Understanding Complex Situations - a Fish Story

The BBC article Nature's spring: Cod bounce back by Richard Black describes the collapse of Atlantic cod stocks that led to the 1993 fishing moratorium.  Unfortunately, the ban on fishing did not result in the expected recovery, for reasons that have been hotly debated.  The recently published paper Transient dynamics of an altered large marine ecosystem suggests that predatory species such as cod, haddock and saithe (pollock) may be making a comeback due to a complex series of interactions and feedback loops.

Overfishing was a key contributor to pushing predatory species to the brink of extinction, but 'solving' that problem did not have the desired effect because the ecosystem shifted into a new state.  The loss of predatory species allowed "forage" species (herring, capelin and sand lance) to explode in numbers.  Forage species not only eat the eggs and larvae of cod but also affected zooplankton, the lowest level of the food chain, resulting in a crash of forage fish.  The article includes a graph showing the oscillations of forage specie biomass, similar to the movement of a weight on a spring.  The paper argues that predatory fish had an opportunity to re-establish themselves during years when forage fish stocks were low.  However, taking age into account, cod and haccock are considerably smaller than they were prior to the moratorium, possibly due to other changes in the ecosystem or genetic shifts caused by selective pressure on larger fish.

Key points I got out of the article:

  • complex systems are rarely 'fixable' in a simple cause/effect sense due to feedback loops and webs of interaction
  • complex systems may settle into one of multiple states, some of which can be stable for long periods of time whereas others can be transitory
  • complex systems can change at a wide range of speeds not only due to factors such as the breeding cycle of species but also response lags in feedback loops

The Algae Competition is grappling with many of the same issues.  When dealing with complex systems, it is easy to slip into 'solution mode'.  However, it may be much more important to gain a deep understanding of the structure and interactions of the system, articulating what a more desirable system state might look like, and then identifying interventions that help nudge the system towards that state.  As described by Donella Meadows in Leverage Points: Places to Intervene in a System, these interventions may be quite counter-intuitive.  The expectation is that asking the right questions will naturally lead to better answers.

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