JOEL E. COHEN
Laboratory of Populations
Rockefeller University & Columbia University
New York, New York© THE ROCKEFELLAR UNIVERSITYIn 1992, Joel Cohen received a phone call from a journalist at Discover magazine. The journalist asked Cohen, a professor of populations at Rockefeller University with doctorates in applied mathematics and public health, “How many people can the Earth hold?” Cohen replied honestly: “I said to him, ‘I don’t know. I’ll try to find out for you.’ I said to myself, ‘This is your business. You’re supposed to know! What’s the matter with you?’”
Cohen spent the next six weeks reading studies that estimated Earth’s human carrying capacity based on a variety of data, from water and land use to food production to mineral availability to energy. “The more I dug, the more fascinated I became that everybody had an answer, but none of the answers agreed,” says Cohen. “They were all based on different assumptions. . . . The substance just was not there.”
Cohen became so irritated with the answers available that he spent the next four and a half years compiling more than 60 studies and developing mathematical models of the planet’s human carrying capacity. The book and Science paper he ultimately published on the topic concluded that Earth’s human carrying capacity is dynamic, uncertain, and ...
