They are scaring ranchers into trying to get rid of them before they are protected. They just think prairie dogs are cute, so they want to save them. A dog town is almost all sand and barren. Sure, the negligible amount of plant growth immediately around the mound is nutrient rich. But there is not enough of it to make a difference.
Prairie dogs eat voraciously.
They also say that it takes 250 some p-dogs to equal the amount that a cow eats in a month. Well, since there are usually a couple thousand dogs in a good town, and they are always in the same spot as opposed to the wandering cow, that pretty well eliminates the grazing in that large section of land. Then the town starts to spread to more land. Leave the shooters alone. They have fun, they make the ranchers feel better, and they really don't affect dog population.