the society, culture, and way of life of a particular area.

I prefer this definition. But I agree that a degree of overpopulation so extreme that resources have to be imported is both unsustainable, and extremely damaging to the species.

Our current civilization is a great example of this. We're in the boom phase of the boom/bust cycle found in animal populations. Once we finally strip enough resources, and go insane enough from the overcrowding, this bust will outshine anything in the past 12,000 years.