Valley chronology taken from Parsons (1991).
Parsons (1991) uses the Valley’s settlement data from 1000 B.C. to AD 1520 to construct a model for chinampa development. Parsons bases his interpretation on the notion that pre-industrial agriculturists lived near the land that they cultivated. For the first 1,500 years of the Valley’s occupational sequence, human settlement is piedmont-, rather than lacustrian, oriented. Parson resolves that because the population is situated away from the lakebed, it is illogical to assume that they were engaged in chinampa agriculture or at least in any significant scale.
After A.D. 800 however, “a whole new cycle of settlement distribution and land use begins.” The collapse of Teotihuacan initiates the dispersal of “large blocks of population.” It is likely that it was one of these “blocks” which settles around the small Classic settlement of Xico, an island in eastern Lake Chalco. Meanwhile, another major settlement is established in the nearby Rio Amecemeca delta. The population of these two locales is estimated at 6,000 to 8,000 people, and according to Parsons, “except for a limited area on Xico island, there would not have been any accessible, naturally well-drained land for this large population.” Therefore, it seems that chinampa agriculture would have been required to support this population; Parsons states, “although direct evidence is still lacking, it appears that there was a definite commitment to swamp drainage and chinampa agriculture in eastern Lake Chalco during the late first millennium A.D. As far as we can now determine, this marks the beginning in the Valley of Mexico of chinampalike agriculture on any significant scale.” Sanders et al. (1979) also reach the same conclusion: “it is difficult to imagine an adequate subsistence base [for Xico Island] without chinampa agriculture.”
Parsons correlates the expansion of chinampa agriculture during the Early Aztec or Middle Postclassic period (A.D. 1150-1350) with the “proliferation” of small settlements over Lake Chalco and, to a lesser degree, Lake Xochimilco. The southern Valley was experiencing tremendous population growth. Moreover, the population was predominantly located in the lake bed/lake shore rather than the in the piedmont. While only 11.5% of the population was settled below an elevation of 2,265 meters during the Terminal Formative (~ 150 B.C.), over 70% were lake bed-oriented during the Middle Postclassic; “thus, for the first time in the entire prehispanic sequence there was an adequate labor force locally available to create and operate a chinampa system on a scale and intensity comparable to that of the historical period.”
The Late Aztec Period (~1350-1520) is marked by additional population growth and further lakebed expansion. It is during this time that significant occupation of Lake Xochimilco takes place.
The apparent absence of Early Aztec swamp drainage and chinampa building in Lake Xochimilco may have had a lot to do with the much greater danger in that region of periodic incursions of saline waters from Lake Texcoco. Occupation of the Xochimilco lakebed by large numbers of chinampa cultivators appears to have occurred only in the context of additional population growth and the implementation of large-scale hydraulic controls associated with the Late Aztec period, after the midfourteenth century (Parsons 1991).
It is this Late Aztec period which marks the peak of chinampa expansion. For instance, upon taking pottery samples from fifty chinampa house sites in the swampy southern basin, Armillas (1971) finds that the “bulk of the material unequivocally dates occupancy to around A.D. 1500.” It appears that chinampa agriculture had reached its heyday at the time of Spanish contact.
Both Armillas and Parsons conclude that chinampa expansion during this time was the result of “direct state intervention and management” (Parsons 1991). Using aerial photomaps, Armillas finds both regularity in chinampa layout and parallel canal orientation (south-southwest to north-northeast axes) and proposes that this scheme represents “planned enterprise [and so state involvement] rather than spontaneous initiative.” Parsons uses the change in scale and organization of chinampas to support the same conclusion. During the Early Aztec period, chinampa cultivation centered around natural islands and lakeshore locales, and “autonomous, community-level swamp drainage” was the norm (Parsons et al. 1985). The Late Aztec settlement pattern for Lake Chalco-Xochimilco, on the other hand, consists of dispersed groups of one to three households. Parsons asserts that these 100+ small household groups found atop chinampa ridges were state dependents or mayeques. The mayeques were “an increasingly important component of Tenochtitlan’s strategy to secure a dependent, tractable agricultural labor force” (Parsons 1991).
Moreover, there is also the argument that extensive chinampa cultivation was not possible without the building of large-scale earthworks (dike-causeways which controlled flooding and salinity). Because these endeavors require an enormous labor input, it seems likely that they were the result of state direction rather than local initiative (Palerm 1955).
It appears as though the Aztec state was expanding its role in the chinampa zone in an attempt to ensure a subsistence base. This however remains speculation. Although population growth, urbanization, and chinampa expansion are clearly correlated, it remains difficult to determine the actual causal relationships (Parsons et al. 1985).
In contrast to Parsons and Armillas, other scholars have argued that the state role in the chinampas has been overexaggerated. Baker (1998) questions both the necessity of state direction and the regularity of chinampa layout. He points out that chinampas were functioning prior to the construction of dikes and continued to function after they were destroyed; therefore, state intervention was not a prerequisite for chinampa expansion. Wilken (1985) asserts that geometric alignment of plots does not necessarily represent a “master plan.” The layout could have been designed to facilitate both drainage and canoe navigation. Wilken also proposes that major canals and dams could have been undertaken “by village work parties coordinated for that purpose but not necessarily subject to central direction.”
Regardless of the role of the state, the chinampas’ important economic role remains unquestioned. While Parsons et al. (1985) assert that chinampa agriculture had the capacity to produce over three metric tons of maize per acre, Armillas’ data suggests that the Chalco-Xochimilco zone, which consisted of 9000 hectares of productive soils, may have produced enough food to support 100,000 people and that at least half of the food was available for distribution among non-farming consumers (e.g. Tenochtitlan’s inhabitants). It was the chinampa farmers, along with the tribute-paying states, which provided the material basis for the Aztec empire by supporting the urban-dwelling non-food producers.
Although it is apparent that the Lakes Chalco and Xochimilco were and continue to be the principal chinampa zone, there is evidence that chinampas did exist on a smaller scale in other portions of the Valley. Sanders et al. (1979) identify “small, localized areas of chinampas” at the base of Cerro Chimalhuacan in Lake Texcoco and in the community of Xaltocan in Lake Xaltocan. The existence of local fresh water springs reduced the salinity of the two lakes at these individual locales and so rendered chinampa agriculture a possibility. Moreover following the construction of the sixteen kilometer dike discussed in the Technology and Water Works section, the western one-third of Lake Texcoco was transformed into a freshwater lake and so opened for chinampa agriculture (Sanders et al. 1979).
Nichols and Frederick (1993) provide more specifics with regards to the Xaltocan chinampas. Ceramics found during excavation and gathered from the lakebed in the vicinity of the chinampa excavation provide the best estimates for when chinampa construction took place. The majority of the sherds were Early Aztec (Aztec I or II). Because Aztec I ceramics are associated with radiocarbon ages between A.D. 770-880, one can presume that that is when the chinampas were built.
As for the chinampas near Chimalhuacan, Moriarty (1969) cites the work of Tolstoy (1958) who dated these chinampas to the Teotihuacan I period and who suggested that the chinampas were developed in response to changing climatic conditions. The gradual dessication of the Valley “made improved agricultural techniques a necessity” (Moriarty 1969).
Climate is clearly an important factor in considering the development of the chinampas, and one which should be more thoroughly explored. Armillas posed the exact same question in 1971: “What environmental conditions spurred chinampa expansion in Aztec times?”
