"By investigating the human-nature dynamics of these past cases of #collapse, the project identifies the most salient interrelated #factors which explain civilisational decline, and which may help determine the risk of collapse today: namely, #Population, #Climate, #Water, #Agriculture, and #Energy." http://www.theguardian.com/environment/earth-insight/2014/mar/14/nasa-civilisation-irreversible-collapse-study-scientists