A doubling of carbon dioxide levels some 200 million years ago may have reduced plants' uptake and release of water — drastically altering local water cycles and leading to a decrease in animal biodiversity.


Margret Steinthorsdottir, now at Stockholm University, and her team examined 91 fossil plants from eastern Greenland, spanning the transition between the Triassic and Jurassic periods. The researchers measured the fossils' stomata — tiny holes through which plants vent water (stoma pictured) — and found that their density and size decreased over the Triassic–Jurassic transition. This suggests that the volume of water released by plants in a process called transpiration fell by 50–60% during a time marked by mass species extinctions and high levels of atmospheric carbon dioxide.

Sediment analysis revealed that the drop in transpiration coincided with increased water run-off and erosion, suggesting that the change may have reduced soil quality, contributing to a decline in biodiversity.

Geology http://dx.doi.org/10.1130/G33334.1 (2012)