Natural extinctions have been occurring for billions of years.
Change in climate, food supply, and other factors can
cause the biome or ecosystem of an area to shift so much that a
species is killed off. Mass extinctions, where huge numbers of
species are obliterated, happen fairly regularly in the Earth's
time-line. The most recent, and the most well-known, happened around
65 million years ago when a catastrophe (some say changing climate,
others say a meteor crash) obliterated over half of the species on
Earth, clearing the way for the rise of the mammals and the eventual
evolution of humans. Today, 99.9 % of all the species that have ever
existed on Earth are extinct. However, human activities, lifestyles, and
unsustainable practices have resulted in an unprecedented rate of habitat loss and endangerment or extinction of species.
When humans they migrated across the Bering Strait from the eastern hemisphere to
the western one 14,00 years ago they unknowingly carried non-native seeds and
pollen with them, resulting in one of the first human-caused imbalance in an ecosystem. When
farming first started to rise about 11,000 years ago, humans selected
the best variations from wild plants to grow as crops, domesticating
and changing the natural plant into something else. This was one of the greatest advancements in human history, but in some areas
that proved detrimental. For instance, when the climate changed in
the Fertile Crescent and became more dry and arid, the nomadic
hunter-gatherers were forced to settle down and start farming so as to have a reliable source of food.
However, the dry and fragile environment couldn't support the rigors
of continuous farming and collapsed, becoming even more desolate and killing off many plant and animal species.
Later, human population booms,
advances in technology, and the use of hunting as a sport by upper
classes all contributed to a rapid decrease in certain animal
populations. Species were targeted and hunted down because because they were good for eating, they were viewed as
pests who killed meat animals that humans ate, or because they made good trophy prizes. In the United
States, wolves and other predators were purposely hunted almost to extinction (many
sub-species were eradicated entirely), resulting in detrimental booms in their prey populations. Native bison, whose population
numbered in the millions, were reduced to a few hundred in less than
eighty years. Entire species or subspecies of tigers, ibex, elk,
bears, and hundreds of birds were driven to extinction by
over-hunting, pollution, and habitat loss. In some cases, the
extinctions happened unknowingly when livestock animals and
crops were traded, or when seeds and animals hitched rides
upon ships and other forms of transportation. When the Society
Islands were first visited, the rats that were on board the ships
migrated to the island and multiplied, endangering the native rare bird
species. The introduction of pigs, deer, goats, and rabbits to New
Zealand, where there were no natural predators to keep the
populations in check, caused an extreme overpopulation that had harmful effects upon the natural ecosystem.
However, it is human
activity resulting in habitat loss that is perhaps the greatest issue
facing endangered species. Unsustainable farming or land use
techniques render huge swathes of land barren. For example, the
introduction of new farming technology in the 1920's caused over five
million acres of previously-unploughed land in Oklahoma and Kansas to
be turned into farmland. The loss of the drought-resistant,
soil-retaining natural prairie grasses of the area, coupled with
overgrazing by cattle and an extreme drought, caused the famous Dust Bowl.
Expanding urban areas and human activities use up natural habitats, and the corresponding pollution endangers many more natural areas.
However,
lots of people working to change this. When humans realized
the effects they were having on the natural world, many people leaped
into action. Organizations all around the world are working hard to
preserve remaining habitats and animal populations, and legislation has
been passed regulating human use of land or protecting endangered
species. One of the most influential laws in the United States was the Endangered
Species Act of 1973. A similar act had been passed earlier that,
while offering some protection, was not broad enough and or powerful
enough to protect species and habitats. The new Endangered Species
Act made plants and invertebrates eligible for protection, allotted
Federal and State funds and resources towards protecting species and
their habitats, and planned for habitat conservation and species
reintroduction. Although many people are not educated about the issue
and many more are not willing to change their harmful lifestyles,
there are a lot of people working very hard to change our habits and
protect already-endangered species and habitats.
Sources:
- Diamond, Jared. Guns, Germs, and Steel: The Fates of Human Societies. New York: Norton, 1999. Print.
- Nilsson, Greta. "The Endangered Species Handbook." The Animal Welfare Institute. N.p., n.d. Web. 26 Sep 2013. <http://www.endangeredspecieshandbook.org/index.php>.
- "Timeline of Extinctions." Wikipedia. N.p.. Web. 26 Sep 2013. <http://en.wikipedia.org/wiki/Timeline_of_extinctions>.
- Trimarchi, Maria. "What Caused the Dust Bowl?." How Stuff Works. n. page. Web. 26 Sep. 2013. <http://science.howstuffworks.com/environmental/green-science/dust-bowl-cause.htm>.
- United States of America. US Fish and Wildlife Service. History of the Endangered Species Act of 1973. Web. <http://www.fws.gov/endangered/esa-library/pdf/history_esa.pdf>.
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