Grass under a fence doesn’t get eaten, giving you a spot where it will always regrow from. Fences decay and need to be replaced, though.

Lightning rods, on the other hand, do not decay, and a line of them can block animals, keep grass safe, and do their normal job of preventing lightning and producing batteries. If something needs a fence I generally make it out of lightning rods. If I’m low on the crafting ingredients, other decor things do the same job.