Overpopulation: is a generally undesirable condition where an organism's numbers exceed the current carrying capacity of its habitat (wikipedia, as good a definition as any other really).
As long as humans are able to remodel their habitat to increase it's carrying capacity, there will not be any human overpopulation on earth.
The surface of the earth never limited population density (HongKong is listed as high as 20.000 people per square kilometer, depending on whether roads, airports and others are taken into account), yet somehow it is expected to limit food production density.
How much mental energy does it require to go from 3d human habitat (skyscrapers) to 3d vegetal habitat (underground farming)?
The only problems we ever faced and will ever face are lack of vision, ignorance and mismanagement.
We are a race of unlimited potential in an unlimited universe, and nothing except our own stupidity can stop us - it does seem to make a good job of it though.