From St. Paul, Minn., at a meeting of the Society of Vertebrate Paleontology
How could ancient landscapes have provided all the vegetation needed to nourish massive herds of hungry, multiton dinosaurs? New laboratory experiments suggest that in the era just before the dinosaurs went extinct, extra carbon dioxide in the atmosphere may have done the trick, boosting plant productivity to at least three times that of today's ecosystems.
During portions of the Cretaceous period, which ended about 65 million years ago, some regions of western North America supported dense populations of large, plant-eating dinosaurs. In that era, the atmospheric concentration of carbon dioxide ranged as high as 2,000 parts per million (ppm)–more than five times today's values. Oxygen made up as much as 30 percent of the air, in contrast to today's 21 percent. Atmospheric pressure then was about 25 percent higher than it is today.