How the extinction of the dinosaurs changed the Earth forever

Since the asteroid impact that wiped out the dinosaurs 66 million years ago, the Earth has undergone not only biological but also enormous geological changes. A new study by scientists at the University of Michigan shows that dinosaurs were "ecosystem engineers" and their disappearance radically transformed rivers, soils and vegetation.

Paleontologist Luke Weaver and his colleagues analysed geological layers in the western US - from the Williston Basin to the Bighorn Mountain region. The scientists noticed a stark contrast between the sediments before and after the dinosaurs' extinction: the earlier layers were saturated with clay soils typical of wetlands, while the later layers consisted of brightly coloured banded rocks indicative of a broad, bendy river system.

Before the extinction, scientists say the dinosaurs destroyed vegetation by trampling and eating it. This prevented the formation of dense forests and therefore stable rivers. The rivers flowed freely, not forming winding channels.

When the dinosaurs disappeared, forests began to grow rapidly, strengthening soils, reducing erosion and holding back river channels. As a result, marshes and spills were replaced by stable meanders, and the geological record shows signs of dramatic environmental change.

As Weaver himself explains, "We usually think that climate changes life, but this study shows that life - in this case, the dinosaurs - may have shaped the landscape and climate itself."

To establish the exact boundary between the pre- and post-dinosaur era, the scientists searched the rocks for the famous "iridium layer" - a thin horizon rich in the element iridium, which comes to Earth mainly with meteorites. Its presence confirmed: the change in geology occurred precisely after the asteroid impact in the Yucatan Peninsula.

In the layers of the Fort Union Formation, formed after the catastrophe, researchers found deposits of low-quality coal (lignite) - evidence of active growth of forests and reduced river floods. All this, as scientists believe, happened because the "landscape destroyers" - dinosaurs - disappeared.

It is especially important, according to scientists, that the K-Pg-extinction events are a good historical analogue to the rapid changes occurring today under human influence.

"Back then, nature changed instantaneously on a geological scale - and we're seeing a similar pattern now," Weaver says.

The study also emphasises the role of large animals in shaping the environment. In the same way that elephants today trample savannahs and interfere with overgrowth, dinosaurs in the past may have "controlled" the ecosystems of entire continents.