JACK STATES

Perspective

Recently in the Casper Star-Tribune, I read with some angst about the massive 19-square-mile breakage of the 47-square-mile Markham Ice Shelf attached to Canada's Ellesmere Island. Of course that amount is minor compared to the 160-square-mile chunk of continental ice that recently broke free from the Antarctic and the thousands of square miles of ice that have, since the early 19th century, melted due to global temperature change.

Many have commented that our current climate-change event is not unusual in the history of the earth. Indeed, if viewed over the 4.6 billion years of its geological history (divided into eras, periods, and epochs) that is correct. Geologists have postulated that there have been over 30 such "ice age glaciations" followed by periods of warming and melt, but only five of them have occurred during the existence of humans. They are collectively known as the Pleistocene Ice Ages that began about 30 million years ago and ended about 10,000 years ago. At its peak, ice covered about 30 percent of the planet. A return to warmer global temperatures ushered in the present geological epoch, the Holocene.

The Holocene then marks when, for the first time in Earth's history, humans have become a predominant geophysical force. It is obvious that at first human population increased slowly. But just in the last two centuries the population and the population growth rate have been high enough to significantly impact our planet. Human activities have modified landscapes and ecosystems, and quite possibly they're starting to modify the global climate by contributing chemicals that enhance global warming.

Among the major changes heralding this two-century old man-caused situation are:

- Vastly altered soils with sediment erosion and non-productive deposition patterns.

- Major disturbances to the carbon cycle and global temperature.

- Wholesale changes in ecology and biological diversity.

- Acidification of the ocean, which threatens the food chain.

- Slash-and-burn agricultural practices.

- Introduction of chemical and radioactive contaminants that result in atmospheric, soil, and water pollution.

Whether the Earth is truly warming and whether or not human activities are playing a significant role in the process are both hotly debated issues. Governments worldwide are concerned because these changes are having far-reaching political ramifications and will affect the welfare of the physical Earth and all life on it. Over the long-term, natural geophysical forces will slowly but inexorably change the looks of Earth's land masses and oceans, but there is general agreement that human activity is playing a significant role in the near-term geologic future.

Geoscientists have proposed official recognition of a new geological time period, the "Anthropocene" (human-caused) epoch. It would mark the period when humans became the predominant force over the Earth's geophysical environment. Naming such a new epoch would also recognize that humans, as a natural force in nature, share responsibility for the state of our planet's environment.

Geologists have been using the term "Anthropocene" informally for at least half a decade. Recently members of the Geological Society of London laid out the case for giving this term scientific status. The Society notes that "since the start of the industrial revolution, Earth has endured changes sufficient to leave a global geological signature." Certainly geologists have identified conditions significantly different from anything found in the entire geological record. If approved, future scientists 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 has pointed out that what the London society 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. It will be up to the International Commission on Stratigraphy to decide whether or not to establish the new Anthropocene epoch. Nevertheless, the Earth has taken an unprecedented geological turn in our time and there is no turning back. So, fellow earthlings, it seems that our hope for the future of our planet is embodied in a course of action we must take today.

Jack States is professor of Biology Emeritus at Northern Arizona University, Flaggstaff, where he has taught for 25 years. He is an adjunct professor of Botany at the University of Wyoming.