Multi-peril pathogen risks to global wheat production: A probabilistic loss and investment assessment

Crop diseases cause significant food and economic losses. We examined the joint, probabilistic, long-term, bio-economic impact of five major fungal pathogens of wheat on global wheat production by combining spatialized estimates of their climate suitability with global wheat production and modeled distributions of potential crop losses. We determined that almost 90% of the global wheat area is at risk from at least one of these fungal diseases, and that the recurring losses attributable to this set of fungal diseases are upwards of 62 million tons of wheat production per year. Our high-loss regime translates to around 8.5% of the world’s wheat production on average—representing calories sufficient to feed up to 173 million people each year. We estimate that a worldwide research expenditure of $350-$974 million (2018 prices) annually on these five fungal diseases of wheat, let alone other pathogens, can be economically justified, equivalent to 2 to 5 times more than the amount we estimate is currently spent on all wheat disease-related public R&D.

Step 1 We first compiled a state-specific data series on U.S. public wheat R&D spending drawing on unpublished annual data files obtained from USDA-CRIS (various years) for the period 1980-2015. Wheat R&D spending concords with spending on research in the Research Problem Areas (RPA) and Knowledge Areas as described above. Together with the annual, state-level estimates of the wheat R&D expenditures incurred by the State Agricultural Experiment Stations (SAESs) maintained by the InSTePP Center at the University of Minnesota (see, e.g., Smith 2017 andPardey et al. 2016), we formed annual estimates of the intensity of wheat in total R&D (i.e., US public wheat R&D / US Public agR&D) for the period 1980-2015.
Using state-level estimates of the cash receipts by farmers for wheat sales taken from USDA-ERS (2020), and the total (farm level) value of cash receipts for all agricultural output taken from the same source, we formed annual, state-level estimates of the intensity of wheat in the total value of agricultural production, VOP (i.e., wheat VOP / ag VOP).
A linear regression was then run on the intensity of wheat R&D against the intensity of wheat value of production, forcing the regression through the origin such that with an R 2 = 0.61, and a standard error on the estimated coefficient equal to 0.0071. The state level intensities and fitted regression are plotted in Figure S3.

Step 2
Using a national level extraction of R&D data from (USDA-CRIS, various years) we estimated that the share of wheat pest and disease related R&D in total public wheat R&D averaged 25.5%, an average that was reasonably stable over the period 1970-2015.
Step 3 Assuming the estimated relationships in steps 1 and 2 are indicative of the structure of wheat R&D throughout the world, we formed estimates of the global wheat R&D spending and related pest and disease research as follows: Global wheat R&D ≈ 0.3923 * ∑ Ag R&D * (Wheat VOP / Ag VOP) Global wheat pest & disease R&D ≈ 0.255 * (Global wheat R&D) where i indexes country. National wheat VOP and ag VOP values were obtained from FAO (2021).
The global wheat R&D and global wheat pest and disease R&D estimates were formed annually for the period 1980-2015 and expressed in 2018 PPP (purchasing power parity) dollars (World Bank 2020) that were obtained using country level implicit GDP deflator (UN, 2020). The $185 million and $540 million data reported in Figure 3 represent a simple average of the respective annual 1980-2015 series.

Supplementary Figure S1. The likelihood of wheat yield losses from fungal diseases
Notes: x-axis represents proportional yield loss reported for different wheat fungal diseases (e.g., 0.1 = 10% yield loss); y-axis represents the density (or likelihood) of different yield loss levels. The histograms represent observed yield loss data. The line plots represent the fitted beta-distributions. Figure S2. The relationship between value of production and public R&D investments for US wheat Supplementary Table S1. Regional multi-peril disease co-suitability Cumulative wheat area share co-suitable for multiple fungal diseases  Table 1 for details on regional groupings of countries.