Right after the 2014 RF takeover of the Crimean Peninsula (little green men), Ukraine put a dam across the river that feeds water to the peninsula. It's been starved of water long enough that there's probably saline intrusion into whatever agricultural lands are there - excepting those significantly above sea level.

That said, there are plenty of viable countries that are net food importers (e.g. Egypt, UAE), but it's definitely an issue if it has a referendum and goes its own way...