Design and characterization of spatial units for monitoring global impacts of environmental factors on major crops and food security

This paper describes the design and characterization of a limited number of areas to be used as spatial monitoring and reporting units (MRU) by CropWatch, the global crop monitoring system ( ) hosted by the Chinese Academy of Sciences. The MRUs are modified and adapted from an existing standard vegetation zoning map. They are designed to be areas of uniform vulnerability as assessed by three sets of variables: environmental (such as climate and NDVI), seasonality (such as intra-annual climate variations and interannual NDVI variability) and agronomy (such as presence/absence of major crops and their yield). The paper pays due attention to within-zone spatial variability for each of the three groups of variables: in general, the variability measured as the average of the spatial coefficient of variation inside MRUs, is much larger for agronomic variables (330%) than for environmental variables (38%) and seasonality (55%). The MRUs provide a rather coherent picture of the variations of global agriculture, for instance, the links between the distribution of crops, agricultural production potential, and environmental variability (over space and time). They closely delineate the distribution of the major nonsugar food crops (barley, cassava, maize, potatoes, rice, soybean, and wheat). The discussion focuses on the relations between the size of the MRUs and the within-MRU variability (spatial heterogeneity) of cropping, and environmental conditions including seasonality. The conclusion stresses that spatial variability in agriculture is bound to be larger than the variability in the environmental variables used to define the units, regardless of the units' size. The size of the spatial units (and therefore their number) is not a very critical constraint for operational impact reporting, especially if impact indicators focus on agricultural areas inside MRUs.