Regional disparities in the CO2fertilization effect and implications for crop yields

Although crop yield generally responds positively to increased atmospheric CO ₂ concentration (CO ₂), the response depends on the species and environmental conditions. Thus, even though global CO ₂ is increasing roughly uniformly, regional yield response to increased CO ₂ will vary due to differences in climate and the mixture of crops. Although CO ₂ effects have been shown to be important for economic and food security impacts of climate change, regional CO ₂ effects are not often considered, and the few studies that have considered them disagree on regional patterns. Here regional yield effects of elevated CO ₂ are examined by combining experimentally determined CO ₂ fertilization effect estimates with grid-level data on climate, crop areas, and yields. Production stimulation varies between regions, mostly driven by differences in climate but also by the mixture of crops. The variability in yield due to the variable response to elevated CO ₂ is about 50–70% of the variability in yield due to the variable response to climate. There is, however, little agreement between studies regarding which regions benefit most from elevated CO ₂. This is likely because of interactions of CO ₂ with temperature, species, water status, and nitrogen availability, but no models currently account for all these interactions. These results suggest that regional differences in CO ₂ effects are of similar importance as regional differences in climate effects and should be included in models.