Climatic change would have affected the population in various ways in differ-ent regions. In the northern Pet´en, no adequate quantities of groundwater exist
except lagoons and aguadas, which would have gone dry without sufficient rain-fall (Dom´ınguez and Folan, 1996; Folan et al., 1995), forcing the population to move elsewhere.[5] In a hilly region of northern Campeche named for its wells (the Chenes in Maya), a lower water table would have dried up shallow wells. The deeper cenotes farther north and the ojos de agua (freshwater springs) along the coasts would not have been capable of supporting a state-level or urban population of even moderate size, given the humidity requirements of an adequate agricultural or horticultural base.
In the case of the Classic collapse, what happened probably varied from place to place. In the Pet´en, decreased rainfall may have provoked an increase in the amount of land planted from year to year, perhaps in the form of larger milpas in an attempt to harvest sufficient grain for survival at a lower per hectare yield. Ac-cording to the pre-Columbian and colonial Chilam Balams (histories written in the Maya language by the priest Balam [Jaguar] using Spanish script; Folan and Hyde, 1985), during times of need urban dwellers would leave the city, possibly for field habitations around a major population center or even for a hamlet next to a perma-nent water source, probably preferring areas where relatives lived (as Faust, 1988, found in oral histories). If malnutrition resulted from reductions in food supplies, health problems would have increased (also referred to in the Chilam Balams) and fertility would have decreased. Finally, the remaining urban populations would de-cline through other means, perhaps also affected by warfare of one type or another, leading to final abandonment of cities [see Braswell (1997) and Freter (1994), for documentation of this process in Cop´an].[6] By the early colonial period, de Landa ([orig. 1566], 1982) considered the Pet´en to be inhabitable only during the rainy season.[7]
The temporal and spatial pattern of the Maya rise and collapse closely fits the data on climatic change of Gunn et al. (1994, 1995). The dated monuments and the occupation of Classic Maya centers from the 4th century to the 9th century, as quantified by Erickson (1973, in Tainter, 1988), indicate a fairly steady population increase after the A.D. 250 drought [one detected by the analysis of Gunn et al.
(1994, 1995), but not by Hodell et al. (1995)], with a plateau occurring around A.D. 475–550 (or a little later), the period known to Maya archaeologists as “the hiatus.” Subsequently, monument construction increased and occupation sites ex-panded until around A.D. 750–775, when they declined rapidly in conjunction with a major drought. This rapid decline was accompanied by a shift toward coastal and surface water areas in the Pet´en and the surrounding region (Folan et al., 1983a;
Rice, 1987).
As the climatic conditions needed for upland horticulture worsened in the south, they may have initially improved in the north (Gunn and Adams, 1981; Messenger, 1990), making possible Puuc cultural development until around A.D. 900–1000,
when the drought spread north. The 10th-century abandonment of the large Puuc center at Uxmal (and its tributary centers) somewhat overlapped that of a still active Chich´en Itz´a, a site associated with the highland cultures of the Valley of Mexico (Folan, 1977:18). Chich´en fell during what seems to have been a period of exces-sive drought. Mayap´an rose probably due to more favorable climatic and hydraulic conditions including multiple cenotes (Gunn and Adams, 1981; Folan et al., 1983a;
Messenger, 1990; Gunn et al., 1994, 1995).
It is important to note that on the Yucat´an peninsula, water is not only needed for agriculture, but is a crucial factor on a number of other fronts as well. Because of the Yucat´an peninsula’s porous karstic topography, water limitations are prob-ably more severe than limitations imposed by food availability. Water has to be available to wash bodies and clothing on a daily basis or one soon acquires skin diseases and parasites that can be debilitating. There must be enough precipitation to flush the surface and subsurface karst basins or the water supplies become con-taminated; distribution of fecal coliform bacteria is widespread in the water table, contributing to gastrointestinal illnesses (Doehring and Butler, 1974; Faust, 1998).
The transition period between the dry and rainy seasons is known locally as “the time when babies die,” or “the time of sickness,” because the waste accumulated during the dry season is mobilized on the surface and enters the water table. This is one of several situations in the Maya lowlands that make a little rain worse than none at all. Unless the earliest rains are followed by enough precipitation to flush the karst, the entire population is subject to dysentery and other maladies, a sit-uation that recurs at the end of the can´ıcula, or dog days of summer (see Faust, 1988:251–252).
It follows from the above discussion that maintaining city water supplies is of particular concern to large urban concentrations in the interior of the penin-sula. In fact, it has been suggested that the plastered surfaces of the temples and plazas were water-collecting systems that fed cisterns capable of supporting the cities (see Faust, 1998:84, for a review of the literature) – a view supported by the temples’ great emphasis on invoking the rain gods (Sharp, 1981). The Gunn–Folan model shows correlations between the largest urban concentrations in the interior and medium-range climate (warm-cool times with precipitation evenly distributed), implying that even the cities, with their complex water systems, were only able to function when precipitation variation was not too extreme, thus enhancing horti-cultural production. Hansen (1996) has found that the urban centers of El Mirador, Tintal, and Nakb´e, among the earliest in the Maya lowlands, were occupied almost exclusively during the Late Preclassic, a period of optimal climate similar to the Late Classic. These early cities used their forests for fuel, investing in the man-ufacture of plaster surfaces that could be used to collect water. The soil of the
uplands, denuded of forest, eroded into the bajos (seasonal swamps; Mart´ınez et al., 1996).
Contemporary Maya farmers report that in addition to planting in the uplands and on the edge of bajos, they have traditionally planted small raised areas called cuyitos (culenculo’ob in Maya) in the flooded bajos during the rainy season and again during the tornamil (second planting), when planting is also done on and be-tween these natural features. This second planting occurs during a drier season, when the bajos are drying but still retain more moisture than other areas. This planting of bajo cuyitos has the form of primitive chinampas (artificially raised fields associated mainly with lagoons and some riverine systems), while that at the bajo edge resembles a floodplain form of horticulture. Together, the Maya have a five-step strategy using three different environments during two different plantings:
the first planting is (1) in the uplands, (2) at the bajo edge, and (3) on cuyitos in the bajo; and the second planting is (4) on the cuyitos and (5) in the area between them on the floor of the bajo (Folan and Gallegos Osuno, 1992, 1996, 1998). Far from being unusable soils, the bajos (in at least some areas) provide for two crops a year, and depending on weather conditions, in some years a third planting may even be possible (T.P. Culbert, 1997, personal communication; Folan and Gallegos Osuno, 1998). The surface area of the cuyitos averages 25 cm 25 cm, or .0625 m2, with 45 cuyitos, or a total of 25 m2per mecate (of 400 m2) that is planted together with the edge of the bajo and the uplands during the first planting. The cuyitos are planted again together with the bottom of the bajo during the second plant-ing. Archaeological research indicates similar practices in the Guatemalan Pet´en (Mart´ınez et al., 1996; Hansen et al., forthcoming). For a discussion of hummock use on the Belizean coast, see Pohl et al. (1996).
Throughout the southern and central lowlands, use of bajos was complemented in the Preclassic and Classic periods by other forms of intensive agriculture, which have been documented in increasing numbers of ground surveys and excavations since the 1970s, when Siemens and Puleston (1972) first published their findings concerning relict raised fields in the area of the upper Candelaria River. In the period immediately following their seminal publication, misinterpretation of some forms of radar imagery produced estimates of extremely large areas covered with raised fields (Adams et al., 1982). Subsequent ground surveys and excavations have confirmed Maya modification of natural water-drainage systems for agricultural or domestic purposes, including raised fields in the El Laberinto bajo of Calakmul and other areas (see Turner, 1979; Matheny et al., 1983; Fedick, 1995a, 1995b;
Culbert, 1996; Dom´ınguez and Folan, 1996; Mart´ınez et al., 1996; Siemens et al., 1996; Fialko-Coxeman, 1997; May Hau, 1997, field notes from Calakmul; Vargas Pacheco, 1997). In some cases these modifications could have made possible two or three harvests per year and would have reduced the time for fallowing, thereby
increasing the harvest per hectare over a multiyear period and supplying the large urban populations estimated for both the Preclassic and the Classic periods. Re-duced population densities following the collapse in the southern and central low-lands would have obviated the need for, and reduced the feasibility of, some inten-sive practices. Under pre-collapse technology, fallow was minimized and irrigated and drained fields required more labor per unit of output, but yields per unit of land were increased. These techniques were therefore only appropriate for dense populations (Culbert, 1977:518).
Pohl et al. (1996) have reported the results of pollen analysis and excavation of raised fields along the Hondo and New Rivers in Belize, an area where ground-water levels are directly affected by changes in sea level. Their research indicates that intensive wetland agriculture emerged very early (1500–1000 B.C.) in the Pre-classic period, taking advantage of hydromorphic soils as groundwater levels fell in response to global climate change. These topographic modifications were later abandoned when water levels rose again in the Late Preclassic period (400 B.C.–
A.D. 250). Pohl et al. (1996) comment on the relevance of their findings for the central southern lowlands. They state:
[Our] explanation of the origin and evolution of wetland agriculture does not apply to the cultivation of seasonal wetlands at higher elevations removed from the influence of sea level. Nevertheless, we question whether these interior wetlands, most notably the bajos of the central Maya region, were ever intensively cultivated. [Pope and Dahlin, 1989, 1993]
Contrary to the above statements, work by Folan and Gallegos Osuno (1992, 1996, 1998), Hansen (1996), Culbert (1996), Fialko-Coxeman (1997), and Fialko et al. (1998) indicates that bajos cultivated today were also cultivated in the pre-Hispanic past. Final evaluation of the existence of intensive agriculture in the in-terior of the peninsula will have to await the results of excavations and pollen and phytolith analysis in that area. Pohl et al. (1996) did research on pollen samples and lake cores indicating serious soil erosion problems postdating the Late Clas-sic period, possibly from overuse of swidden on hillsides (see Jacob, 1995, for Cobweb Swamp, Belize; Pohl et al., 1990, for Albion Island, Belize). This sug-gests the possibility that, following abandonment of raised fields in the Preclassic period (at least in areas affected by rising sea levels), population pressures caused shortening of the fallow period, resulting in accelerated rates of soil erosion. An alternative explanation for soil erosion is the abandonment of terrace maintenance (due to climate change, warfare, or internal rebellion). Terraces are artificial con-structions on deforested slopes subject to degradation by heavy rain and gravity;
without continual repair, the soil washes downhill, accumulating in wetlands and lakes.
In Tabasco, there exists today a form of horticulture called cultivo de marce˜no wherein low areas referred to as popales (named for a resident species, Thalia geniculata) are slashed, burned, and planted during the dry season, in March (hence the term marce˜no). The moist earth produces between 4 and 5 tons of corn per hectare, and may reach levels of 10 tons per hectare. The corn is harvested from canoes at the beginning of the rainy season, in June. If rains are delayed, a second harvest is possible (Mariaca Mendez, 1999; Exhibit, Museo de Historia Natural, Villahermosa, Tabasco, Mexico, 1997). This form of horticulture may be related to the milpa of San Jos´e planted in March in the Pet´en, according to Messenger (1997) and V. Fialko (1998, personal communication).
1.5 Discussion
Monocausal explanations can never comprehensively describe human behavior, al-though social scientists have sought them repeatedly. In the case of the rise and fall of the Classic Maya, Lowe (1985) reviewed the simple causal models and the systematic multifactor models that have become prominent. After computer analy-sis of 12 different systemic models that give different weights to social, economic, agricultural, and political factors, he built his own dynamic model of the Maya col-lapse that incorporates many aspects of the most prominent explanations, including
Cowgill’s emphasis on warfare; Adams’s, Sabloff’s and Willey’s notion that the Maya collapse was not purely internal process, that external pressure played a non-negligible and perhaps decisive role; Thompson’s and Sharer’s formulations emphasizing the destruction of the elite class as a consequence of degenerating material/subsistence conditions; Bateson’s and Holling’s dis-cussion of the effects of decreased flexibility/resilience; and, finally, Willey’s and Shimkin’s view that the collapse was basically due to managerial failure, that a shock administered to Maya polities created administrative overload and thus societal breakdown, or to put it another way, that the special condi-tions that resulted in the collapse were consequences both of the importance of elite administrative apparatus to the whole, and of its relative fragility . . . ecological degradation may also have operated in parallel . . . to induce in-creasing levels of stress in Late Classic times . . . [Lowe, 1985:201–202]
He identifies two thresholds:
One, an impact threshold, describes the magnitude of a shortfall in food sup-ply at the local level, below which negative feedback and a return to equi-librium prevails and above which positive feedback and collapse occur. The other, the collapse diffusion threshold, identifies the point at which the entire system of states comprising the Southern Maya Lowlands becomes unstable.
[Lowe, 1985:206]
An important point relative to the Classic collapse is that it was not the only time that there were droughts and not the only time of urban collapse in the low-lands. Similar processes and interactions appear to have occurred in A.D. 250 and near the middle of the Postclassic, circa A.D. 1350. The virtual abandonment of the interior except along lakes and rivers appears to be the unique mark of the Classic collapse in the southern Maya lowlands. A number of accompanying circumstances probably sealed the fate of the interior area. One was the irreversible, at least on the scale of centuries, degradation of parts of the agricultural environment. This degradation was compounded by a social system that became deeply embroiled in internal warfare, according to Marcus’s (1992, 1997) analysis of hieroglyphic texts.
Cities and their tributary populations, organized as regional states (see Folan et al., 1995, for the case of Calakmul), occasionally waged war against each other in the decades before and during the collapse. This warfare at times interrupted traditional trade routes across the southern Maya lowlands. New forces emerged in the north whose interests lay with seaborne trade with Chich´en Itz´a and other regional states;
they may have sent armies to the south, which may have further disrupted trade and social commerce (D. Rents-Budet, 1995, personal communication). After the fall of Chich´en Itz´a and its successor Mayap´an, incessant warfare among Maya poli-ties was commonplace in the 15th century, continuing into the contact period and later. The conflicts and their outcomes were recorded both in the Chilam Balams of the Maya elite and in Spanish colonial documents (Roys, 1943, 1957; Jones, 1977; Marcus, 1992; Dumond, 1997). Identifying food and water supply as critical problems in the Classic period still leaves open the question of whether these sup-plies per capita declined due to a homemade overshoot of carrying capacity and/or an external change in climatic conditions. The evidence for climate change and its timing strongly support the argument that an alteration in the macroclimate put unusual stress on supplies of food and water, which triggered social, political, and military problems resulting in the Maya collapse.
Accumulating information concerning the effects of El Ni˜no events on present-day regional economies makes the climatic causation more comprehensible. We have little control over climatic shifts and their very costly impacts, even with our industrialized agriculture, storage facilities, and distribution networks. Planning for the future economic development of the peninsula should include the preser-vation of those risk-reduction procedures that are incorporated in the traditional practices of living Maya communities (Faust, 1998), the reintroduction of ancient intensive technologies in areas where they are feasible, and the provision of new technologies appropriate for the prediction of and adaptation to shifts in climate (see Chapter 4). The extended El Ni˜no condition of the 1990s suggests the pos-sibility of fundamental changes to global climate such as mega–El Ni˜nos expe-rienced during past episodes of global warming (Meggers, 1994). The last one
occurred at the beginning of the 16th century, and earlier ones correlate with peri-ods of cultural collapse in the Amazon River basin (Meggers, 1994). The duration of these episodes is unknown, but an informed guess is that they must have lasted for decades to have resulted in such extensive cultural catastrophes (B.J. Meggers, 1998, personal communication). We may currently be at the beginning of a massive test of our contemporary beliefs in the capacity of modern technology to overcome such a challenge to the economic and political structures maintaining contemporary civilization.
Notes
[1] Dating in Maya archaeology has traditionally been stratigraphic and stylistic, based on analysis of the strata uncovered in excavations and the style of architecture, associated ceramics, and hieroglyphic calculations. More recently, carbon-14 and obsidian hydra-tion methods have been used on appropriate materials. Unanswered queshydra-tions remain concerning the duration of various periods, including the Late Classic and Postclassic (particularly in Chich´en Itz´a and Copan).
[2] Much of the following discussion is based on personal observations and field notes by B. Faust, based on field work in Pich, Campeche; the Biosphere Reserve of R´ıo Lagartos, Yucat´an; and Sahcab´a, Yucat´an.
[3] Cenotes do occur in the area around Sahcaba and in the town itself but are much scarcer than sartenejas. This area is too flat and the soils too thin for the creation of natural aguadas found in Campeche.
[4] This results in large part from vegetation growth, which is in turn related to rainfall and soils.
[5] The bottoms of some of these lagoons and aguadas have structures similar to those re-ported earlier in other areas of the peninsula (Stephens, 1988 [1843]:2:148; Faust and Morales L´opez, 1993; Dom´ınguez Carrasco and Folan, 1995; Faust, 1998). Accord-ing to Faust (1998), these include stone linAccord-ings sealed with a lime mortar to prevent loss through seepage, chultuno’ob, and wells in the lowest areas of aguadas that were replenished by seepage.
[6] In some cases, abandonment was followed by the arrival of pilgrims and travelers dur-ing subsequent periods.
[7] The date given for Landa’s observation (1566) is the approximate date according to Tozzer (1941).
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Adams, R.E.W., Brown, W., Jr., and Culbert, T.P., 1982, Radar mapping, archaeology, and
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