Climate Change: Largest Freshwater Lake in the World Turned into a Desert in Only a Few Hundred Years

First Posted: Jun 30, 2015 09:25 AM EDT

Researchers may have discovered a bit more about the startling changes that impacted a massive lake. Scientists have found that the Palaeolake Mega-Chad, which was once the largest freshwater lake on Earth, dried up in a matter of a few hundred years.

In order to better understand the history of this lake, the researchers used satellite images to map abandoned lake shore lines. They also analyzed sediments to calculate the age of these shore lines. In the end, they created a lake level history spanning the last 15,000 years.

The lake was at its peak around 6,000 years ago. During this time, it was the largest freshwater lake on Earth and had an area of 360,000 square kilometers. Today's lake Chad, though, has been reduced to a fraction of that size at only 355 square kilometers.

So what caused this drying? There was a rapid change from a giant lake to desert dunes and dust due to changes in rainfalls from the West African Monsoon. In fact, one part of the lake, called the Bodele depression, is now the single greatest source of atmospheric dust in the world. This dust now helps maintain the fertility of tropical rainforests.

"The Amazon tropical forest is like a giant hanging basket," said Simon Armitage, one of the researchers, in a news release. "In a hanging basket, daily watering quickly washes soluble nutrients out of the soil and these need to be replaced using fertilizer if the planets are to survive. Similarly, heavy washout of soluble minerals from the Amazon basin means that an external source of nutrients must be maintaining soil fertility. As the world's most vigorous dust source, the Bodele depression has often been cited as a likely source of these nutrients, but our findings indicate that this can only be true for the last 1,000 years."

The findings reveal a bit more about this region and show how it turned from a massive lake into a desert area in only a few hundred years.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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