The asteroid impact that wiped out the dinosaurs created a tropical rainforest, research shows.
Researchers used pollen and leaf fossils from Colombia to investigate how the impact changed South American tropical forests.
Since a kilometer-wide space rock slammed into Earth 66 million years ago, the type of vegetation that made up these forests changed drastically.
A team of scientists published the discovery in a prestigious journal Science (Science).
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One of the authors Dr. Monika Carvalho, sa Smithsonian Tropical Research Institute (Smithsonian Tropical Research Institution) in Panama, she said, "Our team examined more than 50.000 fossil pollen records and more than 6.000 leaf fossils before and after the impact."
They found that conifers and ferns were common before the huge asteroid hit what is now Mexico's Yucatan Peninsula.
But after the devastating blow, plant diversity declined by about 45 percent and extinction was widespread, especially among seed plants.
As the forests recovered over the next six million years, flowering plants dominated.
As a result of this transition, the structure of tropical forests also changed. During the late Cretaceous period, when dinosaurs still walked the planet, the trees that made up the forests were widespread. The peaks did not overlap, leaving open sunlit areas on the forest floor.
After the impact, the trees developed dense canopies that allowed much less light to reach the ground.
So how did the impact transform the sparse, conifer-rich tropical forests of the age of the dinosaurs into today's rainforests, with towering trees dotted with colorful flowers and orchids?
Based on pollen and leaf analysis, researchers offer three different explanations.
First, dinosaurs were able to prevent dense forest from forming by eating and trampling the plants growing in the lower levels of the forest.
Another explanation is that the ash from the impact that fell on the ground combined with the soil in the tropics favors faster growing flowers.
A third explanation is that primarily the extinction of conifer species created an opportunity for flowering plants to take over.
These explanations, say the team, are not mutually exclusive and could have together contributed to today's outcome.
“We learned here that under rapid disturbance ... tropical ecosystems do not revert; they get replaced and the process takes a really long time," Dr. Carvalho said.
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