Subject: SpecialMomentArticle
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Date: Thu, 11 Nov 2004 09:33:36 -0500

A special moment in history: the future of
population

(Cover Story) Bill McKibben.

The Atlantic Monthly, May 1998 v281 n5
p55(1998)
Abstract: The human population on Earth is growing at an
alarming rate, despite the decision by most women to have fewer children. The
planet can only support a certain number of people. Questions about what will
happen if that number is exceeded are discussed.

Full Text: COPYRIGHT 1998 The Atlantic Monthly Magazine

Bill McKibben

Beware of people preaching that we live in special times.
People have preached that message before, and those who listened sold their
furniture and climbed up on rooftops to await ascension, or built boats to float
out the coming flood, or laced up their Nikes and poisoned themselves in some
California sub- division. These prophets are the ones with visions of the
seven-headed beast, with a taste for the hair shirt and the scourge, with
twirling eyes. No, bet- ter by far to listen to Ecclesiastes, the original wise
preacher, jaded after a thousand messiahs and a thousand revivals.

One generation passes away, and another generation comes;
but the earth abides forever. . . . That which has been is what will be, that
which is done is what will be done, and there is nothing new under the sun. Is
there anything of which it may be said, "See, this is new"? It has already been
in ancient times before us.

And yet, for all that, we may live in a special time. We
may live in the strangest, most thoroughly different moment since human beings
took up farm- ing, 10,000 years ago, and time more or less commenced. Since then
time has flowed in one directiontoward more, which we have taken to be progress.
At first the momentum was gradual, almost imperceptible, checked by wars and the
Dark Ages and plagues and taboos; but in recent centuries it has accelerated,
the curve of every graph steepening like the Himalayas rising from the Asian
steppe. We have climbed quite high. Of course, fifty years ago one could have
said the same thing, and fifty years before that, and fifty years before that.
But in each case it would have been premature. We've increased the population
fourfold in that 150 years; the amount of food we grow has gone up faster still;
the size of our economy has quite simply exploded.

But nownow may be the special time. So special that in
the Western world we might each of us consider, among many other things, having
only one child--that is, reproducing at a rate as low as that at which human
beings have ever voluntarily reproduced. Is this really necessary?Are we finally
run- ning up against some limits?

To try to answer this question, we need to ask another:
How many of us will there be in the near future? Here is a piece of news that
may alter the way we see the planet--an indication that we live at a special
moment. At least at first blush the news is hopeful. New demographic evidence
shows that it is at least possible that a child born today will live long enough
to see the peak of human population.

Around the world people are choosing to have fewer and
fewer childrennot just in China, where the government forces it on them, but in
almost every nation outside the poorest parts of Africa. Population growth rates
are lower than they have been at any time since the Second World War. In the
past three decades the average woman in the developing world, excluding China,
has gone from bearing six children to bearing four. Even in Bangladesh the
average has fallen from six to fewer than four; even in the mullahs' Iran it has
dropped by four children. If this keeps up, the population of the world will not
quite double again; United Nations analysts offer as their mid-range projection
that it will top out at 10 to 11 billion, up from just under six billion at the
moment. The world is still growing, at nearly a record pacewe add a New York
City every month, almost a Mexico every year, almost an India every decade. But
the rate of growth is slowing; it is no longer "exponential," "unstoppable,"
"inexorable," "unchecked," "cancerous." If current trends hold, the world's
population will all but stop growing before the twenty- first century is
out.

And that will be none too soon. There is no way we could
keep going as we have been. The increase in human population in the 1990s has
exceeded the total population in 1600. The population has grown more since 1950
than it did dur- ing the previous four million years. The reasons for our recent
rapid growth are pretty clear. Although the Industrial Revolution speeded
historical growth rates considerably, it was really the public-health
revolution, and its spread to the Third World at the end of the Second World
War, that set us galloping. Vaccines and antibiotics came all at once, and right
behind came population. In Sri Lanka in the late 1940s life expectancy was
rising at least a year every twelve months. How much difference did this make?
Consider the United States: if people died throughout this century at the same
rate as they did at its beginning, America's population would be 140 million,
not 270 million.

If it is relatively easy to explain why populations grew
so fast after the Second World War, it is much harder to explain why the growth
is now slowing. Experts confidently supply answers, some of them contradictory:
"Development is the best contraceptive"-- or education, or the empowerment of
women, or hard times that force families to postpone having children. For each
example there is a counterexample. Ninety-seven percent of women in the Arab
sheikhdom of Oman know about contraception, and yet they average more than six
children apiece. Turks have used contraception at about the same rate as the
Japanese, but their birth rate is twice as high. And so on. It is not AIDS that
will slow population growth, except in a few African countries. It is not
horrors like the civil war in Rwanda, which claimed half a million lives--a loss
the planet can make up for in two days. All that matters is how often individual
men and women decide that they want to reproduce.

Will the drop continue? It had better. UN mid-range
projections assume that women in the developing world will soon average two
children apiece--the rate at which population growth stabilizes. If fertility
remained at current levels, the population would reach the absurd figure of 296
billion in just 150 years. Even if it dropped to 2.5 children per woman and then
stopped fall- ing, the population would still reach 28 billion.

But let's trust that this time the demographers have got
it right. Let's trust that we have rounded the turn and we're in the home
stretch. Let's trust that the planet's population really will double only one
more time. Even so, this is a case of good news, bad news. The good news is that
we won't grow forever. The bad news is that there are six billion of us already,
a number the world strains to support. One more near-doublingfour or five
billion more peoplewill nearly double that strain. Will these be the five
billion straws that break the camel's back?

Big Questions we've answered the question How many of us
will there be? But to figure out how near we are to any limits, we need to ask
something else: How big are we? This is not so simple. Not only do we vary
greatly in how much food and energy and water and minerals we consume, but each
of us varies over time. William Catton, who was a sociologist at Washington
State University before his retirement, once tried to calculate the amount of
energy human beings use each day. In hunter-gatherer times it was about 2,500
calories, all of it food. That is the daily energy intake of a common dolphin. A
modern human being uses 31,000 calories a day, most of it in the form of fossil
fuel. That is the intake of a pilot whale. And the average American uses six
times thatas much as a sperm whale. We have become, in other words, different
from the people we used to be. Not kinder or unkinder, not deeper or stupiderour
natures seem to have changed little since Homer. We've just gotten bigger. We
appear to be the same species, with stomachs of the same size, but we aren't.
It's as if each of us were trailing a big Macy's-parade balloon around, feed-
ing it constantly.

So it doesn't do much good to stare idly out the window
of your 737 as you fly from New York to Los Angeles and see that there's plenty
of empty space down there. Sure enough, you could crowd lots more people into
the nation or onto the planet. The entire world population could fit into Texas,
and each person could have an area equal to the floor space of a typical U.S.
home. If people were willing to stand, everyone on earth could fit comfortably
into half of Rhode Island. Holland is crowded and is doing just
fine.

But this ignores the balloons above our heads, our hungry
shadow selves, our sperm- whale appetites. As soon as we started farming, we
started setting aside extra land to support ourselves. Now each of us needs not
only a little plot of cropland and a little pasture for the meat we eat but also
a little forest for timber and paper, a little mine, a little oil well. Giants
have big feet. Some scientists in Vancouver tried to calculate one such
"footprint" and found that although 1.7 million people lived on a million acres
surrounding their city, those people required 21.5 million acres of land to
support them-- wheat fields in Alberta, oil fields in Saudi Arabia, tomato
fields in California. People in Manhattan are as dependent on faraway resources
as people on the Mir space station.

Those balloons above our heads can shrink or grow,
depending on how we choose to live. All over the earth people who were once tiny
are suddenly growing like Alice when she ate the cake. In China per capita
income has doubled since the early 1980s. People there, though still Lilliputian
in comparison with us, are twice their former size. They eat much higher on the
food chain, under- standably, than they used to:China slaughters more pigs than
any other nation, and it takes four pounds of grain to produce one pound of
pork. When, a decade ago, the United Nations examined sustainable development,
it issued a report saying that the economies of the developing countries needed
to be five to ten times as large to move poor people to an acceptable standard
of living--with all that this would mean in terms of demands on oil wells and
forests.

That sounds almost impossible. For the moment, though,
let's not pass judg- ment. We're still just doing math. There are going to be
lots of us. We're going to be big. But lots of us in relation to what? Big in
relation to what? It could be that compared with the world we inhabit, we're
still scarce and small. Or not. So now we need to consider a third question: How
big is the earth?

Any state wildlife biologist can tell you how many deer a
given area can sup- porthow much browse there is for the deer to eat before they
begin to suppress the reproduction of trees, before they is for the deer to eat
before they begin to suppress the reproduction of trees, before they begin to
starve in the winter. He can calculate how many wolves a given area can support
too, in part by counting the number of deer. And so on, up and down the food
chain. It's not an exact science, but it comes pretty close--at least compared
with figuring out the carrying capacity of the earth for human beings, which is
an art so dark that anyone with any sense stays away from it.lmost any level
they choose. Hunter-gatherers used 2,500 calories of energy a day, whereas
modern Americans use seventy-five times that. Human beings, unlike deer, can
import what they need from thousands of miles away. And human beings, unlike
deer, can figure out new ways to do old things. If, like deer, we needed to
browse on conifers to survive, we could crossbreed lush new strains, chop down
compe- ting trees, irrigate forests, spray a thousand chemicals, freeze or dry
the tender buds at the peak of harvest, genetically engineer new strainsand
advertise the merits of maple buds until everyone was ready to switch. The
variables are so great that professional demographers rarely even bother trying
to figure out carrying capacity. The demographer Joel Cohen, in his potent book
How Many People Can the Earth Support? (1995),reports that at two recent
meetings of the Population Association of America exactly none of the more than
200 symposia dealt with carrying capacity.

But the difficulty hasn't stopped other thinkers. This
is, after all, as big a question as the world offers. Plato, Euripides, and
Polybius all worried that we would run out of food if the population kept
growing; for centuries a steady stream of economists, environmentalists, and
zealots and cranks of all sorts have made it their business to issue estimates
either dire or benign. The most famous, of course, came from the Reverend Thomas
Malthus. Writing in 1798, he proposed that the growth of population, being
"geometric," would soon outstrip the supply of food. Though he changed his mind
and rewrote his famous essay, it's the original version that people have
remembered--and lam- bastedever since. Few other writers have found critics in
as many corners. Not only have conservatives made Malthus's name a byword for
ludicrous alarmism, but Karl Marx called his essay "a libel on the human race,"
Friedrich Engels believed that "we are forever secure from the fear of
overpopulation," and even Mao Zedong attacked Malthus by name, adding, "Of all
things in the world people are the most precious."

Each new generation of Malthusians has made new
predictions that the end was near, and has been proved wrong. The late 1960s saw
an upsurge of Malthusian panic. In 1967 William and Paul Paddock published a
book called Famine1975!, which contained a triage list: "Egypt: Can't-be-saved.
. . . Tunisia: Should Receive Food. . . . India: Can't-be-saved." Almost
simultaneously Paul Ehrlich wrote, in his best-selling The Population Bomb
(1968), "The battle to feed all of humanity is over. In the 1970s, the world
will undergo famines--hundreds of millions of people will starve to death." It
all seemed so certain, so firmly in keeping with a world soon to be darkened by
the first oil crisis.

But that's not how it worked out. India fed herself. The
United States still ships surplus grain around the world. As the astute Harvard
social scientist Amartya Sen points out, "Not only is food generally much
cheaper to buy today, in constant dollars, than it was in Malthus's time, but it
also has become cheaper during recent decades." So far, in other words, the
world has more or less supported us. Too many people starve (60 percent of
children in South Asia are stunted by malnutrition), but both the total number
and the percent- age have dropped in recent decades, thanks mainly to the
successes of the Green Revolution. Food production has tripled since the Second
World War, out- pacing even population growth. We may be giants, but we are
clever giants.

So Malthus was wrong. Over and over again he was wrong.
No other prophet has ever been proved wrong so many times. At the moment, his
stock is especially low. One group of technological optimists now believes that
people will con- tinue to improve their standard of living precisely because
they increase their numbers. This group's intellectual fountainhead is a
brilliant Danish economist named Ester Boserup--a sort of anti-Malthus, who in
1965 argued that the gloomy cleric had it backward. The more people, Boserup
said, the more progress. Take agriculture as an example: the first farmers, she
pointed out, were slash-and-burn cultivators, who might farm a plot for a year
or two and then move on, not returning for maybe two decades. As the population
grew, however, they had to return more frequently to the same plot. That meant
prob- lems: compacted, depleted, weedy soils. But those new problems meant new
solu- tions: hoes, manure, compost, crop rotation, irrigation. Even in this
century, Boserup said, necessity-induced invention has meant that "intensive
systems of agriculture replaced extensive systems," accelerating the rate of
food produc- tion.

Boserup's closely argued examples have inspired a less
cautious group of popu- larizers, who point out that standards of living have
risen all over the world even as population has grown. The most important
benefit, in fact, that popu- lation growth bestows on an economy is to increase
the stock of useful knowl- edge, insisted Julian Simon, the best known of the
so-called cornucopians, who died earlier this year. We might run out of copper,
but who cares? The mere fact of shortage will lead someone to invent a
substitute. "The main fuel to speed our progress is our stock of knowledge, and
the brake is our lack of imagination," Simon wrote. "The ultimate resource is
peopleskilled, spirited, and hopeful people who will exert their wills and
imaginations for their own benefit, and so, inevitably, for the benefit of us
all."

Simon and his ilk owe their success to this: they have
been right so far. The world has behaved as they predicted. India hasn't
starved. Food is cheap. But Malthus never goes away. The idea that we might grow
too big can be disproved only for the moment--never for good. We might always be
on the threshold of a special time, when the mechanisms described by Boserup and
Simon stop working. It is true that Malthus was wrong when the population
doubled from 750 million to 1.5 billion. It is true that Malthus was wrong when
the population doubled from 1.5 billion to three billion. It is true that
Malthus was wrong when the population doubled from three billion to six billion.
Will Malthus still be wrong fifty years from now?

Looking at Limits the case that the next doubling, the
one we're now experi- encing, might be the difficult one can begin as readily
with the Stanford biologist Peter Vitousek as with anyone else. In 1986 Vitousek
decided to cal- culate how much of the earth's "primary productivity" went to
support human beings. He added together the grain we ate, the corn we fed our
cows, and the forests we cut for timber and paper; he added the losses in food
as we over- grazed grassland and turned it into desert. And when he was finished
adding, the number he came up with was 38.8 percent. We use 38.8 percent of
everything the world's plants don't need to keep themselves alive; directly or
indirectly, we consume 38.8 percent of what it is possible to eat. "That's a
relatively large number," Vitousek says. "It should give pause to people who
think we are far from any limits." Though he never drops the measured tone of an
academic, Vitousek speaks with considerable emphasis: "There's a sense among
some economists that we're so far from any biophysical limits. I think that's
not supported by the evidence."

For another antidote to the good cheer of someone like
Julian Simon, sit down with the Cornell biologist David Pimentel. He believes
that we're in big trouble. Odd facts stud his conversationfor example, a nice
head of iceberg lettuce is 95 percent water and contains just fifty calories of
energy, but it takes 400 calories of energy to grow that head of lettuce in
California's Central Valley, and another 1,800 to ship it east. ("There's
practically no nutrition in the damn stuff anyway," Pimentel says. "Cabbage is a
lot better, and we can grow it in upstate New York.") Pimentel has devoted the
past three decades to tracking the planet's capacity, and he believes that we're
already too crowdedthat the earth can support only two billion people over the
long run at a middle- class standard of living, and that trying to support more
is doing great damage. He has spent considerable time studying soil erosion, for
instance. Every raindrop that hits exposed ground is like a small explosion,
launching soil particles into the air. On a slope, more than half of the soil
contained in those splashes is carried downhill. If crop residuecornstalks,
sayis left in the field after harvest, it helps to shield the soil: the raindrop
doesn't hit as hard. But in the developing world, where firewood is scarce,
peasants burn those cornstalks for cooking fuel. About 60 percent of crop
residues in China and 90 percent in Bangladesh are removed and burned, Pimentel
says. When planting season comes, dry soils simply blow away. "Our measuring
stations pick up Chinese soil in the Hawaiian air when ploughing time comes,"he
says. "Every year in Florida we pick up African soils in the wind when they
start to plough."

The very things that made the Green Revolution so
stunningthat made the last doubling possiblenow cause trouble. Irrigation
ditches, for instance, water 17 percent of all arable land and help to produce a
third of all crops. But when flooded soils are baked by the sun, the water
evaporates and the minerals in the irrigation water are deposited on the land. A
hectare (2.47 acres) can accumulate two to five tons of salt annually, and
eventually plants won't grow there. Maybe 10 percent of all irrigated land is
affected.

Or think about fresh water for human use. Plenty of rain
falls on the earth's surface, but most of it evaporates or roars down to the
ocean in spring flo- ods. According to Sandra Postel, the director of the Global
Water Policy Project, we're left with about 12,500 cubic kilometers of
accessible runoff, which would be enough for current demand except that it's not
very well dis- tributed around the globe. And we're not exactly
conservationistswe use nearly seven times as much water as we used in 1900.
Already 20 percent of the world's population lacks access to potable water, and
fights over water divide many regions. Already the Colorado River usually dries
out in the desert before it reaches the Sea of Cortez, making what the
mid-century conservation- ist Aldo Leopold called a "milk and honey wilderness"
into some of the nastiest country in North America. Already the Yellow River can
run dry for as much as a third of the year. Already only two percent of the
Nile's freshwater flow makes it to the ocean. And we need more water all the
time. Producing a ton of grain consumes a thousand tons of waterthat's how much
the wheat plant breathes out as it grows. "We estimated that biotechnology might
cut the amount of water a plant uses by ten percent," Pimentel says. "But plant
physiologists tell us that's optimisticthey remind us that water's a pretty
important part of photosynthesis. Maybe we can get five percent."

What these scientists are saying is simple: human
ingenuity can turn sand into silicon chips, allowing the creation of millions of
home pages on the utterly fascinating World Wide Web, but human ingenuity cannot
forever turn dry sand into soil that will grow food. And there are signs that
these skeptics are rightthat we are approaching certain physical
limits.

I said earlier that food production grew even faster than
population after the Second World War. Year after year the yield of wheat and
corn and rice rock- eted up about three percent annually. It's a favorite
statistic of the eternal optimists. In Julian Simon's book The Ultimate Resource
(1981) charts show just how fast the growth was, and how it continually cut the
cost of food. Simon wrote, "The obvious implication of this historical trend
toward cheaper fooda trend that probably extends back to the beginning of
agricultureis that real prices for food will continue to drop. . . . It is a
fact that portends more drops in price and even less scarcity in the
future."

A few years after Simon's book was published, however,
the data curve began to change. That rocketing growth in grain production
ceased; now the gains were coming in tiny increments, too small to keep pace
with population growth. The world reaped its largest harvest of grain per capita
in 1984; since then the amount of corn and wheat and rice per person has fallen
by six percent. Grain stockpiles have shrunk to less than two months'
supply.

No one knows quite why. The collapse of the Soviet Union
contributed to the trend-- cooperative farms suddenly found the fertilizer
supply shut off and spare parts for the tractor hard to come by. But there were
other causes, too, all around the worldthe salinization of irrigated fields, the
erosion of top- soil, the conversion of prime farmland into residential areas,
and all the other things that environmentalists had been warning about for
years. It's possible that we'll still turn production around and start it
rocketing again. Charles C. Mann, writing in Science, quotes experts who believe
that in the future a "gigantic, multi-year, multi-billion-dollar scientific
effort, a kind of agricultural 'person-on-the-moon project,'" might do the
trick. The next great hope of the optimists is genetic engineering, and
scientists have indeed managed to induce resistance to pests and disease in some
plants. To get more yield, though, a cornstalk must be made to put out another
ear, and conven- tional breeding may have exhausted the possibilities. There's a
sense that we're running into walls.

We won't start producing less food. Wheat is not like
oil, whose flow from the spigot will simply slow to a trickle one day. But we
may be getting to the point where gains will be small and hard to come by. The
spectacular increases may be behind us. One researcher told Mann, "Producing
higher yields will no longer be like unveiling a new model of a car. We won't be
pulling off the sheet and there it is, a two-fold yield increase." Instead the
process will be "incremental, torturous, and slow." And there are five billion
more of us to come.

So far we're still fed; gas is cheap at the pump; the
supermarket grows ever larger. We've been warned again and again about
approaching limits, and we've never quite reached them. So maybe--how tempting
to believe it! they don't really exist. For every Paul Ehrlich there's a man
like Lawrence Summers, the former World Bank chief economist and current deputy
secretary of the Treasury, who writes, "There are no . . . limits to carrying
capacity of the Earth that are likely to bind at any time in the foreseeable
future." And we are talking about the futurenothing can be proved.

But we can calculate risks, figure the odds that each
side may be right. Joel Cohen made the most thorough attempt to do so in How
Many People Can the Earth Support? Cohen collected and examined every estimate
of carrying capacity made in recent decades, from that of a Harvard
oceanographer who thought in 1976 that we might have food enough for 40 billion
people to that of a Brown University researcher who calculated in 1991 that we
might be able to sustain 5.9 billion (our present population), but only if we
were principally vegetarians. One study proposed that if photosynthesis was the
limiting fac- tor, the earth might support a trillion people; an Australian
economist proved, in calculations a decade apart, that we could manage
populations of 28 billion and 157 billion. None of the studies is wise enough to
examine every variable, to reach by itself the "right" number. When Cohen
compared the dozens of studies, however, he uncovered something pretty
interesting: the median low value for the planet's carrying capacity was 7.7
billion people, and the median high value was 12 billion. That, of course, is
just the range that the UN predicts we will inhabit by the middle of the next
century. Cohen wrote,

The human population of the Earth now travels in the zone
where a substantial fraction of scholars have estimated upper limits on human
population size. . . . The possibility must be considered seriously that the
number of people on the Earth has reached, or will reach within half a century,
the maximum number the Earth can support in modes of life that we and our
children and their children will choose to want.

Earth2 Throughout the 10,000 years of recorded human
history the planetthe physical planethas been a stable place. In every single
year of those 10,000 there have been earthquakes, volcanoes, hurricanes,
cyclones, typhoons, flo- ods, forest fires, sandstorms, hailstorms, plagues,
crop failures, heat waves, cold spells, blizzards, and droughts. But these have
never shaken the basic predictability of the planet as a whole. Some of the
earth's land areasthe Mediterranean rim, for instancehave been deforested beyond
recovery, but so far these shifts have always been local.

Among other things, this stability has made possible the
insurance industry--has underwritten the underwriters. Insurers can analyze the
risk in any venture because they know the ground rules. If you want to build a
house on the coast of Florida, they can calculate with reasonable accuracy the
chance that it will be hit by a hurricane and the speed of the winds circling
that hurricane's eye. If they couldn't, they would have no way to set your
premium--they'd just be gambling. They're always gambling a little, of course:
they don't know if that hurricane is coming next year or next century. But the
earth's physical stability is the house edge in this casino. As Julian Simon
pointed out, "A prediction based on past data can be sound if it is sensible to
assume that the past and the future belong to the same statistical uni-
verse."

So what does it mean that alone among the earth's great
pools of money and power, insurance companies are beginning to take the idea of
global climate change quite seriously? What does it mean that the payout for
weather-related damage climbed from $16 billion during the entire 1980s to $48
billion in the years 1990-1994? What does it mean that top European insurance
executives have begun consulting with Greenpeace about global warming? What does
it mean that the insurance giant Swiss Re, which paid out $291.5 million in the
wake of Hurricane Andrew, ran an ad in the Financial Times showing its corporate
logo bent sideways by a storm?

These things mean, I think, that the possibility that we
live on a new earth cannot be discounted entirely as a fever dream. Above,
Ishowed attempts to calculate carrying capacity for the world as we have always
known it, the world we were born into. But what if, all of a sudden, we live on
some other planet? On Earth2?

In 1955 Princeton University held an international
symposium on "Man's Role in Changing the Face of the Earth." By this time
anthropogenic carbon, sulfur, and nitrogen were pouring into the atmosphere,
deforestation was already widespread, and the population was nearing three
billion. Still, by comparison with the present, we remained a puny race. Cars
were as yet novelties in many places. Tropical forests were still intact, as
were much of the ancient woods of the West Coast, Canada, and Siberia. The
world's economy was a quarter its present size. By most calculations we have
used more natural resources since 1955 than in all of human history to that
time.

Another symposium was organized in 1987 by Clark
University, in Massachusetts. This time even the title made clear what was
happening--not "Man and Nature," not "Man's Role in Changing the Face of the
Earth," but "The Earth as Trans- formed by Human Actions." Attendees were no
longer talking about local changes or what would take place in the future. "In
our judgment," they said, "the biosphere has accumulated, or is on its way to
accumulating, such a magnitude and variety of changes that it may be said to
have been transformed."

Many of these changes come from a direction that Malthus
didn't consider. He and most of his successors were transfixed by sourcesby
figuring out whether and how we could find enough trees or corn or oil. We're
good at finding more stuff; as the price rises, we look harder. The lights never
did go out, despite many predictions to the contrary on the first Earth Day. We
found more oil, and we still have lots and lots of coal. Meanwhile, we're
driving big cars again, and why not? As of this writing, the price of gas has
dropped below a dollar a gallon across much of the nation. Who can believe in
limits while driving a Suburban? But perhaps, like an audience watching a
magician wave his wand, we've been distracted from the real story.

That real story was told in the most recent attempt to
calculate our size--a special section in Science published last summer. The
authors spoke bluntly in the lead article. Forget man "transforming" naturewe
live, they concluded, on "a human-dominated planet," where "no ecosystem on
Earth's surface is free of pervasive human influence." It's not that we're
running out of stuff. What we're running out of is what the scientists call
"sinks"--places to put the by-products of our large appetites. Not garbage dumps
(we could go on using Pampers till the end of time and still have empty space
left to toss them away) but the atmospheric equivalent of garbage
dumps.

It wasn't hard to figure out that there were limits on
how much coal smoke we could pour into the air of a single city. It took a while
longer to figure out that building ever higher smokestacks merely lofted the
haze farther afield, raining down acid on whatever mountain range lay to the
east. Even that, how- ever, we are slowly fixing, with scrubbers and different
mixtures of fuel. We can't so easily repair the new kinds of pollution. These do
not come from something going wrong--some engine without a catalytic converter,
some waste-water pipe without a filter, some smokestack without a scrubber. New
kinds of pollution come instead from things going as they're supposed to go--but
at such a high volume that they overwhelm the planet. They come from normal
human lifebut there are so many of us living those normal lives that something
abnormal is happening. And that something is so different from the old forms of
pollution that it confuses the issue even to use the word.

Consider nitrogen, for instance. Almost 80 percent of the
atmosphere is nitrogen gas. But before plants can absorb it, it must become
"fixed"--bonded with carbon, hydrogen, or oxygen. Nature does this trick with
certain kinds of algae and soil bacteria, and with lightning. Before human
beings began to alter the nitrogen cycle, these mechanisms provided 90-150
million metric tons of nitrogen a year. Now human activity adds 130-150 million
more tons. Nitrogen isn't pollutionit's essential. And we are using more of it
all the time. Half the industrial nitrogen fertilizer used in human history has
been applied since 1984. As a result, coastal waters and estuaries bloom with
toxic algae while oxygen concentrations dwindle, killing fish; as a result,
nitrous oxide traps solar heat. And once the gas is in the air, it stays there
for a century or more.

Or consider methane, which comes out of the back of a cow
or the top of a termite mound or the bottom of a rice paddy. As a result of our
determination to raise more cattle, cut down more tropical forest (thereby
causing termite populations to explode), and grow more rice, methane
concentrations in the atmosphere are more than twice as high as they have been
for most of the past 160,000 years. And methane traps heat--very
efficiently.

Or consider carbon dioxide. In fact, concentrate on
carbon dioxide. If we had to pick one problem to obsess about over the next
fifty years, we'd do well to make it CO2--which is not pollution either. Carbon
monoxide is pollution: it kills you if you breathe enough of it. But carbon
dioxide, carbon with two oxygen atoms, can't do a blessed thing to you. If
you're reading this indoors, you're breathing more CO2 than you'll ever get
outside. For generations, in fact, engineers said that an engine burned clean if
it produced only water vapor and carbon dioxide.

Here's the catch: that engine produces a lot of CO2. A
gallon of gas weighs about eight pounds. When it's burned in a car, about five
and a half pounds of carbon, in the form of carbon dioxide, come spewing out the
back. It doesn't matter if the car is a 1958 Chevy or a 1998 Saab. And no filter
can reduce that flowit's an inevitable by-product of fossil- fuel combustion,
which is why CO2 has been piling up in the atmosphere ever since the Industrial
Revolu- tion. Before we started burning oil and coal and gas, the atmosphere
contained about 280 parts CO2 per million. Now the figure is about 360. Unless
we do everything we can think of to eliminate fossil fuels from our diet, the
air will test out at more than 500 parts per million fifty or sixty years from
now, whether it's sampled in the South Bronx or at the South Pole.

This matters because,as we all know by now, the molecular
structure of this clean, natural, common element that we are adding to every
cubic foot of the atmosphere surrounding us traps heat that would otherwise
radiate back out to space. Far more than even methane and nitrous oxide, CO2
causes global warming--the greenhouse effect-- and climate change. Far more than
any other single factor, it is turning the earth we were born on into a new
planet.

Remember, this is not pollution as we have known it. In
the spring of last year the Environmental Protection Agency issued its "Ten-Year
Air Quality and Emissions Trends" report. Carbon monoxide was down by 37 percent
since 1986, lead was down by 78 percent, and particulate matter had dropped by
nearly a quarter. If you lived in the San Fernando Valley, you saw the mountains
more often than you had a decade before. The air was cleaner, but it was also
dif- ferent--richer with CO2. And its new composition may change almost
everything.

Ten years ago I wrote a book called The End of Nature,
which was the first volume for a general audience about carbon dioxide and
climate change, an early attempt to show that human beings now dominate the
earth. Even then global warming was only a hypothesisstrong and gaining
credibility all the time, but a hypothesis nonetheless. By the late 1990s it has
become a fact. For ten years, with heavy funding from governments around the
world, scientists launched satellites, monitored weather balloons, studied
clouds. Their work culminated in a long-awaited report from the UN's
Intergovernmental Panel on Climate Change, released in the fall of 1995. The
panel's 2,000 scientists, from every corner of the globe, summed up their
findings in this dry but historic bit of understatement: "The balance of
evidence suggests that there is a discernible human influence on global
climate." That is to say, we are heating up the planet--substantially. If we
don't reduce emissions of car- bon dioxide and other gases, the panel warned,
temperatures will probably rise 3.6 Fahrenheit by 2100, and perhaps as much as
6.3 .

You may think you've already heard a lot about global
warming. But most of our sense of the problem is behind the curve. Here's the
current news: the changes are already well under way. When politicians and
businessmen talk about "future risks," their rhetoric is outdated. This is not a
problem for the dis- tant future, or even for the near future. The planet has
already heated up by a degree or more. We are perhaps a quarter of the way into
the greenhouse era, and the effects are already being felt. From a new heaven,
filled with nitrogen, methane, and carbon, a new earth is being born. If some
alien astronomer is watching us, she's doubtless puzzled. This is the most
obvious effect of our numbers and our appetites, and the key to understanding
why the size of our population suddenly poses such a risk.

Stormy and Warm what does this new world feel like? For
one thing, it's stormier than the old one. Data analyzed last year by Thomas
Karl, of the National Oceanic and Atmospheric Administration, showed that total
winter pre- cipitation in the United States had increased by 10 percent since
1900 and that "extreme precipitation events"rainstorms that dumped more than two
inches of water in twenty-four hours and blizzardshad increased by 20 percent.
That's because warmer air holds more water vapor than the colder atmosphere of
the old earth; more water evaporates from the ocean, meaning more clouds, more
rain, more snow. Engineers designing storm sewers, bridges, and culverts used to
plan for what they called the "hundred-year storm." That is, they built to
withstand the worst flooding or wind that history led them to expect in the
course of a century. Since that history no longer applies, Karl says, "there
isn't really a hundred-year event anymore . . . we seem to be getting these
storms of the century every couple of years." When Grand Forks, North Dakota,
disappeared beneath the Red River in the spring of last year, some
meteorologists referred to it as "a 500-year flood"--meaning, essentially, that
all bets are off. Meaning that these aren't acts of God. "If you look out your
window, part of what you see in terms of the weather is produced by our-
selves," Karl says. "If you look out the window fifty years from now, we're
going to be responsible for more of it."

Twenty percent more bad storms, 10 percent more winter
precipitation--these are enormous numbers. It's like opening the newspaper to
read that the average American is smarter by 30 IQ points. And the same data
showed increases in drought, too. With more water in the atmosphere, there's
less in the soil, according to Kevin Trenberth, of the National Center for
Atmospheric Research. Those parts of the continent that are normally dry--the
eastern sides of mountains, the plains and desertsare even drier, as the higher
average temperatures evaporate more of what rain does fall. "You get wilting
plants and eventually drought faster than you would otherwise," Trenberth says.
And when the rain does come, it's often so intense that much of it runs off
before it can soak into the soil.

Sowetter and drier. Different.

In 1958 Charles Keeling, of the Scripps Institution of
Oceanography, set up the world's single most significant scientific instrument
in a small hut on the slope of Hawaii's Mauna Loa volcano. Forty years later it
continues without fail to track the amount of carbon dioxide in the atmosphere.
The graphs that it produces show that this most important greenhouse gas has
steadily increased for forty years. That's the main news.

It has also shown something else of interest in recent
years--a sign that this new atmosphere is changing the planet. Every year CO2
levels dip in the spring, when plants across the Northern Hemisphere begin to
grow, soaking up carbon dioxide. And every year in the fall decaying plants and
soils release CO2 back into the atmosphere. So along with the steady upward
trend, there's an annual seesaw, an oscillation that is suddenly growing more
pronounced. The size of that yearly tooth on the graph is 20 percent greater
than it was in the early 1960s, as Keeling reported in the journal Nature, in
July of 1996. Or, in the words of Rhys Roth, writing in a newsletter of the
Atmosphere Alliance, the earth is "breathing deeper." More vegetation must be
growing, stimulated by higher temperatures. And the earth is breathing earlier,
too. Spring is starting about a week earlier in the 1990s than it was in the
1970s, Keeling said.

Other scientists had a hard time crediting Keeling's
studythe effect seemed so sweeping. But the following April a research team led
by R. B. Myneni, of Boston University, and including Keeling, reached much the
same conclusion by means of a completely different technique. These researchers
used satellites to measure the color of sunlight reflected by the earth: light
bouncing off green leaves is a different color from light bouncing off bare
ground. Their data were even more alarming, because they showed that the
increase was hap- pening with almost lightning speed. By 1991 spring above the
45th parallel--a line that runs roughly from Portland, Oregon, to Boston to
Milan to Vladivostok--was coming eight days earlier than it had just a decade
before. And that was despite increased snowfall from the wetter atmosphere; the
snow was simply melting earlier. The earlier spring led to increased plant
growth, which sounds like a benefit. The area above the 45th parallel is, after
all, the North American and Russian wheat belt. But as Cynthia Rosenzweig, of
NASA's Goddard Institute for Space Studies, told The New York Times, any such
gains may be illusory. For one thing, the satellites were measuring biomass, not
yields; tall and leafy plants often produce less grain. Other scientists, the
Times reported, said that "more rapid plant growth can make for less nutritious
crops if there are not enough nutrients available in the soil." And it's not
clear that the grain belt will have the water it needs as the climate warms. In
1988, a summer of record heat across the grain belt, harvests plum- meted,
because the very heat that produces more storms also causes extra evaporation.
What is clear is that fundamental shifts are under way in the operation of the
planet. And we are very early yet in the greenhouse era.

The changes are basic. The freezing level in the
atmospherethe height at which the air temperature reaches 32 Fhas been gaining
altitude since 1970 at the rate of nearly fifteen feet a year. Not surprisingly,
tropical and subtropical glaciers are melting at what a team of Ohio State
researchers termed "strik- ing" rates. Speaking at a press conference last
spring, Ellen Mosley-Thompson, a member of the Ohio State team, was asked if she
was sure of her results. She replied, "I don't know quite what to say. I've
presented the evidence. I gave you the example of the Quelccaya ice cap. It just
comes back to the compila- tion of what's happening at high elevations: the
Lewis glacier on Mount Kenya has lost forty percent of its mass; in the
Ruwenzori range all the glaciers are in massive retreat. Everything, virtually,
in Patagonia, except for just a few glaciers, is retreating. . . . We've seen .
. . that plants are moving up the mountains. . . . I frankly don't know what
additional evidence you need."

As the glaciers retreat, a crucial source of fresh water
in many tropical countries disappears. These areas are "already water-stressed,"
Mos- ley-Thompson told the Association of American Geographers last year. Now
they may be really desperate.

As with the tropics, so with the poles. According to
every computer model, in fact, the polar effects are even more pronounced,
because the Arctic and the Antarctic will warm much faster than the Equator as
carbon dioxide builds up. Scientists manning a research station at Toolik Lake,
Alaska, 170 miles north of the Arctic Circle, have watched average summer
temperatures rise by about seven degrees in the past two decades. "Those who
remember wearing down-lined summer parkas in the 1970s--before the term 'global
warming' existedhave peeled down to T-shirts in recent summers," according to
the reporter Wendy Hower, writing in the Fairbanks Daily News-Miner. It rained
briefly at the American base in McMurdo Sound, in Antarctica, during the
southern summer of 1997as strange as if it had snowed in Saudi Arabia. None of
this necessarily means that the ice caps will soon slide into the sea, turning
Tennessee into beachfront. It simply demonstrates a radical instability in
places that have been stable for many thousands of years. One researcher watched
as emperor penguins tried to cope with the early breakup of ice:their chicks had
to jump into the water two weeks ahead of schedule, probably guaranteeing an
early death. They (like us) evolved on the old earth.

You don't have to go to exotic places to watch the
process. Migrating red-winged blackbirds now arrive three weeks earlier in
Michigan than they did in 1960. A symposium of scientists reported in 1996 that
the Pacific Northwest was warming at four times the world rate. "That the
Northwest is warming up fast is not a theory," Richard Gammon, a University of
Washington oceanog- rapher, says. "It's a known fact, based on simple
temperature readings."

The effects of that warming can be found in the largest
phenomena. The oceans that cover most of the planet's surface are clearly
rising, both because of melting glaciers and because water expands as it warms.
As a result, low-lying Pacific islands already report surges of water washing
across the atolls. "It's nice weather and all of a sudden water is pouring into
your living room," one Marshall Islands resident told a newspaper reporter.
"It's very clear that something is happening in the Pacific, and these islands
are feel- ing it." Global warming will be like a much more powerful version of
El Ni[plus or minus]o that covers the entire globe and lasts forever, or at
least until the next big asteroid strikes.

If you want to scare yourself with guesses about what
might happen in the near future, there's no shortage of possibilities.
Scientists have already observed large-scale shifts in the duration of the El
Ni[plus or minus]o ocean warming, for instance. The Arctic tundra has warmed so
much that in some places it now gives off more carbon dioxide than it absorbs--a
switch that could trigger a potent feedback loop, making warming ever worse. And
researchers studying gla- cial cores from the Greenland Ice Sheet recently
concluded that local climate shifts have occurred with incredible rapidity in
the past18 in one three-year stretch. Other scientists worry that such a shift
might be enough to flood the oceans with fresh water and reroute or shut off
currents like the Gulf Stream and the North Atlantic, which keep Europe far
warmer than it would otherwise be. (See "The Great Climate Flip- flop,"by
William H. Calvin, January Atlantic.)In the words of Wallace Broecker, of
Columbia University, a pioneer in the field, "Climate is an angry beast, and we
are poking it with sticks."

But we don't need worst-case scenarios: best-case
scenarios make the point. The population of the earth is going to nearly double
one more time. That will bring it to a level that even the reliable old earth we
were born on would be hard-pressed to support. Just at the moment when we need
everything to be working as smoothly as possible, we find ourselves inhabiting a
new planet, whose carrying capacity we cannot conceivably estimate. We have no
idea how much wheat this planet can grow. We don't know what its politics will
be like: not if there are going to be heat waves like the one that killed more
than 700 Chicagoans in 1995; not if rising sea levels and other effects of
climate cha- nge create tens of millions of environmental refugees; not if a 1.5
jump in India's temperature could reduce the country's wheat crop by 10 percent
or divert its monsoons.

The arguments put forth by cornucopians like Julian
Simonthat human intelligence will get us out of any scrape, that human beings
are "the ultimate resource," that Malthusian models "simply do not comprehend
key ele- ments of people"all rest on the same premise: that human beings change
the world mainly for the better.

If we live at a special time, the single most special
thing about it may be that we are now apparently degrading the most basic
functions of the planet. It's not that we've never altered our surroundings
before. Like the beavers at work in my back yard, we have rearranged things
wherever we've lived. We've leveled the spots where we built our homes, cleared
forests for our fields, often fouled nearby waters with our waste. That's just
life. But this is dif- ferent. In the past ten or twenty or thirty years our
impact has grown so much that we're changing even those places we don't
inhabitchanging the way the weather works, changing the plants and animals that
live at the poles or deep in the jungle. This is total. Of all the remarkable
and unexpected things we've ever done as a species, this may be the biggest. Our
new storms and new oceans and new glaciers and new springtimesthese are the
eighth and ninth and tenth and eleventh wonders of the modern world, and we have
lots more where those came from.

We have gotten very large and very powerful, and for the
foreseeable future we're stuck with the results. The glaciers won't grow back
again anytime soon; the oceans won't drop. We've already done deep and systemic
damage. To use a human analogy, we've already said the angry and unforgivable
words that will haunt our marriage till its end. And yet we can't simply walk
out the door. There's no place to go. We have to salvage what we can of our
relationship with the earth, to keep things from getting any worse than they
have to be.

If we can bring our various emissions quickly and sharply
under control, we can limit the damage, reduce dramatically the chance of
horrible surprises, preserve more of the biology we were born into. But do not
underestimate the task.The UN's Intergovernmental Panel on Climate Change
projects that an immediate 60 percent reduction in fossil-fuel use is necessary
just to stabi- lize climate at the current level of disruption. Nature may still
meet us halfway, but halfway is a long way from where we are now. What's more,
we can't delay. If we wait a few decades to get started, we may as well not even
begin. It's not like poverty, a concern that's always there for civilizations to
address. This is a timed test, like the SAT: two or three decades, and we lay
our pencils down. It's the test for our generations, and population is a part of
the answer.

Changing "Unchangeable" Needs

when we think about overpopulation, we usually think
first of the developing world, because that's where 90 percent of new human
beings will be added dur- ing this final doubling. In The Population Bomb, Paul
Ehrlich wrote that he hadn't understood the issue emotionally until he traveled
to New Delhi, where he climbed into an ancient taxi, which was hopping with
fleas, for the trip to his hotel. "As we crawled through the city, we entered a
crowded slum area. . . . the streets seemed alive with people. People eating,
people washing, people sleeping. People visiting, arguing, and screaming. . . .
People, people, people, people."

We fool ourselves when we think of Third World population
growth as producing an imbalance, as Amartya Sen points out. The white world
simply went through its population boom a century earlier (when Dickens was
writing similar des- criptions of London). If UN calculations are correct and
Asians and Africans will make up just under 80 percent of humanity by 2050, they
will simply have returned, in Sen's words, "to being proportionately almost
exactly as numerous as they were before the European industrial
revolution."

And of course Asians and Africans, and Latin Americans,
are much "smaller" human beings: the balloons that float above their heads are
tiny in comparison with ours. Everyone has heard the statistics time and again,
usually as part of an attempt to induce guilt. But hear them one more time, with
an open mind, and try to think strategically about how we will stave off the
dangers to this planet. Pretend it's not a moral problem, just a mathematical
one.

* An American uses seventy times as much energy as a
Bangladeshi, fifty times as much as a Malagasi, twenty times as much as a Costa
Rican.

* Since we live longer, the effect of each of us is
further multiplied. In a year an American uses 300 times as much energy as a
Malian; over a lifetime he will use 500 times as much.

* Even if all such effects as the clearing of forests and
the burning of grasslands are factored in and attributed to poor people, those
who live in the poor world are typically responsible for the annual release of a
tenth of a ton of carbon each, whereas the average is 3.5 tons for residents of
the "consumer" nations of Western Europe, North America, and Japan. The richest
tenth of Americansthe people most likely to be reading this magazineannually
emit eleven tons of carbon apiece.

* During the next decade India and China will each add to
the planet about ten times as many people as the United States willbut the
stress on the natural world caused by new Americans may exceed that from new
Indians and Chinese combined. The 57.5 million Northerners added to our
population during this decade will add more greenhouse gases to the atmosphere
than the roughly 900 million added Southerners.

These statistics are not eternal. Though inequality
between North and South has steadily increased, the economies of the poor
nations are now growing faster than those of the West. Sometime early in the
next century China will pass the United States as the nation releasing the most
carbon dioxide into the atmosphere, though of course it will be nowhere near the
West on a per capita basis.

For the moment, then (and it is the moment that counts),
we can call the United States the most populous nation on earth, and the one
with the highest rate of growth. Though the U.S. population increases by only
about three mil- lion people a year, through births and immigration together,
each of those three million new Americans will consume on average forty or fifty
times as much as a person born in the Third World. My daughter, four at this
writing, has already used more stuff and added more waste to the environment
than most of the world's residents do in a lifetime. In my thirty-seven years I
have probably outdone small Indian villages.

Population growth in Rwanda, in Sudan, in El Salvador, in
the slums of Lagos, in the highland hamlets of Chile, can devastate those
places. Growing too fast may mean that they run short of cropland to feed
themselves, of firewood to cook their food, of school desks and hospital beds.
But population growth in those places doesn't devastate the planet. In contrast,
we easily absorb the modest annual increases in our population. America seems
only a little more crowded with each passing decade in terms of our daily lives.
You can still find a parking spot. But the earth simply can't absorb what we are
adding to its air and water.

so if it is we in the rich world, at least as much as
they in the poor world, who need to bring this alteration of the earth under
control, the question becomes how. Many people who are sure that controlling
population is the ans- wer overseas are equally sure that the answer is
different here. If those people are politicians and engineers, they're probably
in favor of our living more efficiently--of designing new cars that go much
farther on a gallon of gas, or that don't use gas at all. If they're
vegetarians, they probably sup- port living more simply--riding bikes or buses
instead of driving cars.

Both groups are utterly correct. I've spent much of my
career writing about the need for cleverer technologies and humbler aspirations.
Environmental damage can be expressed as the product of Population x Affluence x
Technology. Surely the easiest solution would be to live more simply and more
efficiently, and not worry too much about the number of people.

But I've come to believe that those changes in technology
and in lifestyle are not going to occur easily and speedily. They'll be begun
but not finished in the few decades that really matter. Remember that the
pollution we're talking about is not precisely pollution but rather the
inevitable result when things go the way we think they should: new filters on
exhaust pipes won't do any- thing about that CO2. We're stuck with making real
changes in how we live. We're stuck with dramatically reducing the amount of
fossil fuel we use. And since modern Westerners are practically machines for
burning fossil fuel, since virtually everything we do involves burning coal and
gas and oil, since we're wedded to petroleum, it's going to be a messy
breakup.

So we need to show, before returning again to population,
why simplicity and efficiency will not by themselves save the day. Maybe the
best place to start is with President Bill Clinton--in particular his reaction
to global warming. Clinton is an exquisite scientific instrument, a man whose
career is built on his unparalleled ability to sense minute changes in public
opinion. He under- stands our predicament. Speaking to the United Nations early
last summer, he said plainly, "We humans are changing the global climate. . . .
No nation can escape this danger. None can evade its responsibility to confront
it, and we must all do our part."

But when it comes time to do our part, we don't. After
all, Clinton warned of the dangers of climate change in 1993, on his first Earth
Day in office. In fact, he solemnly promised to make sure that America produced
no more green- house gases in 2000 than it had in 1990. But he didn't keep his
word. The United States will spew an amazing 15 percent more carbon dioxide in
2000 than it did in 1990. It's as if we had promised the Russians that we would
freeze our nuclear program and instead built a few thousand more warheads. We
broke our word on what history may see as the most important international
commit- ment of the 1990s.

What's important to understand is why we broke our word.
We did so because Clinton understood that if we were to keep it, we would need
to raise the price of fossil fuel. If gasoline cost $2.50 a gallon, we'd drive
smaller cars, we'd drive electric cars, we'd take busesand we'd elect a new
President. We can hardly blame Clinton, or any other politician. His real goal
has been to speed the pace of economic growth, which has been the key to his
popu- larity. If all the world's leaders could be gathered in a single room, the
one thing that every last socialist, Republican, Tory, monarchist, and trade
unionist could agree on would be the truth of Clinton's original campaign
admonition: "It's the economy, stupid."

The U.S. State Department had to send a report to the
United Nations explain- ing why we would not be able to keep our Earth Day
promise to reduce green- house-gas emissions; the first two reasons cited were
"lower-than-expected fuel prices" and "strong economic growth." The former
senator Tim Wirth, who until recently was the undersecretary of state for global
affairs, put it nakedly: the United States was missing its emissions targets
because of "more prolonged economic activity than expected."

America's unease with real reductions in fossil-fuel use
was clear at last year's mammoth global-warming summit in Kyoto. With utility
executives and Republican congressmen stalking the halls, the U.S. delegation
headed off every attempt by other nations to strengthen the accord. And even the
tepid treaty produced in Kyoto will meet vigorous resistance if it ever gets
sent to the Senate.

Changing the ways in which we live has to be a
fundamental part of dealing with the new environmental crises, if only because
it is impossible to imagine a world of 10 billion people consuming at our level.
But as we calculate what must happen over the next few decades to stanch the
flow of CO2, we shouldn't expect that a conversion to simpler ways of life will
by itself do the trick. One would think offhand that compared with changing the
number of children we bear, changing consumption patterns would be a breeze.
Fertility, after all, seems biologicalhard-wired into us in deep Darwinian ways.
But I would guess that it is easier to change fertility than
lifestyle.

perhaps our salvation lies in the other part of the
equation--in the new tech- nologies and efficiencies that could make even our
wasteful lives benign, and table the issue of our population. We are, for
instance, converting our econ- omy from its old industrial base to a new model
based on service and informa- tion. Surely that should save some energy, should
reduce the clouds of carbon dioxide. Writing software seems no more likely to
damage the atmosphere than writing poetry.

Forget for a moment the hardware requirements of that new
economy--for instance, the production of a six-inch silicon wafer may require
nearly 3,000 gallons of water. But do keep in mind that a hospital or an
insurance company or a basketball team requires a substantial physical base.
Even the high- est-tech office is built with steel and cement, pipes and wires.
People work- ing in services will buy all sorts of things--more software, sure,
but also more sport utility vehicles. As the Department of Energy economist
Arthur Rypinski says, "The information age has arrived, but even so people still
get hot in the summer and cold in the winter. And even in the information age it
tends to get dark at night."

Yes, when it gets dark, you could turn on a compact
fluorescent bulb, saving three fourths of the energy of a regular incandescent.
Indeed, the average American household, pushed and prodded by utilities and
environmentalists, has installed one compact fluorescent bulb in recent years;
unfortunately, over the same period it has also added seven regular bulbs.
Millions of halogen torchere lamps have been sold in recent years, mainly
because they cost $15.99 at Kmart. They also suck up electricity:those halogen
lamps alone have wiped out all the gains achieved by compact fluorescent bulbs.
Since 1983 our energy use per capita has been increasing by almost one percent
annually, despite all the technological advances of those years.

As with our homes, so with our industries. Mobil Oil
regularly buys ads in leading newspapers to tell "its side" of the environmental
story. As the com- pany pointed out recently, from 1979 to 1993 "energy
consumption per unit of gross domestic product" dropped 19 percent across the
Western nations. This sounds goodit's better than one percent a year. But of
course the GDP grew more than two percent annually. So total energy use, and
total clouds of CO2, continued to increase.

It's not just that we use more energy. There are also
more of us all the time, even in the United States. If the population is growing
by about one percent a year, then we have to keep increasing our technological
efficiency by that much each yearand hold steady our standard of livingjust to
run in place. The President's Council on Sustainable Development, in a
little-read report issued in the winter of 1996, concluded that "efficiency in
the use of all resources would have to increase by more than fifty percent over
the next four or five decades just to keep pace with population growth." Three
million new Americans annually means many more cars, houses, refrigerators. Even
if everyone con- sumes only what he consumed the year before, each year's tally
of births and immigrants will swell American consumption by one
percent.

We demand that engineers and scientists swim against that
tide. And the tide will turn into a wave if the rest of the world tries to live
as we do. It's true that the average resident of Shanghai or Bombay will not
consume as lavishly as the typical San Diegan or Bostonian anytime soon, but he
will make big gains, pumping that much more carbon dioxide into the atmosphere
and requiring that we cut our own production even more sharply if we are to
stabi- lize the world's climate.

The United Nations issued its omnibus report on
sustainable development in 1987. An international panel chaired by Gro Harlem
Brundtland, the Prime Minister of Norway, concluded that the economies of the
developing countries needed to grow five to ten times as large as they were, in
order to meet the needs of the poor world. And that growth won't be mainly in
software. As Arthur Rypinski points out, "Where the economy is growing really
rapidly, energy use is too." In Thailand, in Tijuana, in Taiwan, every 10
percent increase in economic output requires 10 percent more fuel. "In the Far
East," Rypinski says, "the transition is from walking and bullocks to cars.
People start out with electric lights and move on to lots of other stuff.
Refrigerators are one of those things that are really popular everywhere.
Practically no one, with the possible exception of people in the high Arctic,
doesn't want a refrigerator. As people get wealthier, they tend to like space
heating and cooling, depending on the climate."

In other words, in doing the math about how we're going
to get out of this fix, we'd better factor in some unstoppable momentum from
people on the rest of the planet who want the very basics of what we call a
decent life. Even if we airlift solar collectors into China and India, as we
should, those nations will still burn more and more coal and oil. "What you can
do with energy con- servation in those situations is sort of at the margin,"
Rypinski says. "They're not interested in fifteen-thousand-dollar clean cars
versus five- thousand-dollar dirty cars. It was hard enough to get Americans to
invest in efficiency; there's no feasible amount of largesse we can provide to
the rest of the world to bring it about."

The numbers are so daunting that they're almost
unimaginable. Say, just for argument's sake, that we decided to cut world
fossil-fuel use by 60 per- cent--the amount that the UN panel says would
stabilize world climate. And then say that we shared the remaining fossil fuel
equally. Each human being would get to produce 1.69 metric tons of carbon
dioxide annually--which would allow you to drive an average American car nine
miles a day. By the time the population increased to 8.5 billion, in about 2025,
you'd be down to six miles a day. If you carpooled, you'd have about three
pounds of CO2 left in your daily ration--enough to run a highly efficient
refrigerator. Forget your com- puter, your TV, your stereo, your stove, your
dishwasher, your water heater, your microwave, your water pump, your clock.
Forget your light bulbs, compact fluorescent or not.

I'm not trying to say that conservation, efficiency, and
new technology won't help. They willbut the help will be slow and expensive. The
tremendous momentum of growth will work against it. Say that someone invented a
new furnace tomorrow that used half as much oil as old furnaces. How many years
would it be before a substantial number of American homes had the new device?
And what if it cost more? And if oil stays cheaper per gallon than bottled
water? Changing basic fuelsto hydrogen, say--would be even more expensive. It's
not like running out of white wine and switching to red. Yes, we'll get new
technologies. One day last fall The New York Times ran a special section on
energy, featuring many up-and-coming improvements: solar shingles, basement fuel
cells. But the same day, on the front page, William K. Stevens reported that
international negotiators had all but given up on preventing a doubling of the
atmospheric concentration of CO2. The momentum of growth was so great, the
negotiators said, that making the changes required to slow global warming
significantly would be like "trying to turn a supertanker in a sea of
syrup."

There are no silver bullets to take care of a problem
like this. Electric cars won't by themselves save us, though they would help. We
simply won't live efficiently enough soon enough to solve the problem.
Vegetarianism won't cure our ills, though it would help. We simply won't live
simply enough soon enough to solve the problem.

Reducing the birth rate won't end all our troubles
either. That, too, is no silver bullet. But it would help. There's no more
practical decision than how many children to have. (And no more mystical
decision, either.)

The bottom-line argument goes like this: The next fifty
years are a special time. They will decide how strong and healthy the planet
will be for centuries to come. Between now and 2050 we'll see the zenith, or
very nearly, of human population. With luck we'll never see any greater
production of carbon dioxide or toxic chemicals. We'll never see more species
extinction or soil erosion. Greenpeace recently announced a campaign to phase
out fossil fuels entirely by mid-century, which sounds utterly quixotic but
couldif everything went just righthappen.

So it's the task of those of us alive right now to deal
with this special phase, to squeeze us through these next fifty years. That's
not fair--any more than it was fair that earlier generations had to deal with
the Second World War or the Civil War or the Revolution or the Depression or
slavery. It's just reality. We need in these fifty years to be working
simultaneously on all parts of the equationon our ways of life, on our
technologies, and on our pop- ulation.

As Gregg Easterbrook pointed out in his book A Moment on
the Earth (1995), if the planet does manage to reduce its fertility, "the period
in which human numbers threaten the biosphere on a general scale will turn out
to have been much, much more brief" than periods of natural threats like the Ice
Ages. True enough. But the period in question happens to be our time. That's
what makes this moment special, and what makes this moment hard. S

Bill McKibben ("A Special Moment in History") is the
author of several books about the environment, including The End of Nature
(1989) and Hope, Human and Wild (1995). His article in this issue will appear in
somewhat different form in his book Maybe One: A Personal and Environmental
Argument for Single-Child Families, to be published this month by Simon &
Schuster.

Copyright (c) 1998 by The Atlantic Monthly Company. All
rights reserved.