During periods of short supply and/or increased coffee has been often been replaced or augmented by various other ingredients. For example:

... during the American Civil War, Louisianans looked to adding chicory root to their coffee when Union naval blockades cut off the port of New Orleans. With shipments coming to a halt, desperate New Orleanians looking for their coffee fix began mixing things with coffee to stretch out the supply. Acorns or beets (cafe de betterave) also did the trick. Though chicory alone is devoid of the alkaloid that gives you a caffeine buzz, the grounds taste similar and can be sold at a lower rate. -- source