An international group of ecologists and economists warned yesterday that the world will run out of seafood by 2048 if steep declines in marine species continue at current rates, based on a four-year study of catch data and the effects of fisheries collapses.
The paper, published in the journal Science, concludes that overfishing, pollution and other environmental factors are wiping out important species around the globe, hampering the ocean’s ability to produce seafood, filter nutrients and resist the spread of disease.
“We really see the end of the line now,” said lead author Boris Worm, a marine biologist at Canada’s Dalhousie University. “It’s within our lifetime. Our children will see a world without seafood if we don’t change things.”
The 14 researchers from Canada, Panama, Sweden, Britain and the United States spent four years analyzing fish populations, catch records and ocean ecosystems to reach their conclusion. They found that by 2003 — the last year for which data on global commercial fish catches are available — 29 percent of all fished species had collapsed, meaning they are now at least 90 percent below their historic maximum catch levels.
The rate of population collapses has accelerated in recent years. As of 1980, just 13.5 percent of fished species had collapsed, even though fishing vessels were pursuing 1,736 fewer species then. Today, the fishing industry harvests 7,784 species commercially.
“It’s like hitting the gas pedal and holding it down at a constant level,” Worm said in a telephone interview. “The rate accelerates over time.”
Some American fishery management officials, industry representatives and academics questioned the team’s dire predictions, however, saying countries such as the United States and New Zealand have taken steps in recent years to halt the depletion of their commercial fisheries.
“The projection is way too pessimistic, at least for the United States,” said Steven Murawski, chief scientist for the National Marine Fisheries Service, which is part of the National Oceanic and Atmospheric Administration. “We’ve got the message. We will continue to reverse this trend.”
The National Fisheries Institute, a trade group representing seafood producers as well as suppliers, restaurants and grocery chains, said in a statement that most wild marine stocks remain sustainable.
The group’s spokeswoman, Stacey Viera, added that because the global demand for seafood has already outstripped the amount of wild fish available in the sea, her group’s members are meeting the need in part by relying on farmed fish. “To meet the gap between what wild capture can provide sustainably and the growing demand for seafood, aquaculture is filling that need,” she said.
But several scientists challenged that prediction and questioned why humanity should pay for a resource that the ocean had long provided for free. “It’s like turning on the air conditioning rather than opening the window,” said Stanford University marine sciences professor Stephen R. Palumbi, one of the paper’s authors.
Oregon State University marine biologist Jane Lubchenco said the study makes clear that fish stocks are in trouble, even though consumers appear to have a cornucopia of seafood choices.
“I think people don’t get it,” Lubchenco said. “They think, ‘If there is a problem with the oceans, how come the case in my grocery store is so full?’ There is a disconnect.”
The possible collapse of commercial fisheries could have a serious on the global economy, said Gerald Leape, vice president for the advocacy group National Environmental Trust. The industry generates $80 billion a year, Leape said, and more than 200 million people depend directly or indirectly on fishing for their main source of income. Worldwide, a billion people eat seafood as their main source of animal protein.
“This should be a wake-up call to our leaders, both internationally and domestically, that they need to protect our fish stocks. Otherwise they will go away,” Leape said.
In order to reach their conclusions, the paper’s authors looked at nearly three dozen controlled experiments and crunched the U.N. Food and Agriculture Organization’s worldwide catch data going back to 1950. In some cases, they also surveyed ecosystem records — including sediment cores and archival data — going back a thousand years.
The researchers said the loss of so many species is eroding the viability of marine ecosystems and their ability to resist environmental stresses. In 12 marine ecosystems surveyed, they found that a decline in biodiversity of 50 percent or more cut the number of viable fisheries by 33 percent, reduced nursery habitats by 69 percent and cut the ocean’s capacity to filter and detoxify contaminants by 63 percent.
This phenomenon is apparent in the Chesapeake Bay, where the collapse of the oyster fishery has reverberated across the ecosystem. In 1880, there were enough oysters to filter all the water in the bay in three days; by 1988, it took more than a year for the remaining oysters to accomplish the same task.
Hunter Lenihan, a marine ecology professor at the University of California at Santa Barbara, said the mass dredging of oysters from the bay over the past century has transformed its ecosystem.
As the oysters declined, the water became more cloudy, and sea grass beds, which are dependent on light, died off and were replaced by phytoplankton that does not support the same range of species.
“When you removed the oysters through overfishing, that’s when you begin to see a rapid decline in water quality,” Lenihan said. “What it’s done is change the entire production of the bay.”
But University of Washington fisheries professor Ray Hilborn said ascribing a decline in fisheries production to loss of biodiversity was a bit like deciding which came first, the chicken or the egg.
“Do more productive systems lead to more diversity, or is it more diversity leads to more productivity?” Hilborn asked.
Yesterday’s report suggests it is possible to resolve this puzzle. The researchers analyzed nearly 50 areas where restrictions had been imposed to stop overfishing and found that, on average, the range of species in the water increased by 23 percent within five years. That provides reason for optimism, Worm said, because it means sound management can halt the decline of fish stocks worldwide.
“It’s not too late to turn this around,” he said. “It can be done, but it has to be done soon.”
Marine advocates, such as chief scientist Michael Hirschfield of Oceana, said they hope the report would spur countries to reassess their practice of providing roughly $20 billion a year in subsidies for harmful fishing practices.
“The single biggest thing we can do to address this is to eliminate subsidies,” said Hirschfield, adding that European Union countries alone account for 10 percent of these subsidies.