A New Geologic Era
It is a new age of geological time or so some say called the Anthropocene Epoch. This is noted in the in the journal Environmental Science & Technology. (web issue March 29; print issue April 1). This is because of the dramatic recent or potential changes in the world such as climate warming and species extinction. The dawning of this new epoch may include the sixth largest mass extinction in the Earth's history. Whether the new era will be dramatic as the Jurassic with the end of the dinosaur is still to be determined.
An extinction event is a sharp decrease in the diversity and abundance of macroscopic life. They occur when the rate of extinction increases with respect to the rate of speciation. The causes of such extinction events is not clearly known. For example the last one may have been caused by a giant meteor impact.
The classical "Big Five" mass extinctions identified are widely agreed upon as the most significant:
1. Cretaceous—Tertiary extinction event (K-T extinction) - 65 million years ago. About 17% of all families, 50% of all genera and 75% of species went extinct. It ended the reign of dinosaurs and opened the way for mammals and birds to become the dominant land vertebrates.
2. Triassic—Jurassic extinction event - 205 million years ago. About 23% of all families and 48% of all genera (20% of marine families and 55% of marine genera) went extinct.
3. Permian—Triassic extinction event - 251 million years ago. Earth's largest extinction which killed 57% of all families and 83% of all genera.
4. Late Devonian extinction 360-375 million years ago.
5. Ordovician—Silurian extinction event 440-450 million years ago.
The scientists propose that, in just two centuries, humans have wrought such vast and unprecedented changes to our world that we actually might be ushering in a new geological time interval which will alter the planet for millions of years. In other words the present times may be at the cusp of the next extinction event.
The authors contend that recent human activity, including stunning population growth, sprawling megacities and increased use of fossil fuels, have changed the planet to such an extent that we are entering what they call the Anthropocene (New Man) Epoch.
First proposed by Crutzen more than a decade ago, the term Anthropocene has provoked controversy. However, as more potential consequences of human activity — such as global climate change and sharp increases in plant and animal extinctions — have emerged, Crutzen's term has gained support.
Also not clear is when this era began. Did it begin 10,000 years ago with farming or only now? Then again only the future will show whether a mere 10,000 years is a simple aberration over a million plus time period.
Currently, the worldwide geological community is formally considering whether the Anthropocene should join the Jurassic, Cambrian and other more familiar units on the Geological Time Scale.
The authors note that getting that formal designation will likely be contentious. But they conclude, "However these debates will unfold, the Anthropocene represents a new phase in the history of both humankind and of the Earth, when natural forces and human forces became intertwined, so that the fate of one determines the fate of the other. Geologically, this is a remarkable episode in the history of this planet."
For further information: http://www.eurekalert.org/pub_releases/2010-03/uol-tdo032610.php