Greenhouse Wheat

By Robert C. Balling Jr., Ph.D.
Arizona State University

Editor’s Note: This issue marks the debut of noted climatologist Bob Balling’s “Greening Up,” which tracks the latest research on this fascinating aspect of global environmental change.

One advantage of world travel is the chance to sample so many fine foods. After many a European conference on climate change, I’ve enjoyed German wheat beer, which I later learned was basically a liquid form of their equally fantastic bread.

So it was with interest that I perused a recent article in Climate Research entitled “Effects of Climate Change on Europe-wide Winter Wheat and Sunflower Productivity.” In it, P.A. Harrison and R.E. Butterfield, both scientists with the Environmental Change Unit at the University of Oxford, report some good news for lovers of European bread and beer.

Harrison and Butterfield recently married a numerical model of European winter wheat with the output of a climate model simulation for a doubling of atmospheric carbon dioxide concentrations.

According to their projections, Southern European wheat farmers had better get hopping. By the middle of next century, rising CO₂ would mean an incredible increase of nearly 50 percent in winter wheat yield. Their northern European colleagues would enjoy "only" a 20 percent increase. For Europe as a whole, winter wheat yields would average a 27 percent increase (Figure 1).

Figure 1.  Mean winter wheat yields (in tons per hectare) for current climate (1961 to 1990) and for the predicted climate in 2064 for all of Europe.

In the past, two basic numerical models have been used to study the effect of climate change on various crops. Site-scale models, used in many studies to evaluate detailed physiological responses of crops to changes in weather at the daily time scale, are themselves highly detailed, requiring precise inputs for many variables. In the end, they are able to describe the processes of wheat development, growth, and yield. Unfortunately, their highly specific requirements mean these models cannot be used over large complex regions such as Europe.

Large-scale models are available for simulating wheat yields, but these models are highly empirical and rely heavily on statistical relationships that may not be valid under climate change conditions.

So Harrison and Butterfield introduce an alternative method of assessing regional impacts of climate change. Using spatially explicit crop models based on mechanistic principles, their model (called EuroWheat) retains the spatial variability of crop responses across Europe, allowing for climatic shifts in wheat productivity and the evaluation of differential sensitivities to climate change. This sophisticated approach also produces more reliable predictions of wheat responses to climate change than do the simpler, statistically based models. Their result? Looks to be a better mousetrap.

The researchers first checked the EuroWheat model under current conditions, looking at crop development and ultimate yield of the winter wheat for many areas in Europe. Satisfied, they next used general circulation model outputs to estimate conditions in the next century.

The climate model is from the United Kingdom Meteorological Office. It gradually increases the atmospheric carbon dioxide content, reaching 617 parts per million by 2064 (The current concentration is 360) Mean annual temperature rises by 1.8°C, and precipitation goes up by 3.3 percent.

By 2064, winter wheat yields were expected to increase dramatically throughout the continent. The elevated CO₂ “greens up” the wheat, improving growth and helping the plants to use moisture more efficiently. When all is said and calculated, the European Union’s 15 countries wind up with 31 percent more wheat.

Milder winters, wetter growing seasons... And a whopping increase in crop yield? If we’re looking to “put a face on global warming,” let’s find a happy European wheat farmer for the poster.

Prost!

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