MANFRED GOTTSCHALK/WEST LIGHT

Two centuries ago Lord Byron dignified that attitude in verse:

Roll on, thou deep and dark blue ocean--roll!
Man marks the earth with ruin--his control
Stops with the shore

It's no wonder that so many for so long have been complacent about the ocean, secure in the belief that no matter what we toss in--or take out--it will roll on and on. The sea is indeed immense, with an average depth of four kilometers, a maximum of eleven. Almost all the earth's water is there, along with most living things, both in terms of biomass and genetic diversity. It might seem presumptuous, even preposterous, to think that we can change the system that powers climate and weather, shapes planetary chemistry, regulates temperature and is in sum the foundation of earth's life support.

In Lord Byron's time all of the world's sail-powered ships and muscle-powered fishing techniques appeared incapable of harming the ocean or diminishing the number of wild cod, haddock, herring, tuna, oysters, clams--even long-lived, slow-reproducing species such as whales, seals and sharks. The predator-prey relationships fine-tuned during thousands of millennia were merely nudged. For a while the needs of a newcomer, a voracious terrestrial primate, were accommodated. Runoff and wastes from the cities, factories and farms of a billion people 200 years ago seemed to have little effect on ancient ocean ecosystems.

Even 50 years ago, most of the sea was a pristine wilderness. When Norwegian archeologist Thor Heyerdahl and five fellow explorers sailed on a raft, Kon-Tiki, from Peru to Tahiti, they went for weeks without seeing anything--a ship or aircraft or drifting debris--to suggest that there were other people in the world. There were a few troubling signs, however. By then every last Stellar's sea cow had been eliminated by Arctic hunters, several whale species were in sharp decline and wars had been waged over who had the right to take shrinking numbers of cod and herring from parts of the North Atlantic.

By the time astronauts began leaving footprints and a little debris on the moon, human detritus back on earth was beginning to mar majestic waves far from any shore. Heyerdahl reported from the raft Ra II, while crossing the Atlantic in 1970, "far more oil lumps than fish ... " and noted that "scarcely a day passes without some form of plastic container, beer can, bottle ... and other rubbish drifting close by."

Skeptics say he exaggerated, or ask, So what? Why should anybody care if things we don't want on the land are relocated into the sea? And except for a few fishermen, who cares whether or not there are whales or cod or herring?

We should all care. The future of humankind is absolutely dependent on the state of the ocean. Without its aquatic heart and soul, earth would be as barren and inhospitable as Mars. It has taken billions of years, but here it is: a planet with a built-in source of life support. With or without forests, meadows and grasslands, the ocean would roll on, full of life. But without the ocean, there would be no forests, no meadows, no rollicking rain-filled clouds, no life-giving winds, no coral reefs, no cod, no people. Nowhere else in the solar system can we walk around and make a living unencumbered with special gear supplying basic needs. Astronauts who fly high above the earth and aquanauts who descend into the depths swiftly grasp the principle. Learn everything you can about life support; do everything you can to take care of it.