An ancient plague has devastated the Amazon basin in Brazil for at least 4,000 years, a new study suggests.
The report from archaeologists in northern Brazil’s Amazon state of Pará found that the volcanic eruption of a nearby tectonic plate 11,000 years ago spilt sulphur ash across the surface of the forest where the scientists found evidence of fire and trees more than twice the size of today’s.
The scientists analysed tree pollen and animal fossils to piece together the timeline of the deforestation, starting from the fires some 6,000 years ago, to the sediment taken by the researchers from 4,000 years ago and now. The researchers say the sediment shows that fire had been established for an extended period in this area.
A deposit of volcanic ash on a volcanic detour in Pará. Photograph: Carlos Liberte/Annasanta International
“We basically have the longest written chronicle of fire that we have seen in the Amazon basin until this moment,” said Sebastião Gomes of the Carlos Cardozo University and the Universidade Federal de Goiás in Brazil.
The study appears in the journal Nature Ecology & Evolution.
It builds on previous research on the Amazon basin finding that the sprawling forest’s expansion from around 7,000 to 10,000 years ago coincided with the production of huge ash deposits, with one ash deposit measuring the equivalent of a city of 20 million people in 1970 square miles. The deposits in northern Pará reached as high as 900 metres above sea level.
Lying about 270 miles north of Rio de Janeiro, Pará is larger than France and England combined, and covers a total area of roughly 550 square miles. The rugged landscape is prone to forest fires and has suffered from frequent droughts, raising fears about deforestation in a region that is a crucial source of water for millions of people in the Amazon basin.
About 1,800 fires hit the region between 7,600 and 8,200 years ago, as the trees had already started to mature. The researchers say it is possible that the ash deposits were the result of these fires.