What Happened To Nan Madol? The Answer Holds A Grim Warning For Our Future

We live in unprecedented times. With global average temperatures soaring to levels last recorded… well, never , extreme weather events set to disrupt the lives of basically everyone from now on , and sea levels rising , it’s hard to imagine how societies worldwide going to cope in the near future.

But perhaps we can take some cues from the past – and specifically, from the tiny Pacific Island of Pohnpei. It was there, according to a new paper from an international team of researchers, that a period of climatic upheaval hit the then-reigning Saudeleur Dynasty – causing not just the demise of the local regime, but changing the entire course of the island’s history.

It’s a lesson from history – but it may not be one we want to learn.

The story of Pohnpei

Sitting in the Pacific Ocean between Honolulu and Manila, Pohnpei is the largest state of the four Federated States of Micronesia. The entire island is around the size of the city of Philadelphia.

These days, the nation mostly runs on a mix of subsistence farming and financial aid from the US – it was actually only in 1986 that Micronesia gained independence from the latter country, and the currency is still the US dollar.

A thousand years ago, though, Pohnpei was a hive of construction. Starting in the 10th century, with the establishment of the first organized government across the island, the new Saudeleur dynasty set about building the city of Nan Madol: a “monumental complex,” the team describes in their paper, “ megalithic architecture that at one time served as the capital of an island-wide chiefdom.”

Outside of this new study, which used uranium-thorium and carbon dating on hundreds of samples around the site to sharpen up the chronology, not much is known about the city. Few other excavations have been carried out there, and those that do exist have rarely met current standards of evidence and reporting.

What little we do know, though, suggests that Nan Madol in its heyday would have looked very different from the semi-submerged ruins that sit on the eastern shore of Pohnpei.

“Nan Madol is today located in the intertidal zone at the eastern foot of Temwen Island, Pohnpei,” the team writes. “It is a large village, mortuary, and religious complex that consists of over 100 large and small artificial islets constructed with basalt boulders and coral rubble, separated by navigable canals, and surrounded by a massive seawall.”

A millennium ago, however, “the entire site […] may have sat on dry land, instead of its present condition with islets and canals,” they explain.

For a few centuries, Nan Madol was the bustling center of the island government: the dynasty was at its peak, and so was the scale of the building projects in the capital. But fairly suddenly, all that construction just kind of… stopped. By the early 15th century, the site was all but abandoned.

So… what happened?

What happened to Nan Madol?

Any society, they say, is no more than three meals away from revolution. It’s certainly pithy, albeit hammed up somewhat from its original formulation – but in the case of Nan Madol, it might be right on the money.

“The halt in constructions in the early 15th century follows the commencement of the Little Ice Age,” the team points out – a time when the tropical Pacific very suddenly became much drier and colder than before, especially since the “before” in this case was the Medieval Warm Period.

“Around [CE] 1300 the entire Pacific Basin […] was affected by comparatively rapid cooling and sea-level fall, and possibly increased storminess, that caused massive and enduring changes to Pacific environments and societies,” notes one 2010 paper by Patrick Nunn, now Professor of Geography at the University of the Sunshine Coast in Australia.

“For most Pacific societies […] the effects of this [CE] 1300 Event were profoundly disruptive,” Nunn explains, “largely because of the reduction in food resources available in coastal zones attributable to the 70–80-centimeter sea-level fall.”

It’s a compelling, if untested, hypothesis – but it isn’t the whole story. “We analyzed 167 coral ²³⁰ Th ages from 18 islets and 18 charcoal ¹⁴ C ages of 2 islets,” the team reports. “Combined with previous coral and charcoal ages, the results express two major phases of construction." This "potentially links subsidence/ENSO events to the construction sequence.”

If the initials ENSO aren’t ringing any bells, allow us to explain: they’re talking about El Niño–Southern Oscillation. Unpredictable and ill-understood , this phenomenon has the potential to devastate Pacific Island communities even today, thanks to dramatic rises and falls in sea levels, droughts and flash floods, reduced crop yields, and widespread health problems due to bacterial spread.

And for the 15th-century Pohnpeians, it brought something else as well: the Sisyphean task of maintaining their city. “Dating results reveals that the history of construction at Nan Madol reflects a people drawn into a cycle of repair and investment into protections from future coastal disasters,” notes the team. “ENSO events, which would have brought episodic damages, and subsidence, which would have made slow incremental damage, for centuries were met with resilience rather than abandonment or social reorganization.”

“These same forces may have eventually contributed to the end of the island-scale chiefdom and a halt to new construction at its capital,” they write.

What should we learn?

So, there we have it: the tragic story of an island nation that fought climate change and lost, ultimately leading to the complete overthrow of the ruling class and a reorganization of society at large. Surely there’s nothing applicable to today there?

We jest: the fate of Nan Madol is, of course, a cautionary tale about the effects of global warming. “This case gives us a long-term antecedent model for the challenges island communities around the world face through climate change,” the team writes. “As a mirror on the possible fate of island lifeways, our study stands as a prescient warning.”

We’ve already seen some pretty dire consequences from ENSO: villages across the Pacific are being lost to the sea; dozens of islands are straight-up sinking as ocean levels rise; best of all, it’s only going to get worse .

For those who live in these most affected areas, the choice is going to be simple – though not easy. They can either try to fight the rising tide – or, like the one-time residents of Nan Madol, they can cut their losses and move on.

“With the current intensification of variabilities of ENSO in the Pacific Ocean and its counterpart, Indian Ocean Dipole, in the Indian Ocean along with sea level rise exceeding 3mm/year, the coming decades will likely experience the inundation of more islands and an increase in the numbers of climate refugees,” the team write.

“The case of Nan Madol raises the question of whether ongoing climate change will lead to the abandonment of coastal and oceanic communities, or prompt investment in local infrastructure for climate migitation.”

The study is published in the journal PNAS Nexus .