Thanks very much for your thorough read and comment, Tim. I totally agree on that sentence, I got carried away and went for “quick” rather than a more correct “gradual”.

Regeneration is indeed a slow and sometimes inevitable process. As you point out, many places will go back to forest if we leave them alone. If worse comes to worst, when humans will disappear, regeneration will kick in at a steady pace. In my opinion, the question is whether we can do something to actively accelerate the process, or whether we are indeed reversing it (by degenerating ecosystems) or at best slowing it down (as in so-called regenerative agriculture).