RESEARCH ◥ shows field systems in the low-lying wetlands RESEARCH ARTICLE SUMMARY and terraces in the upland areas. The scale of wetland systems and their association with dense populations suggest centralized planning, ARCHAEOLOGY whereas upland terraces cluster around res- idences, implying local management. Analy- Ancient lowland Maya complexity as sis identified 362 km2 of deliberately modified ◥ agricultural terrain and ON OUR WEBSITE another 952 km2 of un- revealed by airborne laser scanning Read the full article modified uplands for at http://dx.doi. potential swidden use. of northern Guatemala org/10.1126/ Approximately 106 km science.aau0137 of causeways within and .................................................. Marcello A. Canuto*†, Francisco Estrada-Belli*†, Thomas G. Garrison*†, between sites constitute Stephen D. Houston‡, Mary Jane Acuña, Milan Kováč, Damien Marken, evidence of inter- and intracommunity con- Philippe Nondédéo, Luke Auld-Thomas‡, Cyril Castanet, David Chatelain, nectivity. In contrast, sizable defensive features Carlos R. Chiriboga, Tomáš Drápela, Tibor Lieskovský, Alexandre Tokovinine, point to societal disconnection and large-scale Antolín Velasquez, Juan C. Fernández-Díaz, Ramesh Shrestha conflict. 2 CONCLUSION: The 2144 km of lidar data Downloaded from INTRODUCTION: Lowland Maya civilization scholars has provided a unique regional perspec- acquired by the PLI alter interpretations of the flourished from 1000 BCE to 1500 CE in and tive revealing substantial ancient population as ancient Maya at a regional scale. An ancient around the Yucatan Peninsula. Known for its well as complex previously unrecognized land- population in the millions was unevenly distrib- sophistication in writing, art, architecture, as- scape modifications at a grand scale throughout uted across the central lowlands, with varying tronomy, and mathematics, this civilization is the central lowlands in the Yucatan peninsula. degrees of urbanization. Agricultural systems still obscured by inaccessible forest, and many found in lidar indicate how these populations http://science.sciencemag.org/ questions remain about its makeup. In 2016, RESULTS: Analysis identified 61,480 ancient were supported, although an irregular distribu- the Pacunam Lidar Initiative (PLI) undertook structures in the survey region, resulting in a tion suggests the existence of a regional agricul- thelargestlidarsurveytodateoftheMaya density of 29 structures/km2. Controlling for a tural economy of great complexity. Substantial region, mapping 2144 km2 of the Maya Bio- number of complex variables, we estimate an infrastructural investment in integrative fea- sphere Reserve in Guatemala. The PLI data average density of ~80 to 120 persons/km2 at the tures (causeways) and conflictive features (defen- have made it possible to characterize ancient height of the Late Classic period (650 to 800 CE). sive systems) highlights the interconnectivity settlement and infrastructure over an exten- Extrapolation of this settlement density to the of the ancient lowland Maya landscape. These sive, varied, and representative swath of the entire 95,000 km2 of the central lowlands perspectives on the ancient Maya generate new central Maya Lowlands. produces a population range of 7 million to questions, refine targets for fieldwork, elicit 11 million. Settlement distribution is not homo- regional study across continuous landscapes, RATIONALE: Scholars first applied modern geneous, however; we found evidence of (i) ru- and advance Maya archaeology into a bold era on September 27, 2018 lidar technology to the lowland Maya area in ral areas with low overall density, (ii) periurban of research and exploration.▪ 2009, focusing analysis on the immediate sur- zones with small urban centers and dispersed The list of author affiliations is available in the full article online. roundings of individual sites. The PLI covers populations, and (iii) urban zones where a *Corresponding author. Email: [email protected] (M.A.C.); twice the area of any previous survey and in- single, large city integrated a wider population. [email protected] (F.E.-B.); [email protected] (T.G.G.) volves a consortium of scholars conducting col- The PLI survey revealed a landscape heavily †These authors contributed equally to this work. ‡ laborative and complementary analyses of the modified for intensive agriculture, necessary These authors contributed equally to this work. Cite this article as M. A. Canuto et al., Science 361, entire survey region. This cooperation among to sustain populations on this scale. Lidar eaau0137 (2018). DOI: 10.1126/science.aau0137 CREDIT: L. AULD-THOMAS ANDRepresentation M. A. CANUTO of the archaeological site of Naachtun, Petén, at twilight. Each ancient structure is marked by a yellow dot. Canuto et al., Science 361, 1355 (2018) 28 September 2018 1of1 RESEARCH ◥ Data collection, processing, RESEARCH ARTICLE and field validation Lidar is an active remote sensing technology that uses laser pulses to map landcover and ARCHAEOLOGY ground surface in three-dimensional space. The PLI effort collected lidar data with a Teledyne Optech Titan MultiWave multichannel, multi- Ancient lowland Maya complexity as spectral, narrow–pulse width lidar system, the most advanced aerial lidar system (28)deployed in the region to date (Table 1). The improve- revealed by airborne laser scanning ments include scanning of the terrain from six different view angles (versus the more usual two of northern Guatemala views) and higher sensor-range resolution, en- abling more precise mapping of topographic Marcello A. Canuto1*†, Francisco Estrada-Belli1*†, Thomas G. Garrison2*†, signatures under short vegetation. The data Stephen D. Houston3‡, Mary Jane Acuña4, Milan Kováč5, Damien Marken6, collection was designed with a nominal laser Philippe Nondédéo7, Luke Auld-Thomas8‡, Cyril Castanet9, David Chatelain8, density of 15 pulses/m2 from a flying altitude Carlos R. Chiriboga10, Tomáš Drápela5, Tibor Lieskovský11, Alexandre Tokovinine12, of 650 m above ground level. The fidelity of Antolín Velasquez13, Juan C. Fernández-Díaz14, Ramesh Shrestha14 this sensor reveals details of local topography, ancient architectural and agricultural features, Downloaded from Lowland Maya civilization flourished in the tropical region of the Yucatan peninsula and and damage from looting (Fig. 2). environs for more than 2500 years (~1000 BCE to 1500 CE). Known for its sophistication The data were collected in 10 polygons over in writing, art, architecture, astronomy, and mathematics, Maya civilization still poses 12 designated survey blocks (Table 1). Each sur- questions about the nature of its cities and surrounding populations because of its location vey block was named for the largest known in an inaccessible forest. In 2016, an aerial lidar survey across 2144 square kilometers of archaeological site within its boundaries; two northern Guatemala mapped natural terrain and archaeological features over several survey blocks in archaeologically unknown areas distinct areas. We present results from these data, revealing interconnected urban were designated Env 1 and Env 2. The current http://science.sciencemag.org/ settlement and landscapes with extensive infrastructural development. Studied through a dataset arose from roughly 33.5 billion laser joint international effort of interdisciplinary teams sharing protocols, this lidar survey pulses, producing about 60 billion returns, of compels a reevaluation of Maya demography, agriculture, and political economy and which 5.2 billion were classified as ground re- suggests future avenues of field research. turns. The average ground densities for differ- ent polygons range from 1.1 to 5.3 returns/m2, the result of varying vegetation densities and owland Maya civilization flourished for the PLI sample, undertaken at far larger scale, canopy coverage across the survey area. Of the nearly 2500 years (1000 BCE to 1500 CE) captured greater variety in topography and an- total mapped area, 23% has an average ground in southern Mexico, Guatemala, and Belize cient settlement for the central Maya Lowlands, return density of 1.1 returns/m2,60%hasaground (Fig. 1), the central part of which consists the demographic and political heartland (9)of return density range of 1.5 to 2.7 returns/m2, 2 L on September 27, 2018 of approximately 95,000 km of rolling the Classic Maya culture. These data provide an and 17% has an average ground return density karst topography interspersed with wetlands (1). opportunity to address current debates in Maya of more than 5.2 returns/m2. These data were Today, this area is largely covered by tropical archaeology and to deepen studies of complex, interpolated to create bare-earth terrain models forest that has severely limited the scale of on- tropical civilizations in the ancient world. with a spatial resolution of 1 m per grid cell. the-ground archaeological research, hindering Some scholars suggest that the Maya Lowlands Identification of archaeological features within regional assessments about ancient urbanism, contained small city-state centers ruled by warring the lidar dataset was iterative (29). The PLI population size, resource management, and so- elites (10–13), in settlements supported by a study region has been subject to thousands of ciopolitical complexity. relatively sparse rural population practicing person-days of pedestrian survey over the course In 2016, the Pacunam Lidar Initiative (PLI) swidden farming (14), with only limited input of eight