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This forest has remained wild for 5,000 years-thanks to the soil

Aerial view of the Putumayo region of the Amazon rainforest in Peru.Credits: Alvaro del Campo, Field Museum of Natural History

We sometimes think that the Amazon rainforest has not been modified by humans and can peep into the Earth’s past. In the last few years, scientists have learned that many parts of the Amazon are completely untouched. The Amazon has been cultivated by indigenous peoples for thousands of years, and only centuries ago there were cities and farmlands. But that’s not the case everywhere.In a new study at PNASResearchers have found that the rainforests of the Putumayo region of Peru have been home to relatively unaltered forests for 5,000 years, and that the people who lived there have found a long-term way to coexist with nature. .. Silica and charcoal in the soil.


“Even experienced ecologists find it very difficult to tell the difference between a 2,000-year-old forest and a 200-year-old forest,” said Nigel, an ecologist and co-author of the paper at the Field Museum of Natural History in Chicago.・ Pitman says. PNAS paper. “There are more and more studies showing that many of the Amazon forests we consider to be wilderness are actually only 500 years old, because the people who lived there were also by Europeans. He died in a pandemic and the forest grew again. “

“Rather than suggesting that the complex and lasting human settlements of the Amazon did not affect the landscape of some areas, our study shows that the serious impact of indigenous peoples on the forest environment is significant. It adds significant evidence that parts are concentrated in nearby nutrient-rich soils, and the use of surrounding tropical rainforests is sustainable and of species that can be detected for thousands of years. It did not cause any loss or confusion, “said Dolores Piperno, a researcher at the Smithsonian Tropical Research Institute and the first author of the study.

Many plants take silica from the soil and use it to produce fine mineral particles called plant stones that provide structural support. After the plants die, these phytoliths remain in the soil for thousands of years. Different types of plants produce different shapes of phytoliths. In other words, you can use phytoliths in the soil to determine what kind of plants have lived there in the past.

For this study, Piperno of the University of Amsterdam and her colleague Crystal McMichael Soil sample From the Putumayo region of the Amazon rainforest in northeastern Peru. That’s where Pitman comes in. In work with the Keller Science Action Center in the field, Pittman participated in Amazon’s “Rapid Inventory Survey,” recording local flora and fauna, and intensive information gathering to build relationships with local people. Take part in the trip. Live there to help build a case to protect the area. Piperno and McMichael contacted botanist Pitman and asked if soil samples could be collected when cataloging trees in the Putumayo area.

This forest has remained wild for 5,000 years--thanks to the soil

Soil samples taken in the rainforest.Credits: Nigel Pitman, Field Museum of Natural History

“Three to four days staying at one of these sites makes me feel like I’m running a marathon. I have to do a lot in a short amount of time, so get up early in the morning and stay up late. And, for some reason, these soil cores had to be taken at the same time, “says Pittman.” Sometimes, we took the soil at midnight or during a marathon when we couldn’t survey the trees. “

To collect the soil, Pitman and his colleagues (such as Field Museum Associates Juan Ernesto Guevara Andino, Marcos Rio Paredes, Luis A. Torres Montenegro) are called wood augers. I used a tool. “This is a long metal rod with a blade on the bottom that, when pierced into the ground and rotated, carves a pillar of soil about 2-3 feet long.” The team teamed up at various heights of the pillar. Soil samples were taken at, placed in plastic bags and shipped to the United States for analysis.

The age of the soil roughly correlates with its depth, with new soil at the top and old soil deeper in the ground. Returning to the lab, researchers use radiocarbon dating to age the soil, carefully classify the samples under a microscope, and indicate the types of plants that were inhabiting the area at that time. I searched for a plant opal.

They found that the currently growing species of trees in the region have grown there over the last 5,000 years. This shows that, unlike the rest of the Amazon, Putumayo had no cities or farmlands before the colonization of Europe.

In addition to plant stones, researchers also searched for fine pieces of charcoal. “In the western Amazon, where it rains all year round, if you find charcoal, you know there were people there,” says Pittman. “There are no spontaneous forest fires caused by lightning strikes, so something burns because people ignite it.”

This forest has remained wild for 5,000 years--thanks to the soil

Peru, the Putumayo region of the inland Amazon rainforest.Credits: (c) Corine Vriesendorp, Field Museum of Natural History

Low level of charcoal inside soil For 5000 years, people lived in the area while the forest was not altered by humans. They coexisted with the forest without changing it.

“One of the scariest things for nature maintenance activists about the findings that most of the Amazon was once towns and arable land is that non-nature maintenance activists are allowed to say this. There is no reason. — 500 years ago, half of the Amazon was cut down and everything is back. That’s not a big deal. You don’t have to worry too much about cutting down the Amazon, ”says Pittman. This study suggests that while people can coexist without altering the wilderness, the Amazon is not simply a resource that can be destroyed and regrown from scratch in the centuries.

The indigenous people were the caretakers of the western Amazon

Long-lasting microfossil particles of dead plants, taken from soil cores collected by scientists in the Amazon basin, were observed under a microscope. Most of the phytoliths investigated by the team were smaller than the width of human hair. Scientists have used soil cores to create a timeline of plant life and fire history in each location about 5,000 years ago. To do this, the team extracted phytoliths and looked for traces of fire such as charcoal and soot. Fires in nearly 10 feet of rainy landscapes each year were almost always of human origin and would have helped clear up vast lands for human use, such as agriculture and settlements. Smithsonian Scientists and their collaborators have discovered new evidence. Prehistoric indigenous peoples can use it in a sustainable way without significantly altering large areas of the western Amazon forest ecosystem, without changing large areas of the rainforest, or reforming their composition. This new discovery is the latest in a long scientific debate about how the Amazon people have historically shaped the rich biodiversity of the region and the global climate system. It provides new suggestions on how the Amazon’s biodiversity and ecosystems are best preserved and maintained today. Credits: Dolores Piperno, Smithsonian.

“For me, these findings do not mean that indigenous peoples did not use forests, but that they used forests sustainably and did not change their species composition much,” says Piperno. .. “During the study, there was no reduction in plant diversity. This is where humans appear to have been positively empowering the landscape and its biodiversity for thousands of years. is.”

“This is an important and hopeful discovery, showing that people have lived in the Amazon for thousands of years, allowing them to thrive and forests to thrive. Because, “says Pitman. “And since this identification forest Is still protected by indigenous peoples, but I hope this study reminds us all of how important it is to support their activities. ”


The Amazon tree species are so numerous that we haven’t found the last one for 300 years


For more information:
Dolores R. Piperno el al., “5,000 years of vegetation and fire history in the Tierra Farmme forest in the Medio Putumayo-Algodón basin, northeastern Peru” PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.2022213118

Quote: This forest remained wild for 5,000 years — Soil acquired from https://phys.org/news/2021-06-forest-wild-yearswe-soil on June 7, 2021 (June 2021) 7 days) is the cause. html

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This forest has remained wild for 5,000 years-thanks to the soil

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