A few years ago, my college at UC Berkeley was searching for a dean. Prof. Joel Cohen was invited to check out the College of Natural Resources. I asked him about his book How Many People Can the Earth Support? over lunch.
A few years ago, he said, a journalist had called him up saying that he was doing a piece on world population and wanted to know from Joel how many people could the earth support. Joel told the caller that he could not answer that question off the top of his head. It could take him a few days and why didn’t he call back in four or five days.
It took Joel three years to definitively answer that question and a fine job he did, in my opinion. The book was published in 1995. I quote from the introduction:
Though the future is hazy, much that is very clear can be known about the present. First, the size and speed of growth of the human population today have no precedent in all the Earth’s history before the last half of the twentieth century. Human numbers currently exceed 5.7 billion and increase by roughly an additional 90 million people per year. Second, the resources of every kind (physical, chemical and biological; technological, institutional and cultural; economic, political and behavioral) available to people are finite today both in their present capacity and in their possible speed of expansion. Today’s rapid relative and absolute increase in population stretches the productive, absorptive and recuperative capacities of the Earth as humans are now able to manage those capacities. It also stretches human capacities for technological and social invention, adaptation, and compassion.
Like in all other things, humans have a limited capacity for compassion too. When resources are severely limited, the thin veneer of civilization is easily scraped off to reveal the underlying unyielding will to survive at the expense of others.
Life is a Random Draw 