Well, the actual cause of their famine was the same as Haiti, basically.

Haiti said, "oh look, we're growing so much food, we need charcoal to cook it with!" then cut down all their forests. Then came rains, and there were no trees to hold the water in the soil, so the topsoil washed away in landslides and... people starved.

North Korea said, "oh look, we can't run tractors and have no fertiliser. Let's just cut down trees and plant more!" Then came rains, and... same deal.

They could have just done more crop rotation, green manure crops, given people private plots of land to till and sell the surplus, planted more trees to encourage local precipitation, and so on and so forth. Instead they went all Pol Pot and drove the people into the countryside to hack at the ground at gunpoint. Which apart from being barbarically inhumane was abominably stupid.

So really the cause of North Korea's famine was not peak oil, but bad husbandry of the land. Peak oil was a catalyst, not a reactant in the equation. So the real lesson is not that peak oil makes people starve - it doesn't - but that peak oil makes people desperate and stupid. That's the real lesson of North Korea's experience.