01 Feb 2012:
Earth’s First Plants
May Have Triggered Ice Ages, Study Says
The first plants to colonize the planet about 470 million years ago may have plunged Earth into a series of ice ages
, according to a new study. Writing in the journal Nature Geoscience
, a team of researchers suggests that the earliest plants — including the ancestors of today’s mosses — caused silicate rocks, such as granite, to release calcium and magnesium ions. This process removed carbon dioxide from the atmosphere and formed carbonate rocks in the oceans, a phenomenon that would have caused the global climate to cool by about 5 degrees C, researchers say. In addition, because new plants also extracted phosphorous and iron from the rocks, the plants would carry those elements into the seas after they died, fueling the growth of plankton that would ultimately sequester carbon at the sea bottom. “Although plants are still cooling the Earth’s climate by reducing the atmospheric carbon levels, they cannot keep up with the speed of today’s human-induced climate change,” said Timothy Lenton, a researcher at Exeter University and lead author of the study. In another new study, researchers suggest that an unusual period of global cooling that ended in the late 19th century — an era commonly known as the Little Ice Age — might have been caused by a series of massive volcanic eruptions
between 1275 and 1300 A.D.