From Jared Diamond’s Collapse: How Societies Choose to Fail or Succeed:

The Norse were undone by the same social glue that had enabled them to master Greenland’s difficulties.  That proves to be a common theme throughout history and also in the modern world … : The values to which people cling most stubbornly under inappropriate conditions are those values that were previously the source of their greatest triumphs over adversity.

Diamond’s book is about societies that have succeeded or failed.  Population control and resource/environmental protection are key to a society’s success.  Overpopulation and environmental degradation lead almost invariably to collapse.  This is a graph of standard population growth:

It shows how a population grows over time.  At first, growth is slow, because there are few individuals reproducing, but growth speeds up as the population increases.  Eventually, growth slows and stabilizes because the population has reached the carrying capacity, that is, the environment can only support so many individuals.

This graph, however, is oversimplified.  In reality, populations often overshoot their carrying capacity and then crash – like this reindeer population:

The population also responded to the high quality and quantity of the forage on the island by increasing rapidly due to a high birth rate and low mortality. By 1963, the density of the reindeer on the island had reached 46.9 per square mile and ratios of fawns and yearlings to adult cows had dropped from 75 and 45 percent respectively, in 1957 to 60 and 26 percent in 1963. Average body weights had decreased from 1957 by 38 percent for adult females and 43 percent for adult males and were comparable to weights of reindeer in domestic herds. Lichens had been completely eliminated as a significant component of the winter diet. Sedges and grasses were expanding into sites previously occupied by lichens. In the late winter of 1963-64, in association with extreme snow accumulation, virtually the entire population of 6,000 reindeer died of starvation. [emphasis mine]

This often results in oscillations – repeating this exponential increase and population crash over and over.

This is a graph of human population growth:

It looks like the beginning of the logistic curve – or the reindeer graph.  It is very likely that we as a species have overshot our carrying capacity.  Our severe environmental problems are caused by the very large  number of people consuming resources.  But will our population decline gradually or crash?

Unlike reindeer, humans have developed many technologies to help us overcome limited resources.  Fertilizer, for example, allows us to grow more food on less land.  But ultimately, humans cannot keep reproducing indefinitely – there are not enough resources and eventually, we would simply run out of room, like bacteria in a petri dish.

Population crashes, like that in the reindeer graph, may not be that frightening on a graph, but in reality, it is horrific.  War, starvation, economic and social collapse are not the overpopulation solution I want to live through.

We must ease the burden on our planet’s resources by consuming less and changing our lifestyles.  Like Diamond makes clear in Collapse, we must also reject some of our closely held values that have led to our current situation.  Growth cannot be the sign of progress – we must instead focus on sustainability.  But even this is a temporary solution.  The reindeer ate less and less and less – and eventually starved.  We should use less, but I don’t want to use so little that life is miserable.

One of the best things we could do as a species to prevent a population crash is to have fewer children.  Many people do not want children, or did not plan to have as many as they did.  We should support people who do not wish to have children, rather than pressuring them to reproduce.  My mother asks about grandchildren often and my grandmother is also anxious for me to have kids.  But I don’t want children!  Sometimes I think I do, but then I realize that I’m just eager to make my family happy. Quite frankly, having children, especially many children, is selfish and irresponsible in our world.

What if we encouraged people to only have children if they really wanted them, and made that possible by making sure that contraceptives were readily and cheaply available?  What if people who do want children very much considered adoption before trying to have a baby?  What if we built our cities differently so that we could walk places and interacted with our neighbors more?  What if we could be part of a supportive community instead of having to create our own by having a family?

I think these what-if’s are not only possible, but necessary, if we want to live a good life.