The Sixth Mass Extinction

Topics: Extinction, Extinction event, Endangered species Pages: 7 (2519 words) Published: September 20, 2010
The Sixth Mass Extinction
The mass extinction of certain animal species and plants that is facing the Earth today has been compared to, although some scientists suspect worse than, the extinction of the dinosaurs. The annihilation of the dinosaurs was caused by the collision of a  large asteroid with the Earth. This current mass extinction, however, is different than any of the five mass extinctions that have been seen by the earth because this extinction is manmade, not natural. With the search for new resources to support mans ever-growing population and new resources to develop medicines, the habitat that has protected so many of the worlds creatures is now being destroyed. Not only are humans destroying the earth’s biodiversity but also what most humans fail to realize is with this extinction life, as humans know it will forever be changed. (Cooper) The earth has witnessed five other mass extinctions. The first extinction was the Ordovician, 440 million years ago, which is speculated to have been caused by glaciations. This caused the destruction of 25 percent of the animal species and plants. The second extinction was the Devonian, 370 million years ago. This caused the demise of about 70 percent of the plant and animal species. This was probably caused by a climate change. The third extinction was the Permian, 250 million years ago. “The most catastrophic of all mass extinctions may have wiped out 96 percent of all marine species and more than three-fourths of the vertebrate families on land. Scientists speculate that the cause may have been volcanic activity, a change in ocean salinity or climate shifts.” (Cooper) The forth extinction was the Triassic, 210 million years ago, the cause of which is unknown. It caused the extinction of “sponges, insects, and vertebrate groups.” (Cooper) The final extinction was the Cretaceous, 65 million years ago. This caused the extinction of the dinosaurs and 85 percent of all the species. A large asteroid hitting the earth on the Yucatan in Mexico caused this. (Cooper)             The introduction of animals not indigenous to the environments that they are brought to drives the native animals to extinction. For example, when "rats, cats and snakes" were brought to "Hawaii and Guam' they drove away and hunted most of the indigenous birds to those islands.  Also, just as Christopher Columbus and his men introduced small pox to the Aztecs, foreign animals introduce different diseases to animals whose immune systems are not designed to fight them resulting death.  The over hunting of the dodo bird was one of the two reasons why they became extinct. The second was the introduction of pigs into the dodo birds environment. Although the pigs did not transfer any diseases to the dodo birds, they contributed by consuming all the birds offspring, eggs (Cooper).             With climate change and pollution growing rapidly, a lot of animals are choosing to migrate out of their natural environment and onto more suitable environments  (Cooper). The polar bear is an excellent example of this. Throughout history it has been observed continuously that polar bears spend a majority of their lifetime onto of "glacial masses", such as ice bergs. With recent climate changes due to global warming, the ice has begun to wither away, causing the polar bears to move onto more stable environments (Rice). It was not until recently the severity of the polar bear population was recognized. (Adler). "Polar bears depend on sea ice to hunt for ringed and bearded seals, their main food source. "The ice is a platform to hunt seals, and if they don't have that platform they are in big trouble," says Ian Stirling, research scientist emeritus at Environment Canada in Edmonton. The bears are poor swimmers, and in the open water seals can easily evade them."(Adler). 

The over-use of greenhouse gases is the primary cause of global warming. Although, greenhouse gases do occur naturally and have been being released for...
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