Maya Wetland Research Articles

Advances in remote sensing of the early Anthropocene in tropical wetlands: From biplanes to lidar and machine learning

This paper reviews the history of remote sensing for mapping ancient Maya wetland fields in Central America and provides a new assessment using machine learning with LiDAR data. We evaluate past uses of radar, multispectral, and LiDAR datasets in Northwest Belize across well-studied wetland field complexes that occur under different vegetation conditions. Next, we compare topographic products derived from LiDAR data commonly used for archaeology and geomorphology. Lastly, we train a machine learning algorithm to detect ancient canals with LiDAR data and test the algorithm on a newly rediscovered field system. The spatial resolution of any dataset must be sufficiently high (2-m or finer resolution) to detect most of these canals reliably. High resolution multispectral sensors can detect canals in open areas, but most wetland complexes are under dense tropical forest impenetrable to multispectral instruments. LiDAR data were the most useful due to the high spatial resolution (0.5-m) and the ability to penetrate canopy, but still have limitations under certain conditions. The intensity of the LiDAR returns with multispectral LiDAR systems can reveal differences in soil and vegetation between ancient canals and fields in places leveled by modern farmers. The algorithm successfully maps ancient canals but has many false positives in natural depressions and drainages. Although the machine learning approach tested here cannot be used on its own, we used it with the LiDAR visualizations to refine the canal estimates from previous studies, mapping nearly 50% more canals in the Central Rio Bravo floodplain than originally published.

Ancient Maya wetland fields revealed under tropical forest canopy from laser scanning and multiproxy evidence

We report on a large area of ancient Maya wetland field systems in Belize, Central America, based on airborne lidar survey coupled with multiple proxies and radiocarbon dates that reveal ancient field uses and chronology. The lidar survey indicated four main areas of wetland complexes, including the Birds of Paradise wetland field complex that is five times larger than earlier remote and ground survey had indicated, and revealed a previously unknown wetland field complex that is even larger. The field systems date mainly to the Maya Late and Terminal Classic (∼1,400-1,000 y ago), but with evidence from as early as the Late Preclassic (∼1,800 y ago) and as late as the Early Postclassic (∼900 y ago). Previous study showed that these were polycultural systems that grew typical ancient Maya crops including maize, arrowroot, squash, avocado, and other fruits and harvested fauna. The wetland fields were active at a time of population expansion, landscape alteration, and droughts and could have been adaptations to all of these major shifts in Maya civilization. These wetland-farming systems add to the evidence for early and extensive human impacts on the global tropics. Broader evidence suggests a wide distribution of wetland agroecosystems across the Maya Lowlands and Americas, and we hypothesize the increase of atmospheric carbon dioxide and methane from burning, preparing, and maintaining these field systems contributed to the Early Anthropocene.

Ancient Maya wetland management in two watersheds in Belize: Soils, water, and paleoenvironmental change

We compare the geomorphology and soil of two ancient Maya wetland agricultural complexes in modern day Belize. This paper focuses on 3000 years of soil geomorphology and paleoecological change to determine the chronology of wetland formation and human use in this region. We also characterize Maya manipulation of the environment over time, especially considering times of ecological or climactic change in the late Holocene. This paper adds to our ongoing research in northwestern Belize, specifically within two recently explored wetland agricultural systems, Neuendorf and Sierra de Agua. Although they are 40 km from one another and in different watersheds, they have similar water chemistry and comparable soil, as well as comparable ancient Maya agricultural field and canal stratigraphy. The Neuendorf wetland fields and associated Maya house mounds and platforms are 1.5 km northeast of the well-studied Chan Cahal residential group/wetland agricultural fields. This ancient Maya settlement zone sits on a small limestone escarpment, about 7–24 m above sea level on the Belizean coastal plain. New trenches and vibracores from this wetland complex support our previous models of wetland formation and human use from the Late Preclassic to the end of the Classic. The Sierra de Agua wetland fields, 40 km to the southwest, are associated with a Maya urban center of the same name. This complex is part of the Irish Creek Wetlands within the New River watershed. In this system, the water table rose around 3000 years before present, which resulted in a different type of field building and agricultural modification, similar to the chinampas models of central Mexico. This new and ongoing research contributes new pollen records, soils and geoarchaeology to the growing regional picture of wetland use and change throughout Maya history.

‘Mayacene’ floodplain and wetland formation in the Rio Bravo Watershed of northwestern Belize

This is the first article to characterize the soil and fluvial geomorphology of the Rio Bravo’s fluviokarst watershed in the Rio Bravo Conservation and Management Area, northwestern Belize. Although the watershed has had little-altered tropical forest cover since c. 1000 BP, humans inhabited it for millennia, especially during the Maya Preclassic and Classic, c. 3000–1000 BP. We studied soils and floodplain formation in four excavation transects in the Rio Bravo to understand long-term human impacts on this watershed. Archaic to Preclassic ( c. 3000–1700 BP) sedimentation rates ranged from 0.82 mm yr−1 at Chawak But’o’ob to 1.5 mm yr−1 on the Gran Cacao floodplain. The late Preclassic through Classic ( c. 2300–1000 BP) rates rose 0.98–2.03 mm yr−1, and the Classic ( c. 1700–1000 BP) rates ranged from 1 mm yr−1 to as high as 9.12 and 16.27 mm yr−1 at ancient Maya wetland field sites. Post Classic rates dropped back in the one dated profile, and the well-developed topsoils indicate long-term surface stability. Older soils at the edges and higher islands of the valley had more vertic features and full Vertisols, whereas Vertic Mollisols and Aquerts have formed in younger sediments. We also present new evidence for late Classic Maya wetland field formation at Chawak But’o’ob, which shows field raising with canalization in this wetland of low ionic water. All the soil profiles with dating and stable carbon isotope evidence exhibited increased δ13C in the profiles through the Classic period sediments, although some were equivocal. The two wetland field δ13C profiles through the Classic period sediments increase by c. 6‰ at Chawak But’o’ob and 3‰ at the Birds of Paradise (BOP) Field center, although earlier BOP profiles increased by as much as 7‰. Hence, this watershed exhibits three large diachronic shifts: from lower to higher and again to lower deposition over pre-Maya, Maya, and post-Maya times. These changes along with earlier evidence for ancient intensive agriculture from 3000 and 1000 BP lie sandwiched between the ancient and contemporary little-altered tropical forest.

The floating gardens of Chan Cahal: Soils, water, and human interactions

Ancient Maya wetland agriculture has been studied since the 1960s, but there are still too few multiproxy excavations to adequately portray this phenomenon. This paper builds on multidisciplinary and multiproxy research near the ancient Maya site of Chan Cahal, near Blue Creek, Belize, with two new excavations, four new cores, 22 new AMS dates, and a new review of the site's water chemistry and archeology. A long-term study of the site's water chemistry has shown its pervasive impacts on wetland formation and limits to agricultural uses. We argue that a reservoir in the midst of the wetlands became inundated above a paleosol during the earliest Maya occupation in the Middle Preclassic, was dredged out during a time of population expansion sometime in the Late Preclassic to Early Classic, and was filled again with ‘Maya clay’ during and after the Classic period. Vibracores through two wetland fields and one canal corroborated our earlier model of Preclassic through Classic inundation of a paleosol by peat formation, flood sands, clay deposition, and gypsum precipitation. These cores produced new evidence for field and canal construction starting in the Late Preclassic. A later addition was a platform added at the very end or after the main occupation ended in the Terminal Classic. A new excavation at Sayap Ha on the Coastal Plain wetlands 7m lower than Chan Cahal experienced a similar history of inundation and aggradation. Here, Maya farmers reclaimed these wetlands with canals and raised fields late in the Late or Terminal Classic and abandoned them soon thereafter. The Sayap Hah fields thus parallel the BOP fields 9km south since both were built and abandoned at a late stage. As a comparison with other wetland field studies, the stable C isotopes of soil humin through soil profiles showed a strong Classic period to present influence of C4 species at Sayap Hah and an increase in C4 inputs in the upper 25cm at both Sayap Hah and the Chan Cahal platform, perhaps due to tropical pasture grasses prevalent here for the last 50years.

Wetland fields as mirrors of drought and the Maya abandonment

Getting at the Maya Collapse has both temporal and geographic dimensions, because it occurred over centuries and great distances. This requires a wide range of research sites and proxy records, ranging from lake cores to geomorphic evidence, such as stratigraphy and speleothems. This article synthesizes these lines of evidence, together with previously undescribed findings on Maya wetland formation and use in a key region near the heart of the central Maya Lowlands. Growing lines of evidence point to dryer periods in Maya history, which correlate to major periods of transition. The main line of evidence in this paper comes from wetland use and formation studies, which show evidence for both large-scale environmental change and human adaptation or response. Based on multiproxy studies, Maya wetland fields had a long and varied history, but most evidence indicates the start of disuse during or shortly after the Maya Terminal Classic. Hence, the pervasiveness of collapse extended into a range of wetlands, including perennial wetlands, which should have been less responsive to drought as a driver of disuse. A synthesis of the lines of evidence for canal infilling shows no attempts to reclaim them after the Classic Period.

Carbon isotopic ratios of wetland and terrace soil sequences in the Maya Lowlands of Belize and Guatemala

Abstract This article provides new data and synthesizes earlier findings on the carbon isotope ratios of the humin part of soil organic matter from a range of sites in the central Maya Lowlands. Changes down the soil profile in carbon isotope ratios can provide an important line of evidence for vegetation change and erosion over time, especially in well dated aggrading profiles. Research thus far has provided substantial evidence for significant inputs from C4 vegetation in buried layers from the Ancient Maya periods in depositional soils but equivocal evidence from sloping soils. We present new findings from soil profiles through ancient Maya wetland fields, upland karst wetlands, ancient Maya aguadas (reservoirs), and ancient Maya terraces. Most of the profiles exhibited δ13C enrichment greater than the 2.5–3‰ typical from bacterial fractionation. Seven of nine ancient Maya wetland profiles showed δ13C enrichment ranging from 4.25 to 8.56‰ in ancient Maya-dated sediments that also contained phytolith and pollen evidence of grass (C4 species) dominance. Upland karst sinks and ancient reservoirs produced more modest results for δ13C enrichment. These seasonal wetland profiles exhibited δ13C enrichment ranging from 1 to 7.3‰ from the surface to ancient Maya-period sediments. Agricultural terraces produced mixed results, with two terraces having substantial δ13C enrichment of 5.34 and 5.66‰ and two producing only equivocal results of 1.88 and 3.03‰ from modern topsoils to Maya Classic-period buried soils. Altogether, these findings indicate that C4 plants made up c. 25% of the vegetation at our sites in the Maya Classic period and only a few percent today. These findings advance the small corpus of studies from ancient terraces, karst sinks, and ancient wetland fields by demonstrating substantial δ13C and thus C4 plant enrichment in soil profile sections dated to ancient Maya times. These studies are also providing a new line of evidence about local and regional soil and ecological change in this region of widespread environmental change in the Late Holocene.

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize. Mary Deland Pohl (editor). Westview Special Studies in Archaeological Research. Boulder: Westview Press, 1990. 300 pp. $62.50 (paper). ISBN 0–8133–7202-X.

Holocene stratigraphy of Cobweb Swamp, a Maya wetland in northern Belize

We investigated the soils and sediments of Cobweb Swamp, adjacent to the archaeological site of Colha in northern Belize, to adumbrate landscape evolution and the impact of the ancient Maya on a tropical palustrine wetland. The Cobweb section exposes a complex and dynamically evolving landscape, with a rich interplay between natural and human forces. The Cobweb depression probably formed as a karstic doline or polje in interbedded limestone and marl of late Tertiary or Pleistocene age. During the latest Pleistocene, a terrestrial marsh covered most of the depression. Slope wash and colluviation from adjacent slopes impacted the depression during the early Holocene, possibly in response to a drier and cooler climate reported to have occurred in the region during this time. After ca. 5600 B.P., the Cobweb depression was affected by relatively rapidly rising sea levels in the area, and a brackish lagoon filled the basin. By 4800 B.P., a peat filled in the lagoon, probably because precipitation of a marl in the lagoon coupled with decreasing rates of sea-level rise enabled emergent vegetation to encroach the shallowing waters. Humans first began to affect the landscape when this peat was at the surface. Massive deforestation, resulting in increased runoff and rising water levels, is the most likely explanation for a fresh-water lagoon that again inundated the Cobweb depression between 3400 and 500 B.P. The Maya Clay was deposited on the edge of this lagoon as the result of upland erosion, almost as soon as deforestation began, but the bulk of the deposit was coincident with the sudden collapse of the Classic Maya civilization ca. 1000 B.P., suggesting that significant environmental degradation was associated with the demise of the Classic Maya. Peat began to fill the Cobweb lagoon sometime before 500 B.P., probably the result of shallower water levels from decreasing runoff resulting from reforestation after abandonment by the Maya.

Freshwater Wetland Plant Communities of Northern Belize: Implications for Paleoecological Studies of Maya Wetland Agriculture

Plant species composition and standing crop in relation to soil and water characteristics were studied to determine which environmental variables are responsible for structure and distribution of marshes in northern Belize. Sampling sites were located in the floodplains of the Rio Hondo and New River and within karstic depressions in the interfluves of the two rivers. Relationships among environmental variables and the occurrence of the individual marsh types, in particular those dominated by Cladium jamaicense, Eleocharis cellulosa, and Typha domingensis were investigated using canonical correspondence analysis. Discriminant analysis was used to select a reduced set of variables for predicting the distribution of dominant species. Eleocharis cellulosa marshes dominated areas with soil and water of high conductivity due to high content of gypsum and calcium carbonate. Nutrient concentrations, namely nitrogen and phosphorus, were very low. Conditions were rather similar in sawgrass marshes (Cladium jamaicense), except for higher water depth and lower conductivity. Marshes dominated by Typha domingensis occupied areas with higher content of nitrogen and phosphorus. Discriminant functions developed for these three marsh communities can be used to help interpret paleoecological data and infer ancient Maya impacts upon marsh development.

Ancient Maya Wetland Agricultural Fields in Cobweb Swamp, Belize: Construction, Chronology, and Function

Ancient Maya Wetland Agricultural Fields in Cobweb Swamp, Belize: Construction, Chronology, and Function

Ancient Maya Wetland Agricultural Fields in Cobweb Swamp, Belize: Construction, Chronology, and Function

AbstractA series of channel/island features at the archaeological site of Colha on the margins of Cobweb Swamp in northern Belize were determined to be relics of ancient wetland agricultural fields. Conformation of the stratigraphy in both mounded and non mounded areas, as examined in pits and trenches, revealed definite human modification of the buried Cobweb Paleosol. Radiocarbon assays of sediment and charcoal suggest the Maya dug ditches in the Cobweb surface by at least A.C. 600 and possibly much earlier, in the Late Preclassic or Middle Preclassic, probably in an attempt to manage water levels and enable crop production on the fertile swamp-margin soils. The wetland fields were buried by the Maya Clay, apparently the result of erosion of the adjacent upland soils. The Maya Clay probably began to accumulate on the Swamp margin as soon as the Maya began cropping the adjacent uplands, but the bulk of it was deposited after about A.C. 850. The Maya may have continued to crop the fertile wetland fields e...

Holocene Palaeosalinity in a Maya Wetland, Belize, Inferred from the Microfaunal Assemblage

A 5.4-m sequence of peat and marl overlying a basal clay in a northern Belize wetland was studied to assess salinity changes over the past 7000 yr. The distribution of ostracods, gastropods, and foraminifers revealed initially freshwater conditions in a terrestrial wetland, changing to at least mesohaline conditions by about 5600 yr B.P. The mesohaline conditions corresponded to the formation of an open-water lagoon (and precipitation of a lacustrine marl) that was contemporaneous with rapidly rising sea level in the area. A mangrove peat filled the lagoon by 4800 yr B.P. probably as a result of increasingly shallow waters as sea level rise slowed and marl precipitation continued. A new lagoon began to form sometime after 3400 yr B.P. Freshwater ostracods and gastropods found in the marl of this lagoon suggest that it formed under near-limnetic conditions. Freshwater input likely resulted from massive deforestation by the Maya that began by 4400 yr B.P. Subsidence of the mangrove peat likely permitted the formation of a lagoon. A peat has filled the lagoon since at least 500 yr B.P.

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize:Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize.

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize:Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize.

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize

Ancient Maya Wetland Agriculture: Excavations on Albion Island, Northern Belize

Ancient Maya Wetland Agriculture: New Insights from Ecological and Remote Sensing Research

Abstract Despite claims that ancient Maya canals are found throughout the central Maya Lowlands, our study of satellite and aircraft imagery indicates that canals are concentrated in three regions: northern Belize, southern Quintana Roo, Mexico, and along the upper Candelaria River and its tributaries in Campeche, Mexico. Earlier reports of lattices of small canals in the karstic depressions, or bajos, of Peten, Guatemala, based on the analysis of airborne radar imagery, have not been verified with other remote sensing data or by field research. Our analyses of this same airborne imagery and Seasat satellite radar imagery demonstrate that the spatial resolution of, and speckle noise in, existing radar imagery make it inadequate for mapping lattice patterns of small canals. Radar imagery and Landsat Thematic Mapper imagery were, however, useful in mapping large canals, which in most cases are connected to lattices of smaller canals. Furthermore, our analyses of wetland soils, vegetation, and hydrology conf...

Ancient Maya Wetland Agriculture: New Insights from Ecological and Remote Sensing Research

Ancient Maya Wetland Agriculture: New Insights from Ecological and Remote Sensing Research

Prehistoric Maya wetland agriculture and the alluvial soils near San Antonio Rio Hondo, Belize

The prehistoric Lowland Maya supported an elaborate civilization, which reached peak population densities in the tropical forests of Guatemala, Belize and southern Mexico during the Classic period between AD 300 and 900. It has been proposed that the Maya turned to labour-intensive construction of raised planting platforms in wetlands for year-round cultivation. Excavations at San Antonio Rio Hondo, northern Belize1, provided the first archaeological data for this hypothesis. In our analysis of data from the San Antonio site, we conclude that the only indisputable evidence that prehistoric wetland cultivation occurred comes from a time before peak population of the Classic period, and that the technique required less labour than previously envisioned. Exploitation of swampy terrain initially involved dry-season cropping without extensive ditching and later ditching, probably for soil drainage.

Prehistoric Raised-Field Agriculture in the Maya Lowlands

The ground pattems found in Pulitrouser Swamp, northern Belize, are vestiges of raised and channelized fields, types of wetland cultivation used by the ancient Maya. This form of hydraulic cultivation was apparently employed sometime between 200 B.C. and A.D. 850. The environment of the swamp, the fields and canals, and one nearby settlement, Kokeal, are described. The evidence indicates that the large number of well-defined ground patterns reported in other areas in the central Maya lowlands are probably vestiges of Maya wetland cultivation.