Asteroid Hit Created Conditions Required to Destroy All Dinosaur Habitats

Around 66 million years ago, an enormous asteroid smashed into the Earth off the coast of what is now Mexico in a catastrophic event that famously led to the demise of the non-avian dinosaurs. According to a first-of-its-kind study, this impact created the climatic conditions to wipe out nearly all viable dinosaur habitats.

Most scientists accept that the asteroid impact was likely the main driver of the subsequent mass extinctions that wiped out around three-quarters of life on Earth at the end of the Cretaceous period (145 to 66 million years ago.) However, some say a period of dramatic volcanic activity at the Deccan Traps in present-day India around the same time may have played a more prominent role.

A team of scientists led by Alessandro Chiarenza, a research associate with the Department of Earth Sciences at University College London, U.K., has found that only the asteroid impact could have created the right conditions to wipe out the dinosaurs.

In the study, published in the journal Proceedings of the National Academy of Sciences, researchers attempted to determine which factor, the asteroid impact or volcanism, had a more damaging effect on the world's climate. Chiarenza said they took advantage of recent improvements in geological, ecological and computational techniques to investigate the issue using a different approach to previous research on the subject, which has tended to focus on the geological record.

The scientists used a global fossil database in combination with ecological techniques to estimate the environmental requirements—such as rainfall and temperature—that different dinosaur species around the world would have needed to survive. They then worked out where in the world these conditions would still exist after an asteroid strike or significant volcanic activity.

"The significant difference is that while in the past people had been looking at only the effects on climate an impact event or volcanic eruptions might have generated, we now add an ecological dimension to the research, testing how those might have eventually influenced the ecology and survival of non-avian dinosaurs," Chiarenza told Newsweek.

"In addition, the climatic simulations on the extinction scenarios used here are probably the more accurate and realistic produced so far."

The team's modeling showed that the asteroid impact would have led to a decades-long, permanent, global winter, that would have rendered the Earth's climate inhospitable for dinosaurs. "It was a bad day," Chiarenza said.

In addition to global fires that probably burned down forests worldwide and produced immense clouds of soot, the impact would have thrown up vast quantities of material into the atmosphere, blocking the sun for decades-to-centuries.

dinosaur, asteroid
A large armored dinosaur witnesses the impact of an asteroid falling on the Yucatán peninsula 66 million years ago. Fabio Manucci

In the subsequent years, this cooled down the planet, killing many of the animals that survived the initial impact but could not adapt either by burrowing or finding shelter in environments like riverbeds or lakes.

The team's models showed that only the asteroid impact could have created the climatic conditions capable of destroying all potential dinosaur habitats, triggering their mass extinction across the planet.

The Deccan volcanic eruptions, on the other hand, which would have also released vast quantities of sun-blocking material into the atmosphere, did not disrupt global ecosystems sufficiently to cause such a mass extinction, leaving some viable habitats in the equatorial regions, according to the researchers.

"Our study confirms...that the only plausible explanation for the extinction is the impact winter that eradicated dinosaur habitats worldwide," Chiarenza said in a statement.

The scientists also found that, in the long-term, warming generated by the release of greenhouse gases from the Deccan volcanoes may have helped to speed up the planet's recovery after the asteroid impact, by buffering the effects of the cooling and enabling new life to evolve.

As the sun-blocking particles thrown up by the impact fell out of the atmosphere, the greenhouse gases would have remained for much longer, helping to increase global temperatures.

In fact, several animal groups, such as birds and mammals actually expanded in the aftermath of the asteroid impact. "We owe our own existence to the survival of those tiny adaptable critters," Chiarenza said.