Elevated CO2 Helps Reduce the Negative Impacts of Air Pollution on Plant Growth
When air pollutants are a source of plant growth stress, the CO2-induced percentage growth enhancement provided by a 300-ppm increase in atmospheric CO2 concentration typically rises in the face of this adversity. In the literature review of Idso and Idso (1994), for example, it rose from 38% when air pollutants were absent to 54% when they were present in harmful quantities. And for a 600-ppm CO2 increase, the response was even greater, rising from a growth enhancement of 46% when air pollutants were absent to an enhancement of 173% when they were present. This beneficent consequence is largely the result of the nearly universal tendency of most plants to reduce their stomatal apertures in response to an increase in atmospheric CO2, which makes it ever more difficult for gaseous pollutants to make their way into the interior of the plant where they can do the most damage.
Subsequent research continues to confirm this basic finding, with a doubling of the air's CO2 content often totally compensating for the debilitating effects of noxious air pollutants, such as tropospheric ozone.
Idso, K.E. and Idso, S.B. 1994. Plant responses to atmospheric CO2 enrichment in the face of environmental constraints: A review of the past 10 years' research. Agricultural and Forest Meteorology 69: 153-203.