The genteel American Beech is currently threatened by disease. Where I live in New England is covered in beeches, and starting last year I have not seen a single one that doesn’t show symptoms of infection: https://www.fs.usda.gov/inside-fs/delivering-mission/sustain...
It's really sad. They are some of the most beautiful trees in my subjective opinion - I love the way their roots branch out a bit above the ground.
I went to see the largest / one of the oldest beeches a couple years back and it had died presumably of this disease. I visited another old growth forest in Pennsylvania too and all the old growth beeches there were dead. In fact, in that forest, though it had never been logged the only large old growth trees I could find more than one or two of, were hemlocks. The chestnut, elm, ash, and now beech all having been taken by newly introduced diseases.
I think, unfortunately, you are right, it's just that it's playing out slowly enough that it's hard for us to see. Over time, natural selection will work its magic and the trees within the species that are more resistant to the disease will reproduce and the genes for resistance will spread throughout the population. The unfortunate thing is that this is not something that happens in a human lifetime, or even many human lifetimes, and it's not going to save individual trees living right now.
Plants don't have an immune system, at least the way we normal think of one. As far as we know, there isn't a way to "vaccinate" them against diseases. Maybe that will change with molecular techniques, but not today.
Probably true to some extent. Though I imagine even if trade were cut in half most of the tree diseases would still get around. The likelihood of a pathogen to get around is not linearly proportional to the volume of trade.
Echoing the sentiments and information here. In California, there's Sudden Oak Death which is killing several native oak species. However, the tree which is most impacted by SOD seems to be the Tanoak, which is not a true oak, but which is a beautiful tree and is crucial to several ecosystems. Several species of fungi are associated with Tanoak, for example. Very sad.
I went to see the largest / one of the oldest beeches a couple years back and it had died presumably of this disease. I visited another old growth forest in Pennsylvania too and all the old growth beeches there were dead. In fact, in that forest, though it had never been logged the only large old growth trees I could find more than one or two of, were hemlocks. The chestnut, elm, ash, and now beech all having been taken by newly introduced diseases.