River Rail Colby Issue
River Rail

When Ecosystem Recovery Hinges on History: Intergenerational Memory and Marine Conservation

How many fish should you catch on an afternoon fishing trip? Marine ecologist Loren McClenachan thinks about the shifting baselines in our perception of recovery and change.

Shifting Baselines

When should the first spring lilacs bloom? How many fish should you catch on an afternoon fishing trip? How far should you have to drive to get to the edge of town? Your answers to these questions depend on your baseline, or the idea we each have in our minds of what is “natural.” We subconsciously attach meaning to our first experiences of something—the arrival of spring, a good day out fishing, or the green space in your town—and assume that all noticeable later changes are somehow unnatural. Predictably, this baseline varies by age. You may remember your childhood home to have been surrounded by trees, having watched the encroachments of development over the course of your life. If you asked your town’s older residents, their memories would be different, greener perhaps.

The loss of memory regarding environmental change across generations has been called “generational amnesia” or “shifting baselines.” Such forgetting has particularly afflicted our sense of the oceans, where we have made fewer observations. As terrestrial animals, humans don’t track underwater change very well, but when people with the strongest connections to the sea describe their experiences, strong evidence for shifting baselines emerges. For example, the then-Ph.D. student Andrea Sáenz Arroyo interviewed members of three generations of fishermen in Baja California in 2005. Compared to the youngest fishermen, those from the oldest generation remembered fish that were five times more abundant, as well as fish that were larger and closer to shore. These accounts are not just “fish tales” or nostalgia for an invented past. In my own work as a historical ecologist, I measured similar changes using photographs of trophy fish caught in the Florida Keys since the 1950s. Over 50 years—or just two human generations—the weight of these fish declined by 90 percent.

It turns out that 90 percent loss in the oceans is typical. When we look for change over time across different species, ecosystems, and ways of measuring, we find similar stories. Ninety percent of tuna and swordfish caught by Japanese long-line fisheries disappeared over the course of 50 years. In the Gulf of Maine, cod stocks have declined by 96 percent since the Civil War. The Canadian writer J. B. Mackinnon called this phenomenon the “10% world.” The world that we think of as “natural,” he noted, is less wild by an order of magnitude than it was in recent human history.

This diminishment matters not only for our own personal sense of connection to the natural world and to past generations but also because our collective ideas of what is natural underlie efforts at conservation and environmental management, and therefore guide the future of the natural world and our relationship to it. In 1995, in his short, influential paper “Anecdotes and the Shifting Baselines Syndrome in Fisheries,” the fisheries scientist Daniel Pauly described the prevalence of generational amnesia among professional fisheries scientists. He argued that the loss of memories of productive and abundant fish stocks over the course of generations has led to a reduction in fisheries management targets. If younger generations of fisheries scientists expect that the ocean is naturally less productive and fish stocks are “naturally” smaller, their targets will align with such baselines and we will all be worse off for it.

In my own work, I have found that this failure to understand loss leads to reduced expectations in fisheries management, endangered species recovery, and ecosystem restoration. For example, when extinction risk for green turtles—a species whose meat has been compared to beef, such that people ranging from 17th-century pirates to modern politicians in Caribbean nations have enjoyed them—is assessed using short-term observations, the populations appear to be fine. If, however, scientists look back in time and use archival documents to understand the drastic population reduction in response to historical hunting, its populations can be assessed as endangered and in need of protection. In cases ranging from fish to turtles to marine mammals, when long-term data are overlooked, conservation scientists underestimate past impact and set future targets that are less ambitious.

Policy Placebos

When shifting baselines result in lackluster conservation targets for fisheries, these goals wind up limiting the recovery potential of the ecosystem. Falsely identified gains also limit such potential. In 2015 one of my research students, Samantha Lovell, set off to the Caribbean islands of Montserrat, Antigua, and Barbuda to interview fishermen and scuba divers about their views of underwater change. We expected that she would find a shifted baseline—as numerous other researchers have replicated Dr. Sáenz Arroyo’s work within the past decade—but we were surprised to also find what Sam called a “policy placebo” effect.

In these islands, conservation actions have been taken, in particular for green turtles, whose populations have locally been driven to near-extinction. In Antigua and Barbuda, for example, seasonal closures on hunting were put in place as a result of exceptionally low population sizes. Because turtles have a generational time twice that of humans, recovery is slow, and the effects of these efforts would not likely be noticeable for decades. However, half the people interviewed by Sam reported that they were seeing more turtles after only three years of protection. One interviewee said, “There are too many turtles and there keep being more.” Sam received similar answers about other recently protected marine animals, including parrotfish, lobster, grouper, and conch.

Sam attributed this surprising response to the good publicity that local conservation policies had received and the widespread public assumption that these policies were already effective.

The policy placebo effect may not be entirely a bad thing for future conservation endeavors, since people are likely to support policies they feel are working. However, coupled with a shifted baseline, the belief that we have already achieved our limited goals is likely to lower both targets for recovery and the motivation needed to sustain restoration efforts.

Unshifting Baselines

Despite the dual syndromes of shifting baselines and policy placebos, there are examples of bright spots occasioned by the reversal of population declines, the use of multigenerational observations to achieve ambitious conservation goals, and the return to historical baseline levels of abundance in certain ecosystems. One of these is in our own backyard, in Maine’s rivers.

One legacy of Maine’s industrial history is the hundreds of dams blocking downstream water flow, which prevents anadromous fish like salmon and small alewives from swimming upstream from the ocean to freshwater lakes to lay their eggs. In preindustrial Maine, these fish were the basis of small-scale fisheries, supporting towns and native communities along Maine’s rivers, and likewise supporting healthy ecosystems feeding predators from coastal cod to inland birds of prey.

As the need for these dams has diminished, many have been removed, and surprisingly the fish have appeared almost immediately. It’s as if, for the past 200 years, alewives have migrated upstream and have stopped at the dam to ask “Is this the year?” until in fact it was. In Benton, a town on the Sebasticook River 10 minutes from Colby College, the removal of a downstream dam in 2008 resulted in an active alewife run for the first time in over two centuries. The fish returned in force: the first cohort of alewives to pass upstream exceeded 1.7 million fish, the largest run on the US East Coast in 2009.

Successful conservation depends on community members buying into such efforts, and in a place rooted in history like Maine, connections to the past play an important role. In anticipation of recovering alewife runs, community members—led by Rick Lawrence, a retired schoolteacher whose eyes sparkle with his clear love for Maine’s natural world—petitioned the state for the reestablishment of historical harvesting rights. Because this request required the documentation of a historical fishery, he and others collected historical anecdotes describing local alewife harvesting, including a traveler’s account that “thousands of barrels” were taken on the Sebasticook River “just above the falls” in Benton in 1796. The town’s petition was successful, and municipal fishing rights were officially restored in 2009.

The restoration of the fishery meant revenue for local harvesters and the town, but the success ran deeper than short-term profits. Sam Lovell and another student, Caroline Keaveney, spent a summer working with me, traveling throughout Maine and asking community members about alewife restoration efforts. We found a strong sense of pride in local restoration projects, which in turn motivated more ambitious recovery goals and conservation action. One alewife harvester said, “Pride [leads to] involvement, and with more involvement you get people who are willing to spend more money, which supports the restoration and the ecosystem.” The case of Maine’s alewife recovery demonstrates a reversal of the shifting baselines syndrome and shows how social and ecological successes can create a positive feedback loop that increases community engagement and interest in restoration efforts.

We humans, optimistic by nature, adapt psychologically to the world we inhabit, wanting badly to feel that everything is okay. Shifting baselines result from humans assimilating ourselves into a degraded environment, and policy placebos result from a desire to have already achieved our goals when we take collective action. However, there is another option, demonstrated by Maine’s recovering river communities. When anecdotes and observations from the past are used to set appropriately ambitious recovery goals, and communities feel connected to its restoration successes, then we can recreate the productive and abundant ecosystems of the past, to move from our 10 percent world toward something closer to the world that members of past generations experienced.


Lauren McClenachan

Loren McClenachan is a marine ecologist interested in long-term changes to marine animal populations. Her research focuses on historical ecology and the applied use of baselines, fisheries conservation, and marine extinction risk and consequences, with the goal of halting declines and promoting recovery of marine animals and ecosystems.


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