Air Pollution Impacts on Global Crop Productivity and Nitrogen Deposition

AGU Fall MeetingDecember 17, 2014

Colette L. HealdAmos P.K. Tai (now at CUHK),

Maria Val Martin (now at University of Sheffield)

Considering the Impact of Air Pollution and Climate on Global Food Security (in an era of rising food demand)

tolerant

sensitive

AIR POLLUTION(Snap peas damage due to ozone exposure)

CLIMATE(Illinois heat wave summer 2012)

Estimating the Climate and Air Quality Impacts on Global Crop Productivity From Historical Record

Rel

ativ

e Y

ield

[Mills et al. 2007]

Wheat

Ozone exposure (ppm-hour)

Tmax

Tmean

Thigh

Tbase

Day since 1 June

°C

based on Butler and Huybers

[2013]

climate ozone(2050) (2000)P P

Estimate yield-O3 relationship from literature estimates of O3 exposure

indices

Estimate yield-climate relationship from a MLR of 1961-2010 FAO crop yields and NCEP/NCAR

reanalysis

How Will Drivers Change in the Future?

2000-2050 changes in maximum daily 8-h average (MDA8) O3 (ppbv)

2000-2050 changes in surface air temperature (K)

Community Earth System Model (CESM 1.1) Simulation

Warming climate, similar in both scenarios. Ozone projections reflect regional pollution control, but RCP8.5 includes large increases in methane (increases O3 background)

stippling=significant

Impacts of Climate Change and Ozone Pollution on Total Crop Production

Future crop productivity very sensitive to ozone pollution & climate change. Uncertainty associated largely with future air quality.

Pollution effect: +0.22 ×1015 kcal

Climate effect: -0.80 ×1015 kcalCombined effect: -0.64 ×1015 kcal

Pollution effect: -0.26 ×1015 kcal

Climate effect: -0.81 ×1015 kcal Combined effect: -1.07 ×1015 kcal

RCP4.5

RCP8.5

106 kcal ha-1-50 -20 -10 -5 -2 -1 0 1 2 5 10 20 50

The rate of undernourishment

in developing countries in 2050 increases by 50%

due to climate and ozone.

Impact of Ozone Pollution and Climate Change on Crop Production Around the World

[Tai et al., Nature CC, 2014]

RCPs Project Important Changes in NOx and NH3 Emissions:What are the Effects on Nitrogen Deposition?

2050-2000N deposition

(RCP8.5)

Emissions, Climate and

Land Use

How N Deposition Will Evolve Compared to Critical Loads

N deposition will be a threat for most ecosystems in Asia; some ecosystems in North America and Europe will be threated despite the large reductions in N emissions…..

Kg

N/

ha

yr

*Critical Loads from Pardo et al., (2011), Bobbink et al., (2010) and Bai et al., (2010).

kgN

ha-1

yr-1

Critical Load: “ input of a pollutant below which no detrimental ecological effects occur over the long-term according to present knowledge” (Padro et al., 2011)

Impact of Future N Deposition on Global Ecosystems

[Val Martin et al, in preparation for GCB]

Changes in anthropogenic emissions will drive future N deposition; contribution from climate and land use changes may be significant in some ecosystems…..

Conclusions

Ecosystem productivity (crops and natural ecosystems) will continue to be at risk due to short-lived tropospheric “pollutants” (O3 and reactive N) in the coming decades.

We need to consider all the elements of global change (emissions, climate, and land use) in predicting future impacts.

The time horizon under consideration is critical, particularly in an era of rapidly changing anthropogenic emissions. And the opportunities to alleviate these impacts are large!