For me it's more important to plant native trees to plant out around the place, rather than exotics which will die. Maybe not such fun, but more use, and food for wildlife. Quite a few giant older trees came down in the recent storms and they all need to be replaced
To me it's important to reduce our dependance on imported foodstuffs. Sweet chestnut, walnut, filberts are all long lived trees that do well UK...
Fruit trees such as traditional apple, pear, sweet cherry? Surely you don't have anything against them being grown here.. so why not widen the spectrum with varieties of peach, apricot and thers including those on my first list.
By your argument I could challenge you against growing potatoes.
I get slightly miffed when i find we're importing nuts we could happily and efficiently grow here and that's before we get to the less common (but available as cold hardy types) such as hickory and pecan. Wales has the right climate for monkey puzzles and they have edible nuts too.
I wasn't suggesting whole forests of my varieties but suggesting we folk with a bit of spare land could help - and frankly i would like to see areas like the new forest being planned on reclaimed pit land to include chestnut and walnut and some fruit trees.. if only to encourage folk to go into that woodland.
Anyone who wants native tree seedlings that's prepared to come to mid-wales is welcome to the hundreds of self-seeded stuff all over my fields at the moment. Too much back-ache for me to go lifting them. Last spring there was one ash tree with several thousand seedlings under it.
The greatest insult of all is importing 'native' seedlings and disease.
Finally... native is relative as to how far back you go in history.