Raven said:
Earth is something like 12 billion people, so our planet can theoretically support more of humanity, but only in an idealistic situation, where resources are shared equally among everyone (e.g. there is enough food in production for everyone to eat comfortably with some left over, yet people still starve).
It's not a matter of sharing, but of distributing. Few people want to keep food for themselves if they have enough while others starve. The problem is, they have no way of giving it to them. Most famines are in remote areas with little or no infrastructure, sometimes cut off by or as war zones or whatever. Afghanistan had a mass famine right when "Enduring Freedom" started, not because it doesn't have any productive fields or because the Taleban, evil as they are, rejected food shipments, but because the entire country has only two major roads, connecting only the major cities in the north and south, leaving the biggest part of the country uncovered, and thus, mostly inapproachable. In Kenya, there was a mass famine in the north a couple of years back, while the south had bursting granaries. The reason: The south, with cities like Nairobi and Mombasa, has a highly advanced infrastructure, with railroads and highways, but the north has only a few roads running through it.
So, there are two possible solutions to the famine problem: Either we support the crisis areas by trying to increase their agricultural value (since most famines are caused by droughts, which are reocurring climatical things, that is pretty pointless), or we simply build a few railroads through the country (convenient, little environmental damage if done right, fresh food everywhere).