More trees will grow back and just as many and just as big, but not in our lifetimes. That's really the rub, isn't it?
No, not really. The rub is (a) what happens in the meantime to all the plants and animals that relied on that original ecosystem, and (b) that what grows back isn't anything like what was there originally unless you spend a lot of time, effort, and money in an attempt to replace/recreate the original ecosystem. And it's never possible to truly do that anyway, so the original ecosystem is lost forever.
A lot of people have the attitude that one patch of green stuff with animals is as good as another patch of green stuff with animals. That simply isn't the case, and the end result of that sort of thinking is a damaged landscape full of collapsed ecosystems containing - if we're lucky - the big pretty and/or iconic things we focussed on, to the detriment of everything else.
Imagine if we wiped out all the Tektronix's and HP/Agilent/Keysights, and just left the Rigols & Siglents standing. I mean they're pretty much the same thing to most people, and we've kept the popular ones anyway, so nothing of value was lost.
Was it?
(BTW I'm an ecologist - but definitely not a 'greenie'...)