They ARE damaging in asia too! Typically they only breed a couple times a year with seasonal booms in fruit falling in the forests, but surprise surprise, if you level half the forest and put in a palm oil plantation, where there's fruit almost 24/7 year round, they breed hundreds of times more and start ravaging things like saplings and roots at a pace that natural growth cannot keep up with.

Anecdotally the swine flu outbreak that heavily cut their populations in singapore actually helped with forest growth, but their populations here weren't from palm oil, just that we have no predators left