Why palm fossils are important for the Amazon rainforest

March 14, 2022
ninahylkjewitteveen

With all the horror chaos in the world, science doesn’t seem like the most important thing. I forgot all about my paper, until I received an email, that… the first chapter of my PhD is published! Some positive news I would like to share with you.  

If you think about a stereotypical scientist, hidden in a lab, investigating every detail of a tiny thing…. that is great description of what I was doing! 

A snapshot of data analysis

For months, bachelor-student Camille Hobus and myself were glued onto our laptops and microscopes to study plant fossils called phytoliths. These phytoliths get buried in the soil after plants die: the last reminder that the plant once grew there.

Our results have been published in this paper: https://doi.org/10.1016/j.revpalbo.2022.104613.
In there, you will find 2 guides on how to identify the phytoliths from palm trees that grow in South America. The guides show how to separate several palms, that we have not been able to identify before. The phytolith fossils these palms produce differ in shape, size, and texture. 

The guides can be used by other scientists that are studying phytoliths in South America. When I was doing a master thesis on freshwater algae, the guides from other scientists were so useful to help me get started! Hopefully, this paper can help other students. I also hope these guides will standardize and improve phytolith research in South America, because more palm types can be identified. 

Living in the rainy and grey Netherlands, one of the first things that announced my summer holidays were the palm trees. Indonesia was the first place where I saw a man climb a palm tree, barefoot using a machete! He was reaching for fruits. In Surinam I saw people making rooftops from dried palm leaves and coconut palm oil. People seemed to use palm trees for everything.

A wild Nina with a wild Açai palm in the jungle of Surinam

Palm trees aren’t just typical for tropical places, they are especially common in the tropics of South America. There are so many palm trees in the Amazon rainforest, some people think they were planted in the past by people that lived in the rainforest long before Europeans arrived. But other people disagree, saying that soil or climate might be responsible. 

To find out why palms are so common in the Amazon rainforest, we can study phytolith fossils. Phytoliths can reveal how many palms were growing in the past. Were there always so many palms in the Amazon? Where there more palms when populations grew, because people were planting them? Or did palm trees react when climate changed in the past? And that is why we studied palm fossils in great detail: to answer these questions! 

How did we separate fossils from different palms? We photographed and measured hundreds of phytoliths from palms. We have studied the shape, size, and texture of palm phytoliths from palms that were used to build houses, make oil or eat the fruits. Next, we used statistical analyses (PCA and pairwise comparisons) to find out which palm trees produce different phytoliths, because of their shape or size. The results were translated into the guides. 

Now, I am using the guides to study palm fossils from the rainforest in Surinam and Ecuador, going back 1500 years. I hope the next chapters of my PhD will tell you more about the history of palms and people there!

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