| The Rise and Fall of a Reindeer Herd 1910-1948 |
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| Click image to enlarge graph |
Scheffer, V.B. 1951. The rise and fall of a reindeer
herd. Scientific Monthly 73:356-62.
This
classical study showed a classical CLIMB AND COLLAPSE population pattern. Unrestrained
growth results in a population that "overshoots" the carrying capacity of its environment.
In 1910, scientists introduced a small herd of twenty-five reindeer onto 40-square mile St. Paul island, Alaska.
The island hosted no bears, timber wolves,
or major competitors allowing the herd to grow at
an unrestrained rate.
Thus, at the outset, the reindeer population grew exponentially until its numbers
exceeded more than 2000 individuals by 1938.
After that peak, however, reindeer numbers fell repeatedly and precipitously in
a collapse that wiped out 99% of population. By 1948, only eight
reindeer still survived. (No data
was able to be collected during World War 2.)
It is important to note that
at the time that the reindeer population collapsed, vast amounts of "open space" remained as the animals themselves only occupied
1/10th of 1% of the "open space" that remained theoretically available.
| Climb and crash of a reindeer herd 1948-1964 |
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| Click image to enlarge graph |
Following the classical reindeer study by Scheffer, as cited above, it was decided to conduct a second
experiment along the same lines to determine if the climb-and-collapse pattern would repeat itself under similar circumstances.
Klein, D.R., 1968. The introduction, increase, and
crash of reindeer on St. Matthew Island. (Alaska) Journal of Wildlife Management 32:350-367.
Notice that this graph of Klein's data also follows a classical
CLIMB AND COLLAPSE pattern. A period of exponential growth carries the population
to its peak, followed by a catastrophic collapse.
Klein’s study
followed the growth of an introduced reindeer population on St. Matthew island, Alaska between 1948 and 1964. In the absence of any predation or competition, the herd grew exponentially to 6,000 animals by the summer
of 1963.
Notice that ninety-nine percent of the population died in the collapse that
immediately followed the peak.
One wonders how many such experiments are necessary
before their clear implications begin to sink in
Our next graph (below) depicts human
population growth over the past ten millennia. The natural restraints on our own growth (primarily disease and hunger)
were largely lifted beginning with the advent of modern agriculture and modern medicine.
Notice that the human graph after 1830, like
the reindeer graphs, also exhibits explosive growth as our numbers began to rocket upward. It
ought to be worrisome, however, that our own population curve is, if anything, much more
severe than the graphs seen in the two reindeer graphs just before their collapse.
so that some scientists describe the human
curve as
HYPEREXPONENTIAL
| Human Population Projected to 2050 |
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| Click image to enlarge graph |
Notice
that a graph of human population between 8,000 B.C. and 2050 A.D. looks much like the exponential graph of each of the two
herds of reindeer pictured above.
Our own runaway growth has resulted especially from
medical advances that have subdued the diseases that once held our numbers in check.
Notice
that in our case, however, our own growth has been far more extreme and far more pronounced than that
seen in the reindeer studies - a phenomenon that some scientists have called "HYPEREXPONENIAL"
Wecskaop examines and critiques recent U.N. population
projections which may represent underestimates of actual population levels that may emerge between now and 2100.
The fourth graph in this set (below)
shows a human population that exhibited generally declining birth rates for approximately four decades - and yet ended up growing at a rate that was 50% faster than when the
study began.
The
text accompanying this graph explains how this apparent contradiction occurred. It is important because
something similar may be about to occur on a worldwide basis.
| Birth Rates and Death Rates in Sri Lanka 1939-1984 |
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| Click image to enlarge graph |
Top Line: Birth rates generally declined throughout the period. Bottom Line: Death rates declined even more.
Result: Despite 45 years of falling birth rates, by 1984 Sri Lanka’s rate of growth was fifty percent
faster than it was when the study began
The good news in Sri Lanka was that: (A) Its birth rates had fallen, and (B) Its
death rates also dropped, allowing its citizens to live longer and healthier lives.
Thus, on two fronts, there were significant advances in bettering human lives. Of course, something else was also happening:
Major advances in medicine, agriculture, and technology lowered Sri Lanka's
death rate even more than its birth rate had fallen – partly due to significant progress in the war against malaria.
This last fact is the lesson that Sri Lanka holds for the rest of the world: Even if we succeed in lowering birth rates around the world, our progress in medical
research and biotechnologies may end up lowering our death rates even more.
Thus, even though both of these trends represent good
news individually, when taken together, our populations may very
well end up growing faster instead of more slowly.
Sri Lanka shows us that we need to look again at our demographic projections
for the century ahead. In those cases where dramatically lower death rates have not been factored in, the published projections,
which are often optimistic, may turn out to be vastly incorrect.
Just as Sri
Lanka grew faster after three decades of falling birth rates, something similar may be about to happen on a worldwide
scale. If a similar set of events takes place worldwide
and affects generations now living, our population by 2100 could end up closer to twelve billion than to the nine or ten billion
imagined by current U.N. projections.
And, if we are already close to or beyond earth's long-term
limits, each of these extra and unexpected billions increases the possibility and seriousness of overshoot
|
| Click image to enlarge graph |
This graph depicts a typical exponential curve
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| Click image to enlarge graph |
Population growth in many species exhibits a sigmoid curve
like the one depicted here. Numbers grow rapidly at first, but then slow as disease, competition, aggression, and predation
take their toll.
In the case of reindeer herds, the absence of
bears, timber wolves, and competitors led to an exponential graph as shown just above.
In the case of
humans, modern medicine and antibiotics, along with technology and agriculture, have resulted in a hyperexponential
graph with extremely worrisome portents for the times in which we live.
WECSKAOP
What Every Citizen Should Know About
Our Planet
List $22.95 ISBN 978-0-933078-18-8
University, Library, and Educational Discounts Available
M. Arman Publishing
P.O. Box 785
Ormond Beach, FL 32175
Voice: 386-673-5576
Fax: 386-951-1101
Copyright 2008, Randolph Femmer.
All rights reserved.
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