The disappearance of dinosaurs shaped the Earth’s landscapes, not just its animals. A new study has found that when dinosaurs went extinct 66 million years ago, they left behind dramatic changes in the structure of rivers and forests across North America, changes so striking that they can be seen in rocks and soil even today.
Dinosaurs Changed Landscapes, And Their Loss Left New Forests
For millions of years, large-bodied dinosaurs acted as powerful “ecosystem engineers”. As they moved in herds, trampling and uprooting plants, they kept forests open and patchy. This meant rivers were restless: they shifted courses, overflowed, and left behind muddy, waterlogged soil. The land was a mosaic shaped by the dinosaurs’ heavy footsteps and grazing.
But when the asteroid hit, causing the sudden extinction of dinosaurs, everything changed. Dense forests sprang up where only scattered trees and open spaces had been before. Without dinosaurs to keep plants in check, trees grew thickly, stabilizing the soil and riverbanks. Rivers became broader, their channels lasting longer instead of constantly changing. In these new conditions, organic-rich swamps formed, laying down coal beds that helped mark the boundary between the Cretaceous and the Paleogene periods.
Following the Clues in Rocks, Soil, and Fossils
Scientists identified five new boundary sites in the Bighorn and Williston basins by looking for iridium, a rare metal left behind by the asteroid impact. Wherever they found it, they also saw the same dramatic switch, from unstable, muddy soils to broad, sandy river channels topped by thick coal beds. This transition happened across a vast stretch of North America, regardless of local climate or geography, suggesting something huge, like the loss of dinosaurs, was the real cause.
Old ideas blamed things like climate change, rising sea waters, or tectonic shifts for these changes in landscape. But the new research carefully checked these theories and found they couldn’t explain the surprising, widespread, and sudden switch in river and floodplain style. Instead, the presence and then absence of herd-forming, massive dinosaurs fit the evidence best, just as elephants shape African landscapes today, only on a much bigger scale.
A New Story of Life and Land
This new picture from rocks, fossils, and soils suggests that the extinction of dinosaurs didn’t just open new doors for mammals and other plants, it also fundamentally reshaped the ground they lived on. It’s a powerful reminder that Earth’s history wasn’t only shaped by climate and catastrophe, but also by the life that once roamed its surface.
