Wetlands represent some of the most biologically productive and diverse ecosystems on the planet. The ancient Maya valued wetlands for their organic soils, year-around water supply, and aquatic animals and plants. Wetlands were selected as some of the earliest farming locations, and also sites where intensive agriculture was developed. The Yalahau Regional Wetland Survey, conducted by Daniel Leonard under the supervision of Dr. Scott L. Fedick, will investigate ancient Maya use of wetlands in the northeastern corner of Mexico's Yucatán Peninsula. In the context of the dry northern Yucatán, the Yalahau region stands out with an extensive network of freshwater wetlands and high levels of biodiversity. This project will assess the extent of wetland farming and evaluate it in the context of wetland ecosystem variation across the Yalahau region.
Maya farmers in the lowlands of Mexico were presented with a mosaic of environments creating various opportunities and constraints for land use and food production. This project will advance understanding of ancient Maya wetland farming, especially in terms of the different techniques used and the range of environments exploited. Additionally, this research will contribute to a growing corpus of data on human-environmental interaction and the effects of climate change and water table fluctuations on agricultural strategies, settlement patterns, and demographic shifts.
The Yalahau Maya built their largest cities and farmed the wetlands primarily between 100 B.C. and A.D. 450. Ancient Maya use of the Yalahau wetlands is indicated by numerous constructed rock alignments previously documented in a wetland located in the El Edén Ecological Reserve. Rock alignments represent a new form of Maya agro-engineering, but it is unknown whether this technology extends beyond El Edén to any of the other 173 wetlands in the Yalahau system. This study proposes that Maya engaged in food production in wetlands with particular soil characteristics and flooding regimes. It is further proposed that within wetlands, rock alignments were built at certain locations in accordance with their function and chronology of use. The survey includes a sample of 25-30 wetlands representing the range of wetland sizes and plant communities. Through use of satellite image-based mapping and ground survey, Mr. Leonard will collect data on rock alignments, vegetation communities, soil types and depths, and topography. Correlating rock alignments with different environmental parameters will help identify possible functions of alignments (e.g., soil traps, fish weirs, water diversions, dikes to protect planting areas).
The broader impacts of this project include the training of undergraduate and graduate students from Mexico and the United States in archaeological survey and mapping. This project advances ongoing collaboration with botanists, soil scientists, and ecologists from several universities in Mexico. Mr. Leonard will also work closely with conservation biologists and several local Maya ecotourism outfits interested in protecting natural and cultural resources from land development and aquifer pumping associated with the Cancun-Tulum tourist corridor. Efforts are underway to nominate the Yalahau wetland system for inclusion in the Ramsar Convention's List of Wetlands of International Importance, and the environmental and archaeological data generated by the project will contribute substantially to these conservation efforts.
The Yalahau Regional Wetland Survey, conducted by Daniel Leonard under the supervision of Dr. Scott L. Fedick, has investigated ancient Maya use of wetlands in the northeastern corner of Mexico’s Yucatán Peninsula. In the context of the dry northern Yucatán, the Yalahau region stands out with an extensive network of freshwater wetlands and high levels of biodiversity. The Yalahau Maya built their largest cities and farmed the wetlands primarily between 100 B.C. and A.D. 450. Ancient Maya use of the Yalahau wetlands is indicated by numerous constructed rock alignments previously documented in a wetland located in the El Edén Ecological Reserve. Rock alignments represent a new form of Maya agro-engineering, but it was unknown whether this technology extended beyond El Edén to any of the other 173 wetlands in the Yalahau system. The goal of this project, therefore, was to assess the extent of wetland farming and evaluate it in the context of wetland ecosystem variation across the Yalahau region. The results of this project include archaeological and environmental data from 25 wetlands in the Yalahau region. In each wetland, plant specimens were collected and vegetation communities were mapped using handheld Global Positioning System units. Fifteen wetland vegetation communities were defined, ranging from swamp forest to peat bog. These plant data, combined with visual inspection of aerial photographs, were used to create detailed vegetation maps for each wetland. In five wetlands, topographic transects were set up in which we measured changes in surface elevation and soil depth from one side of the wetland to the other. These transects confirmed that the 15 vegetation communities occupy fairly restricted elevation ranges, in accordance with their tolerance for flooding. Two water level loggers were installed in wetland lagoons to track changes in wetland water levels throughout the year. The data show that during the rainy season, the near surface water table rises about 1 m, filling the deeper parts of the wetland with about 70 cm of water. Maximum flooding is reached in September, and the wetland is dry again by March. Ancient rock alignments were discovered in 19 of the 25 wetlands studied. In total, 436 alignments were mapped and described. Rock alignments were on average 15 m long, but some discovered during this project reached upwards of 250 m long. Alignments were typically about 30 cm tall, 50 cm wide, and built with rounded boulders and slabs, which were sometimes placed in an upended position. Alignments were found at various elevations in the wetland based on their association with different vegetation communities. A large number (49%) of alignments were found in the sedge community, which is one of the lower elevation zones. But alignments were regularly found in higher zones such as the swamp forest community. The different topographic locations of alignments may suggest different functions, or that they were built at different periods in the past when the flood level was higher or lower. In either case, alignments are often found blocking the low margin of small depressions, or connecting small bedrock islands. Thus the most likely functions seem to have been small dams to trap water and soil, and informal bridges or footpaths providing access from the edge of the wetland to the center. However, further analysis is required to confirm such interpretations. Thirty-five short (< 1m) soil cores were extracted from wetlands using 3 inch diameter PVC tubes. Preliminary analysis indicates wetland soils were more diverse than thought based on earlier studies. Also, several cores showed alternating bands of organic and inorganic sediment, reflecting wet versus dry periods. Radiocarbon dates on the dark organic bands showed that these numerous changes occurred over the last 2000 years. These results address the intellectual merit criteria by showing that ancient wetland manipulation with rock alignments was widespread, at least within the 25-wetland sample. The data on vegetation associations of rock alignments is being used to develop a model predicting the location of alignments in un-surveyed wetlands. Also, soil data is providing details on the nature and timing of environmental changes in the Yalahau region, particularly changes in wetland hydrology that may have disrupted use of the wetlands. The broader impacts of these results stem from the multidisciplinary and binational approach that made them possible. There has been close collaboration on the soils data with soil scientists from the Institute of Geology of the National Autonomous University of Mexico, and collaboration on plant identifications with a botanist from the El Eden Ecological Reserve in Cancun. Several students from Mexico and the United States have been trained and participated in fieldwork. Also, the environmental data, particularly vegetation maps and flood data, may assist efforts to conserve land in the Yalahau region for Jaguar habitat, ecotourism operations, and sustainable use by local communities.
