Carrying Capacity Population

Population Paradox #1

Population Paradox #1—7-2012

            From a biological standpoint, the most important goal of any species—or individual—is to pass on its genetic information. That is the reason that so much time and energy is spent on reproduction. In general, the more progeny, the better.

The exception to this observation is humans, at this time in history.

The human species has been so successful that our numbers have grown enormously. We are not as physically powerful as some animals, nor do we have the weaponry like claws and teeth that many carnivores enjoy. Nevertheless we have become the planet’s top predator.

I can think of no other predator that increased its numbers beyond a sustainable population for long. Prey animals may expand their numbers beyond their territory’s carrying capacity, but then predators feast and the prey population drops. The balance of nature is restored as the predators’ numbers diminish.

Many humans think we can exceed the planet’s carrying capacity permanently. Economists and politicians talk about growing the economy, but seem to have two blind spots—that we live on a finite planet that is already stressed, and that indefinite growth is impossible. The Global Footprint Network’s 2011 Annual Report illustrates these concepts wonderfully. Titled “What happens when an infinite-growth economy runs into a finite planet”, it is available at

The number of people who can live on Earth (its carrying capacity for humans) is not fixed. We have succeeded in increasing the planet’s carrying capacity immensely, thanks to our fantastic inventiveness. First we learned to squeeze food out of much of Earth by devising agriculture. Then we discovered remarkable ways to increase agriculture’s productivity. We have benefitted from stripping our planet of its resources. Fossil energy from below ground provides each person in our country with work that couldn’t be performed by a score of human slaves.

We are so successful that we are exhausting our life-support systems. You know the extent of our destruction: extinction of species, depleted ocean fisheries, polluted air and water, loss of topsoil, climate change, slashed rainforest. Although we lead lives of unparalleled bounty, our progeny will suffer because we have used more than our share of resources.

How would it be if our population had leveled off at, say, three billion? That would be what our numbers were when I graduated from high school, 50 years ago. Of course this question cannot be answered. I remember that the1960’s was a bad time for the environment with DDT, burning rivers and toxic fog. It was also an era when we were still living sustainably, according to Ecological Footprint measures.

As a species we have been victorious in passing on our genes. We have followed the command in Genesis: “…God said unto them, be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.” We humans have been too successful in multiplying, and now we are killing off the fish and fowl. Most ocean fisheries are depleted and many species of fish are endangered. We have also caused the extinction of many species of birds—the Carolina parakeet, passenger pigeon and the dodo are memorable.

All signs are that we will leave too few resources for those yet to come. Our success has endangered our progeny’s future.

What can we do? The first step is to recognize that the Biblical phrase above no longer applies. We have been too fruitful. A current estimate of the number of plants and animals on Earth is over 8 million. We have already permanently exterminated 802 species that we know of, plus innumerable members of creation that were unknown to biologists. We need a second ark for all the endangered species.

I fear that our success as a species will also be our downfall. This is the second of two population paradoxes. The first is that armed conflict was a significant factor in keeping the human population from growing rapidly in the past. Our era, called by some the “long peace”, has allowed our numbers to increase radically. We have outgrown Earth’s carrying capacity and conflicts over resources such as petroleum and water may trigger a catastrophic Armageddon. The paradox is that small skirmishes may have helped prevent total war.

The time has come to realize that what has worked in the past will cause a disastrous future. For our progeny’s sake we must promote small families.

© Richard Grossman MD, 2012

Carrying Capacity Global Conflict Population

Population Paradox—Small wars may prevent apocalyptic conflict

Population Paradox—Small wars may prevent apocalyptic conflict—6-2012

            The reason that I became concerned about human population is that I wanted to work for peace. Long ago I believed (and still do) that overpopulation is likely to lead to armed conflict.

Scarce resources are the most common cause of armed conflict. People are hungry and their neighbors have food, so a raid is initiated to steal their sustenance. Another scenario involves a growing group whose land area is limited. They look envyingly to the other side of their border with rich land and few people; invading a neighboring territory is a common cause of war. The Nazis used Lebensraum (living space) as an excuse to invade adjacent lands, thus catalyzing World War II. Recently we fought the Iraqi war over another valuable resource—petroleum.

Religion is also a common cause of war—even though most religions claim that they want peace. We are afraid of Muslims overrunning our beliefs. We have forgotten, however, what many followers of Mohammed still remember—how the Christians tried to exterminate Islam during the Crusades.

We know that a graph of the human population was almost flat for many centuries before the past couple hundred years. Why was there so little growth for so long, followed by such an amazing acceleration?

Many reasons are given for the past slow increase in our population. High infant mortality, poor hygiene, infectious diseases, and meager food supply all contributed. These factors all changed with the industrial revolution.

There is another cause, however, that we don’t usually consider as a reason for slow population growth. Several books give us a clue. The Great Big Book of Horrible Things (Matthew White) lists the world’s largest mass killings. The Roman gladiators (responsible for over three million deaths) and the Crusades (another three million) are listed. The imperialism of Genghis Kahn destroyed 40 million people, the Atlantic slave trade 16 million and the conquest of the Americas 15 million. Overall, about a half billion people died from the hundred cruel calamities described in this book.

Two books put forth a theory that may be a more significant past cause of mortality. War Before Civilization: The myth of the peaceful savage (Lawrence Keeley) and Constant Battles: Why we fight (Steven Le Blanc and Katherine Register) both posit that our ancestors killed each other in very significant numbers. They look at archeological evidence from around the world, especially right here in the Southwest.

In the past there were small bands of people living all over the world. Recent evidence suggests that these societies were more violent than prior archeologists ever acknowledged. Overall, these authors estimate that 10 to 15 percent of people in prehistoric societies died from conflict.

Disease and starvation weren’t bad enough! It seems that homicide and warfare are important reasons human population grew slowly for millennia. Past people destroyed their neighbors to steal their resources. In some cultures there is even evidence of cannibalism; not only did they kill, but also ate their neighbors’ flesh.

War is a terrible way to limit population growth. Unfortunately, battles and cruelty with extensive loss of life seem to have been the way of life in our dark past.

We are living in a period of relative peace according to Better Angels of Our Nature. A reviewer of this book summarizes its thesis: “…our era is less violent, less cruel and more peaceful than any previous period of human existence.” What may not be self-evident (few of us have the long view of history needed) is that the world has actually become less violent.

This book goes further than just to claim that we are living in an era with decreased armed combat. The author, Steven Pinker, is a Harvard psychologist who believes that we have slowly changed our mores to accept less violence in our personal lives—less spanking of children and less persecution of people for their beliefs, ethnicity, color or sexual orientation. With this current “Long Peace” has come longevity—and more people.

Apparently small raids and “horrible things” kept our population small, and the “long peace” is one cause our numbers have increased so rapidly. Relative peace has allowed our population to outgrow the carrying capacity of our planet by fifty percent! I share a concern with a Pentagon document from 2003. “As famine, disease, and weather-related disasters strike due to … climate change, many countries’ needs will exceed their carrying capacity… which is likely to lead to offensive aggression in order to reclaim balance.”

© Richard Grossman MD, 2012