Swamps are often completely empty of resources and the possibility of adding new resources had been discussed, but there's no telling when this might happen if at all. In the past at least some of them used to have water as a natural resource, but when wells and water pumps were introduced, all natural water sources got nuked. Like deserts, swamps are also often located far away from other places and there is no food to be found. They often have swamp snakes, though, if you don't mind grilling snake meat. Swamps on the map look like transparent blue dashes on a green background.