The theory of overpopulation was explained by Srila Prabhupada at the famous New York Ratha-yatra festival in 1976. I remember clearly, We were at the park, in one of the worlds largest cities, sourounded by thousands of people, and Srila Prabhupada was speaking about how Krsna is feeding the world…
…God is father, supreme father of everyone. If we simply study this verse from the Bhagavad-gītā, that the mother nature is the mother of all living entities and God is the supreme father of everyone… We can study these two lines very carefully. On the earth we can see so many living entities are coming out, beginning from the grass, then so many insects, reptiles, big trees, then animals, birds, beasts, then human beings. They are all coming from the earth, and they are living at the expense of earth. The earth is supplying food to everyone. As the mother gives life or maintains the child by the milk of her breast, similarly, the earth mother is maintaining all different types of living entities. There are 8,400,000 different forms of life, and the earth, mother earth is supplying food. There are thousands of elephants in the African jungle, they are also being supplied with food. And within your room in a hole there are thousands of ants, they are also being supplied food by the mercy of the Supreme Personality of Godhead. So the philosophy is that we should not be disturbed by the so-called theory of over-population. If God can feed elephants, why he cannot feed you? You do not eat like the elephant. So this theory, that there is a shortage of food or overpopulation, we do not accept it. God is so powerful that He can feed everyone without any difficulty. Simply we are mismanaging. Otherwise there is no difficulty.
The Hare Krishna Movement 