Scientists think we may be in the middle of the sixth massextinction in the history of the Earth. A UN report warnsthat 1,183 (12%) of bird species and 1,130 (nearlyone-fourth) of all mammal species are threatened withextinction.
Mass extinctions have occurred five times so far in the fourbillion year history of life on Earth. These are moments inhistory when, for one reason or another, half or more of allspecies die off within a short period of time. We can spotthese mass extinctions from fossil records.
According to Richard Leakey and Roger Lewin, authors of ?The Sixth Extinction,? the first mass extinction occurred450 million years ago. The second took place 100 millionyears later, giving rise to the coal forests. In theTriassic period 250 and 200 million years ago, two massextinctions ended the existence of many species. The mostrecent extinction occurred 65 million years ago, when anasteroid impact caused the demise of dinosaurs.
"In the next 50 to 100 years there is a good possibilitythat there could be a mass extinction of species which ishuman-induced," says Dr. Susan Lieberman, of the World WideFund for Nature (WWF). "We are heading for a crisis. And wehave to act now if we are going to avert this.?
Leakey and Lewin think that 50 percent of the species nowliving on Earth will become extinct in the next 100 years.The WWF says 81 species of freshwater fish have becomeextinct in the last century. 50 of these lived in Africa'sLake Victoria and vanished because of the introduction thereof the Nile perch.
Biologists say that many species will become extinct beforethey are even discovered by humans, especially those livingin tropical rain forests and marine ecosystems. Habitatdestruction by people is one of the biggest causes ofspecies extinction. The UN Food and Agriculture Organizationestimates that forests, which now cover a third of theworld's land surface, have diminished by 2.4 percent since1990. The biggest losses have been in Africa, where 130million acres or 0.7 percent of the forest cover hasvanished in the past decade.
Soaring population, especially in developing countries, putspressure on land and scarce resources. Hungry people burndown forests to plant food and kill off animals withoutregard to their danger of becoming extinct. According to theWWF, "...Current human consumptive pressure is unsustainable.?
Human civilizations can become extinct as well. Read allabout it in ?A Hitchhiker?s Guide to Armageddon? by DavidHatcher Childress,click here.
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