Lidar for Site Prospection

In this review, I explore instances of archaeological discoveries made through lidar prospection that were sensationalized in the press. Over the last two decades, lidar (light detection and ranging) technology has dramatically changed the investigation of past cultural landscapes. Reconnaissance and mapping of ancient spaces, which used to take years, if not decades, to complete, are now prospected in a matter of hours with greater accuracy (Reese-Taylor et al. Reference Kathryn, Armando Anaya Hernández, Monteleone, Uriarte, Carr, Geovannini Acuña, Peuramaki-Brown and Dunning2016). As well, the ability to gather spatial data over large regions has increased the scale at which archaeologists are able to engage with ancient landscapes (Figure 1). Lidar surveys have revealed great expanses of land containing multiple settlements with monumental architecture, infrastructure, and landscape modifications, some of which were previously unknown to a great swath of the populace. As a result, archaeologists now work at much larger scales, fundamentally changing how we conceive of ancient societies in ways that are still unfolding (Bickler Reference Bickler2021; Canuto et al. Reference Canuto, Estrada-Belli, Garrison, Houston, Acuña, Kováč and Marken2018; Chase et al. Reference Chase, Chase, Fisher, Leisz and Weishampel2012, Reference Chase, Reese-Taylor, Fernandez-Diaz and Chase2016; Evans et al. Reference Evans, Fletcher, Pottier, Chevance, Soutif, Suy Tan and Sokrithy2013; Fisher et al. Reference Fisher, Cohen, Carlos Fernández-Diaz and Leisz2017; Inomata et al. Reference Inomata, Carlos Fernandez-Diaz, Triadan, García Mollinedo, Pinzón, García Hernández and Flores2021).

Figure 1. Comparable platform complexes from Veracruz and Tabasco, Mexico, exemplifying a regional landscape analysis aided by lidar (from Inomata et al. Reference Inomata, Carlos Fernandez-Diaz, Triadan, García Mollinedo, Pinzón, García Hernández and Flores2021:Figure 4).

An interesting phenomenon that has developed out of these scientific lidar site mappings is the concept that such prospections often lead to the discovery of formally unknown “lost cities,” a concept fueled by news articles aimed at popular audiences. To examine this press sensationalization, I have selected for analysis three examples of academic articles from among countless publications that highlight lidar findings.Footnote ¹ Each article considered here has recently been published in a major journal and was subsequently the subject of media hype in numerous news outlets. These examples are representative of the types of change in tone, emphasis, and words that skew archaeological findings to the point that they are difficult to distinguish from the pseudoscientific posts that heavily populate our social media.

Example 1: Low-Density Urbanism in the Amazon

On May 25, 2022, Heiko Prümers and colleagues published the results of a lidar reconnaissance in the Bolivian Amazon in the prestigious journal Nature (Prümers et al. Reference Prümers, Jaimes Betancourt, Iriarte, Robinson and Schaich2022). The title of the article, “Lidar Reveals Pre-Hispanic Low-Density Urbanism in the Bolivian Amazon,” was understated, perhaps by design. In my experience, archaeologists generally seek to avoid dramatic wording in their academic papers. The authors clearly note that this work builds on earlier investigations in the region using remote-sensing and field reconnaissance that identified “189 large monumental sites (locally known as ‘lomas’), 273 smaller sites and 957 km of canals and causeways” (Prümers et al. Reference Prümers, Jaimes Betancourt, Iriarte, Robinson and Schaich2022:325; see Lombardo and Prümers Reference Lombardo and Prümers2010; Prümers and Betancourt Reference Prümers and Jaimes Betancourt2014). The findings reported in 2022 highlight the extent of and investment in architecture of two previously known settlements in the region, as well as a “highly integrated, continuous, and dense settlement system” (Prumers et al. Reference Prümers, Jaimes Betancourt, Iriarte, Robinson and Schaich2022:327).

This article was then featured in an online news update by Nature at the time of its publication. The news item, entitled “‘Mind Blowing’ Ancient Settlements Uncovered in the Amazon,” mistakenly emphasizes, in the subtitle, that the urban centers were “the first to be discovered in the region,” which clearly conflicts with what the authors carefully outlined in their own article (Kreier Reference Kreier2022:16). In fact, the use of the term “mind blowing” in the title muddies the lead author’s use of the term in a statement concerning the overall complexity revealed by the lidar survey (Kreier Reference Kreier2022:16).

On May 26, 2022, Nature followed up its original news release with a video entitled “Lasers Reveal Ancient Pyramids and Canals Hidden in the Amazon: Hundreds of New Archaeological Sites Have Been Discovered beneath the Trees” (Bundell Reference Bundell2022). This almost six-minute video is a skillfully edited documentary that features the lead archaeologist, Heiko Prümers, who discloses that the mounds in the area were previously known by people living nearby. This is revealing, as it is the first recognition of local knowledge in the region.

The Smithsonian Magazine picked up the story on May 25, 2022, as well. Their eye-catching title, “Lost Cities of the Amazon Discovered from the Air,” conveys a complete lack of regard for the original academic article authors’ care in contextualizing their discovery (Handwerk Reference Handwerk2022). This news item erroneously states that “scientists have discovered that ancient cities really did exist in the Amazon,” as if the presence of these and other settlements were only exposed by the lidar survey, when in fact Prümers and others—including Michael Heckenberger, who is quoted in the article—have been identifying large settlements in the Amazon rainforest for over two decades (de Souza et al. Reference de Souza, Pahl Schaan, Robinson, Damasceno Barbosa, Aragão, Marimon and Schwantes Marimon2018; Heckenberger et al. Reference Heckenberger, Christian Russell, Fausto, Toney, Schmidt, Pereira, Franchetto and Kuikuro2008; Iriarte et al. Reference Iriarte, Sarah Elliott, Alves, Gonda, Mark, Jonas Gregorio, Jennifer and Josephine2020; Lombardo and Prümers Reference Lombardo and Prümers2010; Prümers and Betancourt Reference Prümers and Jaimes Betancourt2014).

Shortly after these initial news articles were released, secondary internet sources recapitulated content without reading the original article and therefore often echoed the distortions found in the news items (Archaeology Newsroom 2022; Henricks Reference Henricks2022; Snyder Reference Snyder2022). In fact, an Axios article (Synder Reference Snyder2022) erroneously states (in a bold heading) that Prümers and colleagues’ (Reference Snyder2022) publication documents the first time lidar technology was used in the Amazon region, disregarding an earlier study by Iriarte and colleagues (Reference Iriarte, Sarah Elliott, Alves, Gonda, Mark, Jonas Gregorio, Jennifer and Josephine2020) that used lidar to reveal details of circular mound villages and interconnecting roads in southwest Amazonia.

Example 2: Garden Urbanism in the Tropical Rainforest

A more recent article in Science, titled “Two Thousand Years of Garden Urbanism in the Upper Amazon,” was also the focus of a media blitz (Rostain et al. Reference Rostain, Dorison, de Saulieu, Prümers, Le Pennec, Mejía Mejía, Maritza Freire, Pagán-Jiménez and Descola2024). In this study, Rostain and colleagues analyzed lidar commissioned by the Ecuadorian National Institute for Cultural Heritage (INPC) in 2015. The results of their analyses demonstrated a densely populated region, with communities and agricultural fields interconnected by an extensive road system. Within the article, the authors are careful to acknowledge previous studies in the area identifying and exploring large settlements formed by groups of earthen platforms (Rostain et al. Reference Rostain, Dorison, de Saulieu, Prümers, Le Pennec, Mejía Mejía, Maritza Freire, Pagán-Jiménez and Descola2024:183). In addition, the authors note the modern towns in the region, including Macas, the capital of the Morona Santiago province (Rostain et al. Reference Rostain, Dorison, de Saulieu, Prümers, Le Pennec, Mejía Mejía, Maritza Freire, Pagán-Jiménez and Descola2024:184).

The innocuously titled article caused a news frenzy, with an extraordinary number of news outlets promoting the research. Over 19 news outlets, including CNN, BBC, NBC, AP, Newsweek, the Guardian, and the Daily Mail, all ran stories regarding the discovery in the aftermath of the publication (Agence France-Presse [AFP] 2024; Anderson Reference Anderson2024a; CBS News 2024; Dyer Reference Dyer2024; Gao Reference Gao2024; Georgiou Reference Georgiou2024a; Guardian 2024; Guesgen Reference Guesgen2024; Khalil Reference Khalil2024; Larson Reference Larson2024; Mishra and Kumar Reference Mishra and Kumar2024; New York Post 2024; Orie Reference Orie2024; Rannard Reference Rannard2024; Rommen Reference Rommen2024; Silverstein Reference Stein2024; Stein Reference Stein2024; Voice of America 2024; Weissman Reference Weissman2024; Yuhas and Jiménez Reference Yuhas and Jiménez2024). A word cloud of article titles from 13 major outlets represents the relative occurrence of words. A total of 52 unique words were included, the four most frequent being “city/cities” (N = 12), “lost” (N = 11), “Amazon” (N = 11), and “ancient” (N = 7) (Figure 2).

Figure 2. Word cloud generated from media article titles.

This word cloud also reflects the tone of the news articles, emphasizing the discovery of a lost city or cities. The BBC article entitled “The Discovery of the Americas’ Long-Lost ‘Rome’” is perhaps the most sensationalized of the lot (Stein Reference Stein2024). While Rostain and colleagues are measured in their article, the BBC publication imparts comparisons that could be considered overstatements, albeit to make a point. While the impressive evidence of 6,000 structures within 300 km², a well-engineered network of road systems, and an enormous investment in landesque capital in the Amazon dated to AD 300–500 indicates a large population with incredible ingenuity, it hardly compares with Rome, which had a population of roughly one million people at AD 300.

What is striking in the news coverage, however, is the failure to acknowledge previous studies in the area, often by local scholars, that also contributed to current understandings of Amazonian settlements in the study area. The lack of recognition, unconscious or not, downplays the role of local Indigenous knowledge in protecting cultural patrimony. This is in stark contrast to an article published by the Tico Times, a Costa Rican newspaper, which does a credible job of correcting these omissions. In that news report, entitled “Ecuador’s 2,500 Year Old ‘Lost City’ Uncovered—But Is It Too Late?,” AFP journalists point out that one of the largest settlements in the study area covered in the article by Rostain and colleagues (Reference Rostain, Dorison, de Saulieu, Prümers, Le Pennec, Mejía Mejía, Maritza Freire, Pagán-Jiménez and Descola2024) was originally discovered in 1978 (AFP 2024). The AFP news article also notes previous work by Alejandra Sánchez, an archaeologist from the University of Valladolid, who found that the cultural heritage was critically endangered because of erosion, deforestation, and agriculture, which ultimately led to the original lidar scan of the area by the INPC in Ecuador. Sánchez and Argentinian Rita Álvarez presented an analysis of the lidar in 2023, which was referenced by Rostain and colleagues (Reference Rostain, Dorison, de Saulieu, Prümers, Le Pennec, Mejía Mejía, Maritza Freire, Pagán-Jiménez and Descola2024:183, 189). The AFP news article also highlights the work of an Ecuadorian archaeologist, Alden Yépez, who is investigating the interconnected drainage systems in the region. Finally, the news article includes comments by Catalina Tello, director of the INPC, who commits to including the Shuar and Achuar Indigenous people in studies of the area because these people “have safeguarded and cared for all these vestiges” (AFP 2024).

Example 3: Urbanism at High Altitudes

Moving to another area of the world, Michael D. Frachetti and colleagues’ recent publication “Large-Scale Medieval Urbanism Traced by UAV–Lidar in Highland Central Asia,” in the journal Nature on October 23, 2024, provides a perspective from a high-altitude region in Uzbekistan (Franchetti et al. Reference Frachetti, Berner, Liu, Henry, Maksudov and Tao2024). In this highly technical study, the authors outline the use of UAV (uncrewed aerial vehicles)–lidar to create very high resolution surface reconstructions. While the majority of the article details the use of lidar and semiautomated feature detection for the mapping and classification of architecture and infrastructure, including important fortifications, the authors also conclude that the highland cities on the medieval Silk Road were larger than initially thought and instrumental in providing security and connectivity along this critical East–West trade route (Franchetti et al. Reference Frachetti, Berner, Liu, Henry, Maksudov and Tao2024:1123).

Importantly, on the second page of the article, Franchetti and coauthors (Reference Frachetti, Berner, Liu, Henry, Maksudov and Tao2024:1119) clearly state that the sites scanned, Tashbulak and Tugunbulak, were first discovered in 2011 and 2015, respectively. While Nature News (Silvia Reference Silvia2024) reported a very accurate synopsis of the original article, a Nature podcast strayed from the original intent of the article (Howe and Bates Reference Howe and Bates2024). Entitled “Massive Lost Mountain Cities Revealed by Lasers” and published on October 23, 2024, the podcast was somewhat contradictory, leading to a mixed message. The title clearly emphasizes the “lost” nature of the cities, yet in an interview for the podcast, Franchetti and Farhod Maksudov from the Uzbekistan Academy of Sciences, authors of the lidar study, stress that historical records recounted huge cities in the region.

Not surprisingly, major news outlets picked up on the “lost cities” theme. CNN reported “Lost Silk Road Cities Mapped Using Remote Sensing” (Hunt Reference Hunt2024); Scientific America announced “Lost Silk Road Cities Discovered High in the Mountains of Central Asia” (Parshall Reference Parshall2024); NBC titled its news release “Lost for Centuries, Silk Road Cities Are Revealed by Drone Technology” (Peart Reference Peart2024); and Reuters reported “Scientists Document Lost Mountain Cities on Silk Road in Uzbekistan” (Dunham Reference Dunham2024). Out of 22 media reports on the findings, 15 included the word “lost” in the title, one included “forgotten,” and two included either “buried” or “unearthed” (Anderson Reference Anderson2024b; Bower Reference Bower2024; Corbley Reference Corbley2024; Dunham Reference Dunham2024; Elymc 2024; Georgiou Reference Georgiou2024b; Hunt Reference Hunt2024; Kesteloo Reference Kesteloo2024; McPhee Reference McPhee2024; Natale Reference Natale2024; Nazaryan Reference Nazaryan2024; Ng Reference Kelly2024; Parshall Reference Parshall2024; Peart Reference Peart2024; Radley Reference Radley2024; Schwaller Reference Schwaller2024; Sinha Reference Sinha2024; Zahid Reference Zahid2024).

This begs the question, what does it mean to be “lost”? In this specific case, the word “lost” appears to be tied to a lack of scientific documentation. Despite well-known historical documents describing cities in the region and pedestrian surveys recording their presence in 2011 and 2015, the news media’s overt message is that the cities remained unknown until a lidar survey revealed them.