All Three

In my environmental ethics class we discussed the possible causes of ecologically associated precipitious declines of complex societies (of which there have been several throughout history).  Here are three potential explanations:
1.  The Dinosaur: a large scale society depletes resources are at an exponential rate, yet there is no adequate response because the rapid depletion of resources creates short-term economic advantages for the ruling elite.
2.  Runaway Train: Society only functions when growth is present so growth continues, even though it is unsustainable and must ultimately result in collapse.
3.  House of Cards: societies become too large and complex, becoming  inherently institutionally unstable as resources become unmanageable.
Our professor (James Thobaben) posed the question to the class of whether any of these models might apply to our society.
Personally I found it a bit disconcerting, even if unsurprising, that all three might.
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