Fossil Plants Reveal Lush Southern Hemisphere Forests In Ancient Hothouse Climate
Phoenix666 writes:
For decades, paleobotanist David Greenwood has collected fossil plants from Australia-some so well preserved it's hard to believe they're millions of years old. [...]
The fossils date back 55 to 40 million years ago, during the Eocene epoch. At that time, the world was much warmer and wetter, and these hothouse conditions meant there were palms at the North and South Pole and predominantly arid landmasses like Australia were lush and green. [...]
To sustain a lush green landscape, the continent required a steady supply of precipitation. Warmth means more evaporation, and more rainfall was available to move into Australia's continental interior. Higher levels of carbon dioxide in the atmosphere at the time, 1500 to 2000 parts per million, also contributed to the lushness via a process called carbon fertilization. Reichgelt explains that with the sheer abundance of CO2, plants were basically stuffing their faces.
"Southern Australia seems to have been largely forested, with primary productivity similar to seasonal forests, not unlike those here in New England today," Reichgelt says. "In the Northern Hemisphere summer today, there is a big change in the carbon cycle, because lots of carbon dioxide gets drawn down due to primary productivity in the enormous expanse of forests that exists in a large belt around 40 to 60 degrees north. In the Southern Hemisphere, no such landmass exists at those same latitudes today. But Australia during the Eocene occupied 40 degrees to 60 degrees south. And as a result, there would be a highly productive large landmass during the Southern Hemisphere summer, drawing down carbon, more so than what Australia is doing today since it is largely arid."
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