Since the late 1950s, scientists have known about the existence of grand-scale earthworks throughout Bolivia’s Amazonian region of Baures. Recent investigations by archaeologists indicate that some of these earthworks are the remains of a unique, highly productive landscape-scale fishery operated by pre-Columbian native peoples at least 300 years ago. The discovery, made by Dr. Clark Erickson, associate curator of the American section at the University of Pennsylvania Museum of Archaeology and Anthropology, sheds new light on the region’s pre-Columbian Native Americans — peoples with the engineering and environmental know-how to transform a marginal Amazonian environment to a landscape capable of serving a far larger human population than lives in the area today.
Working with a joint U.S./Bolivian research team since 1995, Dr. Erickson has documented a complex artificial network of hydraulic earthworks covering 326 square miles on the flat, seasonally flooded savanna landscape of the Baures region of Bolivia, bordering Brazil. Throughout the landscape there are dense networks of interconnected, linear zigzag structures of raised earth. Dr. Erickson has identified the zigzag structures as permanent fish weirs, or traps, which are designed to take advantage of the seasonal flooding, when fish migrate to and spawn in the inundated savannas. The fish weirs and accompanying artificial built ponds, he contends, together provided a form of intensive aquaculture, allowing easy management and harvest of high protein food — in quantities sufficient to sustain large populations in the otherwise formidable savanna environment.
The savannas of Baures are inundated with a thin sheet of water during the rainy season. Dr. Erickson determined that the early inhabitants of the region built the low, narrow earthworks to control and enhance the movement of fish across this landscape. Small parallel openings where the weirs change direction were used to channel fish into traps. The associated ponds were used for the concentration and live storage of fish during the dry season.
The zigzag structures, which Dr. Erickson believes to have been abandoned about 1700 CE, are similar to fish weirs built by native peoples in Bolivia and throughout the Americas today. There are, however, some important differences. While fish weirs built today are generally constructed in permanent bodies of water and rebuilt each season, the zigzag structures are permanent earthworks that were built across a seasonally flooded savanna. The zigzag structures are longer, more numerous, and more densely placed than contemporary fish weirs. Finally, the complexity of the weirs and large causeways suggest that these structures, unlike today’s fish weirs, may have been used for management of water in the region.
The archaeological importance of the Baures region was first noted by Kenneth Lee, a United States expatriate oil engineer. Mr. Lee encouraged Dr. Erickson and his team of Bolivian and American students to investigate the region in 1995. One flight over the region in a small plane convinced Dr. Erickson of the vast scale of the earthworks, and he began formal fieldwork. The fish weirs were first identified in 1996, providing further evidence of the archaeological importance of the region. In 1996, the Bolivian government declared the region a national archaeological and ecological reserve and named it after Mr. Lee, who died in 1997.
For Dr. Erickson, the research on the fish weirs is one part of a larger, ongoing investigation of the vast complex of pre-Columbian earthworks in the Bolivian Amazon. He and a growing number of anthropologists believe these earthworks, which include raised fields for agriculture and large settlement mounds, causeways and canals, offer testament to a long history of pre-Columbian Native American sophistication and expertise in landscape engineering.
“Prior to the arrival of Europeans, the Native Americans of this region applied their knowledge of hydrology, soils, ecology, and agriculture to build a highly productive landscape,” Dr. Erickson noted. “Although the native peoples were removed from the lands by the Spanish missionaries and by European-introduced epidemics, the abandoned earthworks still influence the vegetation, drainage, and bio-diversity of the region today.”
Dr. Erickson is one of a growing number of archaeologists practicing “applied” or “experimental” archaeology, exploring the practical use of knowledge and technology of the past in the contemporary world. Between 1990 to 1994, Dr. Erickson and colleagues collaborated with native communities in experiments reintroducing raised field agriculture. He hopes to develop an experimental fish weir project in the near future.
“We’re learning that, in the past 12,000 years, indigenous peoples of this region transformed the environment and in the process, had a major role in creating what we now recognize as the rich ecological mosaic of the Neotropics,” Dr. Erickson noted. “Archaeologists can play a major role in documenting and recovering indigenous knowledge of land use and technology that are not recorded in historical or ethnographic documents,” he noted. “Archaeology can contribute to the long-term study of environments and, I believe, provide models for sustainable development based on past uses of the land.”