First world countries have birth rates below replacement levels. Right now, the propaganda that overpopulation is a current threat has worked. We aren't having enough babies to replace deaths by old age and accidents.
This is one justification for open borders and encouraging migration from third world counties. Some poor countries continue to have birth rates above replacement, generating excess population. In a first world country, such as Germany, the pool of workers is shrinking among native born citizens. The creates a scarcity of workers which drives up wages.
Higher wages are good for workers, but reduce the profits of industries. Thus, governments encourage migration to keep wages down and their friends wealthy. And they cultivate a pool of contributors to fund socialist government programs.
From this point of view, when you ask, "how can we stop humans from reproducing?" The obvious answer is either wage a war on brown people 'to save the planet'. (dis-recommended). Or close our borders to illegal intruders and tend to our own, shrinking population.
Without out a constant flow of immigrants, US populations will shrink.
Now, who told you that "saving the planet from overpopulation" is a thing to worry about? Because they were glossing over a whole lot of valuable information when the assumed that this is a current problem.
I would question the biases of that source. They may have an agenda.