Climate change, the loss of biosphere integrity, land-system change, and altered biogeochemical cycles like phosphorus and nitrogen runoff have all passed beyond levels that put humanity in a safe operating space, in turn driving our planet into a new geological epoch – Anthropocene, according to two papers published by Prof Will Steffen of the Australian National University and his colleagues from ten countries. Another team of researchers, led by Dr Jan Zalasiewicz of the University of Leicester, has proposed a start date for the dawn of the epoch – the time of the world’s first nuclear bomb explosion, on July 16th 1945 at Alamogordo, New Mexico.
Researchers have proposed that July 16, 1945 – the time of the world’s first detonation of a nuclear weapon, conducted by the United States Army as part of the Manhattan Project – should mark the start of Anthropocene. Image credit: United States Department of Energy.
“Human activities could drive the Earth into a much less hospitable state – in this research we have more accurately assessed the risk of this happening. We are starting to destabilize our own planetary life support system,” Prof Steffen said.
The first paper by Steffen et al, published in the journal Anthropocene Review, charts the Great Acceleration in human activity from the start of the industrial revolution in 1750 to 2010, and the subsequent changes in the Earth System (the sum of our planet’s interacting physical, chemical, biological and human processes), using a planetary dashboard of 24 global indicators.
“It is difficult to overestimate the scale and speed of change. In a single lifetime humanity has become a planetary-scale geological force,” Prof Steffen said.
Twelve indicators depict human activity, for example, economic growth, population, foreign direct investment, energy consumption, telecommunications, transportation and water use.
Twelve indicators show changes in major environmental components of the Earth System, for example, the carbon cycle, nitrogen cycle and biodiversity.
This planetary dashboard highlights how the trajectories of Earth and human development are now tightly bound.
“We expected to see major changes since 1750, but what surprised us was the timing; dramatic increases have occurred since 1950,” Prof Steffen noted.
For example, since 1950 urban population has increased seven-fold, primary energy use has quintupled and fertilizer use has increased eight-fold.
In turn species are becoming extinct more than 100 times faster than the background rate, and the amount of nitrogen entering the oceans has quadrupled.
“We’ve now entered a new geological epoch, named the Anthropocene, in which the global economic system is the primary driver of change on Earth. We have become a planetary-scale force in a single lifetime,” Prof Steffen said.
The second paper by Steffen et al, published in the journal Science, quantifies risks to nine global systems that regulate the stability of the Earth and provide ecosystem services that societies depend upon, such as maintaining fresh water supplies, soil fertility and climatic stability.
“It should be a wake-up call to policymakers that we’re running up to and beyond the biophysical boundaries that enable human civilization as we know it to exist,” said co-author Dr Steve Carpenter from the University of Wisconsin-Madison Center for Limnology.
For the last 11,700 years until roughly 100 years ago, Earth had been in a remarkably stable state.
During this time, known as the Holocene epoch, everything important to civilization has occurred.
From the development of agriculture, to the rise and fall of the Roman Empire, to the Industrial Revolution, the Holocene has been a good time for human endeavors.
But over the last century, some of the parameters that made the Holocene so hospitable have changed.
“We’ve changed nitrogen and phosphorus cycles vastly more than any other element. The increase is on the order of 200 to 300 percent. In contrast, carbon has only been increased 10 to 20 percent and look at all the uproar that has caused in the climate,” Dr Carpenter said.
“There are places that are really, really overloaded with nutrient pollution. Wisconsin and the entire Great Lakes region are some of those. But there are other places where billions of people live that are undersupplied with nitrogen and phosphorus.”
“For instance, much of Africa is largely lacking these two essential elements. We’ve got certain parts of the world that are overpolluted with nitrogen and phosphorus, and others where people don’t even have enough to grow the food they need.”
“It might be possible for human civilization to live outside Holocene conditions, but it’s never been tried before. We know civilization can make it in Holocene conditions, so it seems wise to try to maintain them.”
According to Dr Zalasiewicz’s team, the end of Holocene and the start of the Anthropocene could be considered to be drawn at the moment of detonation of the world’s first nuclear test: on July 16th 1945.
The beginning of the nuclear age, it marks the historic turning point when humans first accessed an enormous new energy source – and is also a time level that can be effectively tracked within geological strata, using a variety of geological clues.
“Like any geological boundary, it is not a perfect marker – levels of global radiation really rose in the early 1950s, as salvoes of bomb tests took place,” said Dr Zalasiewicz, who is the first author of a paper published in the journal Quaternary International.
“But it may be the optimal way to resolve the multiple lines of evidence on human-driven planetary change. Time – and much more discussion – will tell.”
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Will Steffen et al. The trajectory of the Anthropocene: The Great Acceleration. Anthropocene Review, published online January 16, 2015; doi: 10.1177/2053019614564785
Will Steffen et al. Planetary boundaries: Guiding human development on a changing planet. Science, published online January 15, 2015; doi: 10.1126/science.1259855
Jan Zalasiewicz et al. When did the Anthropocene begin? A mid-twentieth century boundary level is stratigraphically optimal. Quaternary International, published online January 12, 2015; doi: 10.1016/j.quaint.2014.11.045
