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Humans to blame for Creation of World’s Largest hot Sahara Desert: Study

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Hot Sahara Desert, Credits: Wikimedia
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Seoul, March 15, 2017: Challenging a commonly held theory that changes in the Earth’s orbit triggered Sahara desertification, a new study suggests that humans may have played an active role in the transition of a lush green landscape into the world’s largest hot desert thousands of years ago.

The desertification of the Sahara has long been a target for scientists trying to understand climate and ecological tipping points.

Most studies done to date point to changes in the Earth’s orbit or natural changes in vegetation as the major driving forces.

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In a new paper published in the journal Frontiers in Earth Science, David Wright from Seoul National University in South Korea challenges the conclusions of these studies.

“In East Asia there are long established theories of how Neolithic populations changed the landscape so profoundly that monsoons stopped penetrating so far inland,” said Wright.

Evidence of human-driven ecological and climatic change has been documented in Europe, North America and New Zealand, said Wright who believed that similar scenarios could also apply to the Sahara.

To test his hypothesis, Wright reviewed archaeological evidence documenting the first appearances of pastoralism across the Saharan region, and compared this with records showing the spread of scrub vegetation, an indicator of an ecological shift towards desert-like conditions.

The findings confirmed his thoughts.

Beginning approximately 8,000 years ago in the regions surrounding the Nile River, pastoral communities began to appear and spread westward, increasing at the same time the spread of scrub vegetation, the study said.

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Growing agricultural addiction had a severe effect on the region’s ecology. As more vegetation was removed by the introduction of livestock, it increased the albedo (the amount of sunlight that reflects off the earth’s surface) of the land, which in turn influenced atmospheric conditions sufficiently to reduce monsoon rainfall.

The weakening monsoons caused further desertification and vegetation loss, promoting a feedback loop which eventually spread over the entirety of the modern Sahara, the study said. (IANS)

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STUDY: Lakes on Mars dried up 3.5bn years ago

A study reveals that lakes on Mars dried up 3.5bn years ago.

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An image of Mars.
Mars. Pixabay

The discovery of cracks on the surface of Mars by NASA’s Curiosity rover in early 2017 are evidence of lakes that likely dried up 3.5 billion years ago, confirmed a study, revealing details about the red planet’s ancient climate.

In early 2017 scientists announced the discovery of possible desiccation cracks in Gale Crater, which was filled by lakes 3.5 billion years ago.

“We are now confident that these are mudcracks,” said lead author Nathaniel Stein, a geologist at the California Institute of Technology in Pasadena, US.

Since desiccation mudcracks form only where wet sediment is exposed to air, their position closer to the centre of the lake bed rather than the edge also suggests that lake levels rose and fell dramatically over time.

“The mudcracks show that the lakes in Gale Crater had gone through the same type of cycles that we see on Earth,” Stein added.

Representational image for planet Mars.
Representational image. Pixabay

Although scientists have known almost since the moment Curiosity landed in 2012 that Gale Crater once contained lakes, “the mudcracks are exciting because they add context to our understanding of this ancient lacustrine system”, Stein explained, in the paper published in the journal Geology.

“We are capturing a moment in time. This research is just a chapter in a story that Curiosity has been building since the beginning of its mission,” he said.

Also Read: SpaceX to build Mars rockets in Los Angeles

For the study, the team focused on a coffee table-sized slab of rock nicknamed “Old Soaker”.

Old Soaker is crisscrossed with polygons identical in appearance to desiccation features on Earth.

They found that the polygons — confined to a single layer of rock and with sediment filling the cracks between them — formed from exposure to air, rather than other mechanisms such as thermal or hydraulic fracturing, the researchers said.  IANS

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