Human Changes Alter Earth's Geology

How much have humans altered the face of planet Earth? So much that some scientists now believe we have developed ourselves into an entirely new geological epoch.

Geologists divide the Earth's 4.5-billion-year history into various eras, periods and epochs based on major natural events or extinctions. Our current epoch has long been the Holocene, which began about 10,000 years ago at the end of the last ice age.

However, in 2000, Nobel Prize-winning scientist Paul Crutzen coined the term, "Anthropocene" to denote a new Earth epoch marked by the many global changes brought about by humans. The term not only grabbed the attention of many other scientists, but is now finding ample evidence to support it.

Last year, for example, James Hansen, a leading climate scientist at NASA's Goddard Institute for Space Studies, warned that humanity had pushed Earth's natural balances close to a dangerous tipping point by pushing atmospheric carbon dioxide to its highest levels in at least 600,000 years.

That view got added traction last week when geologists at the University of Leicester in the U.K. published a paper supporting Crutzen's argument for a new geological epoch. Their research pointed to human impacts that have not only raised global carbon dioxide levels but altered patterns of erosion and sedimentation around the world, dramatically changed plant and animal life and caused ocean acidity levels to rise.

"Sufficient evidence has emerged of stratigraphically significant change (both elapsed and imminent) for recognition of the Anthropocene -- currently a vivid yet informal metaphor of global environmental change -- as a new geological epoch to be considered for formalization by international discussion," write the report's lead authors, Jan Zalasiewicz and Mark Williams.

Scientists at Duke University recently echoed those findings based on humanity's changes to soil alone.

"With more than half of all soils on Earth now being cultivated for food crops, grazed, or periodically logged for wood, how to sustain Earth's soils is becoming a major scientific and policy issue," said David Richter, a soil scientist at Duke. "If humanity is to succeed in the coming decades, we must interact much more positively with the great diversity of Earth's soils."