Al Bartlett, who recently died, toured universities around the world to explain exponential growth, his excellent videos are here:
When we’ve gone back to the age of Wood after fossil fuels go away, our agricultural system is so dependent on fossil fuels we won’t be able to support over 300 million people. Systems ecologists, who study the carrying capacity of the United States, have estimated that without fossil fuels, the USA can provide food for between 100 million (Pimentel), 150 million (Erlich), and 250 million (Smil 2000).
Matters will be made even worse by how far people live to where the food is grown — more than half of us live near the coasts, but must of the food is grown in the middle of the country. The Ogalla aquifer which provides about a third of our food over the ten high plains states is also drying up.
Any population increase, however small, will eventually saturate the Earth. It doesn’t matter if Egyptian women have gone from having 7 to 3 children. That’s still way too many children. The population needs to drop down to carrying capacity quickly, even one child per woman might be too many given the carrying capacity of Egypt and the decline rate of oil in the future. Egypt is way past their carrying capacity now. They relied on exports of fuel to pay for food, now they are importing oil.
Fossil fuels enabled the human population to grow at a rate of 2.0% for a while –133 times higher than the .00015 rate before fossil fuels and an overall average of 0.833% for the past 300 years, or 55 times higher than the growth rate of homo sapiens for millions of years before that (Hardin):
- Initial human population: 600,000,000 in 1700
- Growth rate .00833 (.833%)
- Time unit: 300 (years)
- Final amount: 7.3 Billion people
If we continue to grow at a .833% rate there’ll be 15 billion people in 2100. Cut that in half, and you’ve still got 10.5 billion people.
We need a negative growth rate of 1 child per woman or less world-wide to stay under the depletion curve of oil and other fossil fuels. It’s too late to do that. It would have never worked anyhow, since capitalism depends on endless growth, businessmen need more customers, religious leaders want more followers, and nations more children to out-reproduce their enemies to win battles. And ultimately it’s part of our biological nature to consume and reproduce at maximum possible levels, like all the other creatures on the planet from algae to elephants.
More exponential growth examples
1) Chapter 8 of Hardin’s Living within Limits:
Assume 2 grams of gold grows at 5% compound interest. In 2,000 years, this would grow to the equivalent of 4.78 x 1042 grams of gold, more than the mass of the earth — 5.983 x 1027 grams – or the equivalent of 800 Trillion earths.
2) Evar Nering, in “The Mirage of a Growing Fuel Supply”.
In my classes, I described the following hypothetical situation. We have a 100-year supply of a resource, say oil — that is, the oil would last 100 years if it were consumed at its current rate. But the oil is consumed at a rate that grows by 5 percent each year. How long would it last under these circumstances? This is an easy calculation; the answer is about 36 years.
Oh, but let’s say we underestimated the supply, and we actually have a 1,000-year supply. At the same annual 5 percent growth rate in use, how long will this last? The answer is about 79 years.
Then let us say we make a striking discovery of more oil yet — a bonanza — and we now have a 10,000-year supply. At our same rate of growing use, how long would it last? Answer: 125 years.
Alice Friedemann at energyskeptic
Garrett Hardin. 1995. Living Within Limits: Ecology, Economics, and Population Taboos. Oxford University Press
Pimentel, D. et al. 1991. Land, Energy, and Water. The Constraints Governing Ideal U.S. Population Size. Negative Population Growth.
Smil, V. 2000. Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.