This question is impossible to answer in the present situation. Had it been posed one or two hundred years ago, we could say education was key. Now that human population has reached epidemic proportions, band-aids are insufficient. Nothing short of a radical reduction of birthrates worldwide, coupled with mechanisms to keep human growth in check, would have any effect. Given the global misery in store if we do nothing, how is this unethical? The only solution I have seen is in fiction. Dan Brown's supposedly evil protagonist in his latest novel Inferno, did come up with just such a solution, at the genetic level, which had no impact on the current generation but great benefits to all future generations. Would this could be made a reality.
There would have been no way to predict this 200 years ago. In 1818, there was just a little more than 1 billion people on the whole earth. That was before people understood what they do now about hygiene. It was before vaccines for the most part and medicine was much less effective. Nobody would have been asking the question of overpopulation. It wasn't a problem. I still don't think it's a problem. Birth rates are going down, quite radically actually in some countries. The problem is not our population is growing too fast. It's that the people we already have are not doing what's needed to make our stay on earth sustainable.