The world's population continues to grow. Shouldn't physicists care?
Albert A. Bartlett
The most sacred icon in the "religion" of the US economic scene is steady growth of
the gross national product, enterprises, sales, and profits. Many people believe that
such economic growth requires steady population growth. Although physicists
address the problems that result from a ballooning population—such as energy
shortages, congestion, pollution, and dwindling resources—their solutions are starkly
deficient. Often, they fail to recognize that the solutions must involve stopping
Physicists understand the arithmetic of steady, exponential growth. Yet they ignore
its consequences, including the first law of sustainability: "Population growth or
growth in the rate of consumption of resources cannot be [indefinitely] sustained."
(See Ben Zuckerman's letter to the editor, Physics Today, July 1992, page 14.)
Sustainability requires solutions that will be effective over time periods much longer than a human lifespan. Indeed, Paul Weisz makes a case on page 47 of this issue that many time-honored 20th-century energy sources, such as petroleum, natural gas, and coal, have been reduced to the point that their longevities are now expected to be of the order of a human lifespan.
Physicists and energy
Among physicists, there is a growing recognition that we have a responsibility to
become more directly involved in the scientific aspects of problems facing society. As an example, consider the April 2002 special issue of Physics Today, which addressed specific energy problems. Let's focus on two of the articles in that issue: Stephen Benka's introductory essay, "The Energy Challenge" (page 38), and Ernest J. Moniz and Melanie A. Kenderdine's lead article, "Meeting Energy Challenges: Technology and Policy" (page 40). The titles alone convey a common commitment to society. In his essay, Benka outlined the magnitude of the challenge by citing projections from the US Department of Energy: Between 1999 and 2020, the world's total annual energy consumption will rise 59% and the annual carbon dioxide emissions will rise by 60%, while the world population increases from 6.0 to 7.5 billion people.
But here's the rub: Scientists may call for solutions to meet the rising demands of
population growth, but as long as we postulate the continuation of that growth, the
attendant problems of energy consumption and increasing CO emissions cannot have long-range solutions. The two articles in Physics Today fail to identify stopping
growth as a necessary condition for the success of any proposed long-range solutions
to the problems caused by population growth.
Scientists have occasionally acknowledged that population growth is the major cause
of our problems. But I wonder whether their general reticence stems from the fact
that it is politically incorrect or unpopular to argue for stabilization of population — at least in the US. Or perhaps scientists are simply uncomfortable stepping outside their specialized areas of expertise.
Unchecked population growth as a source of problems is not news. More than 200
years ago, mathematician Robert Malthus (1766-1834) addressed the issue in his
famous essay. He understood that populations had the biological potential for
steady growth and that food production did not. Today, energy production does not
have the capability of steady growth.
Nevertheless, we are all aware of nonscientists with academic credentials who
proclaim that our modern technology has proven Malthus wrong. The most egregious
of the high priests of endless growth was the late Julian Simon, professor of
economics and business administration at the University of Illinois and later at the
University of Maryland. In 1995, he wrote:
Technology exists now to produce in virtually inexhaustible quantities
just about all the products made by nature. . . . We have in our hands
now . . . the technology to feed, clothe and supply energy to an evergrowing
population for the next seven billion years.4
In the eyes of the general public, the silence of scientists on the problems of
population growth seems to validate the messages of the politically appealing and
influential Julian Simons of the world.
In addressing the problems, Benka noted that "most of the growth in all three areas
[energy consumption, CO , and population] will take place in rapidly developing
parts of the world." It is expedient to blame others, but because the US consumes so
large a fraction of the world's energy resources, we Americans are effectively the
worst offenders in those areas. Our population growth rate of more than 1% per year
is the highest of any industrial nation. The US can't preach that other countries
should limit their population growth unless we are willing to set an example and do
Benka later argued, "It seems certain that the world will continue to rely heavily on
hydrocarbon combustion for the foreseeable future. . . . However we must develop
alternative energy sources." To be fair, Benka was not sanguine about the problem of
energy shortages. His essay is partly a call to arms. But the evidence (see Weisz's
article) indicates that some fossil-fuel resources may be in trouble within the next
few decades. When physicists suggest that the US has resources and technological
potential to meet the needs of an ever-growing economy, it's like inviting the public
to dinner without having checked to see if there is sufficient food in the cupboard.
Most educated people understand that populations can't grow forever. But forever
isn't really the issue. Already, population increases and consumer demand are taking
big bites out of our energy resources. Of natural gas, Moniz and Kenderdine wrote
that "US consumption represents roughly half of that for the industrialized world. . . .
Developing Asia, Central America, and South America . . . are each expected to triple
their demand over the next twenty years." A geological study published in 2003
reports that per capita annual production of natural gas is decreasing in Canada,
Mexico, and the US. Production of natural gas in North America may be near the
start of its terminal decline.
Of petroleum, Moniz and Kenderdine reported that world oil consumption is
expected to grow by 60% in the first two decades of the 21st century and that China
expects a five-fold increase in vehicles by 2020. Some optimistic researchers include
in their tabulation of world reserves the oil shales of western Colorado (about 500
billion barrels); the Athabasca Oil Sands of Alberta, Canada (about 300 billion
barrels, potentially); and the heavy oil under Venezuela (about 2 trillion barrels).
Those quantities are huge compared to the US annual consumption of approximately 6 billion barrels, but the important question to ask is, What is the net energy gained after investing the energy it would take to recover those very hard-toextract
resources? Physicists must include the net energy in any recommendations that we make to use those fuels in the future.
Moniz and Kenderdine also wrote about "products derived from gas-to-liquid conversion [meaning natural gas], gasification of coal, and biomass." But if natural
gas in North America is near the start of its terminal decline, there won't be much
left to convert into other potential uses. They argued that CO emissions can be
reduced by switching to "less carbon-intensive fossil fuels—for example, natural gas
instead of coal for electricity generation—[this is an] economical way to reduce
carbon intensity and meet growing demand." But the switch from coal to natural gas
to generate electricity in the US was made a decade or so ago and the predictable
effects are now evident: declining production, imminent shortages, and the rapid
price increases of natural gas.
Researchers continue to debate when the peak of world petroleum production will be
reached. Analytical estimates range from 2004 to about 2025. But from a per
capita perspective, world petroleum production reached a peak in the 1970s (see the ). I believe future historians may identify this peak as one of the most important events in all of human history.
In the Physics Today essay and article, population growth is given as a cause of the
problems identified, but eliminating the cause is not mentioned as a solution. We
are prescribing aspirin for cancer. Indeed, the solutions outlined in the articles
would only make the problems worse. To appreciate what I mean, consider the
"theorems" of economist Kenneth Boulding.10
The Dismal Theorem:
If the only ultimate check on the growth of populations is misery, then
the population will grow until it is miserable enough to stop its growth.
The Utterly Dismal Theorem:
Any technical improvement can only relieve misery for a while, for so
long as misery is the only check on population, the [technical] improvement will enable the population to grow, and will soon enable more people to live in misery than before. The final result of [technical] improvements, therefore, is to increase the equilibrium population, which is to increase the sum total of human misery.
The Moderately Cheerful Form of the Dismal Theorem:
If something else, other than misery and starvation, can be found which will keep a prosperous population in check, the population does not have to grow until it is miserable or starves; it can be stably prosperous. In 1970, the CBS broadcaster Eric Sevareid rephrased the theorems even more bluntly: "The chief source of problems is solutions."11
Physicists develop solutions to problems, but when the underlying cause of those
problems remains neglected, we are effectively perpetuating a lie—what Mark Twain
has called the silent lie:
Almost all lies are acts, and speech has no part in them. . . . I am speaking
of the lie of silent assertion; we can tell it without saying a word. . . .
For instance: It would not be possible for a humane and intelligent
person to invent a rational excuse for slavery; yet you will remember that
in the early days of emancipation agitation in the North, the agitators got
but small help or countenance from any one. Argue and plead and pray as
they might, they could not break the universal stillness that reigned, from
pulpit and press all the way down to the bottom of society—the clammy
stillness created and maintained by the lie of silent assertion—the silent
assertion that there wasn't anything going on in which humane and
intelligent people were interested.
The universal conspiracy of the silent-assertion lie is hard at work always
and everywhere, and always in the interest of a stupidity or a sham,
never in the interest of a thing fine or respectable. It is the most timid
and shabby of all lies . . . the silent assertion that nothing is going on
which fair and intelligent men [and women] are aware of and are
engaged by their duty to try to stop.12
What do we do?
Here is a list with which to start:
1. Acknowledge population growth as a major cause of societal problems.
2. Debate the question, Which approach leads to greater general good: working to
stabilize populations or working to spread ever-dwindling resources among
3. Research, speak, and write about energy consumption, CO emissions, and
populations, with an understanding that stabilizing population is a necessary
condition for solving these problems.
4. Alter the message given to students in the classroom and to the public. It is
important they recognize that these energy and related problems cannot be
solved without stopping population growth.
The physics community cannot launch a major campaign aimed at stabilizing the US
population. That's not physics. But when physicists assume authoritative roles to
solve the societal problems caused by population growth, professional responsibility
requires that we stress the importance of stopping population growth as a central
part of all solutions. We are not telling lies of silent assertion in the interest of the tyrannies and shams that Twain cites. Rather, we are tiptoeing around the issue in the name of political correctness. We can't be proud of that. As Mark Twain wrote, "[It] is the most timid and shabby of all lies."12
Albert A. Bartlett is an emeritus professor of physics at the University of
Colorado at Boulder.
1. A. A. Bartlett, Am. J. Phys. 46, 876 (1978).
2. A. A. Bartlett, ,
5 (1994). Reprinted in , 6 (Winter 1997ˇ98).
Population and Environment 16
Renewable Resour. J. 15
3. See T. R. Malthus, in
" P. Appleman, ed., W. W. Norton, New York (1976).
An Essay on the Principle of Population: Text, Sources and
4. J. M. Simon, , CATO Policy Rep. vol.
17, no. 5, Cato Institute, Washington, DC (Sept.ˇOct. 1995), p. 131. For a
critique, see A. A. Bartlett, , 342 (1996).
The State of Humanity: Steadily Improving
Phys. Teach. 34
5. W. Youngquist, R. C. Duncan, Nat. Resour. Res. 12, 229 (2003).
6. W. L. Youngquist,
, National Book, Portland, OR (1997), p. 215.
GeoDestinies: The Inevitable Control of Earth Resources Over
Nations and Individuals
7. A. A. Bartlett, Math. Geol. 32, 1 (2000).
8. K. S. Deffeyes, , Princeton
U. Press, Princeton, NJ (2001).
Hubbert's Peak: The Impending World Oil Shortage
9. J. D. Edwards, Am. Assoc. Pet. Geol. Bull. 81, 1292 (1997).
10. K. Boulding, in , Vol. 2, Colorado
Associated U. Press, Boulder, CO (1971), p. 137.
Collected Papers [by] Kenneth E. Boulding
11. E. Sevareid, CBS News, 29 December 1970, quoted in T. L. Martin,
, McGraw-Hill, New York (1973), p. 23.
Malice in Blunderland
12. M. Twain, ,Prometheus Books, Amherst, NY (2002), p. 159.
The Man That Corrupted Hadleyburg and Other Short Works