Cereal species mixtures: an ancient practice with potential for climate resilience. A review

Abstract Food security depends on the ability of staple crops to tolerate new abiotic and biotic pressures. Wheat, barley, and other small grains face substantial yield losses under all climate change scenarios. Intra-plot diversification is an important strategy for smallholder farmers to mitigate losses due to variable environmental conditions. While this commonly involves sowing polycultures of distinct species from different botanical families in the same field or multiple varieties of the same species (varietal mixtures), mixed plantings of multiple species from the same family are less well known. However, the sowing of maslins, or cereal species mixtures, was formerly widespread in Eurasia and Northern Africa and continues to be employed by smallholder farmers in the Caucasus, Greek Islands, and the Horn of Africa, where they may represent a risk management strategy for climate variability. Here, we review ethnohistorical, agronomic, and ecological literature on maslins with a focus on climate change adaptation, including two case studies from Ethiopian smallholder farmers. The major points are the following: (1) farmers in Ethiopia, Eritrea, and Georgia report that mixtures are a strategy for ensuring some yield under unpredictable precipitation and on marginal soils; (2) experimental trials support these observations, demonstrating increased yield advantage and stability under certain conditions, making maslins a potentially adaptive practice when crops are impacted by new biotic and abiotic conditions due to climate change; (3) maslins may balance trade-offs between interfamilial species plantings and varietal mixtures, and expand the total portfolio of traits available for formulating mixtures from varietal mixtures alone; and (4) they may buffer against the impacts of climate trends through passive shifts in species composition in response to environmental pressures. We demonstrate the potential benefits of maslins as an agroecological intensification and climate adaptation strategy and lay out the next steps and outstanding questions regarding the applicability of these cropping systems.