The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions

by Peter Brannen

Fossil plant life attests to the skyrocketing CO2. Plants breathe in carbon dioxide through tiny pores on their leaf surfaces. But there’s a trade-off for having too many pores and breathing easier: it’s also easier to dry out and die. This is why plants keep pores to a minimum: just enough to breathe, but no more than necessary. In times of high carbon dioxide, they’re able to get by with fewer pores as they sip from the CO2-rich air. In 200-million-year-old fossil plants, University College Dublin paleobotanist Jennifer McElwain found that the number of pores on the ancient leaves plummeted over the End-Triassic mass extinction to accommodate what must have been a deluge of volcanic carbon dioxide. As with the End-Permian, there’s also a huge shift in the carbon isotope record over the mass extinction, similarly pointing to a massive influx of carbon to the atmosphere.