The Anthropocene. Christian Schwägerl

^8. See: http://www.nasa.gov/content/goddard/antarctic-ozone-hole-slightly-smaller-than-average-this-year/.

^9. If increasing amounts of carbon dioxide in the lower atmosphere prevent the sun’s rays from reaching Earth’s surface, it will become colder where the ozone layer is. Such an effect led to the first formation of a large ozone hole over the North Pole in 2011, to the surprise of explorers. See: Gloria L. Manney et al., “Unprecedented Arctic ozone loss in 2011”, Nature, vol. 478, (2011): 469–475.

^10. Quoted from a commentary by Will Steffen on Paul J. Crutzen and Eugene F. Stoermer, “The ‘Anthropocene’ (2000),” in Libby Robin, Sverker Sörlin and Paul Warde (eds.): The Future of Nature, (2013): Yale University Press as well as personal communication with Will Steffen.

      ONE Welcome to the Club of Revolutionaries

      WHETHER YOU TAKE A WALK in the hills around your town or along the coast or by a river, you will encounter the results of geological forces that have been at work for millions of years. Magma that once was deep inside the earth has formed rocks and moved tectonic plates. Water has shaped shorelines and carved out deep valleys. Wind erosion has flattened mountains and created massive deposits of soil and sand.

The exact spot on the earth’s surface that now lies beneath the city of Berlin, the German capital, where I live, was once near the earth’s southern pole some 500 million years ago. Tectonic forces moved it north over that immense period of time.¹¹ Only tens of thousands of years ago, the area was covered with huge glaciers; the weight and the power of their melting water created today’s landscape. Without much effort, one can also observe more recent changes due to geophysical forces. I only have to walk 500 yards from home to reach Heidelberger Platz, from where a wide boulevard runs toward the stores and cafés in the center of West Berlin. The difference in slope between one end of the street and the other is so slight that, in this otherwise flat city, most cyclists and motorists barely notice it. But there is a big story behind this slight slope. It was once the bank of a gigantic river that flowed here at the end of the last Ice Age, 12,500 years ago. This Urstrom (glacial river) was filled with icy water several hundred meters high, to the north of what is now Berlin, before the great thaws set in and the glaciers gradually melted away.

      When I cycle down this slope, I hear cars thundering past. I try to imagine the thundering mass of water that used to rush past, which formed the landscape of sand and stone on which the city of Berlin arose in the thirteenth century. The opposite bank of this primeval river is almost six miles away in Prenzlauer Berg, one of Berlin’s hip new districts. The river must have been gigantic and would make today’s River Spree, which runs through the political and cultural center of Berlin, near the Brandenburg Gate, seem like a mere creek.

      When you contemplate Earth’s history—not just by rattling off things you learned at school but by touching stones or letting sand run through your hands or swimming in a river—even a brief encounter can turn into a fantastic adventure. For me, the excitement is even greater when I become aware of the workings of earlier life forms. Many inland hills found on continents are in fact the remains of ancient coral reefs. Many mountain ranges far from the sea are composed of the calcareous skeletons of earlier marine organisms. Thick deposits of coal and oil, which have provided the fuel for industrial prosperity, are the residues of earlier life forms. Here in Berlin, there is a lot of bog and marshland. When you go hiking where fauna and flora are scant, you sometimes feel as if you are in a Zen garden where lots of decaying moss is underfoot; if it were left undisturbed, these mosses would eventually form coal. In bogs like these you can witness geology at work. You can see how the stones here and the earth’s crust are connected to life itself.

      Earth’s surface, as we know it today, has been transformed by a select group of organisms which I refer to as “The Club of Revolutionaries.” These are the life forms that did not die out unceremoniously after a mere couple of million years. These are the species that did not just surrender their molecules to the great recycling process called evolution, to be absorbed by other life forms.

      The Club of Revolutionaries is comprised of species that have caused lasting change and have created new structures, just as fire, water and wind have done. We still encounter them, eons after their biological demise, in the form of bizarre limestone sculptures, or as pitch-black coal seams, deep below the ocean.

      The oldest—and from our point of view, most essential “revolutionary” is the one that has made possible today’s earth, with all its trees and flowering plants, birds and mammals. This revolutionary is a tiny microorganism that has evolved over three billion years. It used to be called blue-green algae but this label was discarded once scientists realized they weren’t dealing with algae at all but rather with bacteria. Since then, such life forms have been referred to as cyanobacteria. They paved the way for life to use the sun’s energy and to spread from sea to land across the whole surface of the planet.

Before cyanobacteria entered the scene, a young earth, amassed from matter orbiting the sun, had already been through some dramatic changes. It had been hit by another celestial body, a space traveler roughly the size of Mars.¹² Theia, as it’s now called, created such impact that the moon was ejected from the earth’s mass. As a result, the planet’s axis of rotation became tilted, leading to tides and seasons. The fiery interior of the earth still holds the heat from that impact—so, in a sense, we don’t live on one planet, but actually two. After Earth’s and Theia’s matter had merged, a core formed, composed mostly of iron, and a new magnetic field developed, shielding the planet’s surface from harmful radiation from space. Next, a primordial atmosphere began to coalesce, consisting of toxic gases that would certainly be fatal to contemporary organisms. And then, approximately 3.7 to 4 billion years ago, a second “Big Bang” occurred, this one biological. Simple molecules morphed into cells that could replicate themselves. The earth now began to sustain life. In continuous cycles of mutation and replication, adaptation and extinction, these first life forms, now known as archaebacteria, evolved. But they were soon to be confronted with an early resource crisis. The chemical energy they needed for survival became increasingly scarce in their primeval world.

      It was then that cyanobacteria entered the scene. Their altered metabolism proved to be superior in one essential respect: whereas archaebacteria were dependent on the earth’s chemical energy, cyanobacteria were able to tap into the sun’s constant flow of energy. They developed molecular networks and metabolic pathways—the ability to convert energy from light and heat to enable small cell photosynthesis. Thus life’s first resource crisis was solved to its advantage, yet if viewed from archaebacteria’s perspective, it also created the first environmental disaster. Photosynthesis generated large quantities of oxygen. This element had already been present in the earth’s atmosphere in its poisonous molecular form, O₂, but only in limited quantity as a trace element.

      Now, cyanobacteria were pumping large amounts of O₂ into the atmosphere. Over the course of millions of years, the concentration of this gas grew, with far-reaching consequences. For archaebacteria, oxygen was poisonous, so they retreated to very remote locations, like deep-sea vents. Cyanobacteria, on the other hand, fared so well in this new oxygenated world that they multiplied, eventually spreading across the oceans and coastal regions, to form extensive mats and vast nodular colonies.

      Thus, cyanobacteria became founders of “The Club of Revolutionaries,” They released so much oxygen into the atmosphere that around 2.6 billion years ago, dissolved iron in the seas began to oxidize and settle to the bottom. Vast deposits of iron ore were formed, used today in the construction of buildings, complex machines and electronic equipment.

      Once the oceans were saturated