A study suggests that the human being began to have an important impact on the environment 5000 years ago.
Let’s do a mental experiment. Suppose the arrow of time does not exist and that we can build a machine to travel to the past. Let us also suppose that we are inspired to make a trip to a time in which the Earth, having the same type of fauna and flora, had not yet been spotted by the hand of man. It would be a time in which a virgin Earth would be waiting for us, populated with life, without pollution and without major human impact. Once there, we could look at a natural world and it would probably seem perfect. At what time would we adjust our time machine ?, in 100 years ago ?, in 10,000 years ?, in 100,000?
It begins to be called with the word “Anthropocene” that era in which the human being has changed the world, probably forever and for worse. But experts disagree about when it started.
Some argue that the Anthropocene began with the industrial revolution. Others say it began with the Neolithic and the agricultural revolution about 10,000 years ago. However, a new study suggests that it started 5000 years ago, when certain habits such as burning thickets for hunting animals were spread.
Erle Ellis, of the University of Maryland, and his collaborators have calculated that the human being transformed at least one fifth of the earth’s surface, except for the polar regions, 5000 years ago. Other studies ensured that this level of transformation was only achieved in the last 100 years.
These researchers argue that this level of transformation was enough to release enough carbon dioxide and change the weather at that time.
Although 5000 years ago there was only a population of a few tens of millions of humans, Nature was in decline due to the fact that each individual needed on average more area than at present to stay. With the adoption of recent intensive agricultural methods, per capita land use is now in Europe only one sixth of what it was 2500 years ago and in Asia one tenth.
Although there was no technology at that time, the impact of land use was greater per person because the methods were much more inefficient.
Until now it was assumed in the models that the per capita land use had remained unchanged during all this time, but archaeological evidence says otherwise.
Thus, for example, sediments in lakes indicate a peak in the presence of particles of charcoal that began 60,000 years ago. This coincides with the time when humans began to use fire to hunt animals and with the use of fire to stimulate grass growth in grasslands. The presence peaks of these particles coincide with the arrival of humans in certain regions of the globe, something that also coincides with the extinction of large animals.
Another example is the soil present under the modern forests of America and Africa, which is enriched with manure and charcoal laid by farmers 2500 years ago.
The planet’s climate has probably been altered by man in prehistoric times, when forest clearing and pasture burning released carbon dioxide into the atmosphere for thousands of years. These researchers estimate that these habits would have increased the presence of this gas by 20 or 30 parts per million. Although it is less than the 120 parts per million that the modern human being has released, this could change the climate, at least locally.
The carbon footprint of a human from 8000 years ago would be about 30 tons of carbon dioxide, that is, roughly one ton per year. At present, the per capita emission is 2 to 3 tons per year.
Human societies, even those of thousands of years ago, have altered ecosystems in a much broader way than previously believed. This new image of a human domain over the world shows that there is no longer any pristine or unaltered site for a long time. There are no virgin forests, but forests recovered from clearings made in the past.
Although the authors say that Nature has adapted to our needs, they reject the question of the current concern for the environment, especially the crazy emission of greenhouse gases due to the burning of fossil fuels. The study also provides solutions or answers to these modern challenges.
One of the lessons is not to look at whether an ecosystem is natural enough or not to deserve protection, but everyone has to be protected. Another interesting point is to recognize that technology has always been our ace in the manga. Intensive agriculture, for example, allowed the human population to grow without needing to occupy much more land.
Although some civilizations, such as the Maya or Mesopotamian, failed to manage their resources, others did, the study says. Between 30,000 and 20,000 years ago the Eurasian tribes changed their strategy due to the decline caused by overhunting. They began to diversify their resources by also hunting smaller animals and even managing the flock populations of the larger ones so that they did not disappear. They also learned to ferment, grind, cook and grill food. This allowed them to use a wider food range and develop techniques that later resulted in agriculture and livestock. All this allowed them to lead more sustainable lives and better endure times of scarcity.
The human being seems to do the easiest thing that can be done at the moment. When hunting and gathering is not enough, then you have to look for more intensive and technological methods that allow you to survive, such as livestock and others. Intensive rice farming began to develop 6000 years ago in the Yangtze River Valley, but was not adopted by other humans in the region for thousands of years, humans for whom hunting and fishing were sufficient.
According to the use of fossil fuels it has allowed to cultivate the same land with less labor, the human being has emigrated from the countryside to the city and a minority feeds a majority. This process has been completed in industrialized countries. where only 1% work in the primary sector, but it has not been completed in other countries such as India or China.
Ellis, if forced to choose, places the beginning of the Anthropocene 5000 years ago, which he says is when the presence of carbon dioxide and methane begins to increase due to the domestication of fauna and the emergence of urban planning and metallurgy on a large scale right after.
So if we want to go with our time machine to an era unchanged by the human being we will have to set a date before that.
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