2021-04-08 22:48:11
It is chilling to think how a one-time, catastrophic event can radically change life on the entire planet. There have been several such events throughout history, but the best known and most recent took place about 66 million years ago. On that occasion, an asteroid or comet more than a dozen kilometers in diameter collided with the Earth with such violence that it took 75% of all terrestrial living beings with it. The crash took place in the Yucatan peninsula and we have described the immediate consequences in detail in this Vanguardia de la Ciencia program.
A few hours before the impact, the region was covered in tropical forests through which a huge variety of creatures roamed, including a wide variety of dinosaur species. A few hours later, for thousands of kilometers around, only destruction and death remained. The consequences of the crash spread throughout the planet and many species, belonging to the animal and plant kingdoms, disappeared forever. But that day marked, at the same time, the beginning of a new era, the surviving species began a slow progress and little by little, over several million years, they managed to recover the lost space and diversify, repopulating the entire planet. .
The impact marked a before and after in terrestrial ecosystems, especially in large tropical forests. A team of scientists, including our guest, the Colombian researcher Carlos Jaramillo, has carried out an analysis of the fossil pollen and the leaves of the plants that populated the tropical forests before and after the impact and has discovered how the ancient Open forests, inhabited by dinosaurs, disappeared and were replaced by the closed tropical forests that have survived to this day.
The results of the research have been recently published in Science, in an article signed, among others, by Mónica Carvalho and Carlos Jaramillo, entitled: Extinction at the end of the Cretaceous and the origin of modern Neotropical rainforests
Carlos Jaramillo describes during the interview how they studied the changes suffered by the vegetation before and after the impact. The researchers collected fossil pollen samples from 39 different locations that helped identify the different plant taxa existing at that time. To the fossil pollen data, the researchers matched thousands of leaf, plant and animal fossils collected in Colombia. The analysis reveals that the tropical forests of the late Cretaceous, before the catastrophe, were characterized by having a dense tree population, but with large clearings through which light penetrated to the ground, there plants without flowers (gymnosperms) such as araucarias, conifers or ginkos had a great role and shared the space with flowering plants (angiosperms). After the catastrophe, during the Paleocene, there was a change and it was the angiosperms that dominated the tropical forests, as they do today. This is how the large tree groups were born in which the treetops join each other creating a closed canopy, that is, a plant cover in height that does not allow sunlight to pass to the surface.
The recovery, however, was not immediate, at least six million years passed before the forests recovered the biological diversity lost on that terrible day when the Earth was hit by an asteroid in Chicxulub.
We invite you to listen to Carlos Jaramillo, a researcher at the Smithsonian Tropical Research Institute, Panama, and at the Department of Geology, Faculty of Sciences of the University of Salamanca.
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