Dinosaurs were ecosystem engineers and study shows how their sudden extinction changed Earth’s rivers

Dinosaurs’ Extinction Reshaped Rivers and Landscapes, Scientists Discover (Image: Julius Csotonyi)

The story of dinosaurs often ends with their sudden extinction. Yet new research shows their disappearance reshaped rivers and landscapes in ways still visible today. Could these lost giants have been nature’s ecosystem engineers?

How Did Dinosaurs Shape Ancient Rivers?

A University of Michigan study suggests dinosaurs controlled vegetation. By trampling plants and knocking trees down, they kept open spaces. This created unstable floodplains where rivers spread widely without strong meanders. Once dinosaurs vanished, forests flourished freely across the land. Dense trees stabilised soil and locked sediments in place. Water then flowed into structured rivers with broad, looping bends.

The study, published in Communications Earth & Environment, highlights how rapidly Earth can change. Lead researcher Luke Weaver said the extinction showed life itself could alter landscapes. It was not only climate or geology shaping environments but also animals themselves.

By preventing thick forests from spreading, dinosaurs served as “ecosystem engineers.” Their abrupt extinction sparked major ecological shifts, according to a University of Michigan study, depicted in this artistic rendering. (Image: Julius Csotonyi)

What Evidence Did Researchers Find?

Weaver and colleagues examined rock layers across the western United States. They focused on formations spanning the dinosaur age and the early mammal era. In Montana and the Dakotas, they studied the Fort Union Formation. This layer was stacked with colourful “pyjama-striped” rocks. Earlier scientists believed they were pond deposits linked to sea level rise. But Weaver’s team realised they were point bar deposits inside ancient meandering rivers.

Above these deposits lay lignite, a low-grade coal formed by plants. The researchers said this showed forests were flourishing, with fewer floods carrying clay and sand. To confirm timing, they searched for the iridium anomaly, a global marker of the asteroid impact. In Wyoming’s Bighorn Basin, they found a thin layer rich in iridium, pinpointing the exact extinction boundary.

Why Does This Matter Today?

The extinction was caused by the Chicxulub asteroid striking Mexico’s Yucatan Peninsula. Its fallout triggered rapid global change. Weaver compared this ancient upheaval with today’s climate crisis. He said current biodiversity loss and environmental change will also appear geologically instantaneous.

Co-author Courtney Sprain added that dinosaur extinction is not only seen in missing fossils. It is also written in the sediments and rivers left behind. Dinosaurs’ role as ecosystem engineers is becoming clearer with new geological evidence.

Weaver said the findings remind us that life and landscapes are deeply connected. Just as forests reshaped rivers after the dinosaurs, human-driven changes today will leave lasting marks on Earth’s record.