The following is an excerpt from Half Wild: People, Dogs, and Environmental Policy by Dave Dempsey.
It was December 1989. Something was clogging the Lake Erie drinking water intake of the city of Monroe, interrupting the flow to city residents. Two days would pass before Monroe was able to supply all of its citizens with drinking water again. What the heck was going on?
An exotic species known as the zebra mussel, Dreissena polymorpha, a European mollusk, had found the Great Lakes a welcoming new home. Stowing away in the ballast water of a commercial vessel conducting cross-Atlantic trade, the mussels had disembarked in the lakes and, with no natural predators, had rapidly proliferated. And they had found surfaces to which they could cling.
Although the interruption of Monroe’s public drinking water supply was the first real alert to the general public that a new pest was in town, scientists had already been aware of the invaders. They had discovered the mussels in Lake St. Clair in 1988. But no one had predicted the explosion of zebra mussel populations in such a short time. Soon the species would become the headliner for a Great Lakes problem reaching back into the 1800s—the intentional and unintentional introduction of non-native aquatic organisms.
It was not the first time that a destructive non-native species had caused such severe disruption that governments were forced to react. In the 1940s and 1950s, the monstrous-looking sea lamprey, equipped with a large mouth containing numerous small teeth, had attacked Great Lakes fish with such voraciousness, sucking the lifeblood out of lake trout and other species, that the United States and Canada had signed the 1955 Great Lakes Fishery Convention to launch a counterattack.
I became familiar with the war on lamprey as a member of the Great Lakes Fishery Commission (GLFC), created by the 1955 convention, from 1994 to 2001. At their peak, before the creation of the GLFC, lamprey had killed more than 100 million pounds of Great Lakes fish each year. The commission was charged with controlling the lamprey.
More than forty years into the contest, government and lamprey were stalemated. Treatment of the lamprey with a targeted chemical at a cost of about $20 million annually, paid out of the GLFC budget, held lamprey generally in check. The annual lamprey fish kill had fallen to less than 10 million pounds. But there was no sign, and no likelihood, that humans would ever eradicate the eels from the Great Lakes. Like many other non-natives, the lamprey had multiplied astonishingly after reaching the upper lakes, and then hit an equilibrium where they could be managed, controlled, but not vanquished. Like a person keeping a chronic illness at bay with medication, Great Lakes fishery managers would need, possibly forever, to treat spawning rivers with toxins.
The anti-lamprey war did breed creativity. Experiments showed that underwater barriers could limit passage of adult lamprey upstream into spawning habitat. Less successfully, researchers explored the idea of lamprey birth control—introducing sterile males, who could theoretically outcompete those capable of contributing to reproduction. Policy makers even explored the idea of capturing Great Lakes lamprey and shipping them to European markets, where the animals are considered good eating. In 1996, the Great Lakes Protection Fund awarded Minnesota Sea Grant funding to conduct a two-year study on the overseas market potential for Great Lakes sea lamprey. At the time, lamprey had a potential market value of over $25 per pound in Europe, and the Portuguese expressed an interest in North American lamprey. Unfortunately, Great Lakes lamprey were too loaded with toxic contaminants to be advisable eating for Europeans or any other humans.
Given the wake-up call of the lamprey invasion, and the consequences of approximately 180 non-native species introductions since European settlement of the Great Lakes watershed by the 1950s, it would have made sense for governmental and scientific Great Lakes experts to be alert to the potential for harm from future non-native migrants. But they either wouldn’t or couldn’t marshal the will to demand preventive action. Experts had warned in the 1970s that zebra mussels could readily colonize the Great Lakes, but governments had taken no action to stop them. And now the cost to taxpayers, sport fishers, and the shipping industry would be staggering. Estimates of the annual cost of non-native mussels to the Great Lakes economy vary from hundreds of millions of dollars to several billion. The national cost was much higher. The Great Lakes were not the last U.S. stop for zebra mussels. In 2021, they had established themselves in more than six hundred lakes and reservoirs in at least thirty-three states.
One of the first newspaper reports about the impact on Monroe’s drinking water intake left until the final paragraph, almost in passing, the consequence of the zebra mussel infestation that would soon prove its most formidable challenge: “The growth of the mussels upsets the food balance in the lake, which could negatively affect salmon, perch, and walleye fisheries.”
That would prove true on a large scale. Zebra mussels and their cousins, non-native quagga mussels, consume the micro-organisms on which desirable Great Lakes sport fish feed. This eating habit would contribute to plunging salmon populations in some areas of the lakes and reduced growth for species like walleye. The future of the Great Lakes sport fishery became uncertain.
The onslaught of zebra and quagga mussels was only the newest chapter in the saga of human-introduced, non-native aquatic species in the Great Lakes. Non-natives had reached the Great Lakes system in all manner of ways. In addition to hitchhiking in ballast water, they had made it to the lakes in bait, illegal transport, dumping of waste fish, inadvertent transport by recreational boats, swimming up the system through canals—and sometimes through intentional acts.
There is still a need for preventive action to protect the Great Lakes from non-native species. A 2021 study identified 144 additional species, both plant and animal, which had the potential to reproduce in the watershed through natural dispersal, hitchhiking, and intentional release. The tools for protective action exist. Can governments depart from practices of the past to act in advance of a crisis?
There is also the question of whether the term “invasive” is accurate. After I gave a talk at Macalester College about the risk of Asian carp invasion of the lakes, a Ph.D. contrarian in the audience rose and begged to differ. He observed that humans are a natural part of the global ecosystem, and thus if their actions resulted in new species reaching the Great Lakes, this was simply the result of natural processes. It is a valid point to consider. What is natural and what is not? What is wild and what is not? Are they false dichotomies?
Once, early in my career, a friend and I stood on a Lake Michigan beach, marveling at the sweeping blue carpet of water covering nearly a 180-degree panorama. It was late autumn, and the water was free of vessels. We remarked on how the lake surface, from that vantage point on that day, was exactly what a human observer would have seen 5,000 years before. We agreed it was an aquatic wilderness area, where people were transients.
That was five years before the zebra mussel introduced itself to Monroe and demonstrated that the Great Lakes—both underwater and at the surface—are no wilderness. Before long, the mussels would transform that surface. By filtering particles of phosphorus, they clarified the water, creating the illusion of a cleaner lake when one gazed downward. Rather, such clarity signaled processes at work that few had anticipated, and whose evolution few could predict.
If the surface of the Great Lakes sometimes resembled a “Big Wild,” this was an illusion. Human action and inaction had transformed the lakes into a cross between an aquarium and a monumental scientific experiment. Invasive species made it clear that these waters were at best half wild.
This work originally appeared in Dave Dempsey, Half Wild: People, Dogs, and Environmental Policy, 2022, published by Michigan State University Press. Reprinted with permission. All other rights reserved.
