The world's oceans could recover from human threat by 2050, says new study

Marine life that's been ravaged by years of fishing activity, nuclear tests and chemical pollution could see a "substantial recovery" by 2050 if world governments invest billions a year in restoration, according to a study released Wednesday.

The paper was published in the scientific journal Nature and co-authored by two researchers from Dalhousie University in Halifax, including marine ecologist Boris Worm. He told CBC's Mainstreet the findings counter previous concerns that some ocean ecosystems might have been irreparably damaged by human activity.

"This study really made me happy," said Worm. "I've been spending 20-years-plus chronicling threats to ocean ecosystems and species decline and so on."

Worm and Dalhousie colleague Heike Lotze were part of an international group of authors that reviewed hundreds of case studies on revitalized marine ecosystems, including:

• A rebound of fish stocks during both world wars due to a decrease in fishing.
• Coral reefs that recovered from nuclear tests in the South Pacific.
• Improved conditions in the Black and Adriatic seas after the collapse of the Soviet Union led to a reduction in fertilizer use.

Worm also provided an Atlantic Canadian example, noting that a major decrease in trawling in the Scotian Shelf led to the recovery of halibut and barndoor skate, two species of fish that had been approaching extinction.

The resilience of the world's oceans has also been severely tested, including by war. The U.S. military carried out 67 nuclear weapons tests in the Marshall Islands, a chain in the Pacific Ocean, beginning at the end of the Second World War. One of the atolls, Bikini, was the site of at least two Hiroshima-size atomic tests as well as the detonation of the world's first hydrogen bomb, estimated at 1,000 times the strength of the Hiroshima bomb. The massive bomb created a crater two kilometres wide and 80 metres deep.

"You would think that place is gone forever, but it wasn't," said Worm.

"Divers go there now because it's one of the best places in the Pacific to see vibrant coral reef ecosystems, huge numbers of fish, sharks, turtles, you name it. The place has just rebounded in a spectacular way."

While clear-cut forests can take generations to recover, marine recovery happens far more quickly, in part because industrialization is far less intense in the oceans, Worm said. He notes the closure of a large section of the Georges Bank fishery off the east coast sparked a massive population boom.

"Within a few years, scallops increased 14-fold in that area and haddock stocks more than sevenfold," said Worm. "And now haddock in that area is more abundant than in the last 100 years."

Potential dividends?

The study's authors issued 45 recommendations, including a call for governments to continue the recovery trend by protecting vulnerable habitats and species, adopting sustainable fishing practices and taking action against climate change.

Researchers put the price tag for such efforts at $10 billion to $20 billion US a year, but Worm said the initiatives would spark a renaissance in the global seafood and ecotourism industries.

"They're essentially paying for themselves because of the value of some of these assets," he said.

"So for example, if we were to keep rebuilding fisheries the way we're attempting here in Canada ... globally the benefits from it would be north of $50 billion a year to the fishing industry, sustainably, year after year."

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