This Mayan City Died Out After Inadvertently Poisoning Its Own Water Supply. Our Mega-cities Could Be Next

As drought ravaged the land, the people of Tikal were dependent on their dwindling water reservoirs, which archaeologists now discover were fatally polluted

Ruth Schuster
Ruth Schuster
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The ancient Mayan city of Tikal, found in northern Guatemala.
The ancient Mayan city of Tikal showing a temple, found in northern Guatemala.Credit: Kimon Berlin
Ruth Schuster
Ruth Schuster

The Mayan civilization in southern Mexico and northern Central America began to take form around 4,000 years ago, and was marked by the first stabs at settlement and farming in the area. Though this was not an organized collective or alliance that called itself “Mayan” but an umbrella term for the peoples of the region, we can still say that in its “classic” phase – from about the year 300 to 1000 – the Mayan civilization would create great urban centers and even city-states, featuring monumental architecture, art, and hieroglyphic writing going back as much as 2,400 years.

And then, around a thousand years ago, it collapsed for reasons still being elucidated to this day. Archaeologists generally agree that the causes of the Mayan civilization decline include war, overpopulation, unsustainable practices to feed that population, and protracted drought.

Now a team of archaeologists reports in Nature that in Tikal, one of two major Mayan city-states, the water reservoirs had become contaminated with heavy metals and toxic algae. That likely contributed to the city’s sudden collapse in the ninth century.

Over a thousand years later, we can’t say we’re doing better. The ancient Mayans could not have grasped the broader climatic causes, or be able to forecast decades into the future. Today, we have technology and forecasting abilities, yet mega-cities around the world are running out of fresh water – from Cape Town in South Africa to Chennai and Bangalore in India, to Mexico City (you know where), São Paulo in Brazil, Beijing in China, Jakarta in Indonesia to London, and the list goes on. Have we (humans) taken sustainable measures that will ascertain a sustainable fresh water supply for human and beast? We have not.

Back in ancient Tikal, one of the foremost of the ancient Maya cities, write David Lentz of the University of Cincinnati and team, the water reservoirs in the city’s heart became so polluted with mercury, phosphate and cyanobacteria that the water would have been poisonous. This contribution to the demise of the city, whose remains are located in northern Guatemala, hadn’t been known until now.

A Guatemalan worker examining a well.
University of Cincinnati grad student Brian Lane climbs out of the Perdido Reservoir at TikalCredit: Nicholas Dunning / UC

Mega-drought in Mesoamerica

The climatic upheavals of Mesoamerica are recognized. In fact, in 2012 a separate team proposed in Science that the Mayan populations had been spurred to massively expand by anomalously high rainfall starting around 400. But from about 660, a trend of aridification began, culminating in terrible mega-droughts that lasted decades, from 820 to 870.

And thus the land lost its ability to sustain the population that had been fruitful and multiplied in wetter times.

Nor could the inhabitants of Tikal tap the groundwater: it was a good 200 meters (nearly 660 feet) below the surface and they didn’t have the technology. Nor did they have access to any rivers or lakes. So they had to rely on storing water in reservoirs that ringed the city, which would fill up during the rainy season, to drink during the dry. But if there was little to no rain, year after year?

The notion of storing water – from flood, rain, snow melt or whatever – goes back thousands of years. The ancients were building dams in the Levant over 6,000 years ago.

An artwork in the ancient Mayan city of Tikal.
An artwork in the ancient Mayan city of Tikal.Credit: Bjrn Christian Trrissen

Today, we know that a collection point for water that has no exit points, and is not periodically cleansed by flooding, will accrue minerals and salts. If water constantly or sporadically enters and only leaves by being extracted or evaporating, a toxic brew may ensue.

The people of Tikal channeled the rainwater from paved plazas to their reservoirs. The team analyzed sediment at the bottom of four of these reservoirs – two in the city center and two peripheral – to elucidate the quality of the water they had contained. The two reservoirs in the city center, called the Temple and Palace reservoirs, were found to have contained toxic levels of mercury, beyond what we would consider today to be heavily polluted – markedly during the “terminal classic period,” just before the city was abandoned.

Where did that mercury come from? Similarly to the source of lead in ancient Roman water systems and even food – the locals used it without fully realizing, or perhaps admitting, that it was deadly. In the case of the Mayans, they made intense use of cinnabar, a blood-red compound containing mercury, in dyes and paints, and in ritual activities.

“Virtually all of the elite burials at Tikal contained copious amounts of cinnabar,” the team writes – up to 10 kilograms (22 pounds) in one elite burial alone. They were also fascinated by liquid mercury, which archaeologists have found at numerous Maya sites, usually in pottery associated with ceremony and burials.

And that explains where the mercury in Tikal’s pools probably came from. The Temple and Palace reservoirs were fed runoff from a ceremonial burial zone, two ball courts, four major temples and two huge palace complexes. The archaeologists do note that, theoretically, mercury could have arrived from volcanic eruptions – but then it would have been more evenly dispersed.

An artwork found in the ancient Mayan city of Tikal.
Wooden lintel from a temple in TikalCredit: Bjrn Christian Trrissen

The archaeologists also found intense phosphate contamination in the late sediment layers of the Temple reservoir, which likely stemmed mainly from food detritus and sewage sanitation issues. In this case, the Mayans situated a kitchen serving the elites living on the Central Acropolis near the Palace Reservoir.

“Hundreds of years of smoky cooking fires and ceramic plates washed in the reservoir added organic material to the waters. To make matters worse, the Maya cooks apparently dumped food wastes right outside of the kitchen,” the archaeologists write, having founded the garbage dump right there. And when it rained, the rain would wash nasties from the kitchen and dump them smack into the reservoir.

The Palace reservoir also featured high phosphate contamination, but the two peripheral ones didn’t.

And finally we have intense cyanobacterial infection of the Temple and Palace. Cyanobacteria (aka blue-green algae) are the scourge of water storage everywhere. Possibly the first form of life on the planet, their survival for billions of years speaks to their hardiness. And the fouler the water with sewage, garbage and sundry spew, the happier they are. This is why water reservoirs globally are now suffering from intense cyanobacterial poisoning: because they’re polluted and the things love it and thrive.

Since they emit substances that are generally toxic to other life, us included, once a cyanobacterial bloom gains sway, it may become the dominant life-form in that body of water forever more. Or a least until an Israeli startup called BlueGreen Water Technologies came along and provided the first-ever affordable solution: as of writing, it has finally been able to treat a water body in China, where treatment had been held up by the coronavirus.

The ancient city of Tikal rises above the rainforest in northern Guatemala.
The ancient city of Tikal rises above the rainforest in northern GuatemalaCredit: David Lentz / UC

A thousand years ago, though, there was no succor for the infested Mayan reservoirs.

Forget the mercury and the phosphates. As the water level in the reservoirs fell and their mineral and phosphate concentration increased, the cyanobacteria would have been joyous. And once they took hold, even irrespective of the mineral contamination, the water was poisonous to drink. Even just using it to wash in could lead to a rash.

The water for drinking and cooking for the Tikal rulers and their elite entourage almost certainly came from the Palace and Temple reservoirs, they write – and thus the elite would have been poisoned with every meal. And thus, the combination of mega-drought with contaminated water reservoirs for the overpopulated city would have spelled the end for the people of Tikal, the archaeologists sum up. 

“The final demise of Tikal was a complex tapestry of interwoven calamities,” they write, and so it came to pass, and will come to pass in a host of cities today unless “the authorities” come to their senses. Almost exactly the same thing, minus the cinnabar, threatens mega-cities worldwide and the proliferation of desalination plants won’t solve the problem of growing populations with dwindling water supplies that are being contaminated by our ubiquitous waste.

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