I thought this was going to be a complaint about how tundra and deserts are comparable tiles, and that tundra is vastly UP compared to deserts. Seriously, let's make a few comparisons:
1) Deserts get a unique wonder, the Petra, which is only available if your city is on or by a desert tile, and which makes desert tiles VASTLY better AND gives you an extra trade route. Later in the game, cities on or by deserts can make a replacement for Nuclear Plants, the Solar Plant, which requires NO resources to build. Meanwhile, tundra gets nothing of the sort.
2) Both desert and tundra tiles have a Pantheon that gives Faith for working them, but, while the tundra version (Dance of the Aurora) does not work if the tile is forrested, the desert version (Desert Folklore) works even on flood plains and oases. Why? In my opinion, if these pantheons are supposed to be balanced against one another, they should EITHER both give Faith for ALL relevant tiles, OR Desert Folklore shouldn't work with oases and flood plains.
3) Tundra requires fresh water to be arable, while desert tiles, for some weird reason, can be farmed whether that tile has access to fresh water or not. Now, I'm not an expert in agriculture, so I don't know whether an arid sand plain, or permafrozen ground is hardest to make fertile, but it does bear worth mentioning that you DON'T see forests growing on desert tiles in this game, which one DOES see on the tundra tiles. Even if tundra tiles without fresh water shouldn't be arable right away, I do think that it should be awailable at Fertiliser or something, perhaps with reduced yield compared fresh-water-less tiles on other tiles.