Famine occurs in provinces each spring, except for the first year. See the Disasters Map.
If a province or city is struck by famine, it produces no income. You cannot place new units there; and any units that stay until the end of the spring turn in the famine-struck area are eliminated.
Exception: If there is a garrison in a province struck by famine, the city (and only the city) does produce income.
Famine may be relieved by making an expenditure of 3d.