A couple more comments, if you'll allow me:
1. It’s interesting to me how some of the most ardent proponents of preservation declare that their main reason for their belief is their will to be left alone / far from the madding crowds of occasional visitors / tourists. I can certainly understand this at a personal level but I find it extremely insufficient, if not damaging, as a political argument.
2. Nevertheless, the Economist article fails to make any mention (actually it does indirectly and in a negative way, without using the term) of the concept of carrying capacity, which, like it or not, must be at the heart of any management plan.
3. One last point, to turn everything upside down: I have noticed that the NPS manages thousands of places/ sites, many of which are not “natural parks”. The “data” provided by the Economist do not make a clear distinction between these different types of sites. Could it be that people are not actually turning away from natural areas? (Data, please! Data!)
Either way, I personally intend / hope to spend more of my euros in your national parks in the years to come. :)