WE HAVE ENVIRONMENTAL PROBLEMS because people are overusing the world’s resources. We can take steps to consume less. But rising world population gradually increases the total resource use again, until we are using as much as we were originally. These figures analyze an abrupt reform in consumption of a resource, and stable use of that resource per person from then on. World population grows at a rate of 1.3% per year.

	Reform	Time Gained
	Cut U.S. energy use to the world average	14 years
	The U.S., with 5% of the world’s population, consumes 25% of its commercial energy1. By using one-fifth as much energy per person as we do now, Americans could cut world energy use by 20%. 20% reduction ÷ 1.3% growth rate = 14 years
	Adopt a vegetarian diet worldwide	24 years
	About 38% of the world’s grain is fed to animals2. One kg of grain produces 0.18 kg of meat3, so that amount is subtracted to compensate for the lost meat production. Meat production would continue from animals fed grass and agricultural waste. .18 x 38% = 7% 38% – 7% = 31% 31% reduction ÷ 1.3% growth rate = 24 years
	Cut U.S. energy use by 5% per year	none
	In this scenario the U. S. uses energy at 95% of its current rate next year, 90% the following year, and so on until in 20 years no energy is being used at all. Since the U.S. uses 1/4 of the world’s commercial energy1, a 5% cut is 1/4 of 5%, or 1.25% of world consumption per year. But world population is growing faster than that, so total world energy use would increase by 1.3% – 1.25% = 0.05%/year. Stress on the world’s resources would never decline.
	Sources: 1. World Watch, Vital Signs 96, 1996. 2. State of the World, Lester R. Brown, Ed., Ch. 5: Reforming the livestock economy. A. Durning & H. Brough, 1992. 3. Ibid., Weighted average of world pork, beef and chicken production. Authors: Bruce Bridgeman, Lysa DeThomas, Pat Kittle Updated February 2000