IS MOSS FROZEN THE PLANET ?

                  Rolling stones may not gather moss, but moss covered stones may have gathered ice during the Ordovician Period, approximately 470 to 440 million years ago.

A team led by botanists and earth scientists from the Universities of Exeter and Oxford recently modeled the process whereby the colonization of the land by plants led to a dramatic reduction in atmospheric carbon dioxide and may have plunged the Earth into a series of ice ages.

When the first land plants, similar to modern mosses, began colonizing the ancient earth, they extracted calcium, magnesium, phosphorus, iron and other minerals from the stones. That exposed the rocks to greater weathering.

The chemical weathering of the calcium and magnesium ions from granite and other silicate rocks would have removed large amounts of carbon dioxide from the atmosphere and eventually deposited it in the ocean in the form of carbonate rocks. Enough carbon may have been pulled out of the air to drop the Earth's temperature by five degrees Celsius (9 degrees F).

Plants themselves also pulled carbon out of the air during photosynthesis. Plants in the water were fertilized by the nutrients washing into the seas from the weathered rocks. As these plants died and settled to the bottom of the ocean, they carried the carbon with them, resulting in another 2 to 3 degree Celsius (3.6 to 5.4 degrees F) drop.

To model how land plants may have frozen themselves out of a home, the team grew a modern species of moss (Physcomitrella patens) on rocks in incubators. Over three months, some lucky scientist had the exiting job of watching moss grow. The effects of the moss were then compared to a control group of rocks that had been incubated without moss.