New study on the collapse of Mayan civilization should be climate wake-up call

[turbinetree]

Under Trump's policies, the megadrought that devastated the Mayans will become the new normal.

JOE ROMM AUG 7, 2018, 12:37 PM

A new study finds that it was a severe and long-lasting megadrought that destroyed the great Mayan civilization a thousand years ago.

But the research has ominous relevance for us today since America’s top scientists have warned us that President Trump’s climate policies will make such civilization destroying megadroughts commonplace in the coming decades.

The Mayans had one of the world’s first written languages, used advanced mathematics, measured timed with an accurate calendar, produced durable rubber three millennia ago, and figured out “how to grow corn, beans, squash and cassava in sometimes-inhospitable places.”

Yet after reaching its height in its “Classic” period (250 AD – 800 AD), the Mayan empire collapsed over the next two hundred years. While many theories have been offered — including environmental degradation, war, and drought — researchers from Cambridge’s Godwin Laboratory for Palaeoclimate Research have shown that the collapse “correlated with an extended period of extreme drought.”

https://thinkprogress.org/a-megadrought-destroyed-the-mayan-civilization-were-next-92e10dea33c5/

[Brother Buzz]

1. As crazy as it sounds, there's evidence of the megadrought under a lake in the Sierra

An underwater forest reveals the story of a historic megadrought

A curved tree saw in his gloved hand, a scuba tank on his back, Phil Caterino worked quickly to slice through a pine branch 100 feet below the surface of a small tarn south of Lake Tahoe. Bubbles streamed from the regulator in his mouth, rising through the blue alpine water and green flecks of algae in Fallen Leaf Lake. That autumn day in 1997, Caterino briefly considered what would happen if he accidentally nicked the air hose running to his mouthpiece, or cut his orange dry suit, letting the 39-degree water rush in. "I'd be at the bottom of the lake, dead in about five minutes," he mused.

Having dived some 400 high-altitude lakes over the course of 30 years -- often reciting a protective Washoe prayer beforehand -- Caterino, director of the Lake Tahoe-based environmental nonprofit Alpengroup, doesn't shy away from occupational hazards. He surfaced a few minutes later, branch in hand. Even though the tree it came from had been stewing underwater for 800 years, it still smelled pungently of sap.

This botanic relic is one of several medieval trees, ranging from 68 to 100 feet tall, standing upright at the bottom of the lake. They grew during a 200-year megadrought in the Sierra Nevada between the 9th and 12th centuries, when precipitation in the area fell to less than 60 percent of the average between 1969 and 1992. Fallen Leaf Lake dropped about 150 to 200 feet below its current level, allowing the trees to grow above the lower shoreline. In the wetter years that followed, the lake quickly refilled, drowning the trees and sealing them in a liquid catacomb, safe from insects and fungi in the deep, low-oxygen water. There are also three older trees, which drowned between 18 and 35 centuries ago, standing upright on the lake floor, which suggests that severe droughts struck even further back in time.

The medieval trees' existence adds to the body of research documenting the Sierra Nevada's past megadroughts. Researchers have found stumps of long-dead trees in rivers, lakes and marshes in the region, indicating not one, but two medieval megadroughts -- the other lasting about 140 years in the 13th and 14th centuries, dwarfing the 20th century's Dust Bowl. Such megadroughts are a frightening prospect, and it's possible they could strike again.

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https://www.hcn.org/issues/44.22/underwater-forest-reveals-the-story-of-a-historic-megadrought