Photo courtesy of Mark Kasianowicz, Massachusetts State House Photographer.
A wood carving of a cod fish has hung in the Massachusetts' State House since 1747. The state's iconic fish has been decimated by overfishing and now faces increasing pressures from climate change.
New England’s fisheries stand at a cross-roads. With the strict fishing limits that went into effect for the 2010 fishing year (which ends in just over a month), fisheries regulators believe we have reached an historic milestone: the end of overfishing in U.S. waters. Or, more accurately, the beginning of sustainable fishing. Reaching this point has been financially painful for New England fishermen (and yes, many would consider that to be a gross understatement). But catch limits are expected to rise in coming years as historically overfished populations begin to recover, leading some in the industry to say that fisheries have reached their lowest point and things are starting to look up.
But here’s the catch (no pun intended). A few years ago, Michael Fogarty of the New England Fisheries Science Center in Woods Hole told me that he expected climate change to overtake overfishing as the primary pressure on fish populations within a decade. Indeed, the impacts of climate change on marine life – including commercially important fish species – are becoming increasingly apparent.
Scientists with the New England Fisheries Science Center in Woods Hole have documented dozens of species of fish and shellfish gradually shifting northward and into deeper offshore waters in response to warming waters.
William Cheung of the University of East Anglia predicts that the poleward movement could be as rapid as two and a half miles per year, and his computer models match up well with what scientists are seeing on the ground (or in the water). That means that the waters around Cape Cod could could be too warm for the region’s iconic namesake within decades.
Then there are the changes in water chemistry that come with rising levels of carbon dioxide – decreasing amounts of oxygen, increasing acidity. Although the idea is still open for debate, many scientists expect the combination of warming and shifting chemistry to cause precipitous declines in the abundance of the microscopic plants at the base of the food chain. Limited food plus inhospitable water conditions are a recipe for one thing – smaller fish. Cheung says we’ll likely see the maximum size of fish cut almost in half by 2050 and predicts a 30% drop in the tonnage of New England fish harvests.
While climate change and overfishing are fundamentally different processes, they present some of the same challenges for fishermen – namely, reducing both the size and number of fish. As a result, many of the strategies for coping with the two problems could be similar. Last week, I mentioned innovative projects around New England aimed at raising profit margins for fishermen catching fewer fish. But there’s another important component: diversification.
Catching smaller amounts of lots of different fish is one way fishermen can catch enough fish to stay afloat financially without putting undue pressure on any one species. But that assumes there’s a market for all those different fish. And that requires willing retailers and informed consumers – people who know how to cook and enjoy herring and redfish, as well as cod and haddock. There’s a growing interest in sustainable seafood, in all its varied possible forms, so there’s reason to be optimistic on this front.
Of course, to blithely say that fishermen can handle climate change and overfishing the same way ignores a fundamental difference. Catch limits and diversification are actually direct solutions to the problem of overfishing. In the case of climate change, the same measures are merely means of adapting to the completely external problem of climate change. The only way to solve the problem is limit greenhouse gas emissions, and that’s not something fishermen can do by themselves.
As carbon dioxide accumulates in the atmosphere, so too in the ocean. The result is a complex web of chemical reactions that, collectively, have come to be known as ocean acidification. Often called “global warming’s evil twin” or “the other carbon dioxide problem”, ocean acidification has risen to widespread notice, if not fame, in the past five years. What follows is the first in a three-part exploration of the diverse chemical and ecological impacts of rising carbon dioxide in the ocean.
