Flooding Induced by Rising Atmospheric Carbon Dioxide

Gregory J. Retallack^*

Dept. of Earth Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA

Giselle D. Conde

Dept. of Earth Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA

Abstract

A direct consequence of rising CO₂ is increasingly devastating flooding, because deciduous plants deploy fewer stomates each year as the atmospheric CO₂ supplies more carbon for photosynthesis. When plants transpire less, more water runs off in streams and floods. Here we quantify this effect with high-resolution observations of changing density and size of stomates of a mesic tree, Ginkgo, since 1754. The observed decline in maximum potential transpiration corresponds with rising water levels in the Mississippi River and represents a potential transpiration decline from 1829 to 2015 of 18 mL s^-1m^-2: a reduction of 29%. Rising atmospheric CO₂ and declining transpiration promote flooding, which handicaps lowland cultivation and renders irrelevant insurance and zoning concepts such as the 100-year flood.

^* gregr@uoregon.edu

Manuscript received 8 Nov. 2019. Revised manuscript received 15 Apr. 2020. Manuscript accepted 20 July 2020. Posted 13 August 2020.

© The Geological Society of America, 2020. CC-BY-NC.

https://doi.org/10.1130/GSATG427A.1