Human-dominated marine ecosystems are experiencing accelerating loss of populations and species, with largely unknown consequences. We analyzed local experiments, long-term regional time series, and global fisheries data to test how biodiversity loss affects marine ecosystem services across temporal and spatial scales. Overall, rates of resource collapse increased and recovery potential, stability, and water quality decreased exponentially with declining diversity. Restoration of biodiversity, in contrast, increased productivity fourfold and decreased variability by 21%, on average. We conclude that marine biodiversity loss is increasingly impairing the ocean’s capacity to provide food, maintain water quality, and recover from perturbations. Yet available data suggest that at this point, these trends are still reversible.2

Dr. Worm warns that if fishing practices continue unabated, there will be a collapse of all fished species by 2050. Take for instance bluefin tuna: Callum Roberts, a professor of marine conservation at England’s University of York and author, has calculated that there is now only one bluefin left for every fifty that were swimming in the Atlantic in 1940. In 1980, 13.5% of all fished species had collapsed. By 2003, the last year for which data on global commercial fish catches are available, this figure had more than doubled to a 29% collapse.2

According to Roberts, “with an ever-accelerating tide of human impact, the oceans have changed more in the last 30 years than in all of human history before.” Today, he adds, “in most places, the seas have lost upwards of 75% of their megafauna — large animals such as whales, dolphins, sharks, rays, and turtles — as fishing and hunting spread in waves across the face of the planet.”

For the last 25 years, politicians have allowed the fishing industry a one-third larger catch quota on average than scientists have recommended as safe.3 Such tactics make Daniel Pauly, a fisheries scientist from Canada’s University of British Columbia describe world fisheries as a giant Ponzi scheme.

Ponzi schemes work by paying investors from the capital in a fund rather than from returns made on their investments. Similarly dependent on a constant input of new capital, the fishing industry is hunting fish to the farthest limits of the oceans and to depths where productivity slows to a trickle. Pauly says the jig is almost up: In 1950, the newly constituted Food and Agriculture Organization (FAO) of the United Nations estimated that, globally, we were catching about 20 million metric tons of fish (cod, mackerel, tuna, etc.) and invertebrates (lobster, squid, clams, etc.). That catch peaked at 90 million tons per year in the late 1980s, and it has been declining ever since.4

Fisheries are now failing because, like in a Ponzi scheme, they are running out of new capital. The real cost of these exhaustive fishing efforts is hidden from consumers, as American fishing fleets are very heavily subsidized. The United States provides nearly $30 billion in subsidies each year — about one-third of the value of the global catch. This level of federal financial aid is mind-boggling when one considers that the fishing industry’s contribution to the GDP in the United States is less than half that of the hair salon industry.4

Some researchers, Dr. Boris Worm among them, feel that an emerging fishery management system called “catch share” holds promise for curtailing overfishing. Catch share limits the annual tonnage of a particular species that can be taken, and the total number of fisherman who can take them. Licensed fisherman own shares of each total permitted catch. Similar to a corporate stock, shares can be bought, sold or traded, and their value fluctuates. The more fish there are, the more the shares are worth. While the name of this system is new — and its practice is new to the United States, similar systems have long been in use in other parts of the world, dating back to feudal times in Japan.

Supporters of catch share programs put forth the logic that if you own something (in this case, the shares of a permitted catch), you are more likely to take care of it. (Think of owning a house as opposed to renting an apartment; if you don’t take care of your house it loses value.) Another advantage is that catch shares would end the race to fish. Bluefin tuna are hugely valuable (partly because they are now so rare) so instead of allowing stocks to recover (as scientists recommend) countries are competing for the few available fish.

Critics of such programs don’t think the catch share logic adds up. Callum Roberts says catch shares are oversold. He warns that buying and selling of catch shares means small family businesses would be selling out to larger firms, putting the ownerships of fisheries into fewer and larger hands. Further, Roberts says, “there is little evidence that the new owners of catch shares feel any responsibility for long-term stewardship of the seas — or indeed that catch shares offer up any wider environmental benefit.5 Having given away public property, it will cost society dear to get it back if we change our minds. Imagine how you would feel if your government gave away all the national forests to industry and then twenty years later used your taxes to buy chunks back to turn them into nature reserves or return them to the public amenities they once were.”

Seth Macinko of the University of Rhode Island sums up the problem of politicians ignoring scientific advice when he says, “Catch shares are seen as a solution to the problem of fisheries management, but we haven’t tried management yet!”

Some look to aquaculture (fish farming) as a means to reduce the burden on our oceans, but these farms are far from efficient, as it takes five pounds of wild fish (fed to farmed fish) to produce just one pound of farmed fish. Fishmeal from wild fish isn’t only fed to farmed fish; it is also fed to livestock for meat, dairy and egg production. In fact, one-third of the world’s fish catch is fed directly to livestock.6 For more on fish farms, see the article in this magazine.

If people feel they must eat fish, it is sensible to eat lower on the food chain (smaller fish like anchovies and sardines). Avoid large, long-lived species. Beyond that, ask these questions when choosing seafood: Is this species in trouble in the wild where these animals were caught? Does fishing for this species damage ocean habitats? Is there a large amount of ocean bycatch taken with this target species? Does this fishery have a problem with discards (undersized/undesirable animals caught and thrown away because their market value is low)?

As Callum Roberts points out in The Ocean of Life, changing course by the smallest degree will put us in a very different place in coming decades. Each sustainable decision we make will add up in the long run.

“When humans get into trouble they are quick to change their ways,” says Dr. Boris Worm. “We still have rhinos and tigers and elephants because we saw a clear trend that was going down and we changed it. We have to do the same in the oceans.”


  • Worm B. Impacts of biodiversity loss on ocean ecosystem services. Science. 2006;314: 787-790.



  •, retrieved August 14, 2012



  • O’Leary, B. et al., “Fisheries Management,” Marine Pollution Bulletin (2011) 62: 2642-48.



  • Pauly, Daniel, “Aquacalypse Now,” The New Republic (2009)



  • Essington, T. E., “Ecological Indicators Display Reduced Variation in North American Catch Share FIsheries,” Proceedings of the National Academy of Sciences 107 (2010): 754-59.



  •, retrieved August 14, 2012



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