The asteroid’s impact, 66 million years ago, probably didn’t just lead to the extinction of the dinosaurs
Photo: SPL / BBC News Brazil
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The impact of an asteroid is known to be the most likely cause of the extinction of the dinosaurs, but what about the plants?
A study carried out in Panama, with samples taken in Colombia, points out that the event gave rise to the tropical forests that we know today on our planet.
The researchers used pollen and fossilized leaves from Colombian soil to investigate how the meteor’s impact changed the rainforests of South America.
After a 12 km wide space rock hit Earth 66 million years ago, the type of vegetation that formed these forests has changed dramatically.
Mónica Carvalho, of the Smithsonian Tropical Research Institute in Panama and co-author of the study, said: “Our team examined more than 50,000 fossil pollen records and more than 6,000 leaf fossils before and after impact.”
The team described their findings in the prestigious science journal Science.
Discoveries
Scientists found that coniferous plants and ferns were common before the huge asteroid hit Earth, where it is now the Yucatan Peninsula in Mexico.
But after the devastating event, plant diversity dropped by about 45% and extinctions spread, especially among seed plants.
Forests recovered over the next 6 million years, but angiosperms, or flowering plants, came to dominate these areas of vegetation.
The structure of tropical forests has also changed as a result of this transition.
Modern tropical forests are dense, with thick tops, unlike what existed at the end of the Cretaceous period
Foto: Getty Images / BBC News Brasil
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During the late Cretaceous period, when the dinosaurs were still alive, the trees that made up the forests were widely spaced.
Their crowns were not on top of each other, leaving open areas that were lit by the sun on the forest floor.
But after the impact, the forests developed a dense formation that allowed much less light to reach the ground.
But how did the impact turn the rich tropical forests into sparse conifers from the dinosaur era in today’s tropical forests, with their tall flowering trees and multicolored orchids?
Radical change
From the analysis of pollen and leaves, the researchers propose three different explanations.
First, the dinosaurs could have prevented the forest from becoming dense by foraging and trampling the plants that grew in the lower areas of the forests.
A second explanation is that the fall of ash after the impact enriched the soils of the tropics, giving an advantage to plants with faster growing flowers.
The third explanation is that the particular extinction of conifer species has created an opportunity for flowering plants to take their place.
These ideas, says the team, are not mutually exclusive and all could have contributed to the result we see today.
“The lesson learned here is that in rapid shocks … tropical ecosystems not only recover, they are replaced and the process takes a long time”, concludes Carvalho.
See too:
What it was like to be a black child in postwar Germany
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