I expect that the problem of feeding the world when fossil energy becomes scarce and when extreme weather events caused by global warming happen more often, has already been well aired on this forum, but without a solution a catastrophe might be only a few years away.
The worlds farming systems are now almost totally powered by diesel fuel. This fact and the use of nitrogen fertilizer and pesticides derived from ancient sunshine has allowed the world population to triple in the last 70 years, but as diesel fuel is finite and it's use produces co2 emissions, it would be a highly dangerous strategy to rely on as the population goes to 9 billion in about 40 years from now.
Our farming system has become a method of converting cheap, plentiful fossil calories in to food calories. When oil becomes expensive and scarce through depletion or geo-political events such as a mid east war, this system will fail, these converted calories will become unavailable and the world population will fall to a level that a system with less fossil energy inputs can sustain. This would mean mass starvation, especially in those countries with advanced farming systems, who also rely on imported oil.
I have posted a video on
http://www.youtube.com/amptrac to help explain what I see as the problem and also one way to power farming without diesel. There might be better ways to do it, but we need to be thinking about them now so that they can be developed in time.