Were Dinosaurs Early Victims Of Climate Change?

Scientists widely believe that dinosaurs were wiped out millions of years ago when an asteroid hit the earth. But a new study says dinosaurs were already having trouble with the way the earth's climate was changing.

The research was published today in the Proceeding of the National Academy of Sciences Journal. Here & Now's Jeremy Hobson speaks with paleontologist Manabu Sakamoto, the lead researcher, who says the results were unexpected.

On the state of dinosaurs before the asteroid collision

“Well, it’s quite common knowledge and there is irrefutable evidence that the asteroid wiped them out eventually at the end. But we are finding actually that, for up to about 50 million years, dinosaurs are already in decline. They weren’t replenishing their lost numbers as quickly as they should have been.”

On the reasons behind the dinosaurs' decline

“Well, we don’t really know what happened precisely so far back in time but there are some prime candidates for this, and one of them are, for instance, changes in temperature. For the majority of the time the dinosaurs were on Earth, the Earth’s climate was a warm, steady hothouse, and then, during the middle of the Cretaceous Period around that time, it started to cool down towards a more of a global cooling. There was prolonged volcanism as well on top of this, so it was pumping out lots of gases into the atmosphere and stratosphere. At the same time, the super continents that were around were starting to break apart and the continents were being separated by large bodies of water and were starting to represent the modern configuration of the continents.”

On climate change playing an important role in speeding up the dinosaurs' extinction

“I would imagine so. These are really large-bodied animals that probably, especially the herbivores, needed to eat a lot of vegetation and if the climate is changing and maybe the vegetation was changing as well. If things like that were happening, I don’t think they were pretty happy about having to shift their diets every so often or maybe they have to migrate more. These are all speculations because we don’t really know for certain.”

On how the mammals were affected by the atmospheric changes that so distressed the dinosaurs

“There’s some arguments that mammals were better adapted to cold climates, that they weren’t as fazed as dinosaurs might have been and so they basically had the upper hand once climates changed. I think the mammals didn’t really care too much because they had this internal combustion system, basically. Although dinosaurs have been debated to have maybe warm bloodedness similar to mammals’, it’s definitive that mammals do have it and they were smaller as well, so they didn’t really care too much how cold or warm it was.”

Whether the dinosaurs would have gone totally extinct were it not for the asteroid hit

“I think eventually, theoretically they would have gone extinct if they continued with their rate but, in reality, it’s possible that some kind of living fossil groups might have survived for a long time without much change, so think of things like crocodiles or lungfish, for instance. They’ve essentially been the same kind of thing for millions of years and maybe some dinosaurs would have survived like that. On the other hand, you have things like birds which are actually living dinosaurs and there’s 10,000 species of them right now. They’re flourishing pretty well after all its other relatives have gone extinct, so you never really know what could have happened.”

On the importance of extinction as a field of study

“l think actually we’ve gotten enough from our recent paper already, but understanding extinctions and the mechanism behind extinctions would really benefit us as a society, especially for preparing for what comes next, especially given that we live in a world of unprecedented extinction rates. Hundreds of species are just going extinct almost on a daily basis. Maybe I’m exaggerating here, but ... having an understanding of what happened in the past will give us a better picture of what we should be expecting in the future.”