Environmental extremism might be reducing its own number of supporters — by advising that the very act of reproducing offspring is something the progressive-minded should consider foregoing. See "How to Save the Planet? Stop Having Children" — the Guardian, Oct. 28, 2014). A few months ago the same publication printed a slightly less draconian dictate. The verdict now is that perhaps just "fewer" children would suffice after all.
These aren’t the only declarations that there are too many of us. The idea has become virtually unassailable, and may well deserve that cachet after all. Still, there are many respected and scholarly voices that have asked in the past — and question now — how many people the planet Earth can support. While it’s impossible to consider every necessity required to sustain future populations, focusing on just the most important requirement — providing sufficient food — gives insight into the complexities and difficulties in making far-ranging, accurate predictions.
In 10,000 B.C., at the dawn of the agricultural revolution, there were only a few million humans spread across the planet. By the time the world’s population was hovering around one billion in 1798, Thomas Robert Malthus was one of the first to address the problem of populations and the resources needed to support them.
Already though quite a few watershed innovations and discoveries had staved off what Malthus assumed must be the end result of ceaselessly increasing numbers on Earth — an inevitable crash. The potato, to highlight just one example, was then a relatively newly established staple being cultivated globally in the centuries after Columbus. The potato was achieving a striking effect to combat malnutrition worldwide. It's still today a nutritional bulwark against starvation.
Two out of every five people alive today, it’s estimated, never would have been born were it not for the introduction of the potato.
In the opening years of the 20th century, owing to Germany’s urgent wartime necessity to manufacture the compounds necessary for munitions, Fritz Haber invented his eponymous Haber process, changing the world once again and with even more dramatic results.
Fixed nitrogen is a relatively scarce commodity on Earth — yet without it chromosomes can’t be built. Even though three fourths of our atmosphere is composed of nitrogen, that stupendous reserve is inert for biological purposes. Fixed nitrogen is created only by lightning strikes and by a few types of cyanobacteria and also by a limited number of species of micro-organisms living amid the root systems of various legumes.
Naturally occurring fixed nitrogen, it has been calculated, can support only a world population of approximately three to four billion. Haber’s genius was to find a way to combine the free nitrogen in the air with the hydrogen in water to produce ammonia, the basic starting compound for either fertilizers or high explosives.
Since there are currently seven billion people — twice the number to be sustained by nature alone — it goes without saying that fully half of the fixed nitrogen found in the average person’s DNA is artificial, and was cooked up in ammonia factories using Herr Haber’s process.
So the question of how many people Earth can feed isn’t a simple one. To answer it requires knowing in advance what mankind’s next weapon against hunger will be. It may not depend exclusively on raw numbers but also on the calculus between changing living standards and technological and societal advances. Agriculture, for example, and the kinds of civilization it can maintain, is at either end of the sustainability spectrum with and without steel heavy plows, knowledge of crop rotation, etc.
Insofar as approaching some impassable limit concerning tapping out the basic resources from which food is produced, that boundary may be some distance ahead. All sustenance on Earth comes from the Sun. Photosynthesis — sunlight converting carbon dioxide and water into sugars — is the unstoppable piston of life, the foundation of the food chain.
Each year plants convert over one quarter trillion tons of carbon dioxide into biomass and food. Indeed, one of the unforeseen benefits of the recent increase in atmospheric carbon dioxide is in what much revered physicist Freeman Dyson calls the "Great Blooming" now taking place. Crop yields are increasing with simultaneous upticks in the proportion of carbon dioxide in the atmosphere. We shouldn’t be running out of sunshine, water, or carbon dioxide any time soon and consequently may be able to feed larger populations than might be imagined today.
Obviously, a trillion people can never live on Earth. But higher numbers than at present need not automatically necessitate a more severely compromised ecology in the future. The real question is the kind of stewardship Earth’s populace — whatever its size — administers on the planet. A sophisticated and prudent society that cleans up after itself would be optimum, whether small, medium or large.
David Nabhan is a science writer, the author of "Earthquake Prediction: Dawn of the New Seismology" (2017) and three previous books on earthquakes. Nabhan is also a science fiction writer ("Pilots of Borealis," 2015) and the author of many scores of newspaper and magazine op-eds. Nabhan has been featured on television and talk radio all over the world. His website is www.earthquakepredictors.com. To read more of his reports — Click Here Now.
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