amazon Archives - ATLANTIS RISING THE RESEARCH REPORT

By Carolina Levis

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Trees that were domesticated by pre-Columbian peoples still dominate the forests of the Amazon Basin. The findings put a dent in the notion that the vast rainforests were untouched by human hands before the arrival of the Spanish explorers in South America. In an article published in Science, an international team including Florian Wittmann from the Max Planck Institute for Chemistry, the scientists report their findings (https://www.science.org/doi/10.1126/science.aal0157).

As far back as 8,000 years ago, the peoples of Amazonia began to domesticate plants such as the Brazil nut, the cacao tree and the acai palm tree. For a long time, it was not clear to what extent the indigenous inhabitants of the forest really transformed the forest by specifically tending to or cultivating certain trees or carrying their seeds over large distances. The international team from the Brazilian national institute for Amazon research (INPA) therefore investigated the occurrence of 85 tree species used for food or as a construction material by the pre-Columbian inhabitants. The scientists looked at data from the Amazon Tree Diversity Network (ATDN). The database contains an inventory of tree species found at approximately one thousand study sites in the Amazon Basin.
The team found that 20 out of 85 domesticated species are abundant in the entire Amazon Basin and dominate large swathes of the rainforest. A study published in 2013 and co-authored by Florian Wittmann identified 4,962 different tree species in total at the ATDN study sites. Only 227 of these were widely distributed. While only five per cent of all tree species are abundant in the Amazon Basin, 24 per cent of the domesticated species occur frequently there. The proportion of abundant domesticated species was thus five times greater than would have been expected if humans had not interfered.
Florian Wittmann comments on the result: “The study sheds considerable light on how many tree species were propagated by humans; for example, Bertholletia, the Brazil nut.” A researcher in Manaus (Brazil) for the Max Planck Institute for Chemistry until 2016, Wittmann is now working at Karlsruhe Institute of Technology (KIT). Genetic studies have demonstrated that there are only very slight genetic differences between Brazil nut trees found in different areas of the Amazon region. Since the differences are much greater among species that have spread through the rainforest by chance, it is very probable that the species’ propagation was helped along by humans. Further investigation is required to confirm such findings concerning other trees, such as the cacao tree.
The study produced another finding: Around archaeological sites, the abundance and richness of domesticated trees increased. The researchers concluded that the American indigenous populations conferred an advantage on useful trees through their activities, thereby changing the ecosystems. The scientists believe that the finding confirms that human activities shaped the Amazon rainforest before the arrival of the Spanish. Florian Wittmann agrees: “Hardly any corner of Amazonia has been left untouched by humans,” the expert on floodplains ecology says. “According to estimates, about ten million people lived there prior to European colonization.”

AR #82

Ancient Cities in the Forest

by William B. Stoecker

The Amazon river basin is known for its immense and lush tropical forests, so one might assume that the Amazon’s land is equally rich. In fact, the soils underlying the forested vegetation, particularly in the hilly uplands, are surprisingly infertile. Much of the Amazon’s soil is acidic and low in nutrients, making it notoriously difficult to farm.

But over the years, archaeologists have dug up mysteriously black and fertile patches of ancient soils in hundreds of sites across the Amazon. This “dark earth” has been found in and around human settlements dating back hundreds to thousands of years. And it has been a matter of some debate as to whether the super-rich soil was purposefully created or a coincidental byproduct of these ancient cultures.

Now, a study led by researchers at MIT, the University of Florida, and in Brazil aims to settle the debate over dark earth’s origins. The team has pieced together results from soil analyses, ethnographic observations, and interviews with modern Indigenous communities, to show that dark earth was intentionally produced by ancient Amazonians as a way to improve the soil and sustain large and complex societies.

“If you want to have large settlements, you need a nutritional base. But the soil in the Amazon is extensively leached of nutrients, and naturally poor for growing most crops,” says Taylor Perron, the Cecil and Ida Green Professor of Earth, Atmospheric and Planetary Sciences at MIT. “We argue here that people played a role in creating dark earth, and intentionally modified the ancient environment to make it a better place for human populations.”

And as it turns out, dark earth contains huge amounts of stored carbon. As generations worked the soil, for instance by enriching it with scraps of food, charcoal, and waste, the earth accumulated the carbon-rich detritus and kept it locked up for hundreds to thousands of years. By purposely producing dark earth, then, early Amazonians may have also unintentionally created a powerful, carbon-sequestering soil.

“The ancient Amazonians put a lot of carbon in the soil, and a lot of that is still there today,” says co-author Samuel Goldberg, who performed the data analysis as a graduate student at MIT and is now an assistant professor at the University of Miami. “That’s exactly what we want for climate change mitigation efforts. Maybe we could adapt some of their indigenous strategies on a larger scale, to lock up carbon in soil, in ways that we now know would stay there for a long time.”

The study was just published in Science Advances. Other authors include former MIT postdoc and lead author Morgan Schmidt, anthropologist Michael Heckenberger of the University of Florida, and collaborators from multiple institutions across Brazil. https://www.science.org/doi/10.1126/sciadv.adh8499).

In their current study, the team synthesized observations and data that Schmidt, Heckenberger, and others had previously gathered, while working with Indigenous communities in the Amazon since the early 2000s, with new data collected in 2018-19. The scientists focused their fieldwork in the Kuikuro Indigenous Territory in the Upper Xingu River basin in the southeastern Amazon. This region is home to modern Kuikuro villages as well as archaeological sites where the ancestors of the Kuikuro are thought to have lived. Over multiple visits to the region, Schmidt, then a graduate student at the University of Florida, was struck by the darker soil around some archaeological sites.
“When I saw this dark earth and how fertile it was, and started digging into what was known about it, I found it was a mysterious thing — no one really knew where it came from,” he says.

Schmidt and his colleagues began making observations of the modern Kuikuro’s practices of managing the soil. These practices include generating “middens” — piles of waste and food scraps, similar to compost heaps, that are maintained in certain locations around the center of a village. After some time, these waste piles decompose and mix with the soil to form a dark and fertile earth, that residents then use to plant crops. The researchers also observed that Kuikuro farmers spread organic waste and ash on farther fields, which also generates dark earth, where they can then grow more crops.

“We saw activities they did to modify the soil and increase the elements, like spreading ash on the ground, or spreading charcoal around the base of the tree, which were obviously intentional actions,” Schmidt says.
In addition to these observations, they also conducted interviews with villagers to document the Kuikuro’s beliefs and practices relating to dark earth. In some of these interviews, villagers referred to dark earth as “eegepe,” and described their daily practices in creating and cultivating the rich soil to improve its agricultural potential.

Based on these observations and interviews with the Kuikuro, it was clear that Indigenous communities today intentionally produce dark earth, through their practices to improve the soil.