is, if ownership is held by everyone, but each individual is allowed to exploit the asset freely, no one has an incentive to conserve the resource. Frequently, the result is disaster.

The greatest “common” of them all, of course, is the world’s oceans, which cover about 72 percent of the earth’s surface. By ancient international law and treaty they and their resources are free and open to everyone. For much of history, that worked very well. But twentieth-century technology and increasing population are rapidly resulting in a tragedy of the commons of epic proportions. Perhaps this impending tragedy can best be understood by looking at the history of that singular beast the Atlantic cod.

The cod is not very prepossessing, but as a commercial product it is a wonder. It is easily caught, and its flaky, white, nonfatty flesh is relatively boneless and simple to preserve by drying and salting. Dried cod (often known by its Spanish name, bacalao ) is about 80 percent pure protein. Equally important for its commercial potential, dried and, especially, salted cod has a very long shelf life. In a world without refrigeration, that was a quality without peer, and cod became a staple of the Western European diet for centuries.

The cod lives generally from twenty to three hundred fathoms deep and prefers the relatively shallow waters of offshore banks. Many seagoing European nations, from Norway to Spain, sought to exploit this abundant and versatile food resource, but it was the Basques who found the mother lode. The Basques, who live in northern Spain and the southwest corner of France, had hunted for whales for centuries, searching far across the Atlantic. In the late Middle Ages they began to bring back cod as well, but nobody knew where it was coming from.

The traditional European codding grounds were in the North Sea and as far west as Iceland, but the Basque fishermen were not to be found there. Instead, each spring the Basque fishing fleet would set sail and, in the fall, return laden with cod, already dried and salted and ready for market. Fish can’t be dried on a ship’s deck, however. So where were the Basques finding and drying their fish? The Basques, needless to say, weren’t telling.

In 1492, Columbus discovered islands far to the west, and soon French and British explorers began searching for a northwest route to the Spice Islands. Although such explorers as John Cabot and Jacques Cartier failed to find the Northwest Passage, they did find cod, lots of cod, and vast stretches of shoreline on which to dry it. They also found something else: Basque fishermen.

When Carrier first visited the mouth of the St. Lawrence River, in 1534, and claimed the land for France, he noted the presence in his new “discovery” of more than

a thousand Basque fishing boats, all happily catching cod.

From Newfoundland to Massachusetts there is a series of banks, exactly the shallow water that cod prefer. The warm water of the Gulf Stream flows up from the south, while the Labrador current flows down from the Arctic. Meeting over the banks, the two currents roil the waters as they mix, stirring up huge amounts of nutrients. The result of this chance congruence of geographic factors is, to put it mildly, cod heaven.

With the Basque secret revealed, there resulted a cod rush—to use the phrase of Mark Kurlansky in his highly entertaining Cod: A Biography of the Fish That Changed the World. By the mid-sixteenth century, 60 percent of the fish being consumed in Europe was cod, most of it caught off North America. One of those who participated in this cod rush, although he would have much preferred to find gold, was Captain John Smith. Immortal for his part in founding Virginia, in 1614, Smith explored a part of the North American coastline to which he gave the name New England. Disappointed in his search for gold, he set his men to fishing for cod while he went exploring in the ship’s pinnace, mapping the coastline from Maine to the cape that was already named for the fish.

Smith’s map and description of New England—and his profits from cod fishing—encouraged the Pilgrims to seek a charter from the Crown to settle there. Indeed, it was the cod that saved the first European New Englanders. In 1640, only eleven years after Massachusetts Bay Company had been founded by the Puritans, it exported 300,000 cod to Europe. Cod was soon also being traded to the West Indies, in exchange for salt, sugar, and molasses. In addition, plowing in the cod waste greatly increased the agricultural productivity of the stony New England soil.

The cod proved the basis of a New England prosperity so considerable that Adam Smith singled it out for praise in his Wealth of Nations. To this day, a wooden sculpture of a cod adorns the walls of the Massachusetts Statehouse in Boston to remind the legislators of the source of their state’s greatness.

The great cod rush differed from the more familiar gold and oil rushes in that cod is a renewable resource. Like a well-managed trust fund, the North American fishing banks should have paid out dividends in the form of cod forever. For several hundred years they did exactly that. As late as 1885, the Canadian Ministry of Agriculture was of the opinion that, “unless the order of nature is overthrown, for centuries to come, our fisheries will continue to be fertile.”

But one century was all it took for a tragedy of the commons to unfold in this entirely unmanaged trust fund. The major fishing nations, each trying to get its share, exploited newly available technology—especially high-powered engine-driven ships, dragnets, and onboard freezing—that simply caught cod faster than

even this prolific species could reproduce.

In hopes of finally exerting some control, the United States and Canada extended their jurisdictions out 200 miles. Then, in 1992, Canada, trying to give the cod a chance to reproduce unmolested for a period and thus save a priceless asset, banned ground fishing (fishing for bottom-feeder fish, principally cod) in most of its Atlantic waters.

It is too soon to know if this will work. But it is not too soon to know that the old system of common ownership does not.