Population: What to Do When There Are Too Many of Us
- Population: What to Do When There Are Too Many of Us
By Robert Engelman, Island Press
June 10, 2008
Editor's Note: The following is an excerpt from More: Population,
Nature, and What Women Want by Robert Engelman. Copyright 2008 by the
author. Reproduced by permission of Island Press, Washington, D.C.
All historical eras are shaped by the material and environmental
realities of their time. Our own reflects the adjustments society and
nature have made to accommodate the unprecedented 6.7 billion human
beings now alive. And those changes are dramatic. The planet is
warming dangerously as a result of the heat-trapping byproducts of our
daily lives. Half of the primeval forests that existed at the end of
the last ice age are gone. A mist of mercury and other toxic metals
from coal combustion falls continuously on land and ocean, and to eat
fish is to absorb these metals yourself. Half of us are now urban,
rarely if ever meeting up with creatures wilder than crows,
cockroaches, and, in some cities, packs of feral dogs.
And this is just where we are today, while the beat of growth goes on.
Little if any of this would have transpired had human numbers peaked
long ago. Such a peak might have occurred by now, even with the gains
in life expectancy of the past century, if the status and reproductive
intentions of women had found consistent support rather than silence
Beginning little more than a century ago, social acceptance of
contraception began to grow and to spread around the world. That led
to dramatic declines in birthrates that gathered force as human
population throttled past a few billion. Who knows how much closer we
would be to a meltdown of Greenland's ice or the collapse of critical
ocean fisheries had this collective wisdom -- a public good derived
from individuals acting in their private interest -- not dampened the
rise of population? Given the increasingly plausible threat of one or
more interacting environmental catastrophes, the slowing of population
growth is a triumph of human wisdom and good fortune. This realization
is only slowly dawning, however, on the community of journalists and
other opinion leaders.
The dominant concerns in many countries about population aging and
decline are hardly baseless. These developments may well challenge
societies. Populations may have more old people than young for a
while, because yesterday's baby boomers are heading toward old age
even as young women are having fewer children. Over time, however,
extreme age disparities should subside as these large generations pass
on, the more so when average fertility returns to close to two
children per woman. Assuming it will.
Some demographers, eyeing the stubborn low fertility of women in most
of Europe and parts of east Asia, are beginning to wonder if such a
return to replacement fertility is possible. Some allude in cautionary
tones to the possibility of a "low-fertility trap," a vast pool of
demographic quicksand that prevents women from ever returning to
replacement fertility once their childbearing average drops below
about 1.5 births. There's no real basis for such speculation, however.
The world is too dynamic and our experience with intentionally low
fertility far too new.
What might eventually unfold is something far more appealing: birth
cohorts of consistently equal size across generations. The most
demographically stable age structure for a population would be for
each year's "class" of babies to be the same size as the one the year
before, and ten, twenty-five, or fifty years before. No single age
group, young or old, would naturally claim any more of society's
attention than any other, at least based on their numbers. That's a
population structure worth striving for.
For now, population aging is the inevitable outcome of two of the most
positive developments of modern times: longer life spans and the
realized intentions of women to have fewer children, later in their
lives. Modern views on human rights and equality hardly would have
allowed most women to continue giving birth to many more children than
they wanted. And populations hardly could have continued growing in
the twenty-first century at the same torrid pace as in the middle
decades of the twentieth. Some populations had to be the first to
experience the leveling off of growth and then decline, and in most
cases this has occurred with no significant increases in death rates.
That's rare, maybe even unprecedented, in human history.
Today, humanity still grows by 78 million people annually-the rough
equivalent of a new Texas, California, and New York each year. Unless
death rates rise catastrophically or birthrates plummet far more than
anyone expects, the end of world population growth is still decades
away. It's reasonable to expect that humanity will grow to 7 billion,
8 billion, or even higher before the number levels off for good
reasons or bad.
What dominates our experience in the first decade of the third
millennium are the technologies and institutions we have invented,
disseminated, tinkered with, and improved over thousands of years to
make human life on such scales possible. We've done well. Not only are
more people alive than ever, but most of us live longer than our
ancestors did. Quite a few of us spend our entire lives in comfort and
with tools and toys that those ancestors never could have imagined.
I stress the adjustments we've made to adapt to our growing population
because I grant Julian Simon, the late twentieth-century champion of
perpetual population growth, this point: we human beings are, if not
the "ultimate resource," at least awfully smart. When the going gets
tough, the tough get patents. Had hunters and gatherers never run low
on food and turned by necessity to cultivating it, we wouldn't have
cities or symphonies or cell phones. I certainly wouldn't be typing on
this laptop, anticipating a book that might appear in a bookstore
window thousands of miles from my home. Innovation indeed is much of
what makes human beings successful, but it also keeps the angels on
the edge of their celestial seats, wondering, Can they do it again?
Each new pressure point creates the need for new innovation, and each
new innovation produces effects of its own, many of them unintended
and quite a few problematic. Why do things bite back, to borrow from
the title of a recent book? One reason (not actually mentioned in that
book) is that it's getting crowded in here. In societies with low
population densities relative to available natural resources,
innovation's side effects often waft away, unimportant and unnoticed.
In high-density societies, there's less tolerance for error, systems
tend to be more sensitively balanced, and the scale of everything that
people are doing is larger relative to the natural world. "When we try
to pick out anything by itself," Scottish American conservationist
John Muir wrote, "we find it is hitched to everything else in the
Universe." So what happens when 7 billion people pick out 7 billion
We're finding out. Much of the human behavior we find unsustainable
today is not so in its essence, but in its scale. Julian Simon used to
say that more people leads paradoxically to more nature, but the
history I've presented in this book makes clear that over the long
sweep of time the trend is otherwise. The planet is in the early
stages of a species extinction episode not seen since the dinosaurs
disappeared. If you could somehow ask Mother Nature what she
attributes this to, I think she'd likely say not just "people," but
"this many people."
Yes, some populous human societies plant trees to anchor vulnerable
soils or set aside tracts of land for recreation or to preserve
important ecosystems. How long the trees will grow remains a question,
however. And the set-asides rarely protect all the land's wild
inhabitants-not to mention the water or the steady climate that
supports ecosystems over the long haul.
Protection is not necessarily forever. When the needs of growing
populations press hard enough, in wealthy and poor countries alike,
"set aside forever" often becomes a hollow promise. The biological
reserve near where I swam years ago in southern Mexico is now
pockmarked by the cleared land of impoverished squatters, whose needs
can't ethically be denied or easily redirected to biologically less
important land. Closer to my own home, the scarcity of affordable
housing is undermining an agricultural reserve meant to save the last
few farms of Montgomery County, Maryland. Wealthy societies tend to do
a better job than poor ones of cleaning up environmental messes, but
they rarely if ever improve upon what was there before the mess was
made. Having more people might contribute in some cases to
strengthening environmental protection, but not enough to matter over
the long term.
In 1984 Simon and futurist Herman Kahn suggested that population
growth can bring about more solitude, because more people own cars and
elude the madding crowds on improved roads. It would be interesting to
poll drivers around the world about this assertion today. Earlier,
Kahn had predicted dramatically new energy sources and undersea cities
by the year 2000. It's not just doomsayers on population and the
environment whose forecasts sometimes don't pan out. So far, the
twenty-first century is not proving at all kind to cornucopian
predictions. While I was writing this book, the last backwaters of
doubt that humans are propelling the planet toward uncontrolled
warming dried up. Those who have claimed in the past that the
environment just keeps getting better and better, thanks to wealth and
technology, today seem strangely quiet.
"Ecosystems are at a tipping point, "wrote the Washington Post, not
usually known for tree-hugging advocacy, "verging on a collapse from
which they won't recover." A front-page news story on "oil's new era"
in the Wall Street Journal gave the last word on the subject to energy
consultant Henry Groppe, who glumly suggested, "We have entered the
era of scarcity and price rationing" ...
Faces of Want
In the industrialized world we feel the impacts of population growth
and density in traffic congestion, in the inability to afford a home,
or in paychecks we might have stretched further in a less crowded
world. In many developing countries the toll is far higher and
climbing faster. To explore this is to wade into the endless debate on
the relative weight of the many causes of modern hunger, poverty, and
violent conflict present in so many developing countries. Some points,
however, are clear and well documented. Well over 800 million
people-the number has been rising in recent years-are chronically
undernourished, and during the 1990s the countries with the highest
population growth rates made the least progress in reducing hunger.
Scarcities of water, closely tied to the tension between nature's
fixed supply and the needs of growing human populations, are
increasingly commonplace. Urban areas bid up water's price. Farmers
lose access to water for irrigation precisely when rising food demand
forces new production to rely on irrigation rather than rain. After
generations of subdivision, farm plots are now so small in densely
populated African countries that few young adults can hope to marry
and launch families without moving to the city. "If I had known I
would have so little land to pass down to my sons," a Zambian tribal
chief once commented to his niece, my friend Wanga Grace Mumba, "I
wouldn't have had so many sons."
Land shortage helps explain the genocidal conflict in Rwanda, which
has one of the lowest ratios of cropland to people and the second
lowest ratio of renewable freshwater to people in mainland Africa.
Such scarcities might also be behind the explosion of child
abandonment seen most often among populations in which fertility is
high and the use of contraceptives rare. Today some parents exile
children they no longer want or no longer can support to urban
streets. Or they sell them into early marriage, prostitution, or slavery.
Certainly the progressive degradation of cropland is among the reasons
that the UN Population Division projects that in 2008, human beings
will cross the threshold to being a mostly urban species. Cities have
long stimulated the rich diversity of human culture, but in the
world's most rapidly growing ones not many people are celebrating.
Almost all urban expansions today are not planned neighborhoods, well
supplied with infrastructure and services, but slums. Health
indicators are often worse in cities than in the countryside that
urban migrants left behind. "I think we know cities in Kenya can
hardly sustain the population they have," observed Doug Keating of
Oxfam International on the prospects for rural exodus to cities as the
organization helped pastoralist communities in northeast Kenya cope
with a withering drought.
The loss of forest cover, closely tied in developing countries to the
ongoing need for more farmland, is among the biggest destroyers of
species in a wave of extinctions comparable to those that occurred in
the earth's remote and unpeopled past. It's an instructive irony that
the places friendliest to the survival of biological diversity include
the Demilitarized Zone between the two Koreas, various guerrilla-held
areas of Colombia, and the "radioactive nature preserve" known as
Chernobyl in the Ukraine.
Without tree roots to anchor it, deforested soil easily changes form
during heavy rains into flowing mud that seeks its own level-sometimes
on top of a village. This is a sadly common story in densely populated
and rapidly deforesting countries from the Philippines to Guatemala.
The Ugandan farmers who hurt themselves falling off their steeply
sloping fields, whose story opened this book, run the risks they do
because nearby level land was deforested long ago and is already taken
or has been farmed to exhaustion.
Human incursions into forests sometimes spur new pathogens to discover
what a vast and inviting pool of protoplasm human bodies present.
We're a bug's banquet. Our domesticated animal companions and
livestock spread their own pathogens around in the wild, threatening
species that have far smaller populations than theirs. We know from
history that most infectious diseases tend to be closely related to
population density and mobility, but the pace of pathogen exchange is
occurring far more rapidly today than ever before. Malarial mosquitoes
thrive in the pond waters of deforested land, and scientists are now
confident that HIV/AIDS made its way from chimpanzees to humans a few
decades ago, probably when a bushmeat hunter penetrated the forest,
butchered his quarry, and absorbed some of its blood.
In some places, even the traditional lifestyles of indigenous people
who thrived in forests for centuries are no longer sustainable.
Wildlife Conservation Society biologists Elizabeth Bennett and John
Robinson calculated that tropical rainforests can support at most one
subsistence hunter per square kilometer. "More than that and you're
depleting the resource," Bennett told the New York Times. "There are
few corners of the tropics at this moment that have so few people. You
can probably still have it in remote sections of Amazonia. In Sarawak
[in Malaysia], the indigenous people have the legal right to hunt. But
there's been a population explosion, and there are three of them for
every square kilometer of forest. That's three times the sustainable
number. If they all employ their rights, they'll hunt out the forest."
Bennett was not blaming indigenous people, who themselves suffer the
effects of the growth of non-indegenous populations around them, for
hunting out the forest. You might just as well blame an individual
driver for a traffic jam. But the unsustainability is real, no matter
how much we respect the dignity of indigenous individuals. It stems
not from subsistence hunting itself, which is ancient, but from
hunters' high population density, which is recent.
Bags of Ice
Thousands of years ago, subsistence hunters running out of prey, like
those in Sarawak, became farmers whose descendents launched the
world's great city-based civilizations. Such past adaptations made
humans what we are today, but humanity stands in a quite different
place now. Sum up the total mass of human beings, add all our pets and
livestock (40 million farm animals are born each year in the United
States alone), and factor in our processing of energy and materials.
We are a biological and geological force never previously witnessed.
What once may have been win-win strategies of adaptation are now more
often win-lose strategies-or desperation lose-lose plays. We are bulls
in a china shop. Almost any turn we make sends the porcelain flying.
The use of fossil fuels and the Industrial Revolution itself began as
science-based adaptations to energy scarcity and unsustainability.
Coal, a dirty fuel long thought inferior to wood, was first used on a
large scale around the sixteenth century as the forests of Europe were
exhausted by large-scale land clearance for farming and the burning of
wood for fuel and iron smelting.
Today, the world burns nearly 5 billion metric tons of coal each year.
That's about three-quarters of a ton for each person on earth, with
comparable combustion of oil and natural gas for each of us-all
driving a human induced warming of the planet whose endpoint we can't
yet imagine. Even though the thought of tempering growth is not yet
mainstream, the implausibility of growth without end is becoming more
obvious in a closed-atmosphere, carbon-constrained world.
Humanity's energy dilemma becomes more obvious when we think clearly
about alternative fuel sources. Adaptations, again, become problems.
The sheer scale of human energy use is so vast that even today's small
steps toward replacing fossil fuels with biofuels boost food prices
and put ecologically valuable land at risk. The calories needed to
keep a Hummer humming could feed a hundred humans. And anyone wealthy
enough to own a Hummer can outcompete a hundred hungry people for the
energy stored in plants.
Enough solar energy to dent fossil-fuel use significantly would
require panels and mirrors covering thousands of square miles of land,
much of it valuable for other purposes. Enough windmills to do the
same would draw howls of protest for visual pollution, their tendency
to slice up heedless birds and bats, and the likelihood that large
enough fields of turbines might even affect local weather.
Storing carbon in new forests will face the constraint that, as one
analyst suggested glumly, "as the human population continues to grow
... the earth's surface will be too disturbed." Hydrogen as a fuel
raises the question not only of what type of energy will be used to
separate the element from water molecules, but of where that water
will come from and what will be the impact of water vapor emitted by
hundreds of millions of vehicles. Nuclear energy leaves us with the
potential for proliferating weapons-grade plutonium and waste that
takes hundreds of human lifetimes to become harmless. "No primary
energy source, be it renewable or nonrenewable," write Jeffrey Chow,
Raymond Kopp, and Paul Portney, analysts with the environmental think
tank Resources for the Future, "is free of environmental or economic
But suppose we fail to make this essential shift away from
carbon-based fuels. Then, we can try to cool the earth's fevered
surface literally with smoke and mirrors-massive injections of sulfur
dioxide mist into the stratosphere, perhaps, or trillions of small
reflective panels sent into orbit around the planet. Feasible? Safe?
Probably not, but such options are taken more seriously as the gap
grows continually wider between actions taken and actions needed to
avert future climate change.
One of my favorite Big Fixes is the oft-mentioned idea of towing polar
icebergs to relieve freshwater scarcity. But how do you lasso an
iceberg? How do you tow it, break it up, and distribute it? One group
of scientists calculated recently that there's enough ice in the
world's largest recorded iceberg -- a frozen island the size of
Jamaica that broke off the Ross Ice Shelf in Antarctica in March 2000
-- to provide everyone on earth a ten-pound bag of ice cubes every day
for the next seventy-five years. The scientists didn't account, of
course, for population growth. But more to the point, what happens
when the iceberg is used up? The world's people will be standing
there, more numerous than ever and parched, waiting for bags of ice
that will no longer arrive.
One way to reduce climate dangers, of course, is to disperse the risk
of unintended consequences by diversifying the alternative sources of
energy used. The more sources of energy, the less any one of them
needs to be relied upon and scaled up to massive proportions. That
makes dangerous side effects and tipping points less likely. Another
strategy for avoiding climate risk is simply to use less energy of all
kinds through improving efficiency. There's plenty of room for that
now. But just as dieting gets harder with each pound lost, the more
efficient energy consumption gets, the harder it is to find the next
improvement in energy efficiency.
For long-term reductions in energy consumption, population decline
counterbalances this problem nicely. The current momentum of
population growth all but guarantees there won't be population
declines for several decades. Those are precisely the decades during
which humanity could make the easiest gains in energy efficiency. And
just about when energy use is about as efficient as it can be in an
imperfect world, human population could begin to shrink. That will
remove much of the burden of squeezing additional water from the stone
of a super-efficient global energy system. The need to reduce demand
for fossil fuels will grow more urgent with each passing year as the
global climate warms and the illusion of endless carbon-free energy
gradually fades. And population decline reduces energy demand, all
else equal, without any hardship for anyone.
This is a more sensible strategy than trying to turn icebergs into ice
cubes, but that idea is at least innocuous. Other proposed Big
Fixes-from genetic engineering to feed the hungry to nuclear energy to
avoid toasting the planet-are dangerous. As a species, we're running
out of resilience to stand the cures for what ails us. Increasing
numbers of people in all walks of life and all corners of the world
are starting to know this in their guts, if not necessarily to think
it through in their heads. About the most appealing vision on the
horizon is the likelihood that rapid human population growth soon will
be something for the history books. Just when we can see the wall
we're hurtling toward, we're braking our demographic growth through
the realized intentions of hundreds of millions of women and their
partners to have just one or two children, when and only when it suits
them to do so.
Dreams of People Everywhere
... There are good reasons why the importance of population growth to
the loss of nature is little studied and rarely remarked on. It's next
to impossible to quantify or otherwise separate out the impact of
demographic scale from the many other reasons the environment appears
to be crumbling around us. But I suspect the larger problem is
ignorance and the resulting hopelessness about population growth ("you
can't stop people from having children") or, worse, the fear of blame.
Who wants to be seen as implying that parents who have three or more
children and want decent lives for them are somehow more at fault for
our environmental problems than governments or corporations or drivers
of sport utility vehicles? It's not that there's any compelling
research absolving population growth as a long-term force in
environmental degradation. It's just that researchers don't like to
risk their reputations by appearing to hold prolific parents
answerable for the sorry state of nature. "No demographer,"
demographer Donald Bogue wrote recently in challenging his colleagues
to explore the social and environmental impacts of migration, "wants
to be seen as a neo-nativist"-or even someone worried about population
This is not only understandable, in many ways it's commendable. The
history of science makes clear that we're in a far better place than
we were in the nineteenth century, when some biologists backed up
racism with dubious science. Most of us would rather err on the side
of believing that every human being is of equal worth and has an equal
right to direct her or his own life. The challenge is to maintain
these convictions and yet objectively face the root causes of
problems, striving to imagine ways to resolve them that are consistent
with our values. Population is one realm where this is not only
possible, but powerfully appealing-the success of a values-based
strategy is already evident. Leave to women, more than to anyone else,
the decision about when and how often to bear children. The history
I've explored in this book suggests that doing so has moderated
population growth in the past, and contemporary evidence makes clear
that it does exactly that
Robert Engelman is vice president for programs at the Worldwatch
Institute. Formerly vice president for research at Population Action
International and founding secretary of the Society of Environmental
Journalists, he has served on the faculty of Yale University. His
writing has appeared in Nature, The Washington Post, and The Wall
Live Simply So That
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