1. Exploring the impacts of surface ozone and particulate matter on global crop production
Luke Schiferl and Colette Heald
8th International GEOS-Chem Meeting
3 May 2017

2. How does air quality (O3 + PM) affect our ability to feed a growing human population?
2010 Crop Production
2010 Population
80 % of global crop production
50 % of global population
[FAO GAEZ]
[CEISIN GPWv3]
[Mg km-2]
[km-2]
Air quality issues
Particulate Matter (PM)
Ozone (O3)
Anthropogenic Influence Since 1850
[µg m-3] [ppb]
[GEOS-Chem v10-01]

3. Ozone Effects on Crop Production
Crop Yield
Healthy
Yield loss dependent on crop type:
maize rice wheat
increasing sensitivity
Various empirical metrics help determine impacts of ozone on crop yield.
Ozone Damaged
[NASA Science Education]
Cumulative exposure:
Mean exposure:
Species-specific Relative Yield (RY)
40 ppb threshold
As used by Van Dingenen et al. [2009] and Tai et al. [2014].

4. Results: Current Air Quality Effects on Crop Production
Maize
Wheat
Rice
−4.9%
−6.9%
−3.4%
∆ Production Due to O3
[Mg km-2]
Current Emissions (2010)
GEOS-Chem v10-01

5. Particulate Matter Effects on Crop Production
shortwave radiation without PM
shortwave radiation with PM PM
gases
diffuse
direct
clouds
diffuse
direct
Diffuse fraction impacts a plant’s
radiation use efficiency (RUE)
carbon fixed ≈ SW radiation × RUE
varying
max ∆RUE
[Greenwald et al., 2006]
from [Sinclair et al., 1992]
relationship uncertain
linear ?
crop yield
[Rochette et al., 1996]

6. Results: Current Air Quality Effects on Crop Production
Maize
Wheat
Rice
−4.9%
−6.9%
−3.4%
∆ Production Due to O3
−0.4%
−1.0%
+0.6%
Net ∆ Due to O3 and PM
Using max ∆RUE = 50% for PM
[Mg km-2]
Current Emissions (2010)
GEOS-Chem v10-01
+ RRTMG
Production enhancement due to PM can offset negative effects caused by ozone damage.
Variation is large between crop, region and sensitivity to DF.

7. Results: Varying PM Effects Based on DF to ∆RUE
Global Total
PM effect on crop production is greatly sensitive to relationship between DF and ∆RUE.
Maize
Wheat
Rice
∆ Production Due to PM [%]
100
Sensitivity to DF (maximum ∆RUE) 50
US+Canada
China+SE Asia
∆ Production Due to PM [%]
Sensitivity to DF (maximum ∆RUE)

8. Effects of Future Air Quality Changes
RCP 4.5 Emissions ( )
Maize
Wheat
Rice
+1.5%
+1.3%
+0.9%
∆ Production Due to O3
+0.9%
+1.1%
+0.5%
Net ∆ Due to O3 and PM
Using max ∆RUE = 50% for PM
[Mg km-2]
While the net effect of future air quality on crop production largely follows changes in O3, PM effects can reduce or override O3 effects.

9. Apply PM Radiation Effects in Crop Model
accounts for resource restrictions such as water and nitrogen
provides physiological constraints on growth
can include shortwave radiation effects on hydrology, etc
Maize
Wheat
Rice
Global Total
Offline
Analysis
pDSSAT
no water stress
no nitrogen stress
Current Emissions (2010)

10. Apply PM Radiation Effects in Crop Model
accounts for resource restrictions such as water and nitrogen
provides physiological constraints on growth
can include shortwave radiation effects on hydrology, etc
Maize
Wheat
Rice
Global Total
Offline
Analysis
pDSSAT
no water stress
no nitrogen stress
with stresses
Current Emissions (2010)

11. Conclusions Future Work
Crop production enhancement due to PM can offset the negative effects caused by ozone damage in certain areas.
Future improvements in air quality may have negative effects on crop production by reducing diffuse light.
Failure to account for air quality influence in crop model may result in substantial model bias.
Extend study to explore ozone effects and
nitrogen cycling in crop model
Future Work
Thank you to the MIT Martin Family Fellowship for Sustainability
and the Abdul Latif Jameel World Water and Food Security Lab (J-WAFS) for funding this work.