Walnut, for instance, started to disappear during World War I because they made airplane propellers out of it, among other things. Then, Dutch elm disease killed most of the elm trees. they are slowly coming back. Hickory is highly valued for tool handles and other applications that require strength and flexibility. American Chestnut was also nearly killed off by disease.
Anytime there is a change to the environment, the flora and fauna will change. Listening to an ornothologists on NHPR, once, a caller lamented on how he didn't hear whipoorwills like he did when he was a kid. The ornothologists pointed out that whipoorwills where a field loving bird and since NH has gained most of its forest back, with the reduction in farming since the beginning of the 20th century, it just isn't the kind of environment they like.
Old growth forests see very different trees than new growth forests.
- Will (Dragonfly)