How many Earths do we need?

In a recent email exchange, my correspondent wrote, “they say if everyone consumed like the US, we would need 2.5 earths.” That sort of claim is commonly made and readily accepted as true. A June 2015 BBC magazine article titled “How many Earths do we need?” begins with the claim “that if everyone on the planet consumed as much as the average US citizen, four Earths would be needed to sustain them.”[1]

Those types of claims are half-truths, and like most half-truths, they confuse rather than clarify. Fortunately, a little bit of reasoning and checking the facts are sufficient to get closer to the truth.

Energy and Technology

Only in the last 250 years or so, there has been both an increase in population and an improvement in the quality of life. It’s all thanks to technology. Agricultural productivity has increased, which means that more food is produced using less land and less labor than before. The increase in agricultural production required more energy and better technology.

In the year 1950, the population of the US was 150 million. Using 1950s technology to support 330 million Americans (the population of the US in 2020) at the 1950 level of consumption would use up 120% more resources than was used in 1950. Supporting 150 million Americans at the 2020 level of consumption given 1950 technology would require more than one earth’s resources. Supporting 330 million Americans at 2020 levels of consumption given 1950 technology would require several earths.

The world population was 2.5 billion in 1950, of which 60% or 1.5 billion lived in extreme poverty. In 2020, there are over three times as many people on earth as in 1950. Yet the per capita consumption has gone up — to the point that less than 10% of the world live in extreme poverty today. What made that tremendous improvement possible? Technology.

Technology made more and cheaper energy available, which increased productivity in every area of human enterprise — agriculture, manufacturing, transportation, mining. More food is grown today using less land than 20 years ago, and the trend will continue. Forest cover has increased 15% in the last 20 years. Every indicator of human flourishing is trending upward.

There are only two resources that are constrained for human beings. Time and Energy. Time is a true constraint, in a sense we do know the upper limit on it and we can’t do much about it. Energy is a soft constraint, there is infinite energy in a universe but we know to use only a tiny negligible fraction of it but each year our ability to use it is advancing rapidly.

In next 100 years humanity will increase its per capita energy to perhaps 1000000x of what it is today. The problems like climate change or food shortage will sound like joke in year 2150. Just like how witches being hunted sounds ridiculous in 2000s.

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