J. Emmett Duffy

Harvesting of wild fish and shellfish from the oceans provides a major source of protein to the planet’s population and supports an industry worth nearly $50 billion annually in the United States alone.

For the most part, Nature provides this service free, in the sense that we do not plow, fertilize, or weed the oceans to nurture these crops. But any business requires infrastructure to produce and deliver its product, and seafood is no exception. The difference is that the seafood industry is more intimately dependent on natural infrastructure in the form of biodiversity—the variety of interacting wild animals, plants, and microbes—and the habitats that support them. In other words, Nature manages the plant and pays the overhead.

The dependence of wild food harvest on diverse natural ecosystems seems intuitively obvious. But how important is it? A few years ago, a group of marine scientists and resource economists set out to answer this question quantitatively for the first time.

We focused on whether and how the variety of ocean life per se (as opposed to particular species of fish, for example) benefits human society. We collected data from a wide and unprecedented range of sources, from laboratory experiments to global surveys of fisheries data. The results, published in Science in November 2006, were strikingly consistent: loss of ocean species steadily degrades natural services critical to human welfare, including fish production.

While it’s easy to understand that loss of fish species is detrimental to fisheries, the new and surprising implication is that the less-conspicuous, easily ignored species—the "bugs" and "weeds" of the sea—are also key players in the ocean ecosystem’s normal functioning. Loss of even these species degrades the ocean’s capacity to provide fisheries and other critical services to humanity, such as coastal erosion control and water purification. As in other industries, such services require infrastructure in good working order.

But what got most attention was the report’s graphic emphasis of a previously documented but underappreciated trend: fisheries throughout the world are increasingly overfished and, if current trends continue, many could be gone—or commercially insignificant—by mid-century. The study found that fisheries were more productive and more resilient to disturbance in more-diverse ecosystems. Thus, the report’s most striking message is that loss of ocean biodiversity is more than just an esthetic issue—it represents a clear and present danger to human society. The reason is that biodiversity provides security. Investing in a diverse portfolio of fish stocks, like a portfolio of business stocks, buffers the investment against market (or environmental) fluctuations and preserves society’s options in the face of change. And if anything is certain in our future, it is change.

So what to do? In general terms, the answer involves three R’s: Reserve unspoiled habitats where possible, Restore degraded ones, and Reconcile human needs with those of the larger ecosystem. The growing network of limited-access or no-take marine reserves is addressing the first of these. Continuing efforts to reduce runoff of toxic materials, and of the nutrients that produce dead zones, is essential to restoring degraded marine habitats.

And where does aquaculture fit in? Whereas the United Nation’s Food and Agriculture Organization estimates that marine-capture fisheries have reached a global ceiling in production, aquaculture is growing rapidly worldwide. Can it save the oceans? That depends entirely on how it’s done. Farming carnivores like salmon can actually cause more environmental harm than wild-capture fisheries do because of their intensive demands for forage fish as feed and their prodigious waste output.

For aquaculture to be part of the solution rather than part of the problem, it must employ animals low on the food chain such as catfish and tilapia, avoid transmitting diseases and genetic defects to wild fish, and produce minimal waste and habitat destruction. All of these things are doable but require effective management and policy.

There is still time to save the seas. But it will take clear thinking, creativity, and political will. The flip side of every challenge is opportunity, which brings us to the third R, reconciliation. The rapidly changing face of the global environment is providing fertile ground for entrepreneurs and venture capitalists searching for ways to provide food, energy, and other human needs in new ways that will be sustainable over the long term. For example, waste from catfish farms might support growth of algae for biofuel production, with algal by-products going back into catfish feed.

Industrial society’s slash-and-burn approach to natural-resource use will not be profitable for much longer, and those focusing on sustainability are at the vanguard of a new economy.

by J. Emmett Duffy is Professor of Marine Science at the College of William and Mary, Virginia Institute of Marine Science, Gloucester Point, VA 23062-1346 ([email protected]).