The shifting baseline problem (part 1)
A big problem with Unanticipated Consequences is that the baseline keeps moving. Here are a few examples.
When I was an undergraduate student living near the Pacific in Southern California in the early 1970s, I would occasionally put on my mask, fins, and snorkel to swim out and get an abalone or two for dinner. It wasn’t hard—on the rocky shores near Laguna Beach, I could easily pick up two or three abs for a weekend dinner.
Starting around 1980, I noticed a decline in the number of abalone in the rocky reefs. You could still find one, maybe two on a good day, but they were becoming rare. When I started abalone fishing I could find 4 or 5 without working very hard.
Now in 2024? They’re just not there anymore. Undergraduate students today might be able to get sea urchins uni for a sushi brunch, but the shellfish has been in a decline for decades, with abalone numbers dropping to near zero.
The decline of abalone populations has been driven by overfishing, disease, and habitat loss.
Both commercial and recreational fishing placed significant pressure on abalone populations. As the nearshore populations became depleted by snorkelers and scuba divers, fishers had to range farther afield to find abalones to harvest.
Then, to make matters worse, in the 1980s and 1990s, a bacterial infection called Withering Syndrome caused widespread decline among abalone in the Channel Islands just off the Southern California coast. The disease spread all up and down and along the central California coast. [Moore]
The abalone decline was masked for some time by a phenomenon called "serial depletion." As one species' population decreased, fishermen would switch to another species, giving the false impression of a stable overall fishery. [Karpov] The slow decline in total abalone numbers were hidden by the relatively invisible nature of the underwater stocks—it’s hard to worry about something that’s more-or-less hidden and slowly changing.
But by the 1990s, the loss of abalone had become critical. In 1993, the black abalone fishery was closed. And in 1996, the remaining pink, green, and white abalone fisheries in Southern California were closed. The entire state has now been closed to abalone collecting, and will remain closed until at least 2026. [NOAA]
You can see the problem: the decrease in abalone along the California shore was masked by being difficult to see, by the effects of serial depletion, and by changes to what people saw as normal. Recognizing the problem came only when—forgive me—the abalone population was under water.
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“Things take time.” You’ve probably heard that since you were a child, and it’s true. But sometimes change happens so slowly that it’s imperceptible except across the time span of decades or lifetimes. This chapter is about the effects that take so long to happen, that it takes decades to recognize that things are going south. In many ways, rapid changes are easy—you can see when things go bad in front of your eyes. But when change takes many years, we can easily overlook it.
This is the problem of long, slow timelines. People tend to define “normal” as their experiences during their own lifetime. It’s only when you talk with previous generations that you realize there are slow consequences too. Climate change, the spread of megacities, the shift in animal or insect populations—each of these is slow, but the consequences are just as bad.
In 1995, Daniel Pauly described the “shifting baseline syndrome” and its implications for fisheries management. Pauly found that each generation forgets what fisheries used to be like, causing a kind of generational amnesia that allows successive generations to accept the current impoverished state of marine fisheries as normal. The generational forgetting of prior fisheries cloaks the changes in fisheries over the years, making it very unclear what the goals of fisheries regulation should be, or even could be. [Pauly]
This amnesia problem “..has arisen because each generation of fisheries scientists accepts as a baseline the stock size and species composition that occurred at the beginning of their careers, and uses this to evaluate changes. When the next generation starts its career, the stocks have further declined, but it is the stocks at that time that serve as a new baseline. The result obviously is a gradual shift of the baseline, a gradual accommodation of the creeping disappearance of resource species, and inappropriate reference points for evaluating economic losses resulting from overfishing, or for identifying targets for rehabilitation measures…” [Pauly, 1995]
Each generation of fishermen accepts the current fish population and size as normal, not realizing how much it has declined over time. For instance, in the 1950s, fishermen in the Gulf of Maine would routinely catch cod over 100 pounds. By the 1980s, a 50-pound cod was considered large. Today, many fishermen have never seen a cod over 20 pounds, and most now consider this normal. This gradual acceptance of diminishing fish stocks as the new norm has contributed to overfishing and made it harder to recognize the extent of marine ecosystem degradation.
This is a story that has been repeated endlessly in fishery management circles. It's especially difficult when the fishery has a long tradition with generations of local fisherfolk invested in the industry, all of whom face economic displacement when their preferred fish become impossible to find.
And it’s not even a recent story.
In the pre-European colonization era of California, Native Americans would frequently dine out so often on particular species of birds (or fish, or mammals) that they would cause a localized extinction. In one notable study, researchers found that prehistoric San Francisco Bay dwellers would repeatedly eat specific kinds of birds into local oblivion, at which point they’d shift their attention to another kind of bird and then eat that species into extinction. [Broughton] First to go were the largest geese species—then the smaller geese—then attention would turn to scoters, then cormorants, then even smaller shorebirds. There’s little evidence that the bird hunters realized that their avian landscape was changing under their gustatory influence—as with the abalone, hunters would shift from one prey species to the next as availability afforded. [ScienceDaily]
Most surprisingly, when European settlers arrived into the Bay area around 1776, they also imported a number of diseases that had dramatic killing effects on the local human population. [Ehrenpreis] The subsequent depopulation because of European diseases led to a massive reduction in hunting pressures on the bird population, leading to hyperabundance. Surprise! In relatively short order there were large flocks of birds all around the Bay. [Preston]
"The wild geese and every species of water fowl darkened the surface of every bay ... in flocks of millions.... When disturbed, they arose to fly. The sound of their wings was like that of distant thunder."
-- George Yount, California pioneer, at San Francisco Bay in 1833
from: The Chronicles of George C. Yount: California Pioneer of 1826, Charles L. Camp, George C. Yount, California Historical Society Quarterly, Vol. 2, No. 1 (Apr., 1923) https://www.jstor.org/stable/25177691
This massive number of birds then became the expected baseline for wildlife populations. In fact, it was a kind of false Eden—the numbers were elevated because the original Native American hunters themselves nearly died out, only to be shortly replaced by European hunters which then caused their own particular kinds of extinctions.
Because birds are very visible, attractive, and easy to identify and count, reliable records have been collected over many decades in North America. Drawing on many different kinds of data for North America, it has become clear that there has been a long, slow, and wide-spread decline in the population of birds over the past half-century, resulting in the cumulative loss of billions of birds across a wide range of species and habitats. The overall loss of birds is not restricted just to rare and threatened species—but is commonplace across those all kinds of birds. [Rosenburg]
What’s caused this gradual decline? It’s what you’d expect: Habitat loss, climate change, unregulated harvesting, electrocutions, oil spills, collisions with human-made structures such as vehicles, buildings and windows, power lines, communication towers, and wind turbines. All told, this is massive bird death by a thousand cuts—any one cause isn’t the problem, it’s all of the causes of bird mortality that combine to a slow, gradual loss. [Loss]
We barely notice this today. Your grandparents might remember back when huge flocks of birds would drop into agricultural fields, or when they would pass by in migration flights in their thousands. But it’s difficult for us to perceive the change with our limited life spans and distracted attention. Nevertheless, it’s a real effect, and a real consequence with many root causes.
We’ll talk more about the shifting baseline in the next post.
== References ==
Broughton, Jack M. Prehistoric human impacts on California birds: evidence from the Emeryville Shellmound avifauna. Ornithological Monographs (2004): iii-90.
Ehrenpreis, J. E., & Ehrenpreis, E. D. (2022). A historical perspective of healthcare disparity and infectious disease in the native American population. The American journal of the medical sciences, 363(4), 288-294.
Karpov, Konstantin, et al. Serial depletion and the collapse of the California abalone (Haliotis spp.) fishery. Canadian Special Publication of Fisheries and Aquatic Sciences (2000): 11-24.
NOAA “Abalone Restoration to Help Boost Dwindling Populations in Southern California” (Nov 17, 2023)
Loss, S. R., Will, T., & Marra, P. P. (2015). Direct mortality of birds from anthropogenic causes. Annual Review of Ecology, Evolution, and Systematics, 46(1), 99-120.
Moore, J. D., Finley, C. A., Robbins, T. T., & Friedman, C. S. (2002). Withering syndrome and restoration of southern California abalone populations. Reports of California Cooperative Oceanic Fisheries Investigations, 43, 112-119.
Pauly, Daniel. Anecdotes and the shifting baseline syndrome of fisheries. Trends in ecology and evolution 10.10 (1995): 430.
Preston, W. L. (2002). Post-Columbian wildlife irruptions in California: implications for cultural and environmental understanding. In Wilderness and political ecology: Aboriginal influences and the original state of nature. Edited by CE Kay and RT Simmons. University of Utah Press, Salt Lake City, Utah, USA, 111-140.
Preston, W. (1996) Serpent in Eden: Dispersal of foreign diseases into pre-mission California. Journal of California and Great Basin. Anthropology 18:2-37.
Rosenberg, Kenneth V., Adriaan M. Dokter, Peter J. Blancher, John R. Sauer, Adam C. Smith, Paul A. Smith, Jessica C. Stanton et al. (2019) Decline of the North American avifauna. Science 366, no. 6461, 120-124.
ScienceDaily (2006) “Early California: A Killing Field -- Research Shatters Utopian Myth, Finds Indians Decimated Birds” - summary of Broughton’s research.