The Sixth Extinction

Only available on StudyMode
  • Topic: Extinction event, Human, Dinosaur
  • Pages : 1 (367 words )
  • Download(s) : 172
  • Published : May 13, 2008
Open Document
Text Preview
The Sixth Extinction
According to the information given by Niles Eldredge, about 30,000 species go extinct annually. The first five major extinctions that have happened in the past were due to natural causes. The first started with severe and sudden global cooling and lost 25% of families. The second happened near the end of the Devonian Period and may or may not have been the result of a global climate change of which 19% of families were lost. Evidence suggests that a bolide impact similar to the end-Cretaceous event may have been the cause of 54% of families lost in the third major extinction. Shortly after dinosaurs and mammals had first evolved at the end of the Triassic Period, the fourth extinction caused 23% of lost families. The most famous extinction is the fifth that took away 17% of families. It wiped out the remaining terrestrial dinosaurs and marine ammonites. Consensus has emerged in the past decade that this event was caused by possible collisions between Earth and an extraterrestrial bolide. Some geologists point to the great volcanic event as part of the chain of physical events that disrupted ecosystems. The current mass extinction is caused by humans. Humans have caused ecosystem stress and species destruction through activities such as transformation of the landscape, overexploitation of species, pollution, and the introduction to alien species. We began disrupting the environment as soon as we appeared on Earth. Phase one began when the first modern humans began to disperse to different parts of the world about 100,000 years ago. Phase two began about 10,000 years ago when humans turned to agriculture. Wherever early humans migrated, other species became extinct. The invention of agriculture accelerated the pace of the Sixth Extinction. Homo sapiens became the first species to stop living inside local ecosystems. Earth can’t sustain the trend in human population growth. It is reaching the limit in carrying capacity....
tracking img