The remains of an extensive ancient agricultural system built and used by Andean peoples centuries ago are found throughout the vast high plain surrounding Lake Titicaca in the Andean countries of Peru and Bolivia (Figs. 1, 2). Raised fields are large elevated planting platforms which provided drainage, improved soil conditions, and improved temperatures for crops. The remains of prehistoric raised fields, elaborate sunken gardens, and agricultural terraces cover tens of thousands of hectares in the region, and provide evidence of the impressive engineering abilities of the peoples who lived there in pre-Columbian times.
Our recent investigations of raised field agriculture demonstrate not only the technological expertise of the past cultures, but also that these systems could be re-used today to make high altitude lands more productive. In a region such as the Andes, where conditions of soil and climate greatly limit agricultural potential, technological methods to augment productivity have been increasingly necessary to support the growing populations of Quechua and Aymara farmers who live there today. The reuse of raised fields may he an economical and ecologically sound alternative to agricultural development based on expensive imported technology.
Until recently, very little was known about the origins and evolution of raised field technology in the Lake Titicaca Basin. Observant Spanish chroniclers in the 18th century described many aspects of the indigenous agriculture, such as terraces and irrigation canals, but they did not mention raised fields. This omission suggests that raised fields had probably been abandoned before the arrival of the Spanish. Questions such as who constructed the fields, when were they built, what crops were cultivated, why the fields varied so much in size and shape, and bow raised field agriculture functioned needed to be answered.
Between 1981 and 1986, 1 directed a small team of researchers investigating prehistoric raised field agriculture in the community of Huatta in the northern Lake Titicaca Basin of Peru. Huatta is located in the center of the largest block of raised field remains, estimated to cover 53,000 hectares. The project, combining archaeology and agronomy, addressed the important questions raised above, as well as those more relevant to modern agriculture, such as estimating the potential productivity of the raised fields and investigating their effects on the local agricultural environment. The investigation was based on archaeological survey and excavation of prehistoric raised fields and selected habitation sites, together with the construction and study of experimental raised field plots (see box). To apply the results of this research, a small-scale development project involving local Quechua farmers was begun in 1982 to put raised fields back into use.
Raised Field Agriculture and the Lake Titicaca Environment
Raised fields are constructed by excavating parallel canals and piling the earth between them to form long, low mounds with flat or convex surfaces. These raised platforms increase soil fertility, improve drainage in low-lying areas, and improve local micro-environments, primarily by decreasing frost risk. The canals between raised fields provide vital moisture during periods of short- and long-term drought. Water in the deep canals might have been used to cultivate aquatic plants and fish, as well as attract lake birds that were an integral part of the prehistoric diet. The raised fields of the Lake Titicaca region are diverse in form and in size, but generally range from 410 m wide, 10 to 100 m long, and are 1 in tall.
The prehistoric raised fields, covering some 82,000 hectares of low-lying land around Lake Titi-caca in both Bolivia and Peru (Fig. 1), have been badly eroded by a combination of wind, rain, flooding, and modern urbanization, but their remains can be seen clearly on the ground and in aerial photographs. They were specifically adapted to the particular environment, crops, and technology available to the indigenous farmers. Most of the land lies above 3800 m (12,500 feet), and nights can be bitterly cold, despite warm sunny days. The year is divided into distinct wet and dry seasons of roughly six months each, but even this situation may vary greatly from year to year, producing an unpredictable, high-rise agricultural environment. Frosts are most common during the dry season, and at the beginning and end of the growing (wet) season, but may occur locally at any time without warning, especially in low-lying depressions at the bases of hills.
The land immediately adjacent to Lake Titicaca has a somewhatmore favorable environment for cultivation, mild enough for special races of corn to be grown in sheltered valleys and on the islands and peninsulas of the lake. The stored heat of the massive body of lake water warms the areas around it, an especially important effect at night when frosts are common. Farther from the lake, this warming effect diminishes, but the entire region around the lake benefits from a slightly higher than average annual rainfall. The major obstacle to lakeside agriculture is that most of the surrounding land is either rocky steep slope or flat, waterlogged lake plain which may be seasonally inundated. Both areas have relatively poor soils and are classified as areas of limited agricultural potential in government studies. Today, large rural populations are located in areas that have better drainage, favorable temperatures, and good soils, combined with access to the lacustrine resources of Lake Titicaca.
Aymara: the indigenous peoples of present-day Peru and Bolivia who speak the Aymara language canihua: an Andean grain crop related to our weed lanibsquar-ters; high in protein
chakitaqlla: the Andean foot-plow, composed of a handle, shaft, and footpeg of wood with a heavy metal cutting /blade bound by leather tongs
flotation: a water separation process used by archaeologists for the recovery of small plant and animal remains from the soils of archaeological sites
pampa: a grass-covered, treeless plain which may he seasonally inundated or waterlogged
pollen analysis: the study of microscopic pollen grains which may give information on past climatic conditions, local environments, or crops cultivated
pollen analysis: the indigenous peoples of present-day Peru and Bolivia who speak the Quechua language
quinua: an Andean grain crop related to our weed lambs-quarters; high in protein
raised fields: large elevated planting platforms with intervening water-filled canals designed to improve drainage, maximize soil fertility, prevent frosts, and/or provide irrigation
The field stratigraphy, but the duration of each phase could not be ascertained through stratigraphic analysis alone. Carbonized remains for radiocarbon dating were not present in raised fields, but six pottery samples recovered from stratigraphic contexts in both the construction fill and the canals could be dated by the thermoluminescence technique. This technique determines the time elapsed since the original firing or last exposure to fire of the ceramic vessel. These dates give us a secure chronology for the raised fields and correlate nicely with the dates from the occupation mounds. The surprisingly early dates between 1000 B.C. and the beginning of our era, and the successive building stages and abandonment periods, demonstrate that the raised field system was not a brief late phenomenon as previously suspected. It appears to have been a relatively early agricultural development which was expanded gradually and was used by many generations of Andean farmers.
Our archaeological survey focused on locating the sites occupied by farmers who constructed and maintained the raised fields around Huatta. Most sites on the pampa in direct association with raised fields were earthen mounds that had once been small farmsteads or hamlets. Several larger sites both on the pampa and in the hills overlooking the plain were once towns with rustic public architecture. All that remains now are the stones that served as the foundations for the adobe structures. The number and distribution of habitation mounds indicate a rather dense population in the raised field area throughout the prehistoric period of raised field use, much larger than that of today, surprisingly. Two of the larger sites (those mentioned above for which dates were obtained) were partially excavated, and showed evidence of long-term occupation. These mounds were the cumulative result of continual rebuilding atop the remains of older, eroded structures. Many of these mounds are still considered to be ideal habitation locations due to their elevation, especially during the seasonal flooding of the pampa. Their garbage middens yielded information about prehistoric subsistence strategies, agriculture, and ceramic and weaving technology.
Plant Fragments, direct evidence of agricultural crops preserved by accidental carbonization, have been recovered by the screening and flotation processing of soils from the garbage midden and mound fill of habitation sites. These samples include fragments of potato and possibly other tubers, and quinua. Also identified were aquatic lake plants and other wild plants that could have been used for making mats, nets, and bags, as thatching material, or as forage for domestic animals. Fish, camelids (probably the domesticated alpaca and llama), guinea pig, and various aquatic birds are represented in abundant bone material recovered in the excavations. The floral and faunal remains are found throughout the sequence of occupation and indicate a remarkable economic stability. All of this evidence indicates a prehistoric subsistence pattern similar to that still practiced today by lake-edge dwelling Aymara and Quechua farmers., a pattern based on a combination of potato and quinua cultivation, herding, fishing, and intensive gathering of wild lake resources. The recovery of thousands of basalt hoe fragments, polished through years of use, attests to their importance in the tool inventory of the ancient agricultural technology. These stone hoes were among the implements used to construct the raised fields. Pottery remains included utilitarian serving and cooking vessels, in addition to ceremonial or fine wares decorated with burnishing, incision, and painting. One nearly complete house structure belonging to the Pucara culture (300 B.C.-A.D. 400) was excavated (Fig. 5), and it has many features similar to those of adobe houses with thatched roofs constructed today in the area.
Interpretations of the Excavations
Our research results show that large farming villages were settled throughout the lake area by 1000 B.C. By 300 B.C., Lake Titicaca society had evolved sufficiently to support large ceremonial and population centers. The site of Pucara in the northern lake basin has approximately 4 km of urban sprawl, complete with pyramidal platforms and temples with semi-subterranean.Simple cultivation on the floating islands as practiced today by the Uru of the Bay of Puno would have been a preadaptation to raised field agriculture, which was later expanded to include lake and river edge cultivation. Population appears to have grown along with agricultural expansion. Labor figures calculated from the experimental raised fields indicate that construction was not necessarily labor intensive, especially if fields were built and used over many generations. Field maintenance was found to be minimal in the experiments, but may increase after several years of cultivation. If fields can he continually used, with fertility maintained through the periodic application of decomposed organic matter from the canals, the initial labor investment for field construction is offset by the longterm benefits of continuous fertility combined with a high yield.
Not only can the Quechua- and Aymara-speaking peoples take great pride in the sophisticated agricultural technology of their ancestors, but they can actually apply it to solve some of the contemporary economic and agricultural problems of Peru and Bolivia. The farmers of the communities participating in rehabilitating raised fields are taking that step. The high productivity of raised field technology not only helps to support the growing populations of the towns and cities of the region where many small farmers have had to migrate in search of a livelihood, but also helps us to understand and preserve this technology for the future. It is ironic that such an immensely important and productive technology is being destroyed in many areas around Lake Titicaca by modern plow farming, urbanization, and road-building.