Figure 18.25: The percentage of people in the world that live in abject poverty is decreasing
somewhat globally, but increasing in some regions, like Sub-Saharan Africa. ( 12 )
Wildlife is threatened by fishing, hunting and trading as population increases. Besides
losing their habitat as land is transformed, organisms are threatened by hunting and fishing
as human population grows. Hunting is highly regulated in developed nations, but many
developingnationsarelosingmanynativeanimalsduetohunting. Wildfisharebeingcaught
at too high a rate and many ocean fish stocks are in peril.
Humansalsocauseproblemswithecosystemswhentheyintroducespeciesthatdonotbelong
in a habitat.Invasive speciesare sometimes introduced purposefully, but often they arrive
by accident like rats on a ship. Invasive species often have major impacts in their new
environments. A sad example is the Australian Brown Tree Snake that has wiped out 9 of
the 13 native species on the island of Guam (Figure18.26).
Pollution is a by-product of agriculture, urbanization, and the production and consumption
of goods. Global warming is the result of fossil fuel burning.
Let’s return to the question of whether humans have exceeded Earth’s carrying capacity for
our species. Carrying capacity is exceeded if resources are being used faster than they are
being replenished. It is also exceeded if the environment is being damaged.
The answer to our original question therefore appears to be yes. Many resources are being
used far in excess of the rate at which they are being replaced. The best farmland is already
in use and more marginal lands are being developed. Most rivers in the developed nations