A Decreasing Increase

This graph shows the rate of human population year-by-year since 1951.  Notice that it has been in decline throughout most of that time.  How is it, then, that the human population has grown by billions during my lifetime and  we expect to gain about  2 billion more people by the middle of the century.

Graph source: worldometers
Note: a 2-percent growth rate results in doubling every 35 years
A 1.2-percent growth rate, every 58 year
During this period, world population nearly tripled, from 2.7 to 7.3 billion

A Dark and Stormy Night

To understand how this is possible I need to start with the story about the misconceptions surrounding population change. This story goes way back, decades ago, to an evening in Cambridge Massachusetts. It was a dark and stormy night on the campus of Harvard University. A young divinity student who would eventually become a professor of mine decided to go to a lecture over at the Harvard business school. The speaker was a famous businessperson, perhaps one of the most famous in the world, though few know his name today.

Because it was a dark and stormy night very few people were in attendance, so Young Tom the divinity student had the opportunity to venture a question after the lecture. His question was this:  “Mr. Kroc, Why are there no salad at McDonald’s?” As I mentioned, this young man was to become an old professor of this old professor, so this was many years ago, before the days of salads at McDonald’s. And the speaker was Ray Kroc, the chief executive of McDonald’s.

“Because it’s a hamburger place!” was his first answer, but Tom  pressed him about the the importance of having other other options.

“Well,” Mr. Kroc continued, “we have done extensive studies of Seventh-Day Adventists and we have learned that there are not enough of them to sustain a salad menu at McDonald’s.” It was from the story that I learned – and I think even young Tom the divinity student had learned – that about half of Seventh-day Adventists in the United States are vegetarian.

“That is not the only reason to be a vegetarian,” Tom replied, now entering a bit of a debate with one of the wealthiest people on the planet.  “What other possible reason could they have?” Mr. Kroc stammered,  for it was truly beyond his comprehension that someone would avoid meat unless they thought God was telling them to.

“Well,” Tom replied,  some people are concerned for animal welfare -- Mr. Kroc grunted but Tom continued -- “and people are trying to eat lower on the food chain because of their concern for starvation around the world.”

“Starvation? There’s no such thing as starvation,” he groused. “Don’t you watch the news?” asked Tom, straining in disbelief. “What about this Sahel? What about the Biafra children?”

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“Well,  if they are starving ... it’s their own fault.”  Blaming the poor for their misery has long been a habit of the wealthy.  And then the punchline: “They’re breeding like rabbits."

Breeding like rabbits.

These three words stopped Tom in his tracks, and caused him to repeat the story countless times, as I have done in the years since I took his class. The rich give birth; the poor breed. And if population growth is making food scarce -- as it was at the time -- it must be because of more breeding.

Demographic Transition

Demographers and geographers know that this is a *misconception, commonly held though it is. Birth rates do fluctuate, but populations grow only modestly when birth rates increase. They grow dramatically when death rates decrease, and during the middle of the twentieth century, they were doing exactly that. Because of improvements in the availability of medicine -- particularly vaccines -- and high-yield crops, death rates fells quickly in many parts of the world -- falling much more quickly than birth rates tend to rise. 

Following World War II, for the first time in human history, death rates decreased in places that were not undergoing enough economic growth to sustain significantly more people. Population growth was therefore both unprecedented and problematic. The 1968 publication of The Population Bomb by Paul Ehrlich was the first widely-known description of the growth itself and of its potential to outstrip resources on a global scale. 

Ehrlich was scorned by some for his pessimism -- though his most dire predictions did actually come to pass -- as many believed that the planet was simply too vast to be impacted seriously by humans. We are indeed on a giant sphere, 8,000 miles in diameter. But all of our resource comes from very near the surface of that sphere, and all of our pollution remains in that same thin layer of the lithosphere, hydrosphere, and atmosphere. 

Geographers also know that not all parts of the sphere are created equal. Seven tenths of the surface is covered by deep salt water, most of which sustains only a minimal amount of biological activity. The vast majority of food from the oceans is found on continental-shelf areas that comprise just 2 percent of the total. Similarly, most land areas are too cold, too high, too wet, or too dry to sustain settled agriculture without significant artificial inputs. Just 13 percent of the land surface is considered arable (farmable), and ALL of the good farmland is already in use either for farming or for more remunerative urban uses. Humans already use all of the good land and a good bit of the marginal land.

Just after Ehrlich's book -- and perhaps to some degree because of it -- the rate of population growth began gradually to decline, as indicated in the graph above. This was the result of many factors, some related to intentional policies and others relating to feedbacks in the system. Known as the demographic transition, the conditions that accelerate population growth often lead to reduced birth rates in subsequent generations, and these changes actually continue to this day. Without them, population would already have passed 10 billion. Have a good look at the worldometers population page for a second-by-second estimate of the population (nearing 7,500,000,000 at the moment) and a lot of other ways of visualizing and understanding of demographic change.

Among many other cool visuals, the worldometer population page includes a 2000-year graph of human population that allows users to zoom in specific time frames. I use it here to approximate period shown on the natural-increase graph at the top of this post.

My Good News from Gorongosa post discusses the ecological implications of the century of rapid population growth from 1950 to 2050, and points to the original article "The Bottleneck," E.O. Wilson's excellent description of how this has happened and what it means. We can be concerned about the inexorable momentum of population growth, while being somewhat relieved that there is an end in sight... at least for those young enough to live to the middle of this century. Natural resources, ecosystems, and species that survive until 2050 will still face challenges from human activity, but a growing human population will not be one of them.

Lagniappe: Salad

Careful readers will note that McDonald's does of course have salads now, and might be wondering whether our young seminarian and his bold questions played a role. Sadly, no. Salad at McDonald's was literally an "over my dead body" thing, not appearing until 1985, when Mr. Kroc (1902-1984) was safely in the ground and for sure not coming back. His wife Joan lived until 2003. I do not know whether she played a role, but I have noticed that she is a generous funder of public radio, a cause I do not imagine Ray would have supported.

And another lagniappe: Science

Humans are innovative of course, and we have placed a lot of faith in science and technology to avert disaster as a population grows rapidly on a finite earth. But we also live in an era -- in the United States, at least -- in which the denial of science is widespread, greatly limiting our ability to employ it for adaptation.

*misconception: no pun intended, but my favorite librarian noticed