Early on, Baskin poses the question of how much biological diversity does any particular ecosystem need to remain functional, or to continue to provide essential life sustaining services? What species can we ‘afford’ to lose, which ones prove to be critical to maintaining life support systems that directly benefit their ecosystem and humanity? And in the Northwest, do salmon qualify as a critical keystone species within the watersheds? As Baskin mentioned, it is important to remember that while humans can do without a given species, the chain reaction that results from the disappearance of that species may eventually cause ecosystem functions to malfunction or cease. The key rivet removed that caused the plane’s wing to collapse may not have been intentionally unscrewed.

Baskin states that if many species in an ecosystem perform the same functions or occupy similar niches, the community should be able to compensate with a similarly functioning species if another should disappear. She gives numerous examples of what happens when certain species cease to carry out their role in the ecosystem and a few that had no replacements; sea otters over-hunted = explosion of sea urchins = decimation of kelp forests = disappearance of kelp dependant communities, and so on. Like sea otters, salmon are unique to their community in that they reverse the flow of energy, bringing nutrients back up into the watersheds. No other species can replace the nutrient retrieval that salmon perform every year in the Northwest, no other species brings back ocean derived nutrients to freshwater ecosystems in mass as the salmon do. If the salmon were to disappear entirely, that role or niche would surely not be immediately replaced by another species.

But the difference between the situation of the otters and the salmon is that we are not just extracting the fish from the water, but destroying their habitat along with them. It is difficult to say whether or not salmon is a keystone species when their natural habitat is plowed over for grazing or piped under a shopping mall. And have we already destroyed other critical species in those same streams? We have already gotten a glimpse of what happens when stocks disappear due to human encroachment, but it’s not just the salmon that vanish, but nearly the entire riverine ecosystem that suffers at the hand of uncontrolled development. We are not just threatening salmon, but whole ecosystems based on freshwater streams are disappearing under pipes and grassy lawns.

Baskin notes that an organisms talent or function may not become apparent until after is gone. I have often wondered if any studies have been done of the nutrient levels of streams where salmon are abundant versus where salmon returns have all but disappeared. What happens to the species that depended on the salmon for nutrients; the dippers, eagles, bears and riparian plants that benefit from the salmon carcasses? Perhaps some of these species carry on, finding alternative nutrient sources, but what of the species that are salmon dependent; are any of these species critical to the ecosystem? It appears that a chain reaction occurs whenever we tamper with natural systems.

Aldo Leopold stated in Sand County Almanac that the first rule of intelligent tinkering is to keep all of the parts. Indeed we do not know of all the functions and purposes of the salmon and their interactions with the many ecosystems they inhabit. Maybe the salmon are not a keystone species in the ocean, but perhaps they play more of a critical role when they enter freshwater. It’s disturbing to sort through the idea of which species are the most critical to save; Baskin likens this biological valuing to technologically ignorant hospital administrators deciding which life support systems are most critical for patient to survive. We simply do not understand all of the interactions of the salmon or any other species to determine whether or not it is critical to ecosystem health and survival.