Extensive, precise laser surveys carried out by aircraft over the tiny Pacific island of Temwen have revealed how advanced the lost city of Nan Madol once was.
This megalithic stone city is sometimes called the “Venice of the Pacific” and has been compared to the mythical Atlantis. It even inspired horror author HP Lovecraft, who used news of the site’s discovery in his 1928 book “The Call of Cthulhu.”
But now dozens of researchers are racing to uncover the full extent of Nan Madol’s ruins as they make plans to preserve the city as a UNESCO World Heritage site. World Heritage.
Their aerial surveys, conducted using LiDAR (Light Detection and Ranging) laser mapping, have revealed “a sophisticated and extensive landscape of agricultural features hidden beneath the vegetation of Temwen Island.”
The discovery promises to rewrite the history of many Pacific Island cultures, showing that societies once thought to be dependent on fishing and tropical natural resources actually practiced sophisticated agricultural planning.
Aerial surveys, conducted using LiDAR or ‘Light Detection and Ranging’, a laser mapping technique, have revealed ‘a sophisticated and extensive landscape of agricultural features hidden beneath the vegetation of Temwen Island’ – proving that planned agriculture was taking place
National Geographic explorer Albert Lin’s documentary series once called the ruins of Nan Madol (seen here from above) the “Ghost Town of the Pacific” in a 2019 edition of the program
“LiDAR,” this international team of researchers noted, “can reveal entire archaeological landscapes hidden beneath dense vegetation.”
‘This has led to it being compared to carbon dating as a groundbreaking technological advance in archaeology.’
Across Nan Madol — and in the dense tropical foliage where more of its ruins still lie hidden — scientists led by Baltimore’s Cultural Site Research and Management Foundation (CSRM) were able to map a network of irrigation terraces that once channeled valuable freshwater reserves through this stone city.
Archaeologists have long agreed that Nan Madol rose between 1100 and 1628 AD and fell after the fall of the local Saudeleur monarchs in the 17th century.
Considering that Temwen Island is barely larger than one square mile, hundreds of times smaller than many Hawaiian islands such as Oʻahu (1,670.7 square miles), the researchers were surprised to see this level of sophisticated landscaping.
As Dr. Douglas Comer, who led the project (and literally wrote the book on mapping archaeological landscapes from space), explained it this way: ‘The consensus among archaeologists was that there was no intensification of agriculture through formal field systems in Micronesia.’
Above are the results of the researchers’ Colorized Multi-directional Hillshade LiDAR Digital Terrain Model, which helped them map out islands and long-vanished man-made waterways at the site
Above is an aerial view of the man-made channels and islets on Nan Madol
But over the years, working with the local College of Micronesia, as well as Stanford, Sandia National Laboratories, and others, Dr. Comer’s team has come to question the older ideas that this culture thrived largely on fermented “breadfruit” (Artocarpus altilis).
This ‘astonishingly complex system of irrigated fields on Temwen Island’, as he put it in his book a press release from the US Department of Stateindicates early and advanced taro root cultivation, which would have provided greater food security and economic power.
“The Temwen system also bears resemblance to some Polynesian terrace systems, including the Kohala field system on the island of Hawaii,” his team wrote in the journal Remote perception in 2019, ‘and recently described the slope terraces at Tutuila in American Samoa.’
“This complexity is consistent with what we see in the LiDAR images of Temwen.”
In order to protect and preserve Nan Madol for posterity now, the team has coordinated with the United State Forest Service and Arbor Global last year to teach locals how to prevent the island’s wild vegetation from eroding the city’s stone structures.
Nan Madol’s protectors learned “how to use and maintain chainsaws, climb trees, prune branches, fell trees, and plant appropriate vegetation for the site,” the U.S. Forest Service said.
These skills are vital to restoring balance to the island’s ecosystem with these historic ruins, particularly the necessary replacement of many of the island’s wild mangrove trees. These grow quickly – up to 1.5 metres per year – partly because they reproduce as ‘mini-tree’ mangrove plants rather than ‘seeds’, literally growing on the ground.
“The vegetation not only hides the wonders of the place, it also destroys them,” said the The CSRM Foundation team put it in 2021.
Above, Kevin Eckert of Arbor Global teaches chainsaw “maintenance and safety” to a local team hoping to protect and preserve the ancient city of Nan Madol.
These forestry skills will be crucial to finally bringing the island’s ecosystem into balance with these historic ruins, particularly by replacing the island’s many wild mangrove trees – which can grow up to 1.5 metres tall in a single year, smothering or tearing apart the ancient ruins.
Above is a digital terrain model (DTM), sometimes called a ‘bare earth model’, derived from the LiDAR scans bouncing off the ground as opposed to what is bouncing off the forest canopy
The researchers had to rely on more than half a dozen software packages to interpret the results of their LiDAR scan data, also known as the “digital terrain model” (DTM).
Sometimes referred to as a “bare earth model,” the DTM maps LiDAR scan results from the ground, as opposed to the results “bounced” back from scanning lasers in the forest canopy.
A ‘Colorized Multi-directional Hillshade LiDAR’ DTM helped Dr. Comer and his team map hidden islands and long-lost man-made waterways at the site
“Multi-directional Hillshade,” they said, “generates grayscale 3D terrain renderings that combine light from six different directions, improving the visibility of terrain features.”
‘This tool proved particularly important in revealing the intricate patterns of flatlands, berms and water channels on Temwen Island. Many of these patterns are subtle, low-relief features,’ too subtle to detect without these pattern analysis tools.
However, the existence of these so-called ‘berms’ – constructed, raised banks along rivers and canals – was not only confirmed by these flying lasers and computer programs.
“Field observations have shown that the earthen walls between the low-lying areas act as water barriers,” Dr. Comer and his colleagues said, “and alter the natural flow directions that you would expect based on the underlying topography.”