This is the sixth in a series of guest posts by Joel Barkan, a previous contributor to “The Intersection” and a graduate student at the Scripps Institution of Oceanography. The renowned Scripps marine biologist Jeremy Jackson is teaching his famed “Marine Science, Economics, and Policy” course for what may be the last time this year (along with Jennifer Jacquet), and Joel will be reporting each week on the contents of the course.

It seems simple enough: we should manage our marine resources to protect the whole ecosystem, not just a single species. That’s the basic premise of ecosystem-based management (EBM), the topic of this week’s class at Scripps (Read a previous post on EBM by Sheril here). EBM is all about interactions: between predator and prey, parasite and host, nutrients and phytoplankton, humans and our environment. The need for EBM comes from too many cases of a single-species management practice resulting in unintended impacts on the surrounding environment.

Take the Atlantic cod, for example, a fish that supported America’s most lucrative fishery in the 19th and most of the 20th century. Atlantic cod was overfished so heavily that its stocks are now virtually commercially extinct. We’ve all eaten cod, but you might not know what it looks like: it’s a voracious predator with an impressive set of teeth. Its jaws are powerful enough to easily crack the shell of all but the biggest, feistiest Maine lobsters. When cod stocks were depleted, the lobster populations boomed, free from the threat of one of their only predators. Now the North Atlantic lobster fishery thrives, while the cod fishery lays dormant. Lobsters are lured into traps by dead, smelly fish, which means millions of tons of Atlantic herring are caught every year and sold to lobstermen as bait. My personal research has indicated that increased herring fishing effort may have driven humpback and fin whales away from their traditional feeding grounds in the Gulf of Maine in search of a different food source.

Did you follow that? We went from cod to lobster to herring to humpbacks. To be fair, even the most fervent supporter of EBM would have struggled to predict that exploiting cod might eventually affect whales. But if the theory of EBM had been around during the heyday of the North Atlantic cod fishery (EBM has only entered the mainstream consciousness within the past two decades), someone likely would have at least raised a red flag. At its core, EBM is about taking a precautionary approach to management. Marine resource managers have historically thrown caution to the wind, even in the face of scientific uncertainty. This reckless style may become a thing of the past—NOAA chief Jane Lubchenco is one of EBM’s most prominent supporters.

EBM is a great idea in theory, but the practice is difficult to implement and even define. I just spent a three hour class learning and talking about it, but before writing this, I still had to brush up on the topic with NOAA’s 1998 Report to Congress on EBM. We can attribute the haziness of EBM to its relative infancy as a concept. As more scientists and policymakers continue to embrace EBM, we may see it transition from merely a good idea to a realistic strategy.