Asteroid that killed dinosaurs responsible for changing tropics into Amazon forest: Study

A new study published in the Journal Science reveals that the asteroid that killed dinosaurs is also responsible for the origin of the neotropical forest. A report by Science news says that the formation of the tropical forests is because of an asteroid that hit earth nearly 66 million years ago. As a part of the study, the researchers analysed  tens of thousands of fossils of pollen, spores and leaves. These were collected from  39 sites across Colombia and dated between 70 million and 56 million years ago. 

(Fossils of leaves and pollen from across Colombia reveal how the tropical rainforests shifted due to the extinction event at the end of the Cretaceous. Before the event, the forests were a sunny, open-canopied mix of conifers, ferns and flowering trees (examples in the bottom half of this image). After the event, the forests were dominated by flowering trees, and developed a thick, heavy, light-blocking canopy (examples in the top half of this image). Image Credits: ScienceNews.org)

Assessing samples 

This was followed by the assessment of forest plant diversity, dominant species and insect-plant interactions. Also, there was a tracking of how these factors have been shifting. According to the reports by Science News, the plant diversity declined by 45 per cent immediately after the asteroid strike. The researchers also discovered that it took 6 million years before the rich diversity of the tropical rainforest rebounded, however, the forests did not remain the same even after this. 

Carlos Jaramillo, a paleopalynologist said, “A single historical accident changed the ecological and evolutionary trajectory of tropical rainforests. The forests that we have today are really the by-product of what happened 66 million years ago”. 

The researchers have given three explanations due to which the changes took place in the tropical forest. Firstly, it was because the forest was kept open because of the dinosaurs who kept moving. Another reason was that the flowering plants got an advantage due to the falling ash from the impact-enriched soil. “The competition for light was not that intense'', said Jaramillo. Lastly, there was a shift  in the chemical composition of the forest soil. Jaramillo explained, “The gymnosperms had this amazing ability to grow with very little food, and could outcompete the angiosperms”. 

(Image Credits: Pixabay/AP)