Large variation in availability of Maya food plant sources during ancient droughts

Paleoclimatic evidence indicating a series of droughts in the Yucatan Peninsula during the Terminal Classic period suggests that climate change may have contributed to the disruption or collapse of Classic Maya polities. Although climate change cannot fully account for the multifaceted, political turmoil of the period, it is clear that droughts of strong magnitude could have limited food availability, potentially causing famine, migration, and societal decline. Maize was undoubtedly an important staple food of the ancient Maya, but a complete analysis of other food resources that would have been available during drought remains unresolved. Here, we assess drought resistance of all 497 indigenous food plant species documented in ethnographic, ethnobotanical, and botanical studies as having been used by the lowland Maya and classify the availability of these plant species and their edible components under various drought scenarios. Our analysis indicates availability of 83% of food plant species in short-term drought, but this percentage drops to 22% of food plant species available in moderate drought up to 1 y. During extreme drought, lasting several years, our analysis indicates availability of 11% of food plant species. Our results demonstrate a greater diversity of food sources beyond maize that would have been available to the Maya during climate disruption of the Terminal Classic period than has been previously acknowledged. While drought would have necessitated shifts in dietary patterns, the range of physiological drought responses for the available food plants would have allowed a continuing food supply under all but the most dire conditions.

Intraseasonal Hydroclimate Variability in the Yucatán Peninsula During the Maya Terminal Classic Period: A Proxy Record of Palaeo-MJO?

<p>Waves in the tropical atmosphere modulate rainfall and water vapor at the intraseasonal scale, including equatorial Rossby waves, Kelvin waves, and tropical disturbances organized by the planetary scale Madden-Julien Oscillation (MJO). The MJO’s regions of enhanced and suppressed convection travel slowly eastward, resulting in a characteristic 30-60 day rainfall cycle at tropical sites. The MJO’s pace and intensity vary over time and by location, influencing monsoons, El Niño-Southern Oscillation (ENSO) events, and tropical cyclone genesis/intensification. MJO-induced teleconnections influence extratropical weather anomalies, i.e. as atmospheric rivers. Despite forecast challenges, modeling studies indicate MJO sensitivity to anthropogenic climate forcing.</p><p>Records of pre-instrumental MJO behavior would advance efforts to assess tropical palaeoclimate and hydroclimate sensitivity to climate forcing factors. Palaeoclimate records of MJO intraseasonal variability have not been captured due to the scale of MJO relative to proxy resolution. Promising weekly dripwater monitoring results from Rio Secreto cave, Quintana Roo, Mexico, however, show the influence of sub-seasonal weather events on speleothem stable isotope proxy records.  We report a possible late Holocene palaeo-MJO signal in a ~weekly stalagmite oxygen isotope (δ<sup>18</sup>O value) record from Cueva Tzabnah, Yucatán, Mexico.</p><p>We re-sampled a well-studied stalagmite, Chaac, across the Maya Terminal Classic Period (c. 800-950 C.E.) and instrumental era. With continuous micromilling at 6.5 μm spacing and stable isotope analysis (CM-2 micromill and small-vial Kiel IV+MAT253), we reached ~50 samples/year. The re-sampled Chaac record reveals expected interannual-decadal hydroclimate signals and better resolves short-term variability. A recurrent pattern of δ<sup>18</sup>O value oscillations over about 4-12 samples (representing approx. 1-3 months). The amplitude of these intraseasonal-scale oscillations is around 0.3 - 0.5‰, smaller than annual/interannual variations. The intraseasonal pattern varies in amplitude, clarity, and frequency over time, similar to the modern MJO.</p><p>Intraseasonal stable isotopic oscillations in Chaac during the modern and Maya Terminal Classic Period most likely reflect local intraseasonal hydroclimate variability. Because this scale of rainfall variations is driven primarily by the MJO, we are investigating this pattern as a possible palaeo-MJO record. We will present the new Chaac record and results of wavelet analysis, and discuss prospects for intraseasonal tropical paleoclimate dynamics.</p>

The Maya Terminal Classic Drought replicated in two stalagmites from Columnas Cave, NW Yucatán

<p>During the Terminal Classic Period (c.800-1000CE) most major Maya centres in the lowlands of the southern Yucatán Peninsula declined and were then abandoned, in what would come to be known as the Classic Maya Collapse. The causes of this societal transformation remain open for debate in modern archaeology. Over the past 25 years, palaeoclimatic records from lake sediments and speleothems have prompted discussion about the role abrupt climate change may have played in the decline. These records largely indicate the existence of a Terminal Classic Drought, a period of increased drought frequency that is approximately contemporaneous with the Collapse.</p><p>The high temporal resolution of speleothem archives makes them an important tool in assessing the validity of these records. Previous work has demonstrated the prevalence of drought in the lowlands of both northern and southern Yucatán during the Terminal Classic and Early Postclassic Periods. However, it has been difficult to build a detailed understanding of regional rainfall changes owing to the large spatial and temporal variability of precipitation over the Peninsula, as observed in the modern day.</p><p>Here we report a high-resolution (100µm), absolutely-dated, replicated record of δ<sup>18</sup>O and δ<sup>13</sup>C variations in two stalagmites from Columnas Cave (Rancho Hobonil) near the Puuc Hills, a dominant region of Maya settlement in north-western Yucatán during the Terminal Classic. The oxygen and carbon isotopic records of the speleothems (designated Hobo-5 and Hobo-6), located <10m apart in the farthest reaches of the cave, can be correlated with one another in great detail. The highest δ<sup>18</sup>O values in both speleothems occur during the Terminal Classic Period, coupled with the onset of an extended period of consistently high δ<sup>13</sup>C values. These are interpreted as representing a period of increased drought frequency; as documented from sediment cores in nearby Lake Chichancanab, located ≈30km from Columnas Cave. These replicated records provide strong evidence for highly variable climatic conditions in the Terminal Classic, when the Puuc Maya underwent several boom-bust cycles. Ultrahigh-resolution (10µm) SIMS isotope and synchrotron µXRF analyses during this critical period have been undertaken to test if an annual record of climatic changes can be developed.</p><p>Radiocarbon data across the Terminal Classic also displays a single abrupt increase in 14C content around 1000CE, indicating a decrease in the dead carbon fraction. This event occurs close in time to the 994CE solar proton event documented in tree rings. If these events are indeed synchronous, it would constitute the first instance of the cosmogenic radiocarbon event being recorded in a speleothem, which would provide a valuable absolute correlation horizon.</p>

MORTUARY RITUALS AND CRANIAL MODIFICATIONS AT CEIBAL: FROM THE EARLY MIDDLE PRECLASSIC TO THE TERMINAL CLASSIC PERIOD

Skeletal remains excavated from the lowland Maya site of Ceibal, representing approximately 117 individuals, provide significant data for the study of changes in bodily treatments and mortuary practices from 1000b.c.toa.d.900. The early Middle Preclassic residents of Ceibal apparently did not bury their dead inside residential structures, which represents a burial practice different from those found at contemporaneous Belizean sites. During this time, tabular erect cranial deformations were found among possible local residents. Sacrificial burials were present by the end of this period, but skeletal remains of violent rituals deposited in public spaces increased from the Middle Preclassic to the Late Preclassic. During the Late Preclassic, tabular erect cranial deformations coexisted with tabular oblique shapes. The Classic period witnessed a prevalence of tabular oblique forms, which were probably tied to local residents. The common placement of the dead under house floors and the preference of ceramic vessels as burial goods also indicate Ceibal's strong affinities with other parts of the Maya lowlands during the Late Classic period. During the Terminal Classic period, there was a resurgence in the placement of sacrificial burials in public spaces and tabular erect cranial deformations were found in possible non-local individuals.

Testing the “tropical storm” hypothesis of Yucatan Peninsula climate variability during the Maya Terminal Classic Period

We examine the “tropical storm” hypothesis that precipitation variability in the Yucatan Peninsula (YP) was linked to the frequency of tropical cyclones during the demise of the Classic Maya civilization, in the Terminal Classic Period (TCP, AD 750—950). Evidence that supports the hypothesis includes: (1) a positive relationship between tropical storm frequency and precipitation amount over the YP today (proof of feasibility), (2) a statistically significant correlation between a stalagmite (Chaac) quantitative precipitation record from the YP and the number of named tropical cyclones affecting this region today (1852—2004) (calibration sensu lato), and, (3) correlations between the stalagmite Chaac precipitation record and an Atlantic basin tropical cyclone count record and two proxy records of shifts in macroscale climate and ocean states that influence Atlantic tropical cyclongenesis. At face value, regional paleotempestology proxy records suggest that tropical storm activity in the YP was either similar or significantly lower than today during the TCP. The “tropical storm” hypothesis has implications for our understanding of the role the hydrological cycle played in the collapse of Classic Maya polities and the role of tropical storms in possibly ameliorating future drought in the YP and other tropical regions.

Drought, agricultural adaptation, and sociopolitical collapse in the Maya Lowlands

Paleoclimate records indicate a series of severe droughts was associated with societal collapse of the Classic Maya during the Terminal Classic period (∼800–950 C.E.). Evidence for drought largely derives from the drier, less populated northern Maya Lowlands but does not explain more pronounced and earlier societal disruption in the relatively humid southern Maya Lowlands. Here we apply hydrogen and carbon isotope compositions of plant wax lipids in two lake sediment cores to assess changes in water availability and land use in both the northern and southern Maya lowlands. We show that relatively more intense drying occurred in the southern lowlands than in the northern lowlands during the Terminal Classic period, consistent with earlier and more persistent societal decline in the south. Our results also indicate a period of substantial drying in the southern Maya Lowlands from ∼200 C.E. to 500 C.E., during the Terminal Preclassic and Early Classic periods. Plant wax carbon isotope records indicate a decline in C4 plants in both lake catchments during the Early Classic period, interpreted to reflect a shift from extensive agriculture to intensive, water-conservative maize cultivation that was motivated by a drying climate. Our results imply that agricultural adaptations developed in response to earlier droughts were initially successful, but failed under the more severe droughts of the Terminal Classic period.

THE ROOTS OF SOTUTA: DZITAS SLATE AS A YUCATECAN TRADITION

The Sotuta pottery complex has been used in the archaeology of the northern Maya lowlands to identify the Terminal Classic period and cultural association with Chichen Itza. The Sotuta complex, however, is made up of many pottery types, the majority of which are inappropriate markers of elite sociopolitical history. It is argued here that Sotuta-complex slate wares developed out of previous local slate wares regardless of the elite sociopolitical changes taking place with the arrival of the Itza. The wares produced and distributed by commoners were independent of elites and have been artificially chained to questions of elite political expansion for which they are inappropriate correlates.