By Leon Kolankiewicz
October 31, 2011
Has Planet Earth been profoundly altered by 7 billion human beings and our ever more potent tools and technology? Could evidence of our presence be discerned by a hypothetical geologist probing and poking rock strata 100 million years from now?
Or, in the vast fullness of geologic time, will most if not all traces of our civilization – both its products and byproducts, its stunning achievements and its prodigious excesses – prove as fleeting as sand castles on the beach, washed away forever by the tides of time?
This is the debate now playing out among geologists, biologists, and other scientists, and reported on recently in the journal Science in its 7 October 2011 edition.
Science, published by the American Association for the Advancement of Science (AAAS), is the most prestigious general scientific periodical in the United States. Along with the U.K’s Nature, it is one of the two most influential scientific journals in the world.
As Science puts it: “There’s no dispute that humans are leaving their mark on the planet, but geologists and other scientists are debating whether this imprint is distinctive and enduring enough to designate a new epoch: the Anthropocene.” Or the “Age of Man.”
When the Ordovician Period gave way to the Silurian some 445 million years ago, widespread, rapid glaciation and associated changes precipitated Earth’s first mass extinction event, exterminating 60% of marine and terrestrial life. This sharp boundary in the earth’s history is etched in the rocks and fossil record and is clearly visible today to geologists at sites across the world.
Some scientists now believe that humanity’s collective impact is so profound and so pervasive that it can be considered in essence a geophysical force comparable to erupting supervolcanoes, asteroid strikes, and massive, continent-shifting tectonic upheaval. In an article for Nature in 2002, chemist and Nobel Prize winner Paul Crutzen first coined the term “Anthropocene.”
Crutzen argued that we humans have nudged the planet out of the Holocene Epoch, which began with the end of the Pleistocene Epoch – the fabled Ice Age – and into a much less stable period dominated by human agency. As Crutzen and environmental journalist Christian Schwägerl write in Yale University’s online publication environment 360:
It’s a pity we’re still officially living in an age called the Holocene. The Anthropocene — human dominance of biological, chemical and geological processes on Earth — is already an undeniable reality. Evidence is mounting that the name change suggested by one of us more than ten years ago is overdue.
Other scientists remain skeptical that human impact is really that long-lasting. Changes that seem enormous to us, tethered as we are to one point in time, might actually prove inconsequential or virtually invisible in the far future. The vast reaches of the geologic time scale, after all, stretch for millions, even billions, of years.
And as Science emphasizes, debates over whether to formally designate a new geologic epoch, era, or period can take decades – even centuries – to resolve. This determination of the International Commission on Stratigraphy (stratigraphy = study of rock strata) to avoid too hasty a decision when deliberating geologic nomenclature and classification reminds one of the tree-like Ents and their ponderous “entmoot” in JRR Tolkien’s classic The Lord of the Rings.
Yet the arguments for such a re-designation are compelling. One member of the Anthropocene Working Group estimates that humans have already modified 80% of Earth’s land surface. Deforestation and conversion to cropland change pollen deposition. Pollen, which remains embedded in sediments for eons, can be studied with great precision by palynologists, that is, practitioners of pollen paleontology.
Human impacts on biodiversity will also greatly change the types and distribution of fossil remains. As a result of habitat loss, invasive species, overhunting, climate change, and pollution, Earth is on the verge of its sixth mass extinction event in its 4.5 billion year history.
Incredibly, at present more than 90% of total vertebrate biomass on earth (that is, the total weight of all living organisms) is comprised of humans and a handful of domesticated animal species. Ten thousand years ago this figure was a mere 0.1%. We are selfishly replacing and displacing all other life forms that aren’t us or that don’t feed our insatiable needs and wants.
Other examples of the unmistakable human signature include:
- Mining and other excavations remove four times as much sediment as the world’s glaciers and rivers move each year.
- Human-induced erosion is more than 10 times the background natural erosion rate.
- Roads, cities, and urban rubble will leave behind distinctive signatures in rock strata.
- As a result of burning fossil fuels and emitting gigatons of light-isotope carbon (C-12) annually, the carbon composition of sea shells, coral, and the shells of plankton foraminifera is shifting away from heavy-isotope carbon (C-13); this will be permanently preserved in the strata.
- Then there are man-made synthetic chemicals, new to nature, such as PCBs and plastics, and radioactive isotopes like cesium from atomic tests.
Whether or not the International Commission on Stratigraphy eventually adopts Crutzen’s suggestion, human beings will continue to exert a powerful influence on the Earth. As Crutzen and Schwägerl observe:
For millennia, humans have behaved as rebels against a superpower we call “Nature.” In the 20th century, however, new technologies, fossil fuels, and a fast-growing population resulted in a “Great Acceleration” of our own powers. Albeit clumsily, we are taking control of Nature’s realm, from climate to DNA. We humans are becoming the dominant force for change on Earth. A long-held religious and philosophical idea — humans as the masters of planet Earth — has turned into a stark reality.
Like it or not.
Leon Kolankiewicz is a Senior Writing Fellow for Californians for Population Stabilization (CAPS) and a consulting wildlife biologist and environmental planner whose professional career spans a quarter-century, three countries and more than 30 states. He can be reached at [email protected] or [email protected]