Totally sucks. Just two food, and no commerce on rivers. Just think about it .
Now, this is how it was done in Orbis, so it might not apply here, but in that modmod you could build farms on ice when playing as Illians.
Actually, I'd
strongly recommend you to try Orbis(Master of Mana is not bad too, but I've only played a couple short games with this one) - the mechanics are tweaked in a way that makes the gameplay much more fitting the fantasy setting. The races are highly individualized, with a lot of additional unique abilities, there is more resources on the map(balanced my different requirements for e.g. city growth), cool fort mechanics(you can claim forts outside your borders, which then expand the borders around themselves), more interesting races etc. - it feels a lot more RPG'ish and IMO fun.
Illians specifically have the ability to turn their borders into ice by default, some of their units are invisible in the snow, have huge bonuses for fighting in snow/tundra, and they get a production bonus from tundras, making the new Ice Age a sensible goal to strive for.
Master of Mana is even more tweaked, with spell research, including battle spells and overland enchantements, completely different economy(you need to e.g. collect wood/stone/metal/leather etc. to equip your troops with better weapons and armour, you need to pay upkeep for city improvements and more), new optional game goals(kinda like huge quests) and probably more that I haven't found out yet.