The point is that this land was not immutably grassland historically, and so the prior point re: its prior state is not inherently valid.

So is the assumption I was responding to, which assumed that there were trees there to cut down in the first place.

I am highlighting that one should avoid the (often settler naturalistic fallacy mindset) that the right thing is what it "used to be", where "used to be" tends to be a somewhat mythological description of the place 50 years ago

I wasn't making any normative claims about what the land should be, just pointing out that this process appears to have been afforestation of an area that, prior to this intervention, was grassland, and so the implicit assumption in the original comment that the local water cycle had already been perturbed may be wrong.