Humans were already changing the environment 11,500 years ago

Doyle Rice | USA TODAY

Man-made environmental change isn't new: A study found human activities such as farming and logging led to erosion around the Dead Sea some 11,500 years ago, the earliest ever discovered.

Scientists from Israel's Tel Aviv University took a core sample — a long, cylindrical section of rock and dirt — from under the Dead Sea. The sample gave the team an accurate sediment record of the past 220,000 years.

Looking at a sample from 11,500 years ago, the researchers detected rates of erosion that could not have occurred naturally.

"Natural vegetation was replaced by crops, animals were domesticated, grazing reduced the natural plant cover, and deforestation provided more area for grazing," said geologist Shmuel Marco, who led the study.

The researchers argue human activity at that time disrupted the natural surface around the Dead Sea, bringing about intensified erosion, Marco said. "We see it in the form of triple and even four times the increase of the sediment supply to the lake."

The research took place as part of a Dead Sea deep drilling project, which harnessed a 1,500-foot-deep drill core to delve into the earth. The Dead Sea area is an excellent natural laboratory for studying geology and climatology, because it offers "a rare combination of well-documented substantial climate change, intense tectonics and abundant archaeological evidence for past human activity," the study said.

The scientists are now looking at the same drill core for evidence of ancient earthquakes: "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."

The study was published in the journal Global and Planetary Change.