Peak Oil, Carrying Capacity and Overshoot: Population, the Elephant in the Room - Revisited (Cont)
Given the fact that our world's carrying capacity is supported by oil, and that the oil is about to start going away, it seems that a population decline is inevitable. The form it will take, the factors that will precipitate it and the widely differing regional effects are all imponderables.
Some questions that we might be able to answer (though with a great degree of uncertainty) are "When will it start?", "When will it end?", "How much control will we have?", "How bad will it be?" and "How many people will be left?"To set the parameters of our model, we need to answer the four questions I posed above.
When Will The Decline Start?
This depends entirely on the timing of Peak Oil.
My conclusion that the peak is occurring now makes it easy to pick a start date. The model starts this year, though a start date five or ten years from now would not affect the overall picture.
When Will it End?
Given that oil is a primary determinant of carrying capacity, the obvious answer is that the situation will stabilize when the oil is gone. The oil will never be completely gone of course, so we can modify that to read, "When oil is unavailable to most of humanity." We know that point will come, because oil is a finite, non-renewable resource, but when will that be?
Based on the model in the figure above I chose an end date of 2082, 75 years from now.
How Much Control Will We Have?Will we be able to mitigate the population decline rate through voluntary actions such as reducing global fertility rates, and making the oil substitutions I mentioned above.
I have decided (perhaps arbitrarily) that the oil substitutions would not affect the course of the decline, but would be used to determine the sustainable number of people at the end of the simulation.
Fertility rates are an important consideration. The approach I've taken is to model the net birth rate, the combination of natural fertility and death rates that give us our current global population growth of 75 million per year. I modified that by having it decline by 0.015% per year. This reflects both a declining fertility rate due to environmental factors and some degree of women's education and empowerment, as well as a rising death rate due to a decline in the the global economy. I do not think that traditional humane models such as the Benign Demographic Transition theory will be able to influence events, given that the required economic growth is likely to be unavailable.
How Bad Will It Be?
This question comes from the assumption that the decline in net births alone will not be enough to solve the problem (and the simulation bears this out). This means that some level of excess deaths will result from a wide variety of circumstances. I postulate a rate of excess deaths that starts off quite low, rises over the decades to some maximum and then declines. The rise is driven by the worsening global situation as the overshoot takes effect, and the subsequent fall is due to human numbers and activities gradually coming back into balance with the resources available.
How Many People Will Be Left?
Taking the carrying capacity effects discussed above into account, I initially set the bar for a sustainable population at the population when we discovered oil in about 1850. This was about 1.2 billion people. Next I subtracted some number to account for the world's degraded carrying capacity, then added back a bit to account for our increased knowledge and the ameliorating effects of oil substitutes. This is a necessarily imprecise calculation, but I have settled on a round number of one billion people as the long-term sustainable population of the planet in the absence of oil.
Comments
The model is a simple arithmetical simulation that answers the following question: "Given the assumptions about birth and death rates listed above, how will human population numbers evolve to get from our current population of 6.6 billion to a sustainable population of 1 billion in 75 years?" It is not a predictive model. It is aggregated to a global level, and so can tell us nothing about regional effects. It also cannot address social outcomes. Its primary intent is to allow us to examine the roll that excess deaths will play in the next 75 years.
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With the exception of the start date, which I put down as 2005 for Peak Oil, these are very subjective issues, with many possible variations.
That said, my guestimate would be around 2 Billion by the end of this century & I hope that figure will be sustainable.
Whilst I fully recognise the consequences here, I must point out that the consequences of trying to maintain "business as usual", would be far greater!