During the fall of the Maya civilization over 1,000 years ago, kings were killed in public, captives were taken hostage, and in one notably violent event in the city of Aguateca, Maya fled their homes during a surprise assault, without time to even grab their belongings.
Though warfare can't be ignored, the toppling of the classic Maya civilization -- renowned for its massive stone temples and astronomical observatories -- is believed to have another formidable culprit: crippling drought. And for the first time, scientists have deduced just how severe this centuries-long drought may have been.
Rainfall was slashed in half over a vast swath of the low-lying Maya lands, researchers demonstrate in a study published in the journal Science on Thursday. Over this 200-year period, rainfall sometimes plummeted by 70 percent in the region, which encompasses much of today's Yucatan Peninsula in Mexico.
"If you imagine your local area, imagine if rainfall was reduced by half -- but [for] over a hundred years," Nick Evans, a lead author of the study and paleoclimatologist at the University of Cambridge, said in an interview.
Many lands would simply turn to desert, or doom once fertile agricultural areas.
Take Los Angeles today, which historically gets 14 or 15 inches of rain a year. A decline by half, combined with the sun drying the land, would almost certainly transform it into an arid desert. And, unlike Californians today, the Maya didn't have the benefit of 21st century aqueduct and reservoir systems. They lived on an expanse of flat land with little surface water.
They needed rain dearly: Stone-carved masks of the Maya's rain god "Chaac" are prevalent throughout the ruins of the society.
Hunting for ancient water
To give the Maya drought a firmer number, Evans and his team gathered sediments from the bottom of Lake Chichancanab, a long, slender, salty lake in the heart of Maya country.
They were in search of the mineral gypsum, which when forming, grabs water from the lake and traps the molecules. During times of evaporation, lakes become heavier in certain types of the water's oxygen and hydrogen, which gave researchers a confident idea of how fast the lake was disappearing.
"It's almost like measuring the lake water itself," said Evans.
Jason Briner, a paleoclimatologist at the University at Buffalo who had no involvement in the research, called the study "very elegant," allowing the scientists to narrow in on just how much -- or little -- rain fell during the decline of the Maya.
"Bottom line: A series of droughts with 50 percent the average rainfall probably played a big role in a major shift in Maya civilization at that time," Briner said over email.
A crippling drought may have further unsettled an already failing political structure, where elite royalty ruled society. Strained agricultural land may have also led to collapses in crop yields.
And overpopulation -- as estimates range that between 3 million and 11 million Maya inhabited the area -- may have precipitated a scarcity of resources, further destabilizing the once infallible elites.
"If it all comes together, you may have a perfect storm," Daniela Triadan, an anthropologist at the University of Arizona who studies the Maya's mysterious past, said in an interview.
The fall of the Maya
The fall of the Maya, however, didn't completely extinguish their people.
"They didn’t quite disappear," Takeshi Inomata, also an anthropologist at the University of Arizona who had no involvement in the study, said in an interview.
Maya descendants still live in the area today. Rather, the major Maya centers, built by elites, collapsed, said Inomata.
These congested cities or population centers were already likely difficult places to live, even in the best of times.
"It was probably incredibly smelly and dirty, with people dumping garbage outside of their houses," said Triadan. "It was sweaty, and hotter than hell."
And then, in some of these heavily populated places, the terrible drought came, and didn't lift for centuries.
However, drought can't explain why everyone in Maya society abandoned their cities and villages.
In the vast expanse of the southern lowlands, Inomata and Triadan said people deserted some flourishing population centers before the drought even hit.
"Why did the southern region seem to be doing well, and then why were they the first to leave and not come back?" asked Triadan. "I don’t think we can reduce it to climatic issues."
The Maya civilization, then, declined in different ways in different areas, over a few centuries.
"The situation in each of these cities wasn’t the same," noted Triadan.
The ancient drought is worth considering today, as climate change is driving precipitation extremes around the globe, like in California and parts of Africa.
"One might argue that we are more resilient to climate change than our predecessors -- that we are able to better weather the types of drought conditions in California, or elsewhere across the West," said Briner.
"As much of the West is currently in flames, I’m not so convinced," he said, noting the large fires currently besieging California.
"And, as many drought-prone areas around the world become drier, climate change will stress the already stressed harder," he added. "Yikes."
