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Fossil trees on Peru's Central Andean Plateau tell a tale of dramatic environmental change

Christian Fernsby ▼ | September 1, 2020
As the Earth's surface transforms, entire ecosystems come and go.
Peru trees
Fossil trees   Peru trees
The anatomy of fossil plants growing in the Andean Altiplano region 10 million years ago calls current paleoclimate models into question, suggesting that the area was more humid than models predict.

On an expedition to the Central Andean Plateau, researchers from the Smithsonian Tropical Research Institute (STRI) and colleagues were astounded to find a huge fossil-tree buried in the cold, grassy plain.

The plant fossil record from this high-altitude site in southern Peru contains dramatic reminders that the environment in the Andes mountains changed drastically during the past 10 million years, but not in the ways that climate models of the past suggest.

Findings from the expedition are presented in the journal Science Advances.

The anatomy of the petrified (permineralized) wood the researchers found is very much like wood anatomy in low-elevation tropical forests today.

Indeed, the altitude then was probably only 2,000 meters above sea level.

But that ecosystem did not last for long.

The arid, intermountain plateau lies at 4,000 meters above sea level.

Five million yearold fossils from the same sites confirmed that the Puna ecosystem that now dominates the Andes' high mountain plateaus had been born: the younger pollen samples were mostly from grasses and herbs, rather than from trees.

Leaf material was from ferns, herbs and shrubs, indicating that the plateau had already risen to its current altitude.