Some two hundred years ago, the Reverend Malthus wrote the first of these 'harbingers of doom' type books. The 'Malthusian Crisis' is named after him, but although there have indeed been numerous famines between his times and our own, civilization did not collapse as he predicted. In fact the British population has increased massively since that time and our biggest problem today is overeating not starvation! Why? Because in any age, those attempting to predict the future can only base their judgements on the social/industrial realities around them and must obviously be unaware of future technological/scientific developments. As steam engines, railways, petrol engines, electricity, aircraft, organic fertilisers etc... did not exist in the good Reverend's times; he was unable to factor them in to his calculations. Hence he saw looming disaster when by the standards of his age, the future was amazingly bright.
Today's prophets of doom make this same mistake. Example:- Pres. Obama may feel America no longer has the industrial strength to lead humanity out into the Cosmos; but China, India and Japan all have plans to establish human colonies on the planet Mars within fifty years, regarding that planet just as Europe's buccaneers once regarded 'The New World'; a vast untapped treasurehouse awaiting those with the courage to claim and tame it.
The liberal/socialist 'doctrines' now gripping the Western World may well bankrupt us as their Soviet counterparts bankrupted the USSR, but despite egalitarian/welfare legislation, homosexual liberation, abortion, credit crunches etc..... mankind as a species today is as resourcefull, intelligent and determined as ever. We also have vastly greater opportunities open to us and I firmly believe that in future centuries our children will exploit power sources that we cannot envision, terra-form Mars, mine the asteroid belt, genetically increase our lifespan and voyage to distant stars; while looking back with amusement on our futile pesimistic attempts at 'prophecy'.