Empires collapse, cultures dissolve and history repeats its self.
Here is an interesting quote I found years ago:
One of the early Church Fathers, Tertullian (c. A.D. 160 - 240), commented on the effects of human enterprise on the earth: “Farms have replaced wastelands, cultivated land has subdued the forests, cattle have put to flight the wild beast, barren lands have become fertile, rocks have become soil, swamps have been drained, and the number of cities exceeds the number of poor huts found in former times . . . Everywhere there are people, communities - everywhere there is human life!” To such a point that “the world is full. The elements scarcely suffice us. Our needs press . . . Pestilence, famine, wars, [earthquakes] are intended, indeed, as remedies, as prunings, against the growth of the human race.” (Gies, Frances and Gies, Joseph. 1994. Cathederal, Forge, and Waterwheel. Harper Collins. N.Y. p. 6.)
The above from: SUPERMAN PLAYS WITH KRYPTONITE DICE (an essay written around 1998) http://sunweber.blogspot.com/2010/05/superman-plays-with-kryptonite-dice.html
It is true there seems to be a life cycle to empires and many scholars have written about it.
This time it is significantly different. It is global. There are so many multishaped balls in the air right now (warming, ocean acidification, depletion of vital resources, water, air, soil, economic bubbles, to name some obvious ones) it is difficult to tell which one or ones will over stay the welcome in the system and make a mess of things.
There are those who understand the bubbling of economics and the shrinking pie. Some are fired up over the diminishing returns of oil or of other resources. The rising ocean or its lowering ph level concerns some. Some feel the heat or watch the tumultuous storms. Of course, there is the cry of too many, too many. And the gritty loss of dirt as a concern. And some will say but you forgot . . . . . . .
And there are of course polydoomers, juggling so many ifs.
There are the polydeniers too, they have so much compartmentalized there is rictus about their smile.
When is it happening? Now grindingly, and tomorrow? Tomorrow perhaps immediately - it won't be pretty no matter.
And it is necessary.