On World Population Day, why you should have paid attention in algebra

The United Nations declared today World Population Day, and noted that from the 7.2 billion people that currently inhabit our planet we will grow to a population of 9.6 billion by 2050. National Geographic has an analysis of how demographers arrive at those estimates, and notes:

Demographers say there is little reason to anticipate a population bomb or doomsday situation. In fact, the population growth rate has already started to slow, and this downward trend is projected to continue through 2050.

This is the good news in a good news/terrifying news scenario. Thanks to development, population growth has slowed and will continue to do so over the coming decades. Most demographers predict that our planet's peak population will occur around 2050, and after that point (as has recently happened in Japan) death rates will equal or surpass birth rates. This will happen not necessarily because of disease, but merely that people will have fewer children and eventually birth rates will drop below death rates.

The terrifying news is that worldwide, we will see a 33% growth in population. One-third more people than we have today trying to subsist on the same resources we currently have available. What makes this doubly terrifying is that within the 7.2 billion people that already inhabit the planet, 5 billion of them want to develop their quality and security of life to match that of the West. Here's some numbers to show why that is so terrifying.

First, the chart below shows the energy consumption per capita of the world and several specific nations. As it shows, as of 2007, China has steadily increased per capita usage approaching the world average of about 1,800 kg of oil equivalent.  Western Europe and Japan hover around 4,000 kg of oil equivalent (and falling), while the US sits at around 7,800 kg of oil equivalent.



Over the next forty years, as world population grows, if world energy consumption per capita moves toward the US per capita rate, we will consume nearly seven times as much energy per year as we do today.  If the world develops only to the rate of the UK, for example, we will "only" consume at a rate three times as much as we do today.

To follow this to a logical conclusion, if we look at the current reserves of fossil fuel, on which we almost completely depend for our quality of life, geometric growth of population combined with geometric growth in development and associated energy use puts exponential stress on reserves.  The table below looks at the level of reserves as of 2010, and then extrapolates usage under the current rate of world consumption, a path that grows consumption by 2050 according to the UK rate of usage, and finally one if the world grows to use energy at the rate we do.  All of these scenarios assume that we increase reserves through exploration or technological improvements by almost a quarter every decade (which  continues the current rate of development).

As the table shows, if we do not get a handle on the rate of our usage, given the population increase, we could run out of fossil fuels by 2047.

I know that this will not happen.  Renewables have increased market share over the past five years at rates faster than predicted.  Energy efficiency improvements in the US, and CAFE standard increases will reduce energy use per capita rapidly.  We have done much to make this potential future much less possible.  But it stands as a lesson.  We cannot ignore that more people are entering the world, more people already here want a higher quality of life, and that we currently consume resources at an unsustainable rate.

The math is there, as long as we are not afraid to see it.