164 CHAPTER 7 Human Population Change and the Environment
Ye a r5001910Number of reindeer1000150020001920 1930 1940 1950
b. Graph of the reindeer population originally introduced to one of the Pribilof
Islands in 1911. Note the population crash, which followed the peak population
attained in 1935.a. A herd of reindeer on one of the Pribilof Islands off the coast of Alaska.
James P. Wright, PE
V.C. Sheffer. “The Rise and Fall of a Reindeer Herd.”
1951 Sci. Month., Vol 73.the number of reindeer plunged to 8, about one-third the
size of the original introduced population and less than
1 percent of the population at its peak (Figure 7.5b).
Recovery of arctic and subarctic vegetation after overgraz-
ing by reindeer takes 15 to 20 years. During that period,
the carrying capacity for reindeer is greatly reduced.- What is population ecology?
- How do each of the following affect population
size: birth rate, death rate, immigration, and
emigration? - How do biotic potential and/or carrying
capacity produce the J-shaped and S-shaped
population growth curves?
carrying capacity. Sometimes a population that overshoots
K will experience a population crash, an abrupt decline
from high to low population density when resources are
exhausted. Such an abrupt change is commonly observed
in bacterial cultures, zooplankton, and other populations
whose resources are exhausted.
The availability of winter forage largely determines the
carrying capacity for reindeer, which live in cold northern
habitats. In 1911, a small herd of 26 reindeer was intro-
duced on one of the Pribilof Islands in the Bering Sea
(Figure 7.5a). The herd’s population increased exponen-
tially for about 25 years, until there were approximately
2000 reindeer, many more than the island could support,
particularly in winter. The reindeer overgrazed the veg-
etation until the plant life was almost wiped out. Then, in
slightly over a decade, as reindeer died from starvation,
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