Greenhouse Gases Helped Dinosaurs Thrive
November 6, 2003
Increasing the concentration of carbon dioxide (CO2) in the atmosphere could make plants grow more vigorously, according to recent experiments. And much higher CO2 levels than are currently in the Earth's atmosphere could explain why dinosaurs thrived.
CO2 is a so-called greenhouse gas implicated in raising average global temperatures. The concentration of CO2 rose over the past century and a half, but has been much higher in past eras.
Extra CO2 in ancient times may have boosted plant productivity to at least three times that of today's ecosystems, say scientists:
- In the Cretaceous era, some 65 million years ago, the atmospheric concentration of CO2 ranged as high as 2,000 parts per million -- more than five times today's values.
- There was also more oxygen, which made up as much as 30 percent of the air, in contrast to today's 21 percent.
- Atmospheric pressure was also about 25 percent higher than today.
- They found that in a hyperbaric (pressure) chamber with 2,000 ppm of CO2, the plants grew five times as fast as those exposed to modern concentrations of CO2.
- Higher levels of oxygen slowed plant growth, but with concentrations of both gases at Cretaceous levels, plants grew about four times as fast -- and after a month produced three times as much new foliage as plants grown under current conditions.
This may explain why the Earth was able to support so many large dinosaurs, say observers.
Source: Sid Perkins, "Ancient Atmosphere Was Productive," Science News, November 1, 2003.
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