Friday, November 11, 2011

7 Billion and Going Strong

According to the United Nations, the world population reached 7 billion on Oct 31st, 2011, the Day of Halloween Day.  And the honor of being the 7 billionth baby went to a girl who was born in the Philippines (see a news report and party photo.)  If UN’s goal was to sound the alarm (again) and draw attention to the concern about our ever increasing world population, they have got my attention.  

There have been continuing discussions by scholars, analysts, and journalists of the recurring worry – how much longer can the planet earth support its ever increasing population and how many people can planet earth sustain. It turns out these questions are very difficult to answer with certainty and the estimates vary widely with different assumptions and extrapolations.  Nevertheless, the exact numbers is not nearly as important as the methodology of the analysis and the few basics and boundary conditions.

To begin with, let us agree on why the population keeps growing and what is required to keep it at a constant level.  The answer to the question of “why” should be intuitive and non-controversial: any system would be growing if the incoming rate exceeds the outgoing rates in long enough time scale.  We experienced it frequently in our everyday life and observed when the rates are not balanced.  For example, we saw our kitchen sink backed up when the drain was clogged; we encountered long delays at bridges and tunnels during rush hours when arrival rate of traffic exceeded the rate of what these conduits can clear.  There is no difference for population: when the rate of births is higher than the rate of death, we can expect the population would grow, ignoring the time lag factor of life span for now.

How have we been doing lately regarding these rates?  The frequently used technical term is the (crude) birth rate (CBR) which is simply the number of births in a given year for every 1,000 persons in a given region.  If you go to Wikipedia and look up the List of countries by birth rate, you can find that for instance, CIA World Factbook estimated in 2009, birth rate by country/region ranged from the highest in Niger (a western Africa country) at 51.60 (per thousand) to the lowest in Japan and Hong Kong at about 7.5, while U.S.’ CBR stood at 13.82 and India was at 21.6.

To make some sense of these numbers, we need to compare them with the (crude) death rate (CDR) of these countries.  Death rate in Niger, Japan, Hong Kong, U.S. and India were estimated by the same document at 14.83, 9.54, 6.76, 8.38, and 6.23 (per 1,000 people), respectively.  In other words, there was an estimated net increase of population of 37, 0.74, and 4.4 per 1,000 people in Niger, Hong Kong and U.S. respectively and a net decrease of 2 per 1,000 people in Japan in year 2009.  Since U.S. had a population about 300 millions, it simply says there was an estimated 1.3 million net increase in population.

An alternate and intuitive way of looking at the growth rate of our population is to consider the total fertility rate, which is the average number of children born to each woman over the course of her life.  The reasoning goes like this: if the average number of female babies born per woman in her childbearing ages is exactly 1, then the population would remain a constant since that female baby would replace the mother, no more and no less.  The equivalent technical term of replacement fertility rate is thus also frequently used which is simply the average number of children, either male or female, required to replace the mother.  Once we account for the skew due to chromosome difference (there are slightly more boys than girls born due to the built-in bias in reproduction process in favor of the Y chromosome) and the infant mortality, the replacement fertility is at about 2.1 births per woman for developed countries and more than 3.0 for many developing and underdeveloped countries.  Niger’s fertility rate of 2009 was estimated to be 7.07 (according to the CIA World Fact Book). 

Some may argue that we should not worry since the world population growth rate has been declining in recent years and has reached a very modest rate of 1.1%.  Ignoring issues of huge disparities among regions and countries for the time being, should we be worried or not?  Professor Emeritus Albert Bartlett of University of Colorado at Boulder had the following to say about the reality of steady growth and how most of us ignore it:  "The greatest shortcoming of the human race is our inability to understand the exponential function."  He was referring to our failure in recognizing how explosive it really is of anything that grows at a constant rate.  Watch the lucid lecture he gave below, entitled Arithmetic, Population, and Energy.   It should convince you with just the first 10 minutes of the videos that steady growth is scary unless it happens to be your investment and bank accounts.

Now we can return to our original questions of how much longer can the planet earth support its ever increasing population and how many people can planet earth sustain.  We are going to focus on the 2nd part of the question since we already have the ideas of the growth rate.  If we have an estimate of how many people the planet earth can sustain, we can easily estimate how long it would take for the population to grow and hit that level with the given population increase rate and various assumption like what Professor Albert Bartlett has demonstrated.

The big picture looks as follows.  We can all agree that the minimum and most basic resources for our survival are obviously food and fresh water (assuming air is not an issue).   It has been estimated that planet earth has over 300 million cubic miles of water but only 3% of it is fresh water.  Further, two third of the fresh water is in frozen form such as ice cap and glaciers which is necessary to keep the earth cool and sea level in check.  In all, we have about 3 million cubic miles of (mostly renewable) fresh water and only 0.3% (or almost 10,000 cubic miles) of it is on the surface (in lakes, rivers, snows, etc).  The rest are underground and not necessarily accessible. 

You may or may not know what we drink directly is just a tiny fraction of our total fresh water consumption.  The dominant consumption of freshwater is actually for food production – 70% of the fresh water consumption is for agriculture.  With today’s efficiency, we need for example, 3,000 gallons or over 11 metric tons (11,000 Kilograms or 24,000 pounds) of fresh water to grow one bushel (about 25 kg or 56 pounds) of corns.  We need about 900 metric tons of water to grow one metric ton of wheat.  And it takes 2,500 gallons or about 10 metric tons of water to produce one pound of beef.   

Some researchers have offered an overall estimate that it takes in average about 3,000 liters (or 3,000 kg) of fresh water to produce food of recommended daily dietary need for just one person.  If you assume that fresh water (renewal) cycle is in average 2 years (too short?), i.e., time takes after the consumption of fresh water till it becomes available and is consumed again, and that majority of fresh water supply is from surface, then with some simple arithmetics, the earth should be able to sustain about 7.5 billion people with decent nutrition.  Now you can understand why there are already so many starving people in the world given uneven distribution and local overpopulations.

We haven’t even talked about the connected issue of the availability of arable land and other limiting factors which are required for food production.  The fact is China, India, and many countries have been busy buying and leasing land in Africa to produce food for their domestic consumptions.  This should give you a pretty good idea of what is going on.  We also have not gone into the details of the assumption of the living standards for some of those estimates.  Obviously, there is a huge difference in the per person consumptions of resources for U.S. and for countries like Niger.  With all these considerations, Ross McCluney estimated in his article of How Many People Should the Earth Support? that the planet earth can support about 6 billion people if U.S. and Western European keep their current level of prosperity and the rest of the world live like Mexicans.  Obviously it is too late to debate that as we already past the 7 billion milestone at the end of last month.  He also estimated that the earth can support 20 billion people if everyone lives like Mexicans and 40 billion if everyone lives like people in today’s northwestern Africa.  But would you be ok to live like that? 

Along with the rich resources and information compiled on the EcoFuture web site, one finds two interesting quotes which still ring true today and worth repeating here.  One was by the late Isaac Asimov, a famous biochemist and writer.  In his Oct 1988 interview with Bill Moyer, he said: "...democracy cannot survive overpopulation. Human dignity cannot survive it. Convenience and decency cannot survive it. As you put more and more people into the world, the value of life not only declines, it disappears. It doesn't matter if someone dies. The more people there are, the less one individual matters."  The other is a popular but un-sourced quote by the late Robert McNamara who was the Secretary of Defense overseeing the escalation of Vietnam War and former World Bank President.  He supposedly had said: “Short of nuclear war itself, population growth is the gravest issue the world faces. If we do not act, the problem will be solved by famine, riots, insurrection and war.”  

What McNamara was referring to have been happening in many places at smaller scales including the ongoing Africa Horn as we speak.   The “good” news is if the problem is not addressed soon enough, it will be solved for us anyway.  Planet earth will continue on for a very long time after you and I died, and with or without humans.  The bad news is the solution is going to be real ugly, much worse than the often criticized China’s one child policy.  There will be conflicts, famines, wars, and massive deaths as people will be fighting for the little remaining available resources.  Meanwhile the continuing deterioration of the environment and climate change could only accelerate the downward spiral and further reduce the available resources.   By then, it will be too late for the occupants of earth to try to reverse it.   What do you think we should do now?

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