The problem is misunderstanding the reasons for having children.
In poor and "
Third World" countries, most people are involved in some form of (usually
subsistence) farming or some equivalent of
living off the land. As a result, one has children - and lots of them - because life is hard and many of them will die. But some of them will survive to farm and then they can support their parents when they are unable to work.
In wealthy countries, most people are involved in some
non-farm occupation where children are not necessary as a potentially productive asset. Which means that in wealthy countries people have fewer children because they are not necessary for future support - we have the ability to purchase
pensions and
life insurance to support ourselves or our families if we die - and thus children represent a consumption item like leasing a Mercedes Benz.
Also, the development of better access to medical care, labor saving developments like machines and electricity, as well as new drugs has increased lifespans everywhere as well as caused death rates to plummet.
As a result of this, what is happening is that the rich countries are either reaching or even exceeding
ZPG (because we're not just having
Zero Population Growth, we are actually losing population) and the poor countries are breeding even faster. In fact, over the last 30 years, it is my understanding that all of the gains in population in the United States has been either through immigration or children of recent immigrants. (Once someone has been here a while they also don't need to have a large family for the same reason as everyone else: we're not heavily dependent upon farming so large families are unnecessary).
Further, most of the problems of food are not due to high levels of population - in fact, in many places there are tremendous surpluses of food - but because of politics and mismanagement of resources. Many years ago, Dr.
Thomas Sowell, a nationally syndicated columnist pointed out that you could fit the entire world's population - all 6+ billion people - into single-family homes at a lower density than most American cities in a space no larger than the size of the State of Texas. (If you include the amount of space necessary to include cropland, then it would require a space the size of the State of Alaska.)