Modern Industrial society seems impervious to the threat of food shortages: Amartya Sen argued in a famous paper that democracies in particular avoided famine much better than any other regime in the past. Because of this, we forget I think how important the supply of food was to states in the ancient and medieval world. The political system of a state in the ancient world could be grievously affected by issues surrounding the supply of food. Livy chronicles in his fourth book just such a moment in the history of Rome- and it does not take more than a shrewd guess (particularly given the unusual number of temples built at this time) to suggest that Rome during its social conflicts suffered from frequent problems with food supply. The Livyan example is interesting though in its own right.
In the consulship of Proculus Geganius Macerinus and Lucius Menenius Lanatus Livy tells us that Rome suffered a 'black' year 'in almost every respect'. As he suggests 'had war been added to the list of miseries scarcely by all the help of the Gods in heaven could the country have survived' (IV 11). Livy tells us that in this year a famine began- the first thing that is interesting about his statement is that he also tells us what he thinks its causes might have been, either a 'bad season' or that 'the pleasures of city life and the excitement of politics which had kept people from attending to their farms'. (IV 11) It is worth noting this in two ways: firstly because it demonstrates descriptively how Livy thought about famine- it could be the product of a moral judgement upon those that suffered it- hence in the end it could bring into question the actual basis of the city. Furthermore the idea that Romans faced famine because they spent their time arguing about politics- brings up in an ancient context a very real problem with democracy- it is, unlike most other activities, something in which the division of labour does not function and consequently it creates an issue with people's attention either being diverted from their job to be a citizen, or sleepwalking into disaster, whilst doing their job professionally.
Livy's discussion of the famine though goes further- and what he describes are the limitations of an ancient world state in confronting a terrible moment in its history. He describes the poor flinging themselves into the Tiber to avoid starvation by drowning. The problem for an ancient state in confronting this famine was two fold. Firstly as we learn from Livy, the methods they had of dealing with it were not really adequate. Lucius Minucius (appointed Controller of Supplies) went round neighbouring states attempting to get corn, he forced people to declare their stocks, diminished the rations for slaves and roused popular feeling against speculators (IV 12). But as Livy declares 'these inquisitorial methods did less to relieve the scarcity than to reveal its extent'.
There was a second kind of response to the famine- which brought into question the stability of the Roman state. Spurius Maelius, a knight, bought up stocks of corn in Etruria (which as Livy says stopped the government buying the corn) and used it to obtain a following in order to mount an attempt upon the crown. His 'generosity won their [the poor's] hearts and crowds of them followed him wherever he went' (IV 13). Livy tells us through the mouth of Minucius that Maelius had bribed the tribunes and assigned the mob leaders tasks (IV 13)- this comes from a senatorial source, and rather than accepting it, it is worth remembering what Livy said earlier about the poor and their food supply. Essentially Maelius got their support through distributing grain- and his political following was a consequence of his wealth and potentially his support in Etruria (Livy just a page before gave us an example of Rome supporting a faction in a town for its own political ends (IV 9-9), I do not think it implausible that Etruria was returning the favour by using famine as a weapon against Rome). Maelius's rebellion failed because a dictator- Cincinnatus making his return- was appointed and arrested and executed Maelius before he could gather his forces. But it is an interesting incident that reveals how vulnerable the Roman state was to its food supply.
Ultimately Rome was a society of a number of wealthy people surrounded by the poor- who were dependent on the harvest. We do not understand the dynamics of its politics unless we understand the problems that a bad harvest presented. As we have noted, the poor were the military strength of Rome's armies- numerically more various than the patricians. Of course the principle danger to the patricians lay in a strike from the poor when another state's army attacked Rome. But there was another danger- in a famine food became a means to control the populace- and as in the case of this famine if the patricians lost control of the food supply, they ceded the loyalty of the plebeians to the controller of that supply. Livy understood this which is why he believed that the revolt of Maelius was so severe- it also points out to me the advantages of empire- we see it so often as a negative, but the scale of empire permitted a politics which was not driven by the harvests in particular small areas. In the days of empire, Rome was supplied by the grain fields of Africa and Egypt- in the days that we are discussing here Rome's stability rested upon whether a harvest succeeded or failed- failure could lead to revolution and civil war- empire addressed that weakness.