Thomas L. Sever

LANDSCAPE ARCHAEOLOGY: Remote-sensing investigation of the ancient Maya in the Peten rainforest of northern Guatemala

Conducting field research in the dense forests of the Peten, northern Guatemala, is as difficult today as it was for A. V. Kidder 70 years ago. However, through the use of airborne and satellite imagery we are improving our ability to investigate ancient Maya settlement, subsistence, and landscape modification in this dense forest region. Today the area is threatened by encroaching settlement and deforestation. However, it was in this region that the Maya civilization began, flourished, and abruptly disappeared for unknown reasons in the ninth century a.d. At the time of its collapse it had attained one of the highest population densities in human history. How the Maya were able to manage water successfully and feed this dense population is not well understood at this time. A project funded by the National Aeronautics and Space Administration (NASA) used remote-sensing technology to investigate large seasonal swamps (bajos) that make up 40% of the landscape. Through the use of remote sensing, ancient Maya features such as sites, roadways, canals, and water reservoirs have been detected and verified through ground reconnaissance. The results of this preliminary research cast new light on the adaptation of the ancient Maya to their environment. Microenvironmental variation within the wetlands was elucidated and the different vegetation associations identified in the satellite imagery. More than 70 new archaeological sites within and at the edges of the bajo were mapped and tested. The combination of satellite imagery and ground verification demonstrated that the Maya had modified their landscape in the form of dams, reservoirs, and possible drainage canals along the Holmul River and its tributaries. The use of Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM), 1-m IKONOS satellite imagery, as well as high-resolution airborne STAR-3i radar imagery—2.5 m backscatter/10 m Digital Elevation Model (DEM)—are opening new possibilities for understanding how a civilization was able to survive for centuries on a karst topographic landscape. This understanding is critical for the current population that is experiencing rapid population growth and destroying the landscape through non-traditional farming and grazing techniques, resulting in socioeconomic problems.

Putting Us on the Map: Remote Sensing Investigation of the Ancient Maya Landscape

A common problem for archaeologists studying ancient settlement in the Maya Lowlands is overcoming the dense vegetation in order to obtain an accurate regional perspective of the presence of archaeological sites, their exact locations and their overall extents. Most often this is done by extensive ground surveys in which many individuals chop parallel paths through the vegetation in search of sites. Once a site is found an effort is made to mark its location on a regional map and to explore its perimeter. Obtaining locational information has been made dramatically easier in recent years with the advent of improved Global Positioning Systems (GPS), however the process of initial identification of sites and the determination of their borders is exceedingly labor intensive and has remained relatively unchanged since the beginning of settlement surveys in the region in the 1950 s. Currently, we are revolutionizing settlement survey in the Maya Lowlands by using remotely sensed data from IKONOS, Quickbird, and Eo 1, satellites as well as airborne AIRSAR radar data. The Ancient Maya built their cities, towns and even their smallest hamlets using excavated limestone and lime plasters. We propose that the decay of these structures provides a unique microenvironment for the growth of vegetation as the levels of moisture and nutrition within the ruins vary substantially from those in the surrounding forest. These microenvironmental differences on the ground are likewise represented by compositional differences in the forest canopy both in the species present and in leaf color (representing moisture/nutritional stress) visible through the analysis of high-resolution satellite data. In this way the detailed analysis of forest composition can reveal a detailed picture of the ancient settlements that lie beneath it. Preliminary examinations using this technique have been very successful and we are refining these techniques in order to efficiently comprehend the details of Ancient Maya settlement in the Lowlands.

Prehistory and Volcanism in the Arenal Area, Costa Rica

AbstractMultidisciplinary research conducted in the tropical rainforest of NW Costa Rica uncovered evidence of human occupation from Paleoindian and Archaic times through four sedentary phases to the Spanish Conquest. The village lifestyle, established by 2000 B.C., was remarkably stable and resilient in spite of the effects of at least nine prehistoric explosive eruptions of Arenal Volcano. Settlements maintained greater economic and political independence than Mesoamerican villages. Maize was cultivated by 2000 B.C., but it did not become a staple, as nondomesticated flora and fauna provided the bulk of the diet. A trend toward more elaborate funerary ritual, and toward greater distances between villages and cemeteries, occurred from 2000 B.C. to A.C. 1200. Optical (photographic) and digital remote sensing detected numerous linear anomalies, many of which have been confirmed as prehistoric footpaths that represent a system of human transportation and communication across the prehistoric landscape.

Biogeography of tropical montane cloud forests. Part II: Mapping of orographic cloud immersion

Abstract This study details two unique methods to quantify cloud-immersion statistics for tropical montane cloud forests (TMCFs). The first technique uses a new algorithm for determining cloud-base height using Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products, and the second method uses numerical atmospheric simulation along with geostationary satellite data. Cloud-immersion statistics are determined using MODIS data for March 2003 over the study region consisting of Costa Rica, southern Nicaragua, and northern Panama. Comparison with known locations of cloud forests in northern Costa Rica shows that the MODIS-derived cloud-immersion maps successfully identify known cloud-forest locations in the United Nations Environment Programme (UNEP) World Conservation Monitoring Centre (WCMC) database. Large connected regions of cloud immersion are observed in regions in which the trade wind flow is directly impinging upon the mountain slopes; in areas in which the flow is parallel to the slopes,...

Remote Sensing Methods

Remotely sensed data allows archaeologists and historic preservationists the ability to detect phenomena previously unobservable to them by nondestructive methods. Archaeologists have successfully used aerial photography since the turn of the century and it continues to be an important research tool today. Multispectral scanners and computer-implemented analysis techniques extend the range of human vision and provide the investigator with innovative research designs at scales previously unimaginable. Pioneering efforts in the use of remote sensing technology have demonstrated its potential, but it is the recent technological developments in remote sensing instrumentation and computer capability that provide for unlimited, cost-effective applications in the future. The combination of remote sensing, Global Positioning System (GPS) technology, and Geographic Information Systems (GIS) is radically altering survey, inventory, and modeling approaches.

Time-series tropical forest change detection: a visual and quantitative approach

Forest change detection over a decadal time frame was conducted for the Maya Biosphere Reserve in northern Guatemala. A simple and logical method of visualizing and quantifying forest change is presented. Analysis of time- series Landsat-Thematic Mapper imagery provided estimates of forest change at three time periods; prior to 1990, 1990 to 1993 and 1993 to 1995. Four dates of Landsat imagery were pre-processed, co-registered to a UTM projection and the normalized difference vegetation index was computed for each date. An unsupervised classification was performed and cluster classes were grouped into time-series change/no change categories. A color coded image was generated which resembled the RBG-NDVI color composite of the 1990, 1993, and 1995 imagery. Land cover information and Geographic Information System (GIS) editing techniques were applied to resolve some confusions between forest change and change in non-forest types. Results indicated that forest clearing rates in the reserve were less than 0.5 percent per year in the early to mid 1990s but the buffer zone clearing rates, at over two percent, were much higher.

Creating and Perpetuating Social Memory Across the Ancient Costa Rican Landscape

For most of the time that Native Americans lived in ancient Costa Rica, we think their travel across the landscape was task-oriented and thus sufficiently randomized to leave no detectable trace. That changed about 500 B.C. in the Arenal area when people separated their cemeteries from their villages, and travel between them was ritually mediated into travel precisely along the same path, in single file, in as straight a line as possible. The inadvertent erosion over centuries of use resulted in paths entrenching to 2 m or more deep. We believe the cultural standard developed over the centuries was that the preferred way of entering a special place was by an entrenched path. Thus, people approaching a special place would have a highly restricted view of their surroundings, but upon entering the special place, it would dramatically open up to view. People created and perpetuated social memory across their landscapes with generation after generation of use. The construction of meaning developed as the paths entrenched, ultimately embedding that meaning deep in people’s belief systems as their pathways were embedding themselves into the landscape. Although chiefdoms never developed in the Arenal area, a series of chiefdoms did develop east of the area at about A.D. 1,000. To satisfy the emergent chief’s needs for monumentality, we suggest here that chiefs chose the “proper entrenched entryway” as exemplified in the Arenal area, for elaboration. On the rocky slopes of the volcanoes monumental entryways were built of stone, and on the fine-grained alluvial plains they were of earthen construction. For instance, the radiating entrenched roads entering Cutris are many meters long, as wide as 50 kilometers, and many meters deep.