What Drives Population - Food or Energy?
assumption among population analysts is that food availability is the main driver of population
growth. In fact, most will go so far as to define the carrying
capacity of an environment primarily in terms of the food that it
offers to the population under consideration. I have two major
problems with this approach to population and carrying capacity, as
My first objection is that this approach
treats carrying capacity as a variable, and the expansion of agriculture as an
increase in carrying
capacity. This requires a definition of carrying
capacity I do not subscribe to. The definition I am most
with is, "The population level
that an environment can support over the
long term without damaging the ecology of the environment".
expansion of agriculture does not meet this definition because putting
new land under the plow or increasing the production of existing
affects habitat, biodiversity, water levels and soil fertility among
many environmental factors. In effect the expansion of agriculture
requires that we draw on the natural capital of the environment.
repayment of this withdrawn capital does not enter the ecological
equation as it should.
The result is, by definition, not sustainable. In fact, the form
of organized agriculture (which I have heard playfully called
"totalitarian agriculture") practiced for the last ten thousand years
is by definition unsustainable, especially when you consider that
virtually all of the arable land on the planet is now under
cultivation. Now, my definition of carrying capacity may be
too strict and may be disputed by other ecologists, but it's the one
that seems most comprehensive and reasonable to me.
My second problem is that energy is never mentioned in mainstream analyses that focus on food. The possibility that this omission may be wrong-headed is hinted at by the well-known studies that found 7 to 10 calories of fossil fuel embedded in every calorie of food we eat. In fact, I have developed a strong suspicion that rising per capita energy consumption has even more to do with population increase than rising food production. To investigate this possibility I created the graph below. It shows population, grain consumption and primary energy consumption from 1965 to 2005, all scaled to allow a visual estimate of correlation.
I know this is not rigorous, but the
differences in correlation are obvious to the eye, and to me energy
consumption shows a better correlation with population
growth than does per capita food consumption. For the moment I am
that anyone who is analyzing population drivers without taking energy
consumption into account is missing a large and crucial
part of the
The implications of this
finding for the future of population growth seem obvious. In
articles I have stated my position that Peak Oil may precipitate a
decline in human numbers. The message of the correlation shown
above is that if rising energy use is a significant
driver of population growth, falling energy use will
probably result in a drop in population. The mechanisms for this
will be quite varied. They will range from declining agricultural
productivity and distribution to breakdowns in urban sanitation
infrastructures and problems with national electrical supplies. No
matter what the proximate causes of human deaths may be, however -
starvation, disease, exposure or heat stroke - the root cause will be
declining energy supplies.
The other significant implication is that
improving humanity's energy supply picture will not halt population growth. It
would certainly not curb it until the bulk of the world's population
had achieved the per capita consumption of the developed world, where
Total Fertility Rates have finally declined below replacement
rates. This is, of course, just a restatement of the Demographic
Transition Model into energy terms, away from the commonly assumed
proximate cause of industrialization.
Copyright 2007, Paul Chefurka
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