There is no scarcity of food. So this theory that overpopulation is nonsense. There cannot be overpopulation. But there is restriction, by nature. Nature will restrict production of food if there are demons. Nature will not provide the demons. You'll find in the Srimad-Bhagavatam, Fourth Canto, nature is quite prepared to supply all the foods, but as soon as there are number of demons, because the whole plan is to correct. Just like the criminals are sent to the prison house for being corrected so that they may not again commit criminals. Similarly, we are all criminals who are in this material world. The purpose is to be corrected. We wanted to imitate Krsna, to become Krsna, and therefore we violated the orders of Krsna, and that criminality means material life.
Lecture on Bhagavad-gita 2.12, London, 18 August, 1973