There is a limit to how many humans the earth can support...
Here is a good read from the Smithsonian Magazine which is a pro science publication and generally trustworthy, and it seems they think that Ehrlich's predictions/possibilities amounted to mostly fear porn-
2 billion people on Earth are under the age of 15.
The forced (fines, bad schools, etc) one child thing didn't work too well in China. We shall see how their 2 child works. The main problem with one child was Chinese parents wanting boys if only allowed one kid.