To some extent, I beg to differ. Historically cultured land, e.g. meadows that has been used for several generations and have a high biodiversity that declines when it ceases to be managed.
Nature tends to know best in the long run, it seems.
It's also a question of what is to be preserved, why and to what ends. That's where the discussion moves from purely ecological facts into an ethical discussion fuzzed by ideology. On the flip-side we have the economist who sees nature as something valuable when it's used for making money. The gap between the two is mindbogglingly huge at times. And this leads us to the necessity of Ecological Economics.