Gallery of Graphs and Demographics

Sri Lanka
Birth rates fell during the forty-five years depicted.
But death rates fell even more due to advances in medicine
and agriculture (and use of DDT to combat malaria).

Result?
After half a century of more or less steadily falling birth rates,
Sri Lanka's population was growing
faster than ever.

Exponential Number Sequences
produce a classical J-curve such as the one in this illustration

It is disquieting that a graph of human population growth over the past 10,000 years
has a marked similarity to the J-curve depicted here. 

We ordinarily associate such
curves with nuclear detonations, dinoflagellate red-tides, runaway monetary inflation,
and the proliferation of cancer cells.

A Classical Bell Shaped Curve

Some spikeweeds are very tall while others are very short
but most spikeweeds are of an intermediate height.

The Rise and Fall of a Reindeer Herd

In the early 1950s, a classical study of  population changes in a reindeer herd was published.
  The study was conducted on St. Paul's island, Alaska.  In 1910, a small herd of
twenty-five reindeer were introduced to the island.

In the absence of any major predators or competitors, the herd slowly began to increse.
In 1929, however, the population began to explode
-- rocketing upward to more than 2000 animals.

Notice the J-curve that was produced initially as the population's numbers soared.
Then there followed an enormous collapse.  During this collapse, more
than 98% of the population died.
Only eight reindeer were still alive when the study ended in 1948.

The missing data is from the war years of World War II.

The Collapse of Wildlife and Wilderness

Wilderness acreage and wildlife populations have both collapsed over the past two centuries,
declining inversely with an ever-increasing number of humans.

A Sigmoid Curve

Some populations exhibit a sigmoid curve.  Early in such sequences,
growth is exponential.  Later, however, increasing feedbacks from the environment
begin to slow further growth more and more.

As the population becomes more and more crowded, death rates
may increase and/or birth rates may fall.  Competition for limited
resources, increased aggression, increased susceptibility to contagious disease,
and the limited ability of the environment to accept and cleanse wastes
can all play a feedback role as population densities increase.

Human Population Growth

Notice that for most of human history our numbers were quite small.
Since 1830, however, advances in medicine and agriculture
have resulted in an unprecedented population explosion --
and we are still headed upwards at approximately 210,000 extra persons per day.

This curve depicts a collapse in wilderness acreage
and wildlife populations over the past two centuries.

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Copyright 2003, Randolph Femmer.
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