Here’s a short quote, but you should read the whole thing:
Only chronic poverty and lower living standards can permanently slow long-term population growth:
Smaller families for the rich than for the poor are explained and predicted by the ecological analysis of the human breeding strategy, as we have seen. But this does not mean that numbers in a rich society will not rise, only that they will rise more slowly. Breeding strategy still ensures that each couple will raise the largest number of children it can afford and, under most conditions of wealth, this is likely to be more than enough to replace the parents. Making the poor wealthy will slow the rate at which children are raised, giving us more time to anticipate or plan the historical happenings that their crowding will bring, but it can never stop the children coming in excess supply. (pp.42- 43)
Neither will birth control work. Since people modify their breeding strategy based on their niche,people in narrow niches will continue to have the optimal number of children for that niche. Access to birth control is still dependent on them actually using it, which is solely a matter of individual choice, absent some sort of compulsion. And those at the lowest niches of society with the fewest resources need to have the largest number of children:
It is essential to realize that people of poor countries have their large families from choice. The poor themselves will tell you that they need to have children to look after them in their old age, or to have sons to go out to work when they are ten years old, or to have daughters whose marriage will bind families together. They might even say that children are a “comfort”; that they like children. These are but ways of saying that they are looking to the number of children decreed by their way of life, or the number demanded for them by the workings of the human breeding strategy. In either language, the poor have large families because they want large families. Providing the poor with birth-control devices will not result in fewer children.
Only desperate poverty has been shown historically to slow the rate of population growth:
But it is still possible for the human breeding strategy to cause population losses, as well as population gains. This will happen when a community is reduced to such despair that the average opinion of the ideal size of family puts it close to zero.Or, if hope yet allows some couples to start families, then the conditions of the people are so desperate that they cannot succeed. A single generation of desperation can remove a whole community for good. It is to this possibility of near total failure of the breeding effort, not to massacres of adults, that we must look for the decline of populations in history…