In 2012 he began to notice some American beech, Fagus grandifolia, that were showing signs of ill health. Beech were already under assault in some regions by beech bark disease (BBD), which is a combination of introduced fungal and insect pests joining forces to attack and kill beech. BBD is widespread throughout northeastern North America, but doesn't seem to have (yet) caused widespread mortality in Ohio. Anyway, the new(?) issue detected by Pogacnik is not BBD.
Mature trees typically form cavities that are used by Barred Owls, raccoons, flying squirrels and a number of other birds and mammals. The roots spawn the growth of one of our most specialized vascular plants, the beech-drops, Epifagus virginiana, which is parasitic on beech roots (without harming the tree). Beech also produce bounty crops of beech nuts some years, and this mast is an important food for numerous animals, including white-tailed deer, turkey, grouse, squirrels, wood ducks, chipmunks and many other creatures. Scores of moth - and some butterfly - caterpillars are also co-evolved with beech and depend on its foliage for food.
A forest deprived of its beech would be a far less diverse woodland.