There is no doubt that a rising population is one of the factors which threatens the world's capacity to support its people, but human population growth is being massively outstripped by the growth in the number of farm animals. While the rich world's consumption is supposed to be boundless, the human population is likely to peak within the next few decades. But population growth is the one factor for which the poor can be blamed and from which the rich can be excused, so it is the one factor which is repeatedly emphasized.