Those predicting an overpopulation
disaster were right about one thing – the world’s population increased
substantially over the last 40 years. In 1970, world population was about
3.7 billion. By the year 2000, world population will top 6 billion – an
increase of 62 percent.

Although the total world population
continues to increase, the rate that the worldÂ’s population is
growing began declining in the 1970s. The table below shows how fast world
population grew for each decade beginning in the 1960s:

The rate of world population
growth peaked in the 1970s and has been falling ever since. In fact the
decline accelerated dramatically in the 1990s.

Of course although the rate
at which world population grew declined, the overall population still
continued to rise dramatically. From 1960-1970, for example, world population
grew by 22.0 percent and the world added another 668 million people. From
1970-80 world population only grew 20.2 percent but, because there were
more people in 1970 to begin with, 747 million people were added to population.
In the 1990s this trend started to reverse itself. Although 824 million
people were added to the worldÂ’s population from 1980-1990, only 804 million
people were added in 1990-2000. The good news is that both the United
Nations and U.S. Census Bureau project that both the rate of growth and
the total number of people added to the worldÂ’s population will continue
to decline through the middle of the 21st century. Current forecasts suggest
world population will stabilize at a little less than 9 billion sometime
around 2055.

Why is the population falling
now? Largely because women are choosing to have fewer children. Trends
in child birth rates are usually tracked by following the total
fertility rate. The total fertility rate is the average number of
children born to a woman of childbearing age. A total fertility rate of
2.1 is considered the level needed to sustain a population with no growth
or decline under modern conditions. In 19xx, the worldÂ’s total fertility
rate was xxx, but by the year 2000 the worldÂ’s total fertility rate is
projected to be 2.8. The developed world as a whole is well below the
zero growth level, with a total fertility rate close to 1.6 – these nations
will see their population decline in the future unless they encourage
immigration or increase life expectancy dramatically. For the less developed
countries, the total fertility rate was about 3.1 – these nations still
have growing populations, though a large part of this population growth
is occurring in Africa. Current projections forecast that the worldÂ’s
total fertility rate will reach 2.3 by 2025 – very close to the zero growth
level.

Why did the total fertility
rates fall? At the moment there is no consensus on this question. Among
the various proposed reasons are: increased economic opportunity; increased
educational opportunity; womenÂ’s expanding access to family planning resources;
cultural changes within societies. Studying human societies and finding
one or two causes is probably doomed to fail – ultimately fertility declined
because women and men chose to have fewer children and simplifying those
individual decisions to form a simple theory is unlikely to prove fruitful.

The decline in total fertility
rates does demonstrate a major problem with the model used by many population
advocates – namely the idea of carrying capacity. Biologists who study
animal behavior created the concept of carrying capacity to describe how
animal populations grow and contract. To oversimplify a bit, a species
such as deer will keep increasing their numbers when food is abundant
until inevitably the herd outgrows its resource base – there are simply
too many deer and not enough forageable food. At this point a shortage
in food develops and the population crashes. Deer starve to death until
the population falls to a much lower level, and then the whole process
starts over.

Some people who think the world
is overpopulated apply this model to human beings. They argued that human
beings would keep increasing their numbers as long as food was abundant,
but once the limits to world resources were exceeded there would be a
huge die off in the human population. The problem with applying this analogy
to human beings is that our species is so qualitatively different from
other species. Human beings can anticipate the future and make changes
to their environments as a result that other animals cannot. It is interesting
to note, for example, that the areas of the world where food has been
most abundant are precisely those areas where human population has grown
the most. If the simple carrying capacity model applied to human beings,
total fertility rates in the developed world should be around 4 or 5 rather
than 1.6.

Before getting more deeply
into that issue, though, how did the world manage to produce more food
in the 1970s?

<-- Doomsayers Growth
in Food Supply –>