Eos, Transactions American Geophysical Union

Pack rats' pine needles indicate ice age shifts in atmospheric CO2


  • Anonymous


Pine needles gathered by pack rats 30,000 years ago indicate that plant physiology changed in response to increasing CO2 at the end of the last Ice Age.

Measurements from nearly 1200 Limber pine needles preserved in pack rat middens from Idaho, Utah, Nevada, and Arizona show that the number of stomata on leaf surfaces decreased as CO2 increased during the last deglaciation. Stomata are leaf pores through which carbon is taken in for photosynthesis and water is lost in evapotranspiration; a plant's water-use efficiency is the ratio of C gained to water lost through the stomata.