I agree, 70-90? THat takes up half of your population. Workers are the key, upgrade them like troops and they will hold thier own as far as harvesting goes. BUT use alternate means as well. I try to use utility boats as often as possible in some remote part of the map. They can harvest fish unitl they are out, or you can set up aquaharvesters, that gets your food up and you dont have to wrroy about rebulding farms so often.
I have about 15 getting carbon, I use a lot of that stuff, and then four ofr nova and ore, and a team of four for building. Sometimes I will split them up, but usully they build fast enough to that I have them build wahtever I need.