New index helps project changes
Farmers have known it for generations that heatwaves, drought and extreme rain are a bad recipe for growing wheat, and now scientists have quantified those impacts. Heat stress, combined with drought or excessive rain is responsible for about 40 percent of the changes in wheat yields from one year to another.
That’s bad news in a world that’s expecting extreme weather to intensify in the coming decades, but at least the stress index developed scientists with the European Joint Research Centre will help communities plan ahead and ameliorate at least some climate change impacts.
The index is based on detailed crop measurements between 1980 and 2010 and spelled out in a study published in the journal Environmental Research Letters earlier this month.
One finding is that in contrast to the common perception, water excess affects wheat production more than drought in several countries. Excessive precipitation and greater cloud cover, especially during sensitive development stages of the crop, are major contributors to reduced yields, as they help pests and disease proliferate and make it harder for the plants to get the oxygen and light they need.
Wheat is critical to global food security, and as climate change increases the duration, frequency and severity of extreme weather events, “it has become increasingly urgent to identify their effects and provide early warnings, in order to ensure market stability and global food security,” the researchers said.
The study was the first to show the effect of individual extreme events and their impacts on particular development stages of the crop (for example, the effect of drought during key development periods such as flowering and grain-filling). Using the enormous database, they showed how those events affected global yields.
The model explicitly accounts for the effects of temperature and soil moisture changes (positive and negative) on global and regional wheat production fluctuations.
A specific case study was carried out at subnational level in France, where wheat was found to be more sensitive to overly wet conditions. In other countries, heat stress and drought are the most important predictors of crop losses. For instance, in Mediterranean countries, drought has a bigger detrimental effect on wheat yields than heat stress.