People in the '80s were certain we'd soon exhaust global coal supplies. The 1880s. Now we are more likely to replace it with alternatives as run out. Before that it would have been kerosene or whale oil.
This isn't unique to fuel.
Minerals were harder to come by in the 1930s, when we had 2 billion people, than they are today, with 7.5. We've made them more abundant not less:
http://www.aei.org/publication/julian-simon-still-more-right...
This is counterintuitive at first, but we're really good at finding more efficient ways to do things.
Or... economies of scale kick in when you have enough people, especially once you don't need to dedicate almost everyone to farming, when you can add some inventors and chemists, say.
Maybe that's why historically humanity has had far more to fear from population crashes than booms.
Turning matter into MIPS is not a sin. Adding processing power is one of the best ways to make stuff more valuable.
