Diamond

"How could a society that was once so mighty end up collapsing?"

The author alludes to the idea the the modern society that we find ourselves in can also suffer from grand collapses that has plagued mankind for tens of thousands of years.  Man is notorious for its strong reactive approaches, compared to its meager preventative approaches. We have been on the brink of utter collapse in the past. In the start of the 1900s, there was a beginning of a food crisis, where there wasn't enough Nitrogen in the soils to feed the ever increasing population. But in around 1911, Fritz Haber discovered a way to create ammonia from nitrogen in the air, and badabing, badaboom, you get 7+ billion humans.

http://en.wikipedia.org/wiki/Fritz_Haber

We were almost all wiped out during the cold war between the US and Russia. The 2 nations had created enough nuclear warheads to irradiate life on the planet about a dozen times over. Fortunately our intellect prevented our destruction.

"Perhaps we can still learn from the past, but only if we think carefully about its lessons."

We need to take this statement to heart in order to succeed as a planet. This is the information age, where the average person who has access to a computer connected to the internet can learn more in a week than the most intelligent people knew back 1,000 years ago. [citation needed]

I believe that our future is bright. I do not think that our modern society will suffer a cataclysmic collapse that will lead to an eradication of the population. Even with the threat of climate change, I think that our prestigious intellect will allow us to weasel our way out of inadvertent doom. 

"Many people fear that ecocide has now come to overshadow nuclear war and emerging diseases as a threat to global civilization."

http://mmazroui.kau.edu.sa/ImageGallery.aspx?Site_ID=0003580&LNG=EN&Gal=450

Planet-wide human annihilation through planetary phenomena (excluding a large meteor or comet hitting the earth) is, I believe, very improbable. Do I think that humans are causing global climate change? Yes. Do I think we can do something about it? Yes. But  even in the worst-case-scenario, I think humans will progress. The dark ages are the most recent historical example of a decrease in average human intelligence and life-expectancy.[citation needed] But in a world of decreased religious upbringings, and a population capable of witnessing world events as they occur from anywhere, another dark age seems improbable. And if the the worst happens, and widespread famine occurs, and there are droughts and floods plaguing the world, someone will engineer a way out of it, just like Fritz Haber did. 

So I'm not scared of the future. I'm stoked!