Using a global atmospheric chemistry model, the authors quantify, for the first time, intercontinental transboundary contributions to crop ozone exposure and subsequent yield reductions in the Northern Hemisphere, applying four metrics (AOT40, M7, M12, W126) to the 2000 growing season to estimate the potential global and regional crop benefits of eliminating anthropogenic NOx emissions.

Using these metrics, model calculations show that for wheat, rice, cotton and potato, eliminating Southeast Asian anthropogenic NOx emissions would produce the greatest global reduction in crop production losses (42.3–95.2%), while eliminating North American anthropogenic NOx emissions would have the greatest global impact on crop production losses for maize and soybean (59.2–85.9%).

Eliminating North American anthropogenic NOx emissions produces the largest transboundary impact, resulting in European production loss reductions of between 14.2% and 63.2%. European NOx emissions tend to produce a smaller transboundary impact.

The authors’ calculations of absolute crop production change under emission reduction scenarios differ between the metrics used, but they find the relative importance of each region’s transboundary impact remains robust between metrics.

They conclude that local air quality and emission control strategies have the potential to partly alleviate ozone-induced crop yield loss in continents downstream, in addition to effectively mitigating local ozone-induced production losses.

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