[perrygeo]

There's good evidence to suggest that most mammals and other K-selected species (long lived with few offspring) will always expand to fill the productive capacity of their niche, and keep doing so until negative feedback pressure kicks in.

Consider the reindeer on St Matthews Island. 20 of them were introduced in 1944 and left to fend for themselves. With plenty of food and no natural predators, by 1963 there were 6000 reindeer (300x population boom!). By 1966 the population had dropped to 42. By 1980, no reindeer left.

Mammals seem particularly prone to this "eat everything is sight and multiply" strategy. Which works, until it doesn't - the herd migrates, adapts, or the population collapses. The problem with the human enterprise is that we've gotten really darn good at engineering solutions to these negative feedback pressures. There's nothing (yet) that can restrain our growth. Which means we're in a St. Matthew's Reindeer situation - dwindling resource base, exploding population, and nowhere left to go.