Dinosaurs and Our Destiny

At the time, more than 200 million years ago, the earth's continents were merged in one massive landmass, Pangea, and New Mexico sat near its equator, about 12 degrees north, rather than the 36 degrees north it is now.

"It's been something that has been noticed for decades that [dinosaurs are] just missing, and people have put out there 'Well, maybe it's related to climate change,' but there hasn't been any kind of mechanistic link," says Jessica Whiteside, a geochemist from the University of Southampton in the United Kingdom and lead author of a study published in June in the Proceedings of the National Academy of Sciences that posits a link.

"What we were able to show was that it wasn't just that it was warm, but that there were these wild extremes in climate because of the higher carbon dioxide of four to six times what we have today," Whiteside says.

That era's so-called hothouse planet, with no polar ice caps and carbon dioxide levels as high as 2,400 parts per million (the planet now is just over 400 ppm), swung through extremes at its tropical latitudes. Droughts were followed by monsoons and punctuated by wildfires that burned as hot as 600 C (1,112 F). Plant life was repeatedly wiped out and soil composition changed so radically as to transform the ecosystem in as little as 10 to 100 years, Whiteside says.

"This unpredictably varying climate made it a tough place to live because you never know might what come next in terms of the environment," says Randall Irmis, curator of paleontology for the University of Utah and a co-author of the study.

Changes occurred too quickly for dinosaurs to adapt. Without consistent food sources, large, warm-blooded herbivorous dinosaurs simply stayed away from the tropics and dominated other parts of the world. Ghost Ranch is, instead, known for Coelophysis, a small, two-legged carnivore.

"When you're a carnivore, you can be very flexible—you can eat anything you can fit in your mouth, so you can change your specific diet more than, say, an herbivore that requires certain types of plants to be around," Irmis says.

The study assembled researchers from eight institutions and used multiple sources of data—fossils, pollen, spores, charcoal from wildfires and soil chemistry—to examine the climate and ecology of the era in which dinosaurs first appeared. The team has been spending several weeks at the ranch near Abiquiú each year since 2006 to study dinosaur origins and early evolution.

"In North America, there's no better place to investigate that than at Ghost Ranch, because there are so many different fossils there, and it's such a rich record," Irmis tells SFR.

These researchers seek out not colorful cliffs that have drawn visitors and artists to the area (one of their field sites appears in a Georgia O'Keeffe painting), but the drabber grays, browns and blacks of ancient stream- and riverbeds, where water may have kept organic content from oxidizing.

The results of this study that peers deeply into the past can tell us a little about the future and how sensitive the climate is to increases in atmospheric carbon dioxide.

"If the predictions for the next 100 to 200 years are correct, we might be entering a climate phase that we haven't experienced in millions of years, and so we have to go back to the geologic record to see what was earth like the last time carbon dioxide was at 800 parts per million or 1,000 parts per million," Irmis says. "So that's one of the ways the age of dinosaurs can be really valuable. They were living in a high-CO2 world with no polar ice caps, so we can use it as a way to investigate what those worlds might be like."

Even though not all the variables line up now—we have ice caps at the poles, for now, and multiple continents spread over several oceans rather than one supercontinent—Whiteside says, "It's quite helpful to see under a variety of changing conditions what happens to life, what happens to the environment and what the temperature response is to CO2."

The accuracy of computer models that predict what the future holds if carbon dioxide emissions continue can be tested by comparing their predictions with the data found at Ghost Ranch. Climate change models can be given the same parameters as what has been documented, and then scientists can see how closely what those models construct resembles what appears in the fossil record.

The Ghost Ranch research shows high carbon dioxide resulting in unpredictable extremes in climate, a greater rate of extreme weather events and a lack of abundant vegetation, Whiteside says, "which could have implications for human sustainability, because we can control what crops we grow, but we can't control what conditions they're grown in."

Santa Fe Reporter