New research led by scientists from Oxford University and Exeter University has shown that the invasion of the land by plants in the Ordovician Period (488-443 million years ago) cooled the climate and may have triggered a series of ice ages.Among the first plants to grow on land were the ancestors of mosses that grow today. This study shows that they extracted minerals such as calcium, magnesium, phosphorus and iron from rocks in order to grow. In so doing, they caused chemical weathering of the Earth’s surface. This had a dramatic impact on the global carbon cycle and subsequently on the climate. It could also have led to a mass extinction of marine life.
The research suggests that the first plants caused the weathering of calcium and magnesium ions from silicate rocks, such as granite, in a process that removed carbon dioxide from the atmosphere and forming new carbonate rocks in the ocean. This cooled global temperatures by around five degrees Celsius.
In addition, by weathering the nutrients phosphorus and iron from rocks, the first plants increased the quantities of both these nutrients going into the oceans, fueling productivity there and causing organic carbon burial. This removed yet more carbon from the atmosphere, further cooling the climate by another two to three degrees Celsius. It could also have had a devastating impact on marine life, leading to a mass extinction whose cause had puzzled scientists.
The team used the modern moss, Physcomitrella patens for their study. They placed a number of rocks, with or without moss growing on them, into incubators. Over three months they were able to measure the effects the moss had on the chemical weathering of the rocks. ..
Links and Source(s):
- The arrival of the first plants cooled the planet so much that it triggered series of ice ages (dailymail.co.uk)
- First land plants plunged Earth into ice age (newscientist.com)
- Earth’s First Plants May Have Triggered Ice Ages, Study Says (e360.yale.edu)
- First plants caused ice ages (eurekalert.org)