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Factors That Threaten Biodiversity
Anthropogenic changes to the environment are changes induced by human activity.
They include habitat loss, pollution, the introduction of invasive species, overexploita-
tion, and climate change. These changes can disrupt an ecosystem and threaten the
survival of some species. Today’s high rate of extinction differs from past mass extinc-
tions. After a mass extinction in the past, new species evolved and biodiversity
recovered after several million years. This time, the recovery might be different.
Humans are changing conditions on Earth faster than new traits can evolve in some
species to cope with the new conditions. Evolving species might not have the natural
resources they need.
Natural resources
are all materials and organisms found in the
biosphere, including minerals, fossil fuels, nuclear fuels, plants, animals, soil, clean
water, clean air, and solar energy.
Overexploitation
One of the factors that is increasing the current rate of extinction is the
overexploitation,
or excessive use, of species that have economic value.
For example, wood from mahogany trees is prized for its beauty and its durability.
These trees are native to tropical areas of the globe. Because they grow so slowly, it
takes about 100 years for a mahogany tree to fully mature. Overexploitation of mahog-
any tree populations and illegal logging have led some varieties of this tree to border on
extinction.
Plants are not the only living organisms that have been subjected to overexploitation.
the great herds of bison that once roamed the central plains of North America were
hunted to the brink of extinction because their meat and hides could be sold
commercially and because they were hunted for sport. At one time, it is estimated that
there were 50 million bison. By 1889, there were less than 1000 bison left.
Passenger pigeons are another example of a species that were overexploited. At
one time, there were huge flocks of these birds that would darken the skies of North
America during their migration. Unfortunately, they were overhunted and forced from
their habitats. By the early 1900s, they had become extinct.
Get It?
Explain
the term overexploitation as it relates to species extinction.
CROSSCUTTING CONCEPTS
Stability and Change
Some scientists think we are living in a time of mass
extinction. As you read about the anthropogenic changes that threaten biodiversity,
think about how the rate of these changes may be changing conditions on Earth
faster than some species can evolve. Create a poster that will get others to think
about factors that threaten biodiversity. Include evidence that illustrates your
points.
WORD ORIGINS
native
from the Latin word
nativus
, meaning
to be born
Lesson 2 • Threats to Biodiversity
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