Most people know the story: An asteroid hit Earth 66 million years ago and the dinosaurs disappeared. But new research shows their loss also changed the very landscape they used to walk.
Geologists analyzing rock layers in Montana and Wyoming found that the extinction of dinosaurs coincided with an abrupt reorganization of rivers and floodplains across North America. The team says dinosaurs acted as “ecosystem engineers,” and their disappearance allowed forests to grow thicker, rivers to settle into steadier paths and swampy areas rich in coal to take over.
“Before the mass extinction, it would be similar what you see in Africa today with open savannahs maintained by large herbivores,” said study co-author Courtney Sprain, Ph.D., a geologist at the University of Florida. “Back then, you had large herds of triceratops wandering around in this region, flattening vegetation.”
Like modern elephants, the trampling and grazing of giant dinosaurs kept landscapes open. Without stabilizing tree cover, rivers were broad, muddy and easily shifted course.
After the impact, everything quickly changed. In the rock record, unstable streambeds gave way to broad, meandering rivers lined with dense vegetation. Coal seams suddenly appear, evidence of swampy, forested floodplains.
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