my thinking is we reach peak oil, the world is not ready to really jump towards diversified renewable energies.
It's really hard to get people to just sit down and fathom just how much energy we consume from oil, natural gas, and coal. Not just how much but the increase rate of demand and consumption and the loss of any one of these will cause mass disruptions to the world economy.
This'll have a knock-on effect on modern day farming techniques which produce vastly more quantities of food with much greater efficiency then traditional methods (sorry vegetarians and the 'organic' food people).
I sometimes worry about it, because the past few years like Russia had a major drought and were severely short on buckwheat grain (their primary food), India a few years ago temporarily stopped the export of rice because of droughts. Saudi Arabia and Gulf states buying land in Thailand and Sudan for the sole purpose of growing food for the client states (Those go out the window i bet in the event a national catastrophe there).
and if you think population growth is a problem, it's still a problem if the populations is declining fast. existing infrastructure needs to be maintained, the national securities of nations are threatened, the economies of major nations (Japan, Russia, Germany, France) inevitably shrink with a shrinking population. Almost everything our civilization is based on is predicated on growth or maintaining the status quo. Whenever there is a fall, bad things follow.
and i view oil as the 'thing' that is at the core of our modern world. It isn't simply a matter that we need to rely on it whether for power or synthesing chemicals to make your asphalt or the wrapper on your chocolate bar. It's that we rely on it too much. It alone has made real physical modern global trade possible around the world, is instrumental in modern farming techniques, and as a result has liftedBILLIONSof people out of incredible poverty. Even if some of those billions are still considered poor by Western standards.
If that floor drops on us suddenly or very quickly on us, were going to see mass starvations we've never seen, and we will see massive regional wars for crucial resources. Not just war for oil. wars for clean water, wars for arable land.
maybe not extinction. but pretty awful. it would certainly be a different world..