Before the 18th Century, disease, famine, and war controlled the population. With improvements in sanitation, medicine, agriculture, trade; and increasing peace, as well as modern inventions making greater use of energy, population has exponentially increased. While the rate of increase its now more linear, it is questionable how sustainable it is for the global population to continue ascending. To live within the carrying capacity of the environment, mankind will need to reduce the forces that contribute to environmental impact, which are environmental impact per person and population. Affluence and technology are other forces.
Personally, I don’t intend on begetting any children, as I am yet to be convinced that mankind can live sustainably with its current population of 7 billion, let alone the projected population of 9 billion in 2050.
Perhaps the best form of population control is self-control, although this is also difficult.