[pen] Dunno about Darren, but I would feel exactly that (and frequently do). We've too few trees as it is, without wasting them on pointless letters, cards etc.
(Projoy) You really can't be allowed to get away with that. The proportion of paper in actual letters compared with the total amount of paper (newspapers, junk mail etc) that comes through my letterbox is very small. In any case, we're not short of trees; there are many more than there were 40-50 years ago, everywhere. To be honest, I'm not that keen on trees, they spoil the view and at one time threatened to undermine my house. Rather overrated, I feel.
[Rosie] Who says my annoyance is confined to only legitimate letters? As to "more trees", I don't know if that's true, although I guess you're more likely to know than I am, But don't we need even more trees at the moment to do Carbon Dioxide conversion? This is the general impression I have gained.
I suspect Rosie is right that there are more trees now than in the 50's. I'm pretty sure, however, that there were many more in the 30's and more still before WW1. Also, the tree-planting boom of the 50's 60's & 70's was mostly conifer plantations. Planting more trees as mixed woodland must be a good thing both aesthetically and as carbon sinks.
IIRC, commercial forestry supplies most of the pulp for paper - and that's a planting-and-harvesting operation of fast-growing monoculture conifers; it doesn't use wood from mixed and deciduous woodland.