Having several bonuses for different terrains seems a bit overpowered. Maybe there should be different excluding policies?
Pastoralism: Production, combat & movement bonus in grassland, plains & desert
Woodcraft: Production, combat & movement bonus in forest & jungle
Winterwear: Production, combat & movement bonus in tundra, snow and hills
Seamanship: Production, combat & movement bonus at rivers, lakes & oceans
This would open for interesting situations where different civilizations have advantages in their home ground. Think Operation Barbarossa, Vietnam war, or any other conflict.