The mitigating factor is that we don't have to start from scratch, we have the knowledge to survive in an energy poor environment, we know what minerals we need and where to find them. Yes we might only be able to find a very small percentage of what we used to but we should be able to find power to supply critical infrastructure and further research into alternative energy once the plug on mainstream energy is pulled. It's true to say life as we know it would end, but that might just mean we're not so consumer oriented.