Have we entered a new geological age (the Anthropocene)?
An interesting article published in the current issue of Environmental Science & Technology explains why we have entered a new geologic period called the Anthropocene.
Denoting the current period of human-dominated activity, adopting this term recognises that human activity is changing the Earth on a scale comparable with some of the major events of the ancient past, and that some of these changes are now seen as permanent (even on geological time-scales).
One of the first steps to formalising this term occurred in 2008 when the Geological Society of London decided that there was merit in considering the possible formalization of this term (meaning that it might eventually join other such units on the Geological Time Scale like the Cambrian, Jurassic and Pleistocene). Now the first (of many) formal steps are being taken by international bodies like the International Union of Geological Sciences.
Evidence of massive environmental change
First, how have the actions of humans altered the course of Earth’s deep history? The answers boil down to the unprecedented rise in human numbers since the early nineteenth century—from under a billion then to over six billion now, set to be nine billion or more by mid-century. This population growth is intimately linked with massive expansion in the use of fossil fuels, which powered the Industrial Revolution, and allowed the mechanization of agriculture that enabled those additional billions to be fed.
The change to the earth’s surface created by the building of megacities have increased by an order of magnitude the natural processes of erosion and sedimentation. The authors of the article say that while this is remarkable (from the geological point of view), if city construction declines or stops altogether then natural geomorphological processes will once again take over (as evidenced by abandoned cities such as Angkor in Cambodia).
Probably more far-reaching are the effects on the earth’s chemical and biological components. Most readers of this blog already understand that the atmospheric concentrations of trace compounds (especially carbon dioxide and methane) have changed considerably (and are of course having major effects on our planet).
We know the effects:
- Global temperature increase (especially at the poles)
- Melting polar regions and glaciers
- Sea-level rise
- Ocean acidification
- Species migration where possible
- Species extinction (at 100-1000 times the background rate, and expected to increase by a further factor of 10 this century)
Global temperature rises will have far-reaching consequences for the biosphere. Species will migrate (if they are able to) to track their optimum climate belt, a phenomenon more pronounced in the oceans than on land – changes in, say, larval hatching times can cause cascade-like changes in entire ecosystems, when these larvae act as food for other animals.
The article goes into some detail about how the boundaries between different geological periods are determined – well worth a read if geology interests you!
(The) current human-driven wave of extinctions looks set to become Earth’s sixth great extinction event.
The authors conclude that …”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.”
