Donella Meadows

Donella Meadows is the author of a syndicated weekly environmental newspaper column which bears the same title as her book. She received her Ph.D. in biophysics from Harvard University in 1968. In 1992, she coauthored Beyond the Limits with Dennis Meadows and Jorgen Randers,

The reason environmentalists are so often gloomy is that they know what the word "exponential" means. The Global Citizen, 1991.

What does "exponential increase" mean? It means growing like this: 1, 2, 4, 8, 16, 32. Doubling and then doubling again and then doubling again. Everyone understands that, right? Not really, not at a gut level. For example, suppose you agree to eat one peanut on the first day of the month, two peanuts on the second . . . and keep doubling every day. By the fifteenth you'll be scheduled to eat thirty-two pounds of peanuts . . . on the twenty-first day the total will have risen to one ton; and by the end of the month, assuming a thirty-day month, it will be five hundred tons. Ibid.

Mexico, with a population of 84 million and a doubling time of twenty-nine years, will, if it keeps that up, grow to 168 million in twenty-nine years and to 672 million within the lifetime of a child born today. Ibid.

Until the 1970s world oil consumption was growing at 7 per cent per year. That means doubling every ten years. (The doubling time of anything growing exponentially is seventy divided by its annual growth rate&endash;seventy divided by 7 percent is a ten-year doubling time.) Every ten years we used as much oil as we had used in all previous history. Every ten years we had to go out and discover as much oil as we had ever discovered before&endash;and then, to keep going, discover twice that much in the next ten years. Ibid.