We could be the transition generation – or the terminal generation. It's our choice.
By the end of this century, within the lifetimes of people alive today, the number of human beings on planet Earth, now over 7 billion, could be just a few hundred million, or even less.
You cannot have infinite growth within a finite system.
Sooner or later that growth must end, collapse, or expand into another, more open system.
We have at least four sub-systems on our planet that are growing exponentially.
The first is population. It is hard to define the carrying capacity of the Earth as it is closely tied to technology.
Technology allows us to grow more food per hectare. It also allows us to control diseases better and to take other steps that allow people to live longer.
There were 1.6 billion people in the world in 1900 and 6.1 billion in 2000.
By 2050 this number could rise to more than 9 billion.
The second sub-system experiencing exponential growth is technology.
According to Moore's Law, the number of transistors in a dense integrated circuit has doubled about every two years.
When we will reach the physical limits to growth with Moore's Law is not clear. Some say it will be within the next few decades, when transistors get into the sub-atomic size. Others say it won't be for centuries.
While not an apparent limit to growth as such, an important boundary in the growth of technology will be when our machines become more intelligent than we are. Again, when that will happen is not clear, but it probably will be within the next few decades.
A third example of exponential growth is industrialization (or matter-energy processing, as some might call it).
Back in 1972 the book “Limits to Growth” by the Club of Rome forecast that we would be facing general system collapse sometime around the middle of this century because of resource depletion or pollution.
Despite efforts to discredit the study, its forecasts continue to be right on track.
Human-caused climate change is perhaps the best example of the effects of matter-energy processing growth – and of our inability to deal with it.
The fourth sub-system exhibiting exponential growth is the arms race.
Despite the end of the Cold War, there are still tens of thousands of nuclear warheads on the Earth – enough to “bounce the rubble” several times over.
More worrisome, the number of states with nuclear weapons or the capacity to create them continues to increase.
The analogy of more people with matches in the powder magazine is hard to avoid.
Other weapons of mass destruction, such as chemical or biological weapons, are no doubt continuing to increase in lethality.
The lethality of conventional weapons also is increasing – so much so that their effects are merging into those of nuclear weapons.
These are all cheery thoughts that many of us have become quite skilled at not thinking about.
However, none of these problems, although serious, appear to be insoluble.
For example, people in high technology cultures tend to have fewer children.
Urbanization also reduces population growth.
Perhaps most importantly in controlling the number of people in the world are equal rights and education for women and girls.
The point is that we need to think about all four sub-systems together as one, and consider all alternatives openly and without bias.