What most of these doomsday scenarios have gotten wrong is the fundamental idea of economics: people respond to incentives. If the price of a good goes up, people demand less of it, the companies that make it figure out how to make more of it, and everyone tries to figure out how to produce substitutes for it. Add to that the march of technological innovation (like the green revolution, birth control, etc.). The end result: markets figure out how to deal with problems of supply and demand.

Steven D. Levitt