The Earth is the same size it was in 1803 when Thomas Malthus published his thoughts on population growth. Then the human population was under 1 billion and now it is over 6.6 billion. Malthus had no clue about the human inventions that would come in the intervening two hundred years between the time he published and now. He understood neither the huge potential of energy from coal, oil, gas and uranium stored in the ground nor the huge potential of the atmosphere and oceans to absorb human caused effluvia.
Malthus did realize however that the size of the Earth was fixed and that an unchecked human population would eventually grow to fill it completely to the limit of their reproductive powers. Because Malthus worked with this problem for a quarter of a century he probably came across Leeuwenhoek’s 1679 projection for maximum human population size of 13.4 billion. Malthus probably would have thought that number ridiculously large given what he knew but Leeuwenhoek probably based his number on the total estimated size of land converting 100% of its potential productivity to human biomass using the then current high technology. That huge number of people does now seem potentially attainable in the next 25 years but it probably isn’t sustainable for very long and certainly not the long term.
I consider, as an estimate, that humanity is half way through its life cycle, the Holocene period. It is just a defensible number and certainly isn’t accurate, but it gives us a fixed point in an otherwise turbulent sea of speculation. The Holocene, the end of the last ice age, was when modern civilizations based on farming began to emerge. So if we set that as our standard of measure and assume we are half way through our life cycle then it becomes reasonable to plan for 12,000 more years of civilized human life. That is a long time but what choosing a seemingly arbitrary number (2,000 more years) does is that it gives an nebulous term like sustainable a more tangible meaning. When you put a specific number like 12,000 years then the current population growth rates or oil consumption rates or pollution rates become totally absurd. They are absolutely unsustainable. For a more thorough discussion of this type of problem see: Orrin H. Pilkey, Useless arithmetic: Why Environmental Scientists Can’t Predict the Future.
Modern economies are based on growth not on stability or sustainability. Growth is a good thing but so is stability and sustainability. What is needed is a librating system of economics, that is one which swings back and forth near some perfect equilibrium point. Actually our current economies all do that but they do so in a wrenching sort of way. What is absolutely necessary for a 12,000 year sustainable humanity is two things:
1. Some sort of voluntary population cap that is well within the Earth’s ability to sustain.
2. The total elimination of Weapons of Extermination WOEs. (Not just WMDs)
I don’t know how to achieve either of those obvious goals. Over the long period of time proposed, living as we do, both of these catastrophes—overpopulation leading to exhaustion of resources and extermination by WOEs—would probably strike repeatedly. It is the sort of thing which appears to be unlikely on a short time scale but repeatedly inevitable on a very long time scale. It is like radioactive decay in that way and there is a certain kind of inevitability about it.
Here is a wonderful desktop population clock to keep you appraised of just how quickly we humans are consuming the planet’s resources and how disease-prone and violent we are.
The Earthark Project and the Lifehaven Project will not save humanity but it will give us a second chance and it is obvious that we will be needing that soon.