Researchers used fossilized pollen and leaves from Colombia to study the collision that changed South America’s rainforests.
After the 12 km-diameter asteroid struck Earth 66 million years ago, the plants that make up the rainforest changed dramatically. The Smithsonian Tropical Research Institute team in Panama publishes the results in the journal Science.
Study co-author Dr Dishica Carvalho said he and his colleagues examined more than 50,000 pollen fossil records and more than 6,000 fossils before and after the accident. They discovered that coniferous plants and ferns were gaining popularity before a giant meteor hit what is now Mexico’s Yucatan Peninsula.
But after the crash, plant diversity declined by around 45% and extinction spread, especially in seed plants. Although forests recover over the next 6 million years, flowering plants gradually become dominant. The structure of the rainforest has also changed due to this change. At the end of the Cretaceous period, when the dinosaurs were still alive, the trees of the forest separated. The plants on the upper floors are not darkened but still leave room for sunlight to shine on the forest floor.
However, the forest after the collision developed a large canopy causing less light to reach the ground. To explain why rainforests with sparsely cultivated pine trees during the dinosaur era evolved into tall rainforests with vibrant flowers like the Amazon rainforest, the team proposed three hypotheses based on the results Analysis of the leaves of fossil plants and chalk.
First, dinosaurs could prevent trees from proliferating by eating and walking on plants growing on lower floors.
The second hypothesis is that the ash that falls from the collision makes the forest soil fertile, which is an advantage for fast-growing flowering plants.
With the third hypothesis, the extinction of conifers allows flowering plants to invade forests. All of the above theories could contribute to the results we are seeing today.
“The lesson here is that under the sudden influence, the tropical ecosystem not only recovers, but is also gradually replaced and this process takes place in a very long time,” said Dr Carvalho.