Wednesday, November 16, 2011

Aztec Urban Agriculture

Chinampa farming in Tenochtitlan
Urban agriculture is a hot topic right now, but it's nothing new. The Aztecs were doing this 600 years ago. Today, the cultivation of crops within cities is expanding all over the world. This practice is being promoted by city administrations, by planners, and by grassroots organizations. Urban agriculture provides food for urban residents; the food is fresh; and the maintenance of green areas has health benefits. This practice is being touted as a positive force in creating more sustainable cities.

The growth of urban agriculture is also the target of a rapidly growing scholarly literature. Agronomists are studying the soil nutrients of urban agriculture, engineers are looking at water supplies, anthropologists and sociologists are examining the social aspects of urban farming. This research targets both developing countries and the developed world.

What people don't seem to realize is that urban agriculture was quite extensive in ancient cities. Although a few writers acknowledge that ancient societies practiced urban agriculture, they view it as in isolated and rare practice limited to a few isolated places. Most writers about modern cities, of course, just ignore deep history. To them, urban agriculture is something new, a product of the sustainability movement. For example, the "Solutions" website wrote in November 2010 that urban agriculture is "a new movement."

In fact, urban agriculture was a "new movement" several thousand years ago.  The history of ancient urban agriculture has yet to be written, but there are some good archaeological and historical examples from the area where I do fieldwork, ancient Mesoamerica. Swedish archaeologist Christian Isendahl (2010) performed chemical analysis of ancient soils to show that the ancient Maya grew crops within their low-density cities. Calixtlahuaca, the Aztec-period urban site where I am working now, was a giant cultivated hillside; people built stone terraces for their houses and for gardens. But the most spectacular example of ancient urban agriculture in Mesoamerica was the Aztec capital Tenochtitlan.

Tenochtitlan, the island capital
Urban agriculture at Tenochtitlan is not a new discovery. It was known to Europeans from the time Hernando Cortés and his band of Spanish soldiers entered the Aztec capital in 1519. They remarked on the many green areas devoted to farming. The famous Aztec chinampas (often incorrectly called "floating gardens) covered many acres of the city. Built on a island in a large lake, Tenochtitlan was crossed by many canals. Indeed, the Spaniards called it "the Venice of the New World."

The chinampas are a remarkable form of agriculture. They were very intensively cultivated, with three to four crops a year. The chinampas are an example of a more widespread farming system called raised fields. This was a system of farming in swamps or shallow lakes. Soil was scooped up from the lake bottom and piled onto long parallel rows. The fields were sometimes held in place with trees or wood stakes. Crops planted on top of the rows had easy access to water, and the soils were very rich. Periodically the canals between the fields were cleaned out and the muck piled on top of the field (a process known as "mucking"). This material was rich in decaying organic material, a great natural fertilizer.

Aztec map of a chinampa area
Raised fields were devised a thousand years or more before the Aztecs in lowland Mesoamerica, and the system was  used by the Classic Maya (AD 0-800). In South America, raised fields were invented independently, and large systems were built in the Llanos de Mojos of Bolivia, and around the edges of Lake Titicaca between Bolivia and Peru.

By the time Tenochtitlan was founded (AD 1325), this was an ancient agricultural method in Mesoamerica, although rare in the highlands. The Mexica people founded their city in the shallow waters of Late Texcoco. As the city expanded, vast areas of chinampas were constructed at the city edges.The island was located in an area where the salty waters of Lake Texcoco met the fresh waters of Lake  Xochimilco in the south. When Tenochtitlan grew large, a system of dikes was built to keep the salty waters away from the city (and to control flooding).

Urban chinampa fields in Tenochtitl
A remarkable Aztec map (black-and-white figure at right) shows one area of Tenochtitlan with large canals and footpaths, blocks of parallel chinampas, and the houses of farmers. Soon after the Spanish conquest, the Aztec peoples started using the machinery of the Spanish legal system, including written wills. These chinampa farmers left
their houses and fields to their descendents, and the wills often contain maps of their holdings. The next figure shows some of these drawings, compiled from such wills by ethnohistorian Edward Calnek. Most farmers owned two or three fields, located adjacent to their houses. As shown by the painting of Tenochtitlan at the top of this entry, the Aztec capital (with its 100,000+ inhabitants) was ringed with chinampas.

In addition to Tenochtitlan, Lakes Xochimilco and Chalco (south of the city) were covered with chinampas in Aztec times. Although this system was highly productive, it met only a portion of the food needs of the imperial capital. Food was also obtained through the markets and through taxes.

Chinampero in 1900

After the Spanish conquest, Tenochtitlan became Mexico City. Lake Texcoco was drained and the chinampas no longer functioned. In Lake Xochimilco, however, the chinampas continued to be farmed in the colonial period and are still active today, growing flowers and vegetables for the Mexico City market.
Tourist boats at the "floating gardens"
The chinampero (chinampa farmer) in this great 1900 photograph (from the 3rd edition of my book, The Aztecs) is using a flat-bottom canoe of the type used by his Aztec ancestors. Today, the Lake Xochimilco chinampas are a tourist attraction. You can ride in a larger version of these canoes and see the fields up close, and you can even be serenaded by a mariachi band in a boat (for a fee). For tourists, the chinampas are called "floating gardens." These fields obviously do not float. That label probably comes from the practice of using floating rafts for germinating the plants, which are then transplanted into the chinampa surface.

Urban fields in Zinacantepec, 1579
The chinampas of Tenochtitlan are one of the more spectacular examples of ancient urban agriculture, but they are far from unique in the Aztec world. An early colonial map from Zinacantepec ("place [or hill] of the bat"), shows fields and houses in and around the town. Zinacantepec, located near Toluca and Calixtlahuaca, was a city-state prior to the Spanish conquest. This early map probably preserves much of the ancient settlement pattern (with the addition of a Christian church). Look closely at the nine houses surrounding the church. This was the downtown area of the town, and the artist had painted much of the area between the houses in green, indicating cultivated fields (the green is faint, but clearly present in this part of the map).

Medieval urban herb garden
A search of ancient and premodern cities in other parts of the world would no doubt turn up many other examples of urban agriculture. Just this morning I just found a great color illustration of a Medieval urban herb garden from a 15th century French manuscript.

When writers today call urban agriculture a "new movement," they are in error. But I am less interested in correcting such errors than in bringing to light a whole world of urban possibilities that existed in past times. The more we know about the past, the better we will be able to plan for the future. Look at the quotation from Winston Churchill in the top right corner of this blog: "The farther back we look, the farther ahead we can see." Or, in the words, of former Supreme Court Justice Sandra Day O'Connor, “It’s very hard to know where you’re going if you don’t know where you’ve been.”

Here are some sources on the Aztec chinampas. The first complete and scholarly book on the city of Tenochtitlan to be published in English is now in press (Rojas 2012); it has much good information on chinampas and other features of the island city.

Ávila López, Raúl
1991    Chinampas de Iztapalapa, D.F. Colección Científica, vol. 225. Instituto Nacional de Antropología e Historia, Mexico City.

Calnek, Edward E.
1973    The Localization of the Sixteenth Century Map Called the Maguey Plan. American Antiquity 38:190-195.

2003    Tenochtitlan-Tlatelolco: The Natural History of a City / Tenochtitlan-Tlatelolco: La Historia Natural de una Ciudad. In El urbanismo en mesoamérica / Urbanism in Mesoamerica, edited by William T. Sanders, Alba Guadalupe Mastache, and Robert H. Cobean, pp. 149-202. Proyecto Urbanismo dn Mesoamérica / The Mesoamerican Urbanism Project, vol. 1. Pennsylvania State University and Instituto Nacional de Antropología e Historia, University Park and Mexico City.

Rojas, José Luis de
2012    Tenochtitlan: Capital City of the Aztec Empire. University Press of Florida, Gainesville. In press,

Smith, Michael E.
2012    The Aztecs. 3rd ed. Blackwell Publishers, Oxford.

For more context on urban agriculture see:

Boone, Christopher G. and Ali Modarres
2006    City and Environment. Temple University Press, Philadelphia.

Isendahl, Christian
2010    Greening the Ancient City: The Agro-Urban Landscapes of the Pre-Hispanic Maya. In The Urban Mind: Cultural and Environmental Dynamics, edited by Paul Sinclair, Gullög Nordquist, Frands Herschend, and Christian Isendahl, pp. 527-552. Studies in Global Archaeology, vol. 15. Department of Archaeology and Ancient History, Uppsala University, Uppsala.

Ljungkvist, John, Stephan Barthel, Göran Finnveden, and Sverker Sörlin
2010    The Urban Anthropocene: Lessons for Sustainability From the Environmental History of Constantinople. In The Urban Mind: Cultural and Environmental Dynamics, edited by Paul Sinclair, Gullög Nordquist, Frands Herschend, and Christian Isendahl, pp. 367-390. Studies in Global Archaeology, vol. 15. Department of Archaeology and Ancient History, Uppsala University, Uppsala.

Sunday, November 6, 2011

Defining cities and urbanism (again)

I just found out that my post "What is a city? Definitions of the urban," is the most popular post in this blog. Since my views on this topic have been changing slightly, perhaps it is time for more consideration of the topic. The earlier posts contrasts two definitions: the demographic definition (cities are places with lots of people and social complexity) and the functional definition (cities are places whose activities affect a larger hinterland). In Mesoamerica, these opposing definitions have been most commonly invoked in comparisons of Teotihuacan and the low-density Maya cities. This iconic comparison, from Sanders and Price (1968) is informative:

Are these both cities? Teo and Tikal at the same scale

My thinking these days has shifted slightly. I am less concerned now with coming up with complete definitions of city and urban than with exploring the different kinds of features that make up the concept of urban. The different definitions of urbanism (the two I have discussed, and others as well) vary in the weight given to three main features: Population, complexity, and influence. Settlements can be urban-like on one, two, or all three of these dimensions. The one we choose to emphasize depends on our goals.


In the traditional (demographic) definition of urbanism, population is of primary importance -- both the number of people and the density per unit of area. For the functional definition of cities, the population doesn't matter much. Right now, in our project on semi-urban settlements, population is the most important attribute. These are places like refugee camps and internment camps that are formed rapidly, and we are looking to see whether they have neighborhood organization. For our purposes, it doesn't really matter whether these places exhibit social complexity, or influence on a hinterland. What makes them "semi-urban" or city-like is their aggregation of people in one place. Similarly, Roland Fletcher's important work on settlement size (Fletcher 1995) is about the role of population size and population density on human settlement dynamics.


My university campus
Social complexity or variation is part of Louis Wirth's (1938) demographic definition of urbanism. This refers to occupational specialization, social classes or wealth variation, ethnic or cultural differences. Large population concentrations do not necessarily exhibit social complexity; large villages are an example. Settlements with urban functions--that is, settlements that influence a hinterland--almost always have some kind of social complexity. If a settlement has administrative functions, then it probably has government officials, bureaucrats of various types, perhaps military personnel--which means it would have social complexity. The same holds for economic or religious urban functions. But can a settlement be socially complex but NOT have a large population or urban functions? This would have to be some kind of self-contained highly specialized installation, perhaps a university campus or a large medieval monastery in a rural area.


Urban influence: capital city (Addis Ababa)
Urban functions are activities and institutions in a settlement that affect or influence a larger hinterland. This is what I mean by influence. A settlement can be large but have little complexity and little hinterland influence (e.g., a large agricultural village), or it can be complex with little influence (e.g., the college campus mentioned above). This dimension of "urban-ness" is important because it addresses the roles of cities in their societies. Cities are important nodes in a regional landscape, and the concept of influence points to the varying roles they play. So from a general perspective, when I need to define cities or urbanism, I usually point to the functional definition (as in my 2008 book, Aztec City-State Capitals).

Population, complexity and influence capture much of what we usually mean when we talk about concepts of the city or urban settlement. Most definitions of city and urban can be constructed from variations in these three factors. But sometimes we learn more by focusing less on such definitions and more on the individual dimensions. These three factors, and the ways they vary across time and space, are crucial components of the wide urban world

Fletcher, Roland
1995    The Limits of Settlement Growth: A Theoretical Outline. Cambridge University Press, New York.
Smith, Michael E.
2008    Aztec City-State Capitals. University Press of Florida, Gainesville.
Wirth, Louis
1938    Urbanism as a Way of Life. American Journal of Sociology 44:1-24.