Moles damage lawns through their digging and tunneling, which can uproot plants, disturb roots systems, and leave mounds and tunnels of dirt throughout the lawn, according to Ohio State University Extension. When moles tunnel, their movement disturbs the dirt, which often causes grass or plant roots to dry out.
Although they do cause some damage, moles can also be quite beneficial for lawns, notes Virginia Cooperative Extension. As moles are insectivores, they eat the larvae of many potentially harmful pests. In addition, their movement helps to improve the quality of the soil. When moles tunnel through a lawn, they loosen and aerate the soil and mix the various layers of organic and inorganic matter.
Shallow tunneling species like the eastern mole usually cause much more damage to lawns, according to Michigan State University Extension. With shallow tunneling species, it is usually possible to see all of the tunnels raised above the lawn. In contrast, with deeper tunneling species such as the star-nosed mole, only the mounds that mark the entrances or air holes in the tunnels are visible. These moles usually dig at least 6 inches below the surface, which is deep enough to cause less of a disturbance to root systems.