Pre-Columbian agriculture in the Amazon Basin

Pre-Columbian agriculture in the Amazon Basin refers to the farming practices developed by the indigenous communities of the Amazon rainforest before the European conquest. Contrary to the common misconception of the pre-Columbian rainforest as a pristine wilderness untouched by human influence, agricultural communities in the Amazon Basin actively shaped and managed their environment prior to the arrival of European colonists.  Eye witness accounts by Spanish and Portuguese explorers describe populous cities and flourishing agriculture. Population estimates for the pre-Columbian Amazon Basin range from a few million people to up to 10 million. After the population collapse following the European conquest, these communities were largely forgotten. Recent scientific research has helped to reconstruct the story of these lost settlements.

Agriculture in pre-the Columbian period

The transition from small foraging or hunter/gathering groups to more advanced agricultural societies occurred roughly 4,000 years ago in the Amazon Basin, though the exact timing of this transition varied by sub-region. The more advanced farming systems involved intensive arboriculture as well as staple root and seed crops. These systems supported stable settlements with relatively large populations. The reports of early European explorers described large “well-fed populations along the bluffs, surrounded by orchards on the uplands and seasonal fields in the floodplains.”

As elsewhere in the Americas, the European conquest brought the collapse of indigenous populations and the advanced agricultural systems of the pre-Columbian Amazon Basin were largely forgotten. Starting in roughly the year 2000, formal research projects (using molecular data, microfossil botanical techniques, remote sensing, and plant genetics) have resurrected the story of human settlement of the Amazon Basin – it is no longer thought to have been a primeval forest at the time of European contact and can now be considered, along with Mesoamerica, as an “early and independent cradle of agriculture”.

Forest and plant domestication

By 15,000 years ago, human colonization had reached most of the western South American landmass. The earliest solid evidence of human presence in tropical forests in eastern Brazil dates to about 13,000 years ago. By about 11,000 years ago, evidence points longer terms stays at fixed locations within the tropical forest – “people settled into their landscapes, staying for longer and: or more frequently returning to specific locations and they frequently manipulated and altered their environments by creating clearings in forests and/ or burning them”.

Through diverse activities seeking to favor useful species, they engaged in ‘forest domestication’ that altered the plant composition of the Amazon jungle, essentially changing the distribution and density of useful tree species (e.g. Brazil nuts and Açai-do-parà). The spatial pattern of this forest transformation radiated outward from human activity (concentrated on rivers), with spaces near settlements, campsites and trails undergoing more intensive change that remote spaces. Recent data for the region between the Purus and Madeira rivers indicates that the concentrations of useful species are detectible as much as 40km from major and even minor rivers.

Archeo-botanical evidence indicates that food cultivation began in South America between 11,000 and 7,600 years ago. The earliest crops were leren and arrowroot, but over time a more diverse array of plants were cultivated.  Within this context of primitive agricultural practice, plant domestication is thought to have been a slow and gradual process. About 6,000 years ago, the transition from foraging and small-scale farming to larger scale and more sophisticated farming practice accelerated the process of plant domestication. In this context, plant domestication was rapid and diverse, making the Amazon a major source of domesticated plant species. Prior to European contact, domestication had influenced at least 83 plant species in pre-Columbian Amazon Basin, including cacao, hot peppers, manioc, pineapple, sweet potato and tobacco and “as well as numerous fruit trees and palms at least another 55 imported neo-tropical species.”

Soil management

Amazonian soils are nutrient-poor in central and northwestern Amazon and are moderately rich in southwestern Amazon. ‘Anthrosoils’ are soils whose fertility has been enhanced by humans, which was a common practice worldwide among the agriculture communities of the late Holocene. Although scientists disagree about the degree to which human intervention or natural phenomena (e.g., flooding) were responsible for observed soils,^, pre-Columbian settlements appear to have been active, over the centuries, in enhancing certain soils, which are now known as terra preta (dark earth in Portuguese), or Amazon Dark Earths.

Terra preta integrated microscopic charcoal particles in high concentrations (which gives the soil its distinctive black coloration) as well as pottery shards; organic matter such as plant residues; animal and human feces; and fish and animal bones. The durable presence of charcoal particles in the soil enhanced the soil’s ability to retain nutrients essential for plant growth. A product of indigenous soil management and slash-and-char agriculture, the charcoal is stable and remains in the soil for thousands of years, binding and retaining minerals and nutrients.

Agroforestry and intercropping

Pre-Columbian indigenous peoples practiced agroforestry, which combined tree cultivation with other crops. This approach created a diverse ecosystem that offered both food and other resources, such as timber, fibers, and medicinal plants. Intercropping, or the cultivation of multiple crops within the same plot, was another practice used to maximize resources and yield. Plant intercropping was another agricultural practice employed by indigenous civilizations in the pre-Columbian Amazon Basin. It involved the cultivation of multiple crops within the same plot of land, often in close proximity or even intermingled. This practice allowed for efficient land use, enhanced soil fertility, and a diverse range of crops that complemented each other’s growth.

Infrastructure and water management

With the development of remote sensing technology (and also due to deforestation), it has been possible to document the pre-Columbian period's extensive agricultural infrastructure. These include tens of thousands of raised agricultural beds, as well as hundreds of kilometers of causeways and roads, canals; artificial cuts between river meander bends, artificial ponds and fish weirs. In addition, many indigenous groups developed techniques for cultivating aquatic resources. They constructed raised fields, known as “floating gardens,” in marshes and floodplains. These gardens were designed to withstand seasonal flooding and provided a consistent source of crops such as water chestnuts and arrowroot.

Pre-Columbian population and population collapse

Several Spanish and Portuguese explorers from the 16th and 17th century noted the flourishing communities along the Amazon and other rivers.  However, little historical documentation exists on the pre-Columbian human population in the region vary and current estimates rely on various estimation techniques that yield highly variable results.:  conservative estimates place it at one or two million people, whereas the highest estimates are between 8 and 10 million people. The arrival of European settlers brought about the collapse of these agricultural systems and the populations they supported. The farming settlements would not survive the introduction of European diseases and forced labor, and their farming practices were largely forgotten.^,

Today, there is growing interest in studying and preserving the knowledge of pre-Columbian agricultural practices in the Amazon Basin. Much of the region remains unexplored from this point of view. Indigenous communities, researchers, and environmentalists are working together to study, revive and adapt these methods to modern challenges such as deforestation, climate change, and food security.