The earliest evidence of humans altering the geology of the planet has been uncovered from the depths of the Dead Sea. A new study has documented how 11,500 years ago, soil erosion, thought to be a result of the beginnings of agriculture in the region, washed sediment into the body of water, and physically changed the geological processes.
We know now that we are altering the environment in a dramatic fashion, from the formation of new rock types made from plastic to the acidification of the waters. But humans have been around for a long period of time, and so it is important to understand these fundamental processes, including at what point we as a species started to significantly alter the Earth’s geology and ecosystems.
The study, published in the journal Global and Planetary Change, used 450-meter-long (1,500 feet) core samples taken from the Dead Sea basin. These records of sediment from the inland sea cover roughly 220,000 years’ worth of environmental change. At around 11,500 years ago, however, the researchers noticed that there was a significant increase across the region of sedimentation of the sea, thought to be as a result of increased soil erosion from the surrounding lands.
They found that there was a roughly three times increase in fine sediment entering the Dead Sea due to seasonal floods around this period of time. Yet this massive flux of soil into the bottom of the Sea cannot be explained by the tectonic activity of climatic shifts known to have happened in the region during the Holocene, when this was observed. It does, however, match up with when humans in the Levant started undertaking wide-scale agriculture.
“Natural vegetation was replaced by crops, animals were domesticated, grazing reduced the natural plant cover, and deforestation provided more area for grazing,” explained Tel Aviv University’s Professor Shmuel Marco, who led the study. “All these resulted in the intensified erosion of the surface and increased sedimentation, which we discovered in the Dead Sea core sample.”
Yet while it is clear that humans have indeed been altering the environment for a long period of time (before agriculture we were no doubt burning grasslands and forests to flush out prey), there is no doubt that there has been a step change in the last 150 years. Since the industrial revolution kicked off in the 19th century, humans have been changing the Earth at a considerable and alarming rate.
“Human impact on the natural environment is now endangering the entire planet,” said Professor Marco.
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