An Imprint on the Planet

Sueddeutsche Zeitung, 21 October 2014

An imprint on the planet

Human civilization has left any number of traces in nature. But are the changes dramatic enough to still be seen in the distant future? Geologists are discussing whether the “Anthropocene” has begun

The new era begins in the kitchen drawer. It’s the place where cling wrap and aluminum foil are stored in lots of households. Pieces torn from those rolls usually do their duty only for a short period of time, in the fridge or elsewhere, before being tossed to the bin, scrunched to a ball. It‘s hard to image in Germany with its passion for separating waste, recycling what’s possible and burning the rest, but the world over a lot of these materials end up in the environment – or the landfill, if things go well.

Aluminum and plastic, those are two globally available products of the technical civilization, They are made from raw materials dragged from the depths of earth and brought into a usable form with high energy input generated from more raw materials. But then they end up in great quantities on the surface of earth. „We are producing enough aluminum to cover the USA and a good part of Canada“, says Jan Zalasiewizc of Leicester University in England. „And enough plastic to wrap the earth in it.“

Both materials are thus unmistakable signs of the times. Not only is their use connected to an incredible waste of resources. But both also simply weren’t around in previous epochs. Should archeologists or geologists of future millennia find aluminum or plastic while excavating a former dump or the ruins of a city, they will instantly know the remnants of which era they have found: the second half of 20th century, first decades of the 21st century – the beginning of the era of the anthropocene.

This term has been discussed by scientists and artists for a good dozen of years. It was introduced in the year 2000 by Paul Crutzen, the Chemistry Nobel laureate, who has been honored for his role in the discovery of the ozone hole. Anthropocene means that mankind has started to leave such obvious marks in nature, that for the whole future they will be found in the strata of sediments and minerals of the underground as clear signs of a distinct geological epoch. An epoch mankind created. Just the way mass extinctions and other events count as the dawns of their respective new ages which can be seen in rocks and cliffs.

Not all scientists have accepted the concept of the anthropocene yet. „During their training geologists used to be drilled on the notion that mankind was insignificant in natural history“, says the science historian Naomi Oreskes of Harvard University, who once got a degree in that subject herself. „We were told: If earth’s history was an outstretched arm you could wipe out all traces of mankind’s existence by rasping once across a fingernail.“

Officially mankind still lives in the holocene, the geological era that started at the end of the last ice age and helped civilization to develop by providing very stable conditions on earth. But the signs are on the wall that mankind has disturbed that stability by its hunger for resources and by climate change. „Wherever we go, our aerosols have already been there“, says Rüdiger Kruse, a member of the Bundestag from the ruling CDU-party. He has been driving the discussion on the anthropocene forward in the political arena.

In charge of announcing a new geological age is the International Commission on Stratigraphy (which is the scientific analysis of epochs according to layers of earth). It has set up a task force of 30 experts to look into the anthropocene debate. They have been working on the question since 2009, says the task force’s chairperson, the English geologist Jan Zalasiewicz, mainly by digital channels and contacts. Last week they met for the first time in analog space to discuss their progress in public. The occasion was the opening of an exhibition on the anthropocene in the „Haus der Kulturen der Welt“ (House of World Cultures) in Berlin. It has taken over the former congress center, which people in Berlin famously called „Schwangere Auster“ (pregnant oyster), located right next to the chancellor’s office .

Zalasiewicz and his colleagues have lots of examples besides aluminum and plastic that help to recognize the beginning of the anthropocene in earth’s strata. There are lead compounds left by gasoline fumes before the stuff was eliminated from the fuel or the tips of ball point pens which are oftentimes made from the very durable ceramic tungsten carbide. And bricks, 1,3 trillion of which are fire-hardened every year. And concrete, of course, of which mankind has produced 500 billion tons so far, almost exclusively since 1950.

Even the landscape bears traces of mankind. In the USA alone there are around 568,000 disused mines, says James Syvitski of the University of Colorado in Boulder, „and probably ten times as many the world over“. Coal and ore pits and facilities for the production of limestone as a raw product of cement have a yearly turnover of 13 billion tons of soil. According to Syvitzki that is the same amount as 32 Chinese Walls and corresponds to the sediments washed to the ocean by all of the mayor rivers of the world. Mankind also has erected 48,000 big dams of 45 meter height or more. They provide clean energy to nearby residents and help them meet their water demands. But they also effectively stop transport of sediments to river deltas which have started to sink as a consequence. „The cities in those parts of the coastline often dip into the ocean at four times the rate the water line is coming up as a result of climate change“, says Syvitzki.

His colleague Mark Williams, also from Leicester, compares the recent changes of earth to one of the most important epochs in natural history: the Cambrian explosion. It happened 540 million years ago and brought forth dozens of new phyla of organism – many of which became the ancestors of today’s animals. “Some of them started to dig burrows. We are finding traces of their dens, their mobility, their diet, their droppings”, he says. Mankind left all that as well, just bigger by magnitudes: Skyscrapers, underground stations, harbours, mines and the pools of sewage plants, with are often arranged into a pattern by the dozen.

To get a clear, workable definition of the anthropocene, however, the experts of the task force are looking for a unique attribute that will recognizably mark the beginning of the new era far from today’s population centers. For Colin Waters of the British Geological Survey that sign is the plutonium fallout from the atmospheric atom bomb tests between 1952 and 1963. That radioactive material was distributed globally by the jet stream, coming down mainly in mid latitudes both sides of the equator. It can be detected clearly in sediments of Australia’s Lake Victoria, for example. At a depth of 80 centimeters the first traces are found, 20 centimeters above that lie the peak emissions dated to 1963. As plutonium-239 has a half-life of 24,000 years, the beginning of the new era will be easily seen 100,000 years from now.

Another global marker could be the sudden change in the isotopic ratio of carbon. C-13 contributes about one percent in atmospheric molecules like carbon dioxide or methane, the lighter C-12 is much more common. But the ratio has changed measurably since about 1750 by about 1,5 per mill and that trend has accelerated since 1950, making C-12 ever more common. The reason is that mankind has spent just decades to burn fossil fuels formed in millions of years which were depleted in C-13 by the processes in ancient plants that gave rise to oil, gas and coal.

In view of all these changes Bernd Scherer, who heads the “Haus der Kulturen der Welt”, is certain that „mankind is already writing natural history”. He sees the anthropocene as “a paradigm to understand the changes in the various fields”. But he also recognizes there are many hurdles to form a cultural concept into a scientific one.

“To speak of the anthropocene and its many negative consequences means challenging the belief in progress deeply rooted in many societies”, says Naomi Oreskes. This belief might have engendered doubts in one of the first geologists to consider mankind’s influence over earth. It was 1924 when the British geologist Robert Sherlock wrote his book “Man as a Geological Agent”, Oreskes recounts. “He thought then that man’s influence was inconsistent in its direction. Today we see it differently: There is lot of evidence that its sum is negative.”

The discussion in science is bound to drag along for quite a while, Jan Zalasiewicz is certain. “Whatever has started has just started and the biggest changes of the anthropocene are still ahead of us.” There is a good chance that his peers will think it premature to declare the beginning of a new age. The task force the geologist from Leicester heads plans to submit its report to a conference in 2016 to make its way through the Commission on Stratigraphy. “Discussions like this used to take decades”, he says with an ironic smile.