UNLV geoscientist Matthew Lachniet and an international team of researchers used stalagmites to unveil a 2,400-year climate history from southwestern Mexico. This discovery, coupled with archaeological evidence, links the rise and fall of ancient Mesoamerican civilizations to changing rainfall. The findings were reported Jan. 23 as a “Pre-Issue Publication” of the journal Geology.

Little is known about what contributed to the fate of the prosperous ancient Mesoamerican city of Teotihuacan, though historic evidence suggests periods of above average rainfall followed by extreme drought might have played a role.

“Mexico and the American southwest are linked by climate processes in the Pacific Ocean. Our new record shows that dry conditions, likely linked to El Nino processes, recurred frequently over time,” said Lachniet. “The point to be made is that civilization runs on water. Take away a water supply and the civilization may fail.”

Lachniet and his team collected and analyzed a stalagmite from Juxtlahuaca Cave in Guerrero, Mexico. The cave is in the core region of the North American Monsoon, a climate phenomenon primarily responsible for rain in most of Mexico and parts of the American Southwest. The cave was also a great source for stalagmites – common cave formations formed over thousands of years as minerals from water droplets crystallize and accumulate. Much like tree rings, they can accurately record the rainfall history of an area.

“Only recently have scientists started to unlock the secrets of stalagmites as ancient rain gauges,” said Lachniet. “Stalagmites from tropical regions provide a much longer record than tree rings. They also grow rapidly which allows us to pinpoint climate variations on near-annual timescales.”

The team correlated the region’s cultural milestones with measured rainfall. Above average rainfall between the first and third centuries coincided with the rise of the early Mesoamerican city of Teotihuacan. At its peak, more than 125,000 people lived around the massive pyramids in the highly developed city.

Conversely, a 500-year drying trend, including a drought of more than 150 years, coincided with rapid population decline in Teotihuacan around 550 CE. The drought likely impacted spring-fed agriculture practices in the semi-arid Mexican Highlands.

“We can’t say with certainty that other social factors were drivers of the cultural change, but we now have well-dated and robust climate information to compare,” said Lachniet. “Climate change was the norm for the region dating back thousands of years, and similar variations are to be expected for the future.”

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The longest running Citizen Science survey in the world, Audubon’s annual Christmas Bird Count (CBC) will take place from December 14, 2011 to January 5, 2012. Tens of thousands of volunteers throughout North America will brave winter weather to add a new layer to over a century of data.

“Audubon was a social network before the world ever heard the term,” notes David Yarnold, Audubon President & CEO. “Each December the buzz from our social network goes up a few decibels, as people with the knowledge and the passion for birds provide what no organization alone can.”

“It’s a globally recognized example of crowd-science,” says Gary Langham, Audubon’s Chief Scientist, who took his young daughter and wife on last year’s CBC. “Audubon’s Christmas Bird Count is also a tradition that does good things for families, communities, and the conservation movement.”

Scientists rely on the remarkable trend data of Audubon’s CBC to better understand how birds are faring in North America and beyond our borders. ”Data from Audubon’s Christmas Bird Count are at the heart of hundreds peer-reviewed scientific studies,” adds Dr. Langham; “CBC data have informed the U. S. State of the Birds Report, issued by the Department of the Interior, and modeled after Audubon’s annual reports begun in 2004.

For example, in 2009, CBC analyses revealed the dramatic impact Climate Change is already having on birds across the continent.” ”Everyone who takes part in the Christmas Bird Count plays a critical role in helping us focus attention and conservation where it is most needed.” said Audubon’s Christmas Bird Count Director, Geoff LeBaron.

“In addition to Audubon’s reports on the impacts of Climate Change on birds and our analysis of Common Birds in Decline, it is the foundation for Audubon’s WatchList, which most identified species in dire need of conservation help.”

The Audubon Christmas Bird Count began in 1900 when Frank Chapman, founder of Bird-Lore (which evolved into Audubon magazine) suggested an alternative to the “side hunt,” in which teams competed to see who could shoot the most game, including birds.  Chapman proposed that people “hunt” birds only to count them.

Chapman’s initiative was described by British actor John Cleese in this video clip from The Big Year. Last year’s count shattered records. A total of 2,215 counts and 62,624 people tallied over 60 million birds. Counts took place in all 50 states, all Canadian provinces, plus 107 count circles in Latin America, the Caribbean, and the Pacific Islands.

The first ever CBC tally was submitted from Haiti, where the count circle is located at Les Cayes, the birthplace of John James Audubon. In Colombia, the Audubon count is a crucially important monitoring system of biodiversity in the country.

Audubon CBC data not only helps identify birds in most urgent need of conservation action; it reveals success stories. The Christmas Bird Count helped document the comeback of the previously endangered Bald Eagle, and significant increases in waterfowl populations, both the result of conservation efforts.

Counts are often family or community traditions that make for fascinating stories. Accuracy is assured by having new participants join an established group that includes at least one experienced birdwatcher. Count volunteers follow specified routes through a designated 15-mile (24-km) diameter circle or can arrange in advance to count the birds at home feeders inside the circle and submit the results to a designated compiler.

All individual Christmas Bird Counts are conducted between December 14 and January 5 (inclusive) each season, with each individual count occupying a single calendar day.

The journal Nature issued an editorial citing CBC as a “model” for Citizen Science.

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