Add an overgrazing mechanic - if too many livestock eat the grass in an area in too short a time they will no longer be able to eat the grass (either take them to some fresh grass or use a trough) If an animal is in an overgrazed area they will display a label on the popup when looked at Adapted from the OverfishedArea mechanic, both systems now share a new DepletedArea class which shares the same grid