The idea that we're heading toward a population crisis might seem frighteningly feasible to anyone who has ever visited a shopping mall, but the problem isn't as dire when you look at the data. Economists like Max Roser point out that across the world, fertility rates are in fact shrinking. Today, the average household has around 2.5 children, as opposed to the five or six that our horndog ancestors had on average during the 1960s.
If a little thing called "history" is to be believed, this (in conjunction with increased modernization, lower poverty rates, and a rise in education levels across the world) means population sizes will level off fairly soon. You see, back during England's Industrial Revolution, as living conditions improved and mortality rates fell, families that were used to having many children per household no longer needed to, because the ones they had survived childhood now. The abundance of unexpectedly non-dead kids led to a surge in population which took almost a century to correct itself, but that process is happening much faster in today's newly developed countries. This is why your parents seemed to have 27 aunts and uncles, while you have like three. According to UN projections, the Earth is expected to reach around 10 or 11 billion people in the next hundred years, then sorta cool it with the people-making.
What's that, you say? Earth is already disastrously overpopulated? Well, as population has increased, worldwide poverty has dropped just as fast. Hell, you could make the argument that slowing population growth causes just as many problems. The things you see as symptoms of overpopulation on the news (famine, refugees, mass poverty, etc.) are always localized -- the results of civil wars, dictators, or natural disasters fucking up specific areas. Worldwide, the data so far has been very clear: More people equals a higher standard of living. We've even increased our per-capita food production, quashing the idea that there's some set finite amount of food or resources that will run out as the population increases.