The asteroid impact that killed off the dinosaurs gave birth to our planet’s tropical rainforests, a study suggests.
Researchers used fossil pollen and leaves from Colombia to research how the impact changed South American tropical forests.
After the 12km-wide space rock struck Earth 66 million years ago, the sort of vegetation that made up these forests changed drastically.
The team has outlined its findings within the prestigious journal Science.
Co-author Dr. Mónica Carvalho, from the Smithsonian Tropical Research Institution in Panama, said: “Our team examined over 50,000 fossil pollen records and quite 6,000 leaf fossils from before and after the impact.”
They found that cone-bearing plants called conifers and ferns were common before the large asteroid struck what’s now the Yucatan in Mexico.
But after the devastating impact, plant diversity declined by roughly 45% and extinctions were widespread, particularly among seed-bearing plants.
While the forests recovered over subsequent six million years, angiosperms, or flowering plants, came to dominate them.
The structure of tropical forests also changed as a result of this transition. During the late Cretaceous, when the dinosaurs were still alive, the trees that made up the forests were widely spaced. the highest parts didn’t overlap, leaving open sunlit areas on the forest floor.
But post-impact, forests developed a thick canopy that allowed much less light to succeed in the bottom.
So how did the impact transform the sparse, conifer-rich tropical forests of the dinosaur age into the rainforests of today, with their towering trees dotted with multi-colored blossoms and orchids?
Based on their analysis of the pollen and leaves, the researchers propose three different explanations.
Firstly, dinosaurs could have kept the forest from growing too dense by feeding on and trampling plants growing within the lower levels of the forest.
A second explanation is that falling ash from the impact enriched soils throughout the tropics, giving a plus to faster-growing flowering plants.
The third explanation is that the preferential extinction of conifer species created a chance for flowering plants to require over.
These ideas say the team, isn’t mutually exclusive, and will all have contributed to the result we see today.
“The lesson learned here is that under rapid disturbances… tropical ecosystems don’t just bounce back; they’re replaced, and therefore the process takes a very while,” said Dr. Carvalho.