When people started to change the planet

No one knows exactly what day of the week an asteroid of nine kilometers with a diameter crashed into that place, which would then become the Yucatan Peninsula. It is known that this day came about 65 million years ago, and that the days that followed were colder, darker, and less and less dinosaurs were seen.



The collision changed all life support systems on Earth, throwing huge amounts of dust into the air, evaporating huge volumes of water and running hundreds of earthquakes and volcanic eruptions. The impact, and the mass extinction that followed it, marks one of the most well-known geological boundaries, between the decline of the Cretaceous period and the dawn of the Paleogene period. Humans are an unscheduled version of such an asteroid, in the sense of global influence on the planet; they changed it so much that many scientists believe that it deserves its own geological epoch - the anthropocene. And although no one knows which day people have become a force of nature, a couple of scientists believe that they can derive an equation to calculate the year when it happened.



This planet is 4.5 billion years old. Almost three quarters of this time life existed on it. “The earth is usually in equilibrium, and the feedback forces maintain the balance of the atmosphere and temperature over long periods of time,” said Owen Gafni , a writer and co-author of a new study published in the journal Anthropocene Review. In times of equilibrium, life forms evolve more slowly, extinctions rarely occur, and biodiversity increases. And then there is a collision with an asteroid or a megavulcan eruption. Or the Earth tilts the axis of rotation by half degrees. Each such cataclysm changes the atmosphere, temperature, the composition of the oceans and dozens of other processes that determine who is able to survive.

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• By 1700, land used by humans was only 5% of the Earth, by 2000 it was 55%.

• Greenhouse gas emissions, caused by humans, increase the acidity of the oceans at almost the same rate as before the massive Permian extinction (it’s the greatest extinction) that began 300 million years ago [according to 2012 — 252.2 ± 0.5 million years old].

• According to the most modest estimates, the current extinction rate is 10 times higher than the highest rate during periods of ecological equilibrium.



“Such examples can be scribbled so long that it will be boring to discuss all the ways in which humankind is changing the planet,” said Erl Ellis , a landscape ecologist at the University of Maryland. The controversial point is, in his words, in an attempt by the authors of the work to find out the exact date after which people began to dominate the planet.



Ellis is a member of the working group whose task is to select preliminary work on the definition of the anthropocene as a formal geological epoch. The formalization of this concept will be a landmark event, and causes heated debate among scientists. But the question is not whether human activity leads to a change in life on Earth. “No one is arguing about this,” says Ellis. The real problem of the working group lies on a practical plane: will the activity of people entail the appearance of a stratigraphic layer worthy of study by future geologists? What is the meaning of giving a name to a layer of stones that doesn't exist yet? “The introduction of a new era does not give any benefit to specialists in stratigraphy and archeology, working with stones and versed in the processes of their formation,” says Ellis. However, Ellis belongs to a minority of scientists from the anthropocene working group who believe that this era is deeply rooted in the history of mankind. “The industrial revolution took place much earlier than the 1950s,” he says. “You can also consider the amazing effect of agriculture, a few thousand years old, on the biosphere.”



Co-author Gaffney, climatologist Will Steffen of the Australian National University, also participates in this working group. In the new work, this pair of scientists describes an equation comparing the effects of the last several hundred years with the base level of the Holocene lasting the last 11,700 years. “We have chosen the key processes of the Earth and the speed of their change,” says Gafni. Most of the time, the systems were in equilibrium - stably held by phlegmatic solar activity, the inclination of the earth's axis at 26.5 ° [according to NASA , 23.44 °], and the absence of island-sized stones falling from the sky.



According to their calculations, human activity, by its results, eclipsed the sun, the Earth, and sometimes falling stars, and became the main process that shaped life, around 1950 or so. “This coincides with the first atomic bombs that added tracked radiation to the atmosphere, tracked in sedimentary rocks,” says Gafni. And they are not the first to pay attention to the period immediately after the war. The 1950s, some researchers call the " great acceleration " in which a thriving middle class led to spikes in global GDP graphs, agricultural land use, paper production, dam construction, car ownership, international tourism, and other signs of consumption. The Stephen and Gafni equation simply adds to the argument that the anthropocene began with color TVs.



Gaffney acknowledges the conclusions that follow from such statements - they say, a rather small part of the people is responsible for the anthropocene and everything connected with it. “Our key conclusion is that the main reason for global change is the production and consumption of goods by the upper and middle class of people all over the world,” he says. “The definition of an anthropocene can lead to serious social consequences and has the potential to change human perceptions, just as the Darwinian theory of evolution or Copernicus' heliocentric astronomy led to paradigm shifts.”



People are not the first to change the world, and probably they will not be the last. 2.3 billion years ago, unicellular organisms, cyanobacteria, developed photosynthesis, inhaled carbon dioxide and filled the atmosphere with oxygen. Their collective outburst of gases is sometimes referred to as the “ oxygen holocaust, ” since it stifled a large percentage of the anaerobic life that dominated the Earth. The cyanobacteria were so successful that their small bodies as a result condensed into huge oil reserves. And when the anthropocene layer is formed, carbon dioxide burnt from oil will cause its beautiful dark shade.