The Dinosaur-Killing Asteroid Created Modern Rain Forests
About 66 million years ago, the earth was covered with giant dinosaurs. A massive asteroid impacted the planet in the area that is now the Yucatán Peninsula. The massive impact resulted in the extinction of most species on the planet and left the planet shrouded in darkness from dust and debris in the atmosphere. A new study has shed light on the origins of modern rain forests and could help scientists understand how rain forests might respond to changing climates in the future.The study was led by researchers at the Smithsonian Tropical Research Institute and shows that the asteroid impact that ended the reign of dinosaurs 66 million years ago also led to the extinction of 45 percent of plants in the area now known as Columbia. The extinction of those plants made way for the flowering plants dominating modern tropical rain forests. Researchers say they look for tropical plant fossils to determine how the rain forests changed after the asteroid impact.
The team examined more than 50,000 fossil pollen records and more than 6000 leaf fossils from before and after the impact. Before this study, very little was known about the effects of the extinction on the evolution of flowering plants that now dominate the American tropics. Pollen and spores from rocks older than the impact show that rain forests were equally dominated by ferns and flowering plants. Conifer trees were common in the area, and after the impact, the conifers disappeared almost completely.
Flowering plants took over after the impact, and plant diversity didn't recover for about 10 million years after the impact. Leaf fossils help the team learn about the climate and local environment in the past. The team says that pre-impact tropical forest trees were further apart and allowed light to reach the forest floor.
Within 10 million years after the impact, some tropical forests were dense with their leaves and vines casting shade on smaller trees and plants below. The team also found no evidence of legume trees before the asteroid impact, but there was great diversity and abundance of legume leaves and pods after the impact. Legumes are a dominant family in tropical rain forests today.