Laboratory Manual for Introductory Geology 4e

FIGURE 18.15 Local (left) and large-scale (right) deforestation by clear-cutting.
4. Human activities pollute natural environments. Toxic gases and liquids produced
by automobiles, factories, power plants, and other forms of human technology
can have serious impacts on vulnerable species or entire ecosystems. The gradual
disappearance of plants and animals from many lakes in the northeastern
United States was eventually traced to acid rain, produced by atmospheric pollution
from power plants in the Midwest. Indiscriminate dumping of highly toxic
industrial waste has also polluted rivers and lakes, requiring long-term and very
expensive remediation measures.
EXERCISE 18.6
How Quickly Can Humans Hunt a Species to Extinction?
Name:
Course:
Section:
Date:
The moa, a giant flightless bird, was hunted to extinction on New Zealand in the early 1400s. The human population of
New Zealand was no more than 2,500 at the time when the moa went extinct. We can make some simplified calculations
to see how many moas were hunted per year.
(a) Humans first settled New Zealand and began hunting moas in 1314. The last moa was killed around 1425. How
many years did it take for humans to hunt moas to extinction?
years
(b) The founding human population of New Zealand was about 400 people. There were about 159,000 moas in New
Zealand when humans first settled the islands. The complex equations that ecologists use to calculate population
change are beyond the scope of this course, but we can roughly calculate how many moas each human would
have to hunt per year using arithmetic. Assuming no change in the human population and ignoring the decreasing
numbers of moas, we can solve the following equation:
number of moas
Rate of hunting 5
number of humans 3 1
number of years
How many moas would each human have to hunt per year to cause their extinction in the time you calculated in
question (a)?
moas/year
(c) Studies show that there were about 1,500 people living in New Zealand when moa hunting was at its peak. With
this human population size and a moa population of 159,000, how many moas would each human have to hunt per
year to cause their extinction in the time you calculated in question (a)?
moas/year
(continued )
18.3 HUMANS AS AGENTS OF ENVIRONMENTAL CHANGE AND EXTINCTIONS
493