Ideas that add up #14

Ideas that add up #14

Complex, species-rich ecosystems, such as coral reefs or tropical rainforests, are able to persist in relatively predictable environments…. In contrast, harsher and more unpredictable environments tend to make for simpler ecosystems.

Robert May in FT, October 20th 2012

Stable environments promote complex ecosystems — those with more species and more interactions among them. This is because the genetic dice can be rolled enough times to permit the emergence of increasingly specialized exploiters of the available resources. When this stability is disrupted by an environmental shock, such as the introduction of an invasive alien species, complex systems may suffer a cascade of failure.

Stressed and volatile environments, however, keep species diversity in check. Nature’s experiments are winnowed out by environmental surprises before they have a chance to multiply and prosper. The result is a simpler ecosystem which is robust within a tolerated range of fluctuation.

Something called the May-Wigner Stability Theorem gets cited to explain this mathematically. Enough for me that it makes sense as elegantly as does the theory of natural selection.

  • Stability => complexity; complexity => vulnerable at times of change.
  • Volatility => simplicity; simplicity => robust at times of change, until the degree of change exceeds tolerated limits.

In other words, when a stable, complex system begins to change, due to external pressures, it will tend to shed complexity and default in the direction of simplicity. For an ecosystem, that means fewer species and a simpler network of relations among them. For a Byzantine bureaucratic organization it means fewer departments, teams, projects, people…. Meanwhile, a system which is already adapted to volatility will have less surplus to shake off to start with, but is prone to catastrophic collapse when change exceeds that system’s limits.

This principle is applied in the news article above to analyse the causes of systemic failure in banking and finance. It can be seen in the flourishing and demise of unique human languages and cultures. And it accurately describes shrinking species diversity in today’s stressed planetary ecosystem.

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