During an Annual Meeting session, researchers discussed how climate change has caused fish species around the world to leave their known ecosystems. | Ashley Gilleland/AAAS
BOSTON – Fisheries around the world are likely to come under increasing pressure from climate change. But effective, cooperative management approaches can blunt the projected impacts on both fish stocks and on the billions of people who depend on them – and in some cases even improve the health of key fisheries.
“The future is potentially prosperous, but only if we take action now to adapt to the kinds of changes that we now anticipate,” said Christopher Costello, professor of environmental resource economics at the University of California, Santa Barbara, at a press briefing at the 2017 AAAS Annual Meeting.
Costello and two other researchers presented their analyses of different aspects of the threats and opportunities for fisheries management in the age of climate change.
Costello has developed a global-scale model of projected changes in the world’s major fish stocks due to the effects of climate change. The projected changes boil down to two main effects: changes in productivity and changes in range, or species’ distribution in the world’s oceans.
His analysis suggests that more than half of the world’s fisheries are likely to shrink in productivity. And as certain key species shift their distribution, there will be new winners and losers.
“As a general statement, we find that the higher latitudes tend to be the ones that gain from climate change, where fish stocks are likely to become more productive and more prevalent,” Costello said. “And the areas near the equator and tropics are likely to lose.”
That change in productivity and distribution threatens to hit low-income countries in low latitudes the hardest, said Michael Harte, professor of marine geography at Oregon State University.
“We know that inventive rights-based management and tenured-base practices can help get management right in the age of climate change,” said Harte. “If we succeed in doing this well, the world’s fisheries can do better than they are today. If we fail to get it right, the losers will be the people who can least afford it. They depend on fisheries for their food and incomes and they don’t have many alternatives. If the fish go, they’re in trouble.”
But with more effective management approaches, Costello agreed, “we can actually be better off on all three margins: more fish in the water, greater food provision and higher profits.”
Jake Kritzer, director of diagnostics and design at the Environmental Defense Fund, discussed his work looking in detail at a region that is being particularly hard hit by climate change: the waters of New England, where a long-term decline in the productivity of Atlantic cod is expected.
Kritzer examined a fundamental component of fisheries management: how catch limits are set. If the catch limit numbers are set too high, the ecosystem suffers. If the limits are too low, fishermen can lose their livelihoods. “Can we go about setting catch limits for fisheries that are more inherently resilient?” he asked.
His study found that sliding the “exploitation rate” up and down as fish numbers changed – instead of harvesting at a fixed rate regardless of the size of the population – optimized use of the fishery.
“Making that simple change,” he said, “tracking [fish] population size more closely, yielded much better outcomes for nature and for people. It could build more resilience into fisheries management.”
Other best practices, in some cases, are ancient.
“Looking at fisheries that are successful and models to be replicated that could counter balance these climate effects, many are based on providing secure fishing rights to fishermen,” Kritzer said. “Some people see this as a new, radically different way of managing fisheries. In fact, it’s rooted in approaches that many indigenous communities have had in place for millennia. Some of the best-managed fisheries in the developed world got to that level of success simply by reinvigorating or codifying these traditional tenure systems.”
Michael Harte’s research suggests that, as climate impacts intensify, a cooperative, trans-boundary approach to fisheries management will also be critical to protecting both fish species and the livelihoods of fishing communities around the world.
“A zero-sum approach doesn’t work in these fisheries,” he said, “and climate change just exacerbates that situation, because the stocks are moving. You can’t put barbed wire in the ocean. The challenge is that, when the fish move, the people can’t. If you’re in Indonesia, say, and productivity declines and the fish move, a fishing community can’t just move somewhere else.”
His work on a more “human-centric” approach to fisheries management highlights the benefits of cooperation. “We’re trying to show, if you don’t cooperate, this is what you’re losing. And then, what are the best practices that lead to good cooperation?”
As an example of a successful management framework, Harte cited the Parties to the Nauru Agreement, a coalition of Pacific island states that collectively manages their tuna fisheries. “The stock is shared and moves between all their waters. Instead of acting individually and allowing foreign vessels to come into each country’s waters and take their catches and be uncoordinated, they’re now working together as a coalition. And they’re generating hundreds of millions of dollars a year in benefits back to their local economies.”
The stakes of climate-adaptive fisheries management are high: about three billion people depend on fish for a significant portion of the protein in their diet.
“Globally some 800 million people suffer from food deficiency,” Harte noted. “By 2050 we have to increase food production by close to 100 percent to feed 9 billion people on this planet. These small scale fisheries supply food and incomes livelihoods for close to a billion people.”
“If we don’t get it right,” Harte said, “we’re going to potentially see a resumption of fish [trade] wars, a return to overfished and collapsed fish stocks, and a squandering of a critical food and economic resource.”