Already, 29% of species that are fished — including bluefin tuna, Atlantic cod, Alaskan king crab, Pacific salmon and an array of California fisheries -- have collapsed and the pace is accelerating, the report says.
In addition, ocean ecosystems will be unable to recover from shrinking populations of so many species of fish and other sea creatures, the scientists reported in the journal Science.
The report is the first comprehensive assessment of the potential consequences of ongoing declines in the diversity of life in the world's oceans. In recent years, marine scientists have warned about the extreme toll of overfishing in many regions, but the new report offers one of the most dismal predictions for the future of the world's fisheries.
Yet, there is still hope, the scientists concluded.
If more protections are put into place, such as new marine reserves and commercial fishery closures, the volumes available for food will surge and the oceans can recover, they said.
"The good news is that it is not too late to turn things around," Worm said. "It can be done, but it must be done soon."
Delving into recent catch data from around the world as well as a thousand years of archives in regions such as San Francisco Bay, the researchers concluded that estuaries, coral reefs, wetlands and oceanic fish are all "rapidly losing populations, species or entire functional groups."
The scarcity of a highly nutritious food supply for the world's growing human population is the most visible effect of declining ocean species. But the scientists said other disruptions also are occurring as ocean ecosystems unravel species by species.
The loss of diversity "sabotages the stability" of marine environments and their ability to recover from stresses, the report says.
Water quality is worsening and fish kills, toxic algal blooms, dead zones, invasive exotic species, beach closures and coastal floods are increasing, as wetlands, reefs and the animals and plants that filter pollutants and protect shorelines disappear. Climate change also is altering marine ecosystems.
"Our data highlight the societal consequences of an ongoing erosion of diversity that appears to be accelerating on a global scale," the scientists reported. "Our analyses suggest that business as usual would foreshadow serious threats to global food security, coastal water quality and ecosystem stability, affecting current and future generations."
The authors of the report are 14 marine biologists and economists, eight from California institutions: Scripps Institution of Oceanography, Stanford University's Hopkins Marine Station, Santa Barbara's National Center for Ecological Analysis and Synthesis and UC Davis' Section of Evolution and Ecology. The study was funded by the National Science Foundation, the University of California and UC Santa Barbara.
Andrew Sugden, Science's international managing editor, said the strength of the new report "lies in the breadth of the array of information the authors used for their analysis."
The researchers combined information from a variety of sources, from small-scale local experiments to United Nations fisheries databases.
Worm and his colleagues said the similarities surprised and disturbed them. Even the smallest experiments -- measuring biodiversity in a few square meters -- mirrored the declines seen in entire ocean basins.
"Kinds of seafood that were very common and quite abundant in past decades are not there now," said co-author Stephen Palumbi of Stanford University.
Palumbi warned that "unless we fundamentally change the way we manage all the oceans species together, as working ecosystems, then this century is the last century of wild seafood."
The National Fisheries Institute, a U.S. fishing industry group, questioned the findings, saying that federal statistics "show more than 80% of fish stocks are sustainable and will provide seafood now and for future generations."
The group said that for the past quarter-century, wild fisheries worldwide have provided between 85 and 100 million metric tons of seafood annually, and that aquaculture, also known as fish farming, is filling the growing demand.