Geoffrey Carr notes: "...the demographic shift that all populations (so far) have undergone as they have enriched themselves. For the negative exponent is starting to show up, and its cause is not lack of space or resources, nor yet is it conflict or disease (even AIDS, malaria and tuberculosis make only a small difference in global terms). Instead, it is the thing that the doomsters feared most after population growth — economic growth."
"Perhaps the answer lies in the old idea of r and K selection. Indeed, the terms r and K come from variables in two-term logistic equation that describes real population dynamics. K-selected species, people may remember from their college ecology classes, have few offspring but nurture them lovingly. Those that are r-selected have lots, but display a Devil-take-the-hindmost attitude to their issue's survival. The crucial point is that K-selected species live in safe, predictable environments, while r-selected ones live in unsafe, unpredictable ones. If the individuals of a species were able to shift opportunistically between r and K strategies in response to shifts in the environment, then something like the demographic transition in response to wealth might be the result."