Geologists wonder if they should add a new epoch to the geological time scale. They call it the Anthropocene – the epoch when, for the first time in Earth's history, humans have become a predominant geophysical force. Naming such a new epoch would also recognize that humans now share responsibility with natural forces for the state of our planet's ecological environment.

Geologists have been using the term informally for at least half a decade. Now members of the Stratigraphy Commission of the Geological Society of London have laid out the case for giving the term official scientific status.

Presenting that case in the February issue of GSA Today magazine, the team notes that "since the start of the industrial revolution, Earth has endured changes sufficient to leave a global stratigraphic signature." It is different from anything found in the entire geological record up to that point. That means the team expects future geologists examining this record will recognize a distinct break with the Holocene ("recent whole") epoch that covers the past 10,000 years.

Atmospheric chemist and Nobel Prize winner Paul Crutzen at Germany's Max Planck Institute for Chemistry in Mainz says this presents humanity with an awesome challenge. He has pointed out that what the London team calls the "novel biotic, sedimentary, and geochemical change" now being written into the geological record reflects the emergence of human intelligence and technology as a geophysical force. On his website, he explains this means that "to develop a world-wide accepted strategy leading to sustainability of ecosystems against human stresses will be one of the great future tasks of mankind." He adds that it will take "intensive research and wise application of the knowledge" gained to develop sustainable environmental management.

Soil scientist Daniel Richter at Duke University in Durham, N.C., would agree. In an announcement of his work last month, he explained that human-induced changes to the world's soils are enough in themselves to justify saying we have entered the "Anthropocene (or man-made) age." He notes, "With more than half of all soils on Earth now being cultivated for food crops, grazed, or logged for wood, how to sustain Earth's soils is becoming a major scientific and policy issue."

He adds, "If humanity is to succeed in the coming decades, we must interact much more positively with the great diversity of Earth's soils."

Dr. Richter cites Africa as an example of this challenge. There, widespread farming without nutrient recycling threatens continent-wide soil infertility. He adds that, globally, "expanding cities, industries, mining, and transportation systems all impact soil in ways that are far more permanent than cultivation." Richter is part of an international group that has set up the first global long-term soil research network. This will help develop the knowledge needed for worldwide soil management.

In making the case for a new epoch, geologists such as the London team cite many other aspects of human geophysical impact. It will be up to the International Commission on Stratigraphy to decide whether or not to establish a new Anthropocene epoch. But it is clear that Earth has taken an unpre­cedented geological turn in our time and there is no turning back.