INAH
The Mayan "Long Count" calendar and theories about its connection to an apocalypse in 2012 have long been a topic of controversy.
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updated 12/5/2011 6:13:50 PM ET 2011-12-05T23:13:50

For generations, the Maya thrived in an advanced, complex civilization in modern-day Central America. But then their society collapsed in the eighth and ninth centuries. Now, a new study finds that the Maya may have had a hand in their own apocalypse.

Deforestation in Central America before Europeans arrived contributed to drought in the region, according to the research presented Monday here at the annual meeting of the American Geophysical Union. Researchers have long suspected that drought contributed to the demise of Mayan civilization, though other factors such as conflicts and overpopulation may have also hastened the Maya's doom.

Using new reconstructions of vegetation stretching back 2,000 years, NASA Goddard Institute for Space Studies climatologist Benjamin Cook and colleagues found that forest-clearing by Mayan farmers worsened drought conditions in the area.

In fact, past research has shown similarly that the ancient South American Nazca civilization (known for large geoglyphs called Nazca lines ) may have caused its own demise by clear-cutting large swaths of forest.

In the case of the Mayans, how did relatively primitive farmers manage to affect the weather? When the Mayans cleared forests, they exposed land surface with a higher albedo, or reflectivity, than the dark-green forest canopy. This land surface reflected energy back into the atmosphere rather than absorbing it, lessening the amount of energy on the land surface available to do things like convect water vapor to form clouds and thus rain. The result, Cook said, was a decline in precipitation by 10 percent to 20 percent.

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With less rain, the soil dried out, so any extra energy went to warming the surface rather than evaporating water. The result was a rise in surface temperature by 0.9 degrees Fahrenheit (0.5 degrees Celsius). The lack of rainfall and boost in heat would have been bad news for a society whose survival depended on their farmlands.

Cook and his colleagues compared vegetation cover during pre-Columbian years (before A.D. 1492) and then after the Europeans' arrival. The fallout from the European invasion destroyed the population by up to 90 percent in areas, and the result was a regrowth of forest as human pressures were reduced. Cave records confirm the pattern of drying during deforested periods and more precipitation when forests bounced back.

According to Cook, an examination of these records suggests that deforestation contributed to about half of the drought experienced by the Mayans. Rainfall levels declined by as much as 20 percent over the Yucatan between A.D. 800 and A.D. 950.

"I wouldn't argue that deforestation causes drought or that it's entirely responsible for the decline of the Maya, but our results do show that deforestation can bias the climate toward drought and that about half of the dryness in the pre-Colonial period was the result of deforestation," Cook said.

Today, the fate of the Maya is again of interest, given rumors of a 2012 "apocalypse" predicted in Mayan calendars. Maya experts say that these rumors are wrong-headed and that the Mayan people would have thought of the calendar restarting on that date, rather than the world ending.

More pressingly, deforestation is once again rampant in Central America, Cook told an audience at the AGU meeting: "We could see these sorts of things happen again."

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

© 2012 LiveScience.com. All rights reserved.

Explainer: Tales of seven cities, lost and found

  • Science / AAAS

    The Lost City of Z, a fabled metropolis of unimagined riches deep in the Amazon rain forest, has eluded explorers for centuries. But recently documented traces of a well-planned constellation of walled settlements arranged around central plazas and linked together with arrow-straight roads in the Upper Xingu region of the Brazilian Amazon may be the civilization that gave birth to the legend, scientists say. This image shows the charred remains of a house in the region that was uncovered as part of an archaeological project led by the University of Florida's Michael Heckenberger.

    Click the "Next" label for six more tales of cities lost or found.

    — John Roach, msnbc.com contributor

  • Atlantis legend inspires hotel chain

    Joel Ryan  /  AP

    According to the Greek philosopher Plato, Atlantis was a powerful society that disappeared under the sea in a torrent of earthquakes after it failed to take the city of Athens. Some scholars consider Plato's account as purely fictional; others have scoured the world for evidence of its existence. One disputed theory holds that Atlantis was on a portion of the Mediterranean island Cyprus that was submerged during an earthquake thousands of years ago. The mythical allure of the lost city has spawned a luxury hotel chain. In this image, fireworks explode over the opening of the Atlantis resort in Dubai.

  • What happened to the lost colony of the Americas?

    Gerry Broome  /  AP

    Sometime in the late 1580s, 117 English colonists disappeared while attempting to become the first to settle the New World. Their settlement on what would become Roanoke Island, N.C., was found abandoned in 1590. To this day, scientists, scholars and the plain curious can't agree on what happened. Some people believe the colonists assimilated with neighboring Native Americans; others think they were either killed by their neighbors or sunk at sea while trying to flee. In the image shown here, Frank Ray, a member of the Lost Colony Center for Science and Research looks for clues that could help solve the mystery.

  • Lost city of Ubar found

    NASA

    From about 2,800 BC to AD 300, the city of Ubar in the Arabian Desert served as an outpost for the lucrative trade in frankincense, a sweet-smelling gum resin. Then, according to myth, the city sank in the sand, lost forever. And so it was until archaeologists armed with everything from ancient texts to remote-sensing technology on the space shuttle went looking for the lost city. The diffuse reddish streaks in this radar image from the space shuttle show ancient paths leading to and around the ancient site, which had literally sunk into an underground water hole. Ubar's discovery is an example of scientific sleuthing verifying ancient lore.

  • Lost city of the Incas remains a mystery

    Giulio Magli

    In 1911, U.S. explorer Hiram Bingham scrambled up a steep mountain side in southern Peru and encountered an ancient city of sorts beneath the undergrowth. The site, Machu Picchu, is popularly known as the Lost City of the Incas. What exactly the city was, however, remains a mystery. Scholars have variously theorized it was the birthplace of the Incas, a private estate, and a spiritual destination. Prior to Bingham's encounter, the city was lost to the jungle for about 500 years.

  • Itil, lost capital of Khazars, found?

    Dmitry Vasilyev  /  AP

    The excavated buildings shown here south of Moscow, Russia, may be remains of Itil, the capital city of the Khazars, a Russian scientist has reported. The Khazars ruled the steppes from Northern China to the Black Sea between the seventh and 10th centuries. Once conquered by the Russians, Itil disappeared without a trace. Some scholars believe it was swamped by the nearby rising Caspian Sea in the 14th century. Scientist Dmitry Vasiley at Astrakhan State University believes these flamed brick buildings are part of what was once Itil.

  • Layers of Troy found in Turkey

    Warner Bros. via Reuters

    Homer's epic poem the "Illiad" famously describes a war in the city of Troy, replete with tales about the heroic Greek warrior Achilles and a wooden horse. Questions about whether the city really existed appeared resolved in the 1800s when journalists, archaeologists and others zeroed in on a site and excavated the ancient city. The so-called archaeological Troy consists of nine cities built on top of one another and denoted with Roman numerals. Scholars believe Troy VI and Troy VII correspond with the city described in the Iliad. This image from the movie "Troy," which was based on the Iliad, shows the famous Trojan horse.

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