Maize storage losses, climate, and climate change in Zambia

Maize is the major food staple in Eastern and Southern Africa; it is mostly produced and stored on small-scale farms, prone to storage losses from pests (in particular maize weevils and larger grain borer, LGB), and likely to be affected by climate change. To target interventions to reduce storage losses, good loss estimates are needed, but obtaining representative scientific observations is expensive. Alternatively, losses can be obtained from farmers’ estimates. In this paper, representative farmer survey data from Zambia are combined with climate data to estimate storage losses, analyze their relationship with climate, and estimate the effect of climate change on storage losses. Farmers did not generally consider storage pests to be a major problem, and indeed, losses in maize stored as grain are modest at 11.5%, but losses in cobs are much higher at 18.7%. Total losses were estimated at 25.4%, or a quantity of 656,000 tonnes, valued at US$ 198 million, but these varied considerably between regions (from 7.8% to 35.4%) and districts (up to 41.2%). A logistic model was estimated, with a strong relationship between losses and climate (temperature and relative humidity). Relative losses were extrapolated over the country and multiplied with maize production to calculate absolute losses and their geographic distribution; they were found to be highly concentrated in three provinces, with half of the losses found in just 11 districts. An increase in average annual temperature of 1 °C was estimated to increase losses to 29.7%, or 177,000 tonnes of maize. The study concluded that farmer surveys to estimate georeferenced losses, in combination with climate data, provide good tools to estimate storage losses, focus interventions on reducing storage pests to the most important geographic areas. Further, the methodology is convenient to predict future losses due to climate change, but the accuracy of the predictions still needs to be verified. It was further recommended that extension efforts focus on reducing storage time in cobs, as grain can be better protected, especially with hermetic storage technologies, and concentrate on the priority districts identified here.