Why the overpopulation of Earth is a myth
Many people believe that the Earth is overpopulating, however, they don't stop to think about the facts.
Earth's total surface area is over 510 million square kilometers. I believe that can easily support 100 Billion people, because that is only about 200 people per square kilometers, and most of Western European countries has a density much higher than that, and they don't seem to have any problem with it.
Also I believe that overpopulation claim is a myth, because we are hardly useing even the land area on earth, especially not the oceans. My estimate is that we use only about 3-4% of the land area on earth, and the land are of the planet is only about a quarter of the whole surface area. Not only can we use oceans to grow plants, but we can also build plant towers (vertical farms), grow plants in the air using floating farms (earth atmosphere expand to about 100 km above sea level), we could grow food underground (earth's crust is roughly 5 km thick), and even in low earth orbit. We could also grow food in deserts, Antarctica, Siberia, and Northern Canada. Beside all that, there are technological developments in production (not just genetic engineering).
According to http://ga.water.usgs.gov/edu/earthhowmuch.html, there is 1 385 995 980 cubic kilometers of water on earth. According to http://en.wikipedia.org/wiki/Water_use, 4286 cubic kilometer of water is used annually on earth. Dividing the two, we get: 323 399. What this means is that water on earth can sustain this times the current population. If the population of earth is 7 billion people, multipling we get, that the water supply on earth can sustain over 2 263 trillion people.