Friday, December 4, 2020

Great news for coho salmon! Perhaps....

An article in Science magazine describes the new discovery that a little-known chemical used as a tire-preservative may be killing large numbers of coho salmon near roadways (due to the runoff of tire dust). This is being hailed as a tremendous success for salmon, the final chapter in a long search for the 'smoking gun' of coho salmon declines in the Pacific Northwest.

But the allure of the 'smoking gun' idea illustrates a deeper problem of our collective desire for simple answers from reductionist science. At our peril, we continue to forget that all ecological problems have to be viewed as potentially having multiple causes operating at multiple spatial and temporal scales.

The LA Times article is framed in such a way as to suggest that we should expect this level of precision in identifying a single primary source of mortality, and that this is needed before substantial action is taken. Other salmon species—and many other species—are likely declining not primarily due to this one chemical, but rather to the interacting effects of several known stressors (including climate change, other pollutants, diseases, habitat loss including dams and stream simplification), all of which can be managed. And if we wait until we’ve got a smoking gun, we will fail to address the true problem, which is multi-causal.
For Fraser River sockeye salmon, the problem is clearly multi-causal,
likely spanning the whole salmon life cycle. Does that mean we should
give up? No. Image from Marmorek et al., 2011.

E.g., quoting Peter Moyle from the LA Times article: “The challenge when you talk about declines of really sensitive fish like coho salmon, is that there are so many things that are affecting them simultaneously, it’s hard to pinpoint one”. It is hard, but sometimes or perhaps often it’s impossible, because it’s not a single smoking gun that’s the problem.
Joe Dillon: “Now that they’ve gotten it nailed down to one compound — that’s amazing. It’s also really helpful that something could be done about it”. Something can be done about all the known major stressors.
Matt St. John: “When you find a causal link like this that is controllable, we need to take this type of information seriously.” Yes, but we also need to take seriously the science that suggests that for most species, their downward decline is a cumulative function of several stressors, each of which may have mostly sublethal effects alone.
Even coho salmon, good news requires that government and industry act on this science and on other stressors that are also undermining coho survival and reproduction. In the past, such action has been stymied or delayed by pointing to each of the other stressors as suggestion that costly action won't even necessarily fix the problem. Let's not let such obfuscation interfere again.

More broadly, we have to recognize the limitations of this obsession with tidy reductionist science, and acknowledge the necessity of complex-adaptive-system science for most problems of the Anthropocene.


Marmorek, D., D. Pickard, A. Hall, K. Bryan, L. Martell, C. Alexander, K. Wieckowski, L. Greig and C. Schwarz (2011). Fraser River sockeye salmon: data synthesis and cumulative impacts. Cohen Commission Tech. Rep. Vancouver, B.C., ESSA Technologies Ltd: 273. 

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