tundra farm?

[Heroes]

I conquer Spain and notice that they have several farms on tundra tiles, generating 2 foods (I learn civil service, but don't learn biology yet). My worker moves to another tundra tile nearby, but doesn't see the farm option. What's going on? Tundra farm is only a feature of AI?

 

[Shillen]

You can farm tundra if it has fresh water.

 

[Heroes]

You can farm tundra if it has fresh water.

Emm, grassland and plain doesn't need fresh water to make farm (after civil service), why tundra needs it?

 

[Shillen]

Because Sid Meier says so?