Uncovering the 4,000 year-old secrets of rice farming in the Amazon

A Northumbria academic has been involved in an innovative research project in South America, uncovering how Amazonian farmers grew rice 4,000 years ago.

Dr Bronwen Whitney, a Senior Lecturer in Physical Geography, is an expert in past environmental change and how tropical plant communities have responded to historical disturbances. Her ongoing research into past climate change in South America’s large wetlands has contributed to understanding of how increased rainfall led to rice becoming an important crop able to be cultivated in the South American lowlands.

Dr Whitney helped archaeologists uncover evidence of how ancient South Americans learned to manipulate wild rice so they could grow bigger crops with larger grains. She created a model to track the size of botanical rice remains through time. The increased size of rice remains beginning 4,000 years ago, compared to wild ancestors, is an indication of domestication. 

Rice was initially grown at river or lake edges, but the researchers found microscopic plant remains on higher ground level. This suggests that rice began to play a bigger role in the diet of people living in the area, with more being farmed as time went on. They also found changes in the ratio of husk, leaf and stem remains at different ground levels which suggests that the Amazon residents became more efficient harvesters over time.

This is the first study to show when wild rice first began to be grown for food in South America and the evidence uncovered could highlight this source of genetic material to modern day plant breeders who work to develop rice crops which are less susceptible to disease or adapted to future climate change. The study also showed how important the huge wetlands of lowland South America were in providing food for early human settlers.

The findings have been published in the journal Nature Ecology and Evolution.

Dr Whitney explained: “Past peoples left imprints on their landscapes lasting hundreds of years on their landscapes from various activities, such as house building, timber extraction, and importantly, food production. Knowing how people shaped and manipulated their landscapes is central to conserving our environmental and cultural heritage.

“Ancient landscapes exist all over the world and although we think of the Amazon as ‘wild and pristine’, it was once a centre of crop domestication. Our regional climate reconstructions showed that the timing of domestication in lowland South America occurred just as annual rainfall began to rise. There are many archaeological sites located in semi-permanent wetland regions here, which suggests just how important the rice crop was to these early inhabitants.”

Dr Whitney teaches students on Northumbria’s Geography and Environmental Sciences courses. She added: “Here in Northumberland, there are imprints of medieval field workings in upland areas which are used only for pasturing or grouse shooting. Our students are introduced to these anthropogenic landscapes from their first week of teaching, and it is useful for them to know that this is not a phenomenon restricted to Northern Europe.”

Northumbria University’s Department of Geography and Environmental Sciences is ranked in the top 30 in the UK for research power, with over half of its research outputs ranked as being ‘world-leading’ or ‘internationally excellent’ in the 2014 Research Excellence Framework.

Academics are undertaking global projects funded by, or in collaboration with, organisations including the British Antarctic Survey; the US National Science Foundation and the Natural Environment Research Council. This particular study was part-funded by the European Research Council included academics from the University of Exeter and Brazil’s Universidade de São Paolo and the Universidade Federal do Oeste de Pará.