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

By Richard

I am a retired obstetrician-gynecologist who has been fortunate to live and work in the wonderful community of Durango, Colorado for 40 years.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.