Thomas Malthus is an almost universally derided figure. He predicted that over time human population growth would outstrip our ability to increase the food supply, and thus he is the intellectual father of those who believe there are Limits To Growth.
Events after Malthus seemed to prove him wrong. Populations grew without limit, and economies grew right along with them, despite great disparities in the distribution of the wealth created. Nowadays, this history of growth is simply extrapolated into the indefinite future. Unending growth is assumed to be a permanent fixture of ever-expanding human societies, despite the embarrassing (and thus generally ignored) finiteness of the planet we live on. (Population growth rates are assumed to slow considerably in the future, mainly as a result of greater wealth producing greater freedom of choice.)
I am excluding human colonization of the solar system and planets revolving around other stars for reasons I consider all too obvious at this point, but that is a separate post.
As Salon's Andrew Leonard recently pointed out, the answer to Malthus' critics has always been just you wait and see!
The original "dismal scientist's" main contribution to economics — the theory that the growth of population would always outrun the growth of production, thus dooming humanity to crushing poverty — was proven wrong by the Industrial Revolution almost immediately after he set his thoughts down on paper. Few theorists whose names have endured for centuries have been more spectacularly off the mark. In almost every measurable way, the world is immensely richer than it was at the time of Malthus, even in the face of a surge in global population that the economist would never have dreamed remotely feasible. For at least the last century Malthus' ideas have been routinely dismissed in introductory economics textbooks and scoffed at by most mainstream economists, whether liberal or conservative, Keynesian or Chicago School.
Not only has food production outpaced population growth, thanks to technological innovation, but the richest nations on the planet tend to be the ones in which the birth rate drops the fastest — the so-called demographic transition. So Malthus was wrong twice...
And yet his dystopian vision that humanity's lot, our inescapable fate, will be grinding, desperate poverty, lives on. Down for more than 200 years, but not yet out, because there's always a get-out-of-jail-free card for Malthus: Just wait.
Just wait until the technological wellsprings of innovation run dry, when even the most advanced genetic modification technologies can no longer boost food yields. Just wait until peak oil puts an end to the age of cheap energy, until the oceans are over-fished and the atmosphere is choked with carbon dioxide. Just wait until Chinese and Indians and Brazilians consume with the same unsustainable abandon as Americans. Malthus isn't wrong — he just isn't right ... yet.
Leonard's summary of the issues is fair. In the spirit of that debate, I offer you this Malthusian peak phosphorus chart.
A Hubbert-like model of future phosphorus production showing a peak in 2033, referenced in 15 facts you absolutely need to know about phosphorus (slide #6). Phosphorus comes from two sources: manure and phosphate rock (slide #3). You can see that the data is quite scattered, but the bell, or gaussian, curve fit appears to be based on assumed economically recoverable reserves for phosphate rock of 15,000 million tons, as cited in David Vaccari's Phosphorus: A Looming Crisis. Vaccari cites the current R/P (reserves to production) ratio as 90 years, meaning that we have that many years of phosphorus left at current consumption levels.
Phosphorus (P) is elemental, meaning that phosphorus atoms on Earth are neither created nor destroyed—they just get moved around. Phosphorus is a nutrient essential to all life on Earth. Being elemental, it is irreplaceable. Although phosphorus is fairly abundant on Earth, large, economically minable quantities of phosphate rock are not. Along with potassium and nitrogen, phosphorus is an essential ingredient of fertilizers that support large-scale agriculture. It was this "Green Revolution" that feeds the burgeoning populations that Malthus thought could not be fed.
I think the Foreign Policy article Peak Phosphorus provides an excellent overview of the issues, so I will quote it at length—
From Kansas to China's Sichuan province, farmers treat their fields with phosphorus-rich fertilizer to increase the yield of their crops. What happens next, however, receives relatively little attention. Large amounts of this resource are lost from farm fields, through soil erosion and runoff, and down swirling toilets, through our urine and feces. Although seemingly mundane, this process cannot continue indefinitely. Our dwindling supply of phosphorus, a primary component underlying the growth of global agricultural production, threatens to disrupt food security across the planet during the coming century. This is the gravest natural resource shortage you've never heard of...
Phosphorus is used extensively for a variety of key functions in all living things, including the construction of DNA and cell membranes. As it is relatively rare in the Earth's crust, a lack of phosphorus is often the limiting factor in the growth of plants and algae. In humans, it plays an essential role in bone formation. Without a steady supply of this resource, global agricultural production will face a bottleneck, and humankind's growing population will suffer a serious nutrition shortage.
The world's reliance on phosphorus is an unappreciated aspect of the "Green Revolution," a series of agricultural innovations that made it possible to feed the approximately 4.2 billion-person increase in the global population since 1950. This massive expansion of global agricultural production required a simultaneous increase in the supply of key resources, including water and nitrogen. Without an increase in phosphorus, however, crops would still have lacked the resources necessary to fuel a substantial increase in production, and the Green Revolution would not have gotten off the ground.
Thus we have another looming threat to human populations in the 21st century, which I call The Age Of Scarcity. There is lots of stuff to talk about regarding phosphorus and potash, a source of soluable potassium, so I will have to provide further details in another post.
So was Thomas Malthus wrong? I don't think so. Just wait and see...