The relationship between humans and the Amazon Rainforest has not always been a harmonious one. However, recent research suggests that the Indigenous peoples of the Putumayo region helped to cultivate the rainforest, leaving it virtually unaltered for 5,000 years. Perhaps humans coexisting with nature is possible after all.
The study, published in PNAS, looked at soil samples in the Putumayo region of the Amazon in Peru to find evidence of human impact on the land. The researchers found that the trees still growing in the region today have been growing there for the last 5,000 years – evidence that the area has not been home to cities and farmland in that time. Traces of charcoal found in the soil, however, indicate that people did live there, they just did so in a way that had minimal impact on their environment.
“To me, these findings don’t say that the Indigenous population wasn’t using the forest, just that they used it sustainably and didn’t modify its species composition very much,” said Dr Dolores Piperno of the Smithsonian Tropical Research Institute, who led the study, in a statement. “We saw no decreases in plant diversity over the time period we studied. This is a place where humans appear to have been a positive force on this landscape and its biodiversity over thousands of years.”
To come to these conclusions, the team dug a 0.6–0.9 meter (2–3 foot) deep column into the ground, taking samples of soil from different heights along the column. The deeper samples represented older soil and vice versa. Back in the lab, samples were carbon-dated to determine their age and then sorted under a microscope to look for evidence of microscopic mineral particles, known as phytoliths. Phytoliths are essentially posthumous evidence of plants – they are produced by plants from silica in the soil and linger for thousands of years after a plant dies. Each phytolith is unique to a specific plant and so can be used to decipher which plants have grown in an area in the past.
Over 5,000 years' worth of samples, no species loss was detected. These findings suggest that contrary to common belief, the Amazon is not untouched by humans, but rather has been cultivated by them for thousands of years. The management of the rainforest by Indigenous peoples appears to have been vital in preserving its biodiversity and will continue to be important in the fight to prevent its collapse. As Nigel Pitman, a co-author on the paper, said: “since this particular forest is still being protected by Indigenous peoples, I hope this study reminds us all how important it is to support their work.”