I have a book on koalas and they definitely do just keep breeding to starvation, Kangaroo Islands is one place, another was on an island on the Murray River. They were placed on a large island within the river to isolate them from dogs and farmers, they just kept on breeding, killed all the trees and then themselves.
On the other hand, kangaroos etc don't breed up unless there is sufficient food to sustain them and we have noticed that in a drought our resident magpies and kookaburras seem to have less babies.
New topic
I am amazed how wasteful the young green generation is, on one hand they talk of saving the planet and on the other they throw things away and buy another simply because there is a new version.
Dress shops catering to the young set release up to 20 new lines a week because some of the younger working females will only wear something once, then they throw it away. They are buying 5-10 new tops a week, as most of these are synthetics they would be coming from oil based products I believe.
Mercury is a nasty for sure, that is why I think it is weird that we now have to use light bulbs with mercury in them. I shudder to think how much mercury will be leaching into the water ways in about 10 years time and then forever as we chuck the broken/dead ones into land fill. Not green at all IMO