Welcome to this small suggestion I grew!
So, we all know Terraria's unique flora can grow without any process, like watering and fertilizing. So, I suggest this small behavior change!
NPCs will throw some brown powder (Fertilizer) and water the ground when there are grass blocks with flora growing near them, as to look like if they are caring for the plants. If there are only grass blocks with no flora growing, then they will throw some seeds. It would also promote planting to the players so global warming would be reduced (Okay this one I'm not sure)
Note: This doesn't affect the environment in any way, it's just an aesthetical change.
Thanks for reading! Tell me what I can improve on! Technically this doesn't need sprites, but if you want to give