Ancient “Pickled” Leaves Give a Glimpse of Global Greening

Reichgelt and his colleagues analyzed the carbon composition in 72 fossil leaves found in Foulden Maar, representing 18 tree species. They also mapped the density of their stomata: When CO2 levels are higher, plants get the carbon they need from fewer stomata, meaning they also lose less water through the open pores and can grow in drier locations.  The results indicated that in the early Miocene, atmospheric CO2 shifted from 450 to 550 parts per million and then back to 450 parts per million over the 100,000 years represented in the Foulden Maar deposit. “That seems like a smoking gun to us: an increase in carbon dioxide that was responsible for a temperature increase that then led to the Antarctic deglaciation,” Reichgelt said. - EOS