We owe a lot to the asteroid impact that killed the dinosaurs 66 million years ago. For one thing, it gave us the lush tropical rainforests that help keep our planet healthy. That's according to a first-of-its-kind study published Friday in Science that looks at the effects of the Chicxulub impact on tropical forests using 6,000 leaf and 50,000 pollen fossils collected from Colombia over 20 years. The fossils, representing the region's biodiversity between 72 million and 58 million years ago, show Colombia's pre-impact rainforest was home to coniferous trees and was more sparse and less humid than we know it today, per Ars Technica. The impact wiped out half of the plant species there, and after roughly 6 million years of recovery, the conifers did not return. Instead, the flowering plants that were less common pre-impact began to dominate.
"We see the forests change their structure," becoming more dense and humid, and eventually leading to the thick canopy we know today, study co-author Monica Carvalho says. That may be because the dinosaurs' extinction meant there were fewer animals around to eat the plants and carve paths through them. It's also possible that cone-bearing conifers just didn't prosper as well in the post-impact tropics, while flowering plants benefited from carbon-rich soils left over from tsunami events, as well as from wildfire ash that served as fertilizer. "The lesson learned here is that under rapid disturbances ... tropical ecosystems do not just bounce back," Carvalho tells the BBC. "We can relate this to nowadays because we're also transforming landscapes, and that lasts forever—or at least a very long time," study co-author Carlos Jaramillo tells Scientific American. (Read more rainforest stories.)