(photo credit: WIKIMEDIA COMMONS/IAN AND WENDY SEWELL)
The earliest geological sign of the impact of humans on the environment has been discovered by Tel Aviv University scientists at the Dead Sea.
According to the researchers, the erosion took place 11,500 years ago during the Neolithic Revolution, as societies underwent a wide-scale transition from hunting and gathering to agriculture and settlement, resulting in a much larger human population that continued to grow exponentially.
The study’s results were recently published in the journal Global and Planetary Change.
The vast majority of climate scientists agree that climate-warming trends over the past century have been caused by human activity, said Prof. Shmuel Marco, head of TAU’s School of Geosciences, who led the climate change research team.
Within a core sample retrieved from the Dead Sea, researchers discovered basin-wide erosion rates dramatically incompatible with known tectonic and climatic regimes of the period recorded.
The researchers are currently in the process of recovering the record of earthquakes from the same drill core. “We have identified disturbances in the sediment layers that were triggered by the shaking of the lake bottom,” Marco said. “It will provide us with a 220,000- year record – the most extensive earthquake record in the world.
“Human impact on the natural environment is now endangering the entire planet,” Marco said. “It is therefore crucial to understand these fundamental processes. Our discovery provides a quantitative assessment for the commencement of significant human impact on the Earth’s geology and ecosystems.”
Marco’s team included TAU post-doctoral student Dr. Yin Lu, and Prof. Dani Nadel and Prof. Nicolas Waldman, both of the University of Haifa. It took place as part of the Dead Sea Deep Drilling Project, which harnessed a 1,500-foot-deep drill core to delve into the salt water body’s basin. The core sample provided the team with a sediment record of the last 220,000 years.
“Natural vegetation was replaced by crops; animals were domesticated; grazing reduced the natural plant cover; and deforestation provided more area for grazing,” said Marco. “All these resulted in the intensified erosion of the surface and increased sedimentation, which we discovered in the Dead Sea core sample.”
The Dead Sea drainage basin serves as a natural laboratory for understanding how sedimentation rates in a deep basin are related to climate change, tectonics, and impact on the landscape, he explained.
“We noted a sharp threefold increase in the fine sand that was carried into the Dead Sea by seasonal floods,” said Marco. “This intensified erosion is incompatible with tectonic and climatic regimes during the Holocene, the geological epoch that began after the Pleistocene some 11,700 years ago.”