Yes almost all our troubles are due to over population, however this doesn't apply to NZ, we are just affected by the problem in the rest of the world coupled with global warming because of the population over load.
It's not the least charm of a theory that it is refutable. The hundred-times-refuted theory of "free will" owes its persistence to this charm alone; some one is always appearing who feels himself strong enough to refute it - Friedrich Nietzsche