8 Billion and Counting - Now What?

 Margan and I host a Current Events group here at our retirement community twice a month. This coming one will be mine to prepare and I chose the little noticed event this month that we now have 8 billion fellow humans as neighbors on our spaceship Earth. That is a lot of humans. When graphed out, the population on Earth looks like this over time:

I joined the club in 1948 when the estimated global population was 2.5 billion. It was 4 billion when I graduated from medical school and you can see the rise on the graph since then.

I am drawn back to my first microbiology course in 1967 (3.5 billion humans then) and the concept of the bacterial growth curve. If one inoculates a test tube containing appropriate nutrients with a bacterium such as E. coli one can calculate a growth curve that looks like this over several days:

Initially the bacteria do nothing spectacular as their metabolism accommodates to the conditions in the tube (lag phase). Then they become active and divide as rapidly as every 20 minutes and their numbers climb (exponential phase). That slows as the nutrients in the system are exhausted (stationary phase), followed by death of the population at the end (death phase). 

See any similarities in the curve? Yep, humans are on the exponential phase of our growth curve, which really picked up after World War II. Are we headed to the fate of our inoculum of E. coli in the test tube? Depends.

Both the Earth and the test tube are closed systems. A major difference is that humans possess a brain and can alter the environment they inhabit as well as alter their behavior. Obviously, E. coli can neither alter their environment except toward its degradation (exhaustion of nutrients and accumulation of toxins) nor think their way to possible solutions.

That sounds hopeful for humans. Except human behavior is today tilted toward extractive activities (we take things from the Earth such as minerals, including fossil fuels) and return mostly toxic things in return (greenhouse gasses, plastics, heavy metals). Any discussion of what 8 billion people means for the planet cannot occur without discussing our trashing of the environment. 

A reason we have multiplied so fruitfully is because of industry. We depend on fossil fuels for the very energy that underpins civilization. The world of 1804 on the first graph above was as different from the world of 1927 as it is from the world of 2022. In 1804 the fastest method of travel was by horse. In 1927 internal combustion engines allowed us to fly at speeds of almost 200 mph. In 2022 we jet around the world in hours and think nothing of it. 

Elizabeth Kolbert writes for the New Yorker and has written many books about climate change. She won the Pulitzer Prize for her book The Sixth Extinction: An Unnatural History. I highly recommend this one as well as her most recent book Under a White Sky: The Nature of the Future because her grasp of science is excellent and she is a superb writer. Her most recent article in the New Yorker, published on 21 November, is Climate Change From A to Z. I will use her materials to provide context for the milestone of 8 billion humans. There are varying estimates about what will happen to Earth’s human population over the remainder of this century. Because fertility rates are dropping in most developed nations, one prediction is slowing of population growth over the coming decades. That said, lesser developed countries in Africa and Asia have seen fertility rates decline but not as much as in countries such as the U.S. and China. Overall the forecast is still for 10 billion or so humans and a population globally that is older than today’s. 

How will climate change affect this? Read Kolbert’s New Yorker article for as up-to-date an assessment as possible. Our current political scene is not one that encourages enthusiasm for a good outcome for humanity. There will be climate refugees on our current trajectory. Will they be welcomed as contributors to labor in countries whose native population is aging and shrinking? Or will xenophobia overcome the pragmatic possibilities for saving our species. As Kolbert notes in The Sixth Extinction, it has been caused by Homo sapiens. Homo sapiens could well solve the problem of an increasing population by causing its own extinction.