continental shelf.

Experts say that by now we've lost 20 percent of the vast delta existing a century ago. This estuary, once 10 times the size of Grand Canyon National Park, had served as New Orleans' great natural defense against hurricane winds and storm surges. After Hurricane Katrina, many New Orleans residents angrily accused the Corps of having destroyed this natural defense. Scientists have since pointed as well to the oil industry, which had dredged 10,000 miles of canals throughout the mangroves. Experts believe these service canals, used to tap oil and natural gas, unilaterally caused the loss of some 1,000 square miles of delta -- about half the land lost in the past century. Though costs of restoring New Orleans and the delta are estimated to reach $60 billion, a spokesman for the oil industry called its saccage of the wetlands "insignificant."

We continue, as well, to plunder ocean waters. In deep-sea trawling, fishermen drag heavy equipment across the ocean bottom. Because sea life swarms around craggy rocks, the undersea mountain ranges, called seamounts, are particularly prolific. Trawlers draw their equipment recklessly along these ranges, crushing corals, dragging boulders, catching targeted profitable fish but also destroying everything else. Even more bewildering is the continued saccage of the shallow coastal waters, down to 65 feet, where sunlight meets phytoplankton and fields of Posidonia, grasses in which fish lay their eggs, flourish. These shallow waters, one-half of 1 percent of total ocean space, support 90 percent of all sea life. More than two decades have passed since the OECD warned its members about the economic foolishness of plundering fragile coastal waters and habitats by building breakwaters and sea walls, dredging for sand and gravel, and dumping dredge spoils. Yet the practices continue. In just the 11 years since Cousteau's death, his precious Posidonia oceanica, his nursery of the Mediterranean, has become endangered.

Cousteau once related a parable for the sin of saccage. He was describing his experiences in searching for ancient shipwrecks. "On the bottom, the wrecks eventually open up and are covered by mud," he said. "After a few centuries, you can spot them only by seeing the tips of the necks of amphora sticking up above the sands or by a few artifacts scattered around on the bottom." Knowing that exquisite artworks had been found in the early years of the 20th century in an area of the Aegean near Antikythera, Greece, Cousteau and his crew decided on an expedition. They discovered that trawlers had scraped the bottom bald. Nonetheless, they managed to find some treasures. More than 2,000 years ago when the Romans sacked ancient Greece, a departing Roman ship had sunk with a cargo of loot. From the sands of the bottom, one of Cousteau's divers also disengaged a beautifully shaped miniature bronze arm. From what priceless artifact, Cousteau wondered, had trawlers possibly broken the piece? When he later visited the National Archaeological Museum of Athens, Cousteau spotted a bronze figure that had been found at the Antikythera site in 1901. It was missing a limb. The little arm found by his team fit exactly.

Razed by trawlers, the bottom of the Aegean has been stripped of countless clues it could have provided to the ancient wrecks and artworks it engulfs. Saccage destroys both natural and cultural treasures. How fitting that the plunder, pillage, and looting of Antikythera stands as a metaphor for the global saccage of our past, present, and future.