Pompei, when Vesuvius erupted. People had time to flee, not everyone did for various reasons. It was the boiling frog effect. Rapa Nui, one of the most isolated islands. Populated by Indonesian sailors. 15 000 people. Population declined to 3000 and later 600 to 700 when james cook visited the island. Civil wars and The diseases brought by the europeans caused the deaths Invading species of rats also brought down the population of trees and birds.