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This paper argues that a locust plague in the province of Africa in 125 BCE was a key factor in the change in agriculture of the region from a regime noted for its arboreal produce to one focused more on grain production. This locust plague accounts for the different agricultural systems noted in several authors. Diodorus (20.8.3–4) and Polybius (1.29.6–7) said that many estates in Africa prior to the locusts grew olives, vines, and other fruits, whereas Sallust (Iug. 17.5) and Pliny (NH 15.3.8), writing about periods after the plague, characterized Africa as good only for grain and not for trees. The surviving accounts of the locust plague of 125 are all problematic. Livy's account (Periochae 60) is brief as is Obsequens' and those of Augustine (CD 3.31) and Orosius (Hist. adv. pag. 5.11) date from more than five centuries after the fact and explicitly state their bias towards events happening when pagan gods were the official deities. Understanding the locust plague can inform the observations and assertions of these Roman authors.

Several scholars have used the locust plague to explain Gaius Gracchus' actions in the late 120s BCE. Garnsey and Rathbone (1985) saw this event as one of the reasons for Gracchus' desire to stabilize Rome's grain supply. Desanges (2006) briefly cited the episode as a deciding factor in Gracchus' decision to found a colony at Carthage. This paper tests those hypotheses and places them on firmer footing by using scientific observations of locusts that suggest that the ancient sources are trustworthy. The destruction caused by these locusts, combined with the Gracchan colonization several years later, brought about a change in the agricultural regime in Africa, a point which has not yet been considered.

Modern studies of desert locusts reveal the locusts' range during times of plague and their diet. In plagues of the past 50 years, locusts reached the area of the former Roman province of Africa. Furthermore, the preferred diet of adult locusts is olives, vines, and other fruits, while nymphs eat stalked plants (Tarai and Doumandji 2009). All these were reported to have grown on the estates of Africa. The small glimpse into locust behavior we get from ancient sources corresponds to modern observations of desert locusts.

This paper asserts that the destruction caused by the locust plague and the following colonization changed the agricultural regimes and created the perception, found in Sallust and Pliny, that Africa was only suitable for grain. When colonists arrived in Africa two or three years after the plague, the countryside would still have been fairly stressed following the plague of 125. Most orchards would have produced very little fruit for several seasons due to damage. Any newly planted trees would have needed at least ten years before producing an abundant harvest. Instead, the colonists, who could not afford such investments of time and capital, would have turned to grain, which ensured returns within a season or two. Since grain grew more quickly and required less investment, the colonists grew grain instead of trying to revive the orchards that previously covered part of Africa. These factors account for the perception by later Roman authors that Africa was suited only for grain, though in fact that perception was an artifact caused by locusts and the short-term decisions of new colonists.

Bibliography

  • Garnsey, Peter and Rathbone, Dominic. "The Background to the Grain Law of Gaius Gracchus," JRS 75(1985): 20--25.
  • Desanges, Jehan. " Témoignages antiques sur le fléau acridien" in L'homme face aux calamités naturelles dans l'antiquité et au moyen âge, edited by Jacques Jouanna, Jean Leclant, and Michel Zink. Paris: Diffusion de Boccard, 2006. 221--235.
  • Tarai, N. and Doumandji, S. "Feeding preferences of gregarious nymphs and adults of the Desert locust, Schistocerca gregaria Forskal (Orthoptera, Cyrtacanthacridinae) in different habitats at Biskra oasis, Algeria" Advances in Environmental Biology 3.3(2009): 308--313.