Now nearly everyone can see, on a home screen, some of the wonders scientists are discovering in the oceans as they descend to unprecedented depths in submersibles, map the seafloor, and track the migrations of whales, sharks, and sea turtles via satellite. We watch, and gradually the ocean with its living creatures enters our personal world.

At the same time we are learning that the oceans’ intricate web of life is being torn apart. Scientists have long been warning that unless humans stop overfishing and other destructive activities, much of the planet’s once-abundant marine life will be lost.

"Fisheries are the major catastrophe that has befallen the animals in the ocean," says Daniel Pauly, director of the Fisheries Center at the University of British Columbia and board member of Oceana, an organization devoted to ocean conservation. His words echo from a video posted on Oceana’s website. "It’s almost as if we use our military to fight the animals of the ocean--and we are winning the war. We are gradually exterminating them." Hundreds of scientists around the world agree that overfishing is one of the greatest threats to the ocean, along with pollution, habitat destruction, and climate change.

In response, a worldwide ocean conservation movement has surfaced and is gathering strength. It involves governments, international agencies and conservation groups, aquariums and universities, small island communities, and countless individuals. Some of the most promising recent marine conservation successes were sparked by individuals and small groups.

In the Pacific Ocean, hundreds of marine protected areas (MPAs) have been established in the past few decades, mostly on the western side. An MPA is a geographically defined marine area within which fishing and other human activities are banned or limited to varying degrees.

Because the best habitat areas are frequently the most productive fishing grounds, MPAs are often controversial. Research and experience so far, however, support the view that they can help depleted fisheries to recover, as the fish populations they protect "spill over" to adjacent areas. The reserves also offer a kind of insurance against the impacts of global warming and ocean acidification, especially for coral and other calcifying organisms (see Ocean Acidification). "Research suggests that ecosystems that are more biodiverse may be more resilient," points out Cheri Recchia, director of the Marine Protected Areas Monitoring Enterprise of the California Ocean Science Trust.

In the United States, California leads the way as it works to complete the first network of ecosystem-based marine reserves in state waters, some of which will be no-take areas where marine life is completely protected. But overall, this country lags behind many others. Australia has the world’s largest network of no-take reserves, covering more than 38,610 square miles. In 2004, the government rezoned the Great Barrier Reef Marine Park, placing more than 20 percent of each of 70 bioregions within the network. In 1977, New Zealand became one of the first nations to establish a no-take reserve, and now has a network of 31.