How Many Earths?

When I let myself think about the future of the planet, or rather the future of humanity’s time on the planet, the one word, or concept, or theme I keep coming back to is population.

It may even trump the climate issue, as if anyone’s keeping score, in that even if we weren’t altering our biosphere in dramatic and destructive ways, we would still have to contend – as we sought out new living space, more arable land, and as yet undiscovered fresh water supplies – with overshoot, the idea first proposed by the cleric and scholar Thomas Robert Malthus in his 1798 work, An Essay on the Principle of Population.

For much of the late 20th century, the work of Malthus was in bad odor with academia. The adjective Malthusian , or the broad concept of Malthusianism, was synonymous not with a thoughtful and well-researched concern for humanity’s growing numbers, but rather a sort of dim-witted and somewhat old-fashioned hysteria about growth. The Green Revolution, we were told, had proved Malthus wrong, once and for all. Through technology, and agricultural science, we would continue to push back the boundaries on food production, the efficient use of fresh water, etc., etc. Those in the know were not worried!

It’s not that the smart set thought there would be permanent continued exponential growth. They did envision a flattening off of the growth curve eventually, but this would happen voluntarily, the thinking went, as people currently living in poverty achieved much or all of the prosperity that those in the West and/or industrialized North had come to take for granted.

This so-called Demographic Transition had been observed throughout the 19th and 20th centuries in country after country. In essence, as modern consumer goods became available to the masses, as health and health care improved, as life expectancy increased, average family sizes went down, and they went down dramatically. People didn’t need so many children, either as free labor, or as a source of care in their elder years. This process had been observed again and again; first in places like England, and America, then in other parts of the world as industrialization and development spread.

(This was felt to be a lucky thing, because people were also recognizing, during these years, that essentially every other proposed method of curtailing population growth, including the heavy-handed coercion of China’s one-child policy, was next to useless.)

So, in this context, poverty alleviation was not simply a moral goal that would produce a fairer and more just world; it was also a deeply pragmatic goal that would result in a livable world.

It’s important to note that this faith in the benefits of the Demographic Transition also fit hand-in-glove with one of the bedrock principles of modern economics: that, to survive, an economy—any economy, a national economy, the world economy—has to grow. Without growth, without ever more productivity, ever more output, ever more everything, there would be economic depression, and the whole system would risk collapse.

But then, towards the late 1960s, this faith, this ideology, started to be questioned.

The late Edward Abbey famously summed up the emerging countervailing argument with his assertion that “Growth for the sake of growth is the ideology of the cancer cell.”

What all these experts — the public health folks, the demographers, the economists — had failed to consider, and largely continue to fail to consider, is the original fact that had so bothered Malthus: the Earth, the planet itself and the biosphere, is a closed system, one with finite space, and finite resources.

Joe Romm, then of, in a conversation with Thomas Friedman, put it pretty concisely:

“We created a way of raising standards of living that we can’t possibly pass on to our children… We have been getting rich by depleting all our natural stocks — water, hydrocarbons, forests, rivers, fish and arable land — and not by generating renewable flows…You can get this burst of wealth that we have created from this rapacious behavior…But it has to collapse, unless adults stand up and say, ‘This is a Ponzi scheme. We have not generated real wealth, and we are destroying a livable climate …’.”

In other words, like sailors on an extended voyage, we can alter the rate at which we use our stores and provisions, for better or worse, but in the end we have what we have.

Unlike sailors, though, who might eventually happen upon an island from which to refresh their stores, the earth when viewed from space is sailing alone. Other planets, even habitable planets may exist, but neither we, nor our children, nor our children’s children are going to see them. Like it or not, we have to make THIS work.

One group that has put particular thought into this dilemma is the Global Footprint Network.

Thomas Friedman summarizes their work as follows:

…the Global Footprint Network, an alliance of scientists…calculates how many “planet Earths” we need to sustain our current growth rates. G.F.N. measures how much land and water area we need to produce the resources we consume and absorb our waste, using prevailing technology. On the whole, says G.F.N., we are currently growing at a rate that is using up the Earth’s resources far faster than they can be sustainably replenished, so we are eating into the future. Right now, global growth is using about 1.5 Earths. “Having only one planet makes this a rather significant problem,” says [Paul] Gilding. This is not science fiction. This is what happens when our system of growth and the system of nature hit the wall at once.

The GFN site offers the following chart to illustrate the point.


Once you get your head around this number, you realize this number of “1.5 earths needed to sustain current growth rates,” means the number of earths necessary to sustain the status quo—the status quo with all its excesses: vast, almost sickening wealth in the hands of a very few; crushing poverty for billions. 1.5 earths, to essentially do nothing other than keep on keeping on.

There’s a second number that I would suggest is equally if not more important. And that is the number of earths needed to supply sufficient resources to extend the Demographic Transition to all the people on the planet and thereby effectively curtail population growth.

What is that degree of prosperity? I think there we have to essentially guess.

If you peg that degree of wealth and health, on the high end, as being equal to the lifestyle of the average US citizen, then five earths would be needed. If you shoot for the lifestyle of the typical Brit, something more moderate, it’s 3.5 earths. If you aim for the typical Argentinian, on the lower end, it’s 1.7 earths.


It’s hard to imagine all the Wall Street bankers and Washington insiders, not to mention their counterparts in London, Berlin, Moscow, or Beijing, accepting the rather abrupt demotion to living like the Argentinian middle class—I think you’d have troops in the streets long before then—but this is a thought experiment.

At any rate, regardless of which country’s lifestyle we ended up setting as our goalpost or benchmark for ushering in a worldwide Demographic Transition, the takeaway is clear. We don’t have the resources for it, so it’s not going to happen. So what does that mean?

Let’s summarize.

The human population is headed towards greater and greater — in fact unsupportable — numbers.

The one benign, non-coercive, non-“harmful” force (at least with regard to respecting human rights) that effectively bends population growth curves and causes humans to reliably have fewer and fewer children, is the spread of wealth and health.

But…to give every man woman and child on the earth a level of prosperity somewhere between that of the Argentinians and the Americans (both of which have roughly a 1% annual growth rate) would require between 1.7 and five planets worth of natural resources.

Between 1.7 and five earths.

When we just have the one.

Take-home: the world’s population growth isn’t going to slow down anytime soon, at least not for benign reasons like poverty alleviation.

It may nonetheless slow, at some point, because it is forced to do so, but the reasons will instead be war, and famine, and disease.

My guess is Malthus would take no satisfaction in that.


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