Food systems vitally depend on croplands, which are a scarce natural resource. Croplands are also heterogeneous, differing in productive capability and in environmental context. Some are in regions of high biodiversity conservation importance, others in regions vulnerable to food insecurity. In this study, life cycle assessment was used to quantify cropland scarcity footprints, cropland biodiversity footprints and cropland malnutrition footprints for 9341 individual Australian adult daily diets. Dietary cropland scarcity footprints averaged 7.1 m2yr-e person-1 day-1, exceeding a target of 6.1 m2yr-e person-1 day-1, consistent with the proposed global cropland planetary boundary of 15% of the ice-free land area. Discretionary foods, which are energy-dense and nutrient-poor foods high in saturated fat, added sugars and salt, and alcohol and are not essential to a healthy diet, made the largest contribution, followed by fresh meats and alternatives, breads and cereals, fruit, dairy and alternatives and vegetables. Around 45% of the variation in cropland footprint between individuals was explained by differences in total dietary energy intake. Diets characterised by higher diet quality and lower cropland scarcity footprint required only 4.2 m2yr-e person-1 day-1 and recommended diets based on the food choices of this subgroup required 5.9 m2yr-e person-1 day-1. Eating within the global cropland planetary boundary appears realistic if Australians greatly reduce their intake of discretionary foods and moderate their food choices within the "meat and alternatives" food group.
Keywords: biodiversity; diet quality; dietary guidelines; discretionary food; environmental impact; land use; life cycle assessment; sustainable diet.