I was in a v busy Keswick at the weekend, after a walk over Catbells (like the M25, but in my defense it was ds' first fell at 7mths!) and in the whole day I saw 2 "ethnic minority" people.
The whole place was full of white middle class.
I think although the mosaic project is admirable, it is a more complex picture - white working class, minorities of all financial/location etc are not present in significant numbers. Accommodation/gear is expensive if you are on a budget, and culturally the idea may not be appealing.
I don't see national parks as essentially exclusively white, but I can see why those who do go may feel they don't belong, as they are such a minority - a huge contrast to their experience in the cities.
I was trekking in Nepal and the difference in cultures was really marked - to locals the landscape was a working one, either to farm in or to earn money portering or guiding. To foreign tourists it was leisure. Maybe a similar difference in attitude exists over here? I don't know.
Schemes getting school kids out on residentials from inner city schools, and an increase in school veg plots/teaching where milk comes from would be a start in a long term change in attitudes, on all sides.
Lovelytinofspam a National park is purely a defined area that is protected from development etc. To you and me its just a lovely area to walk in, the same as an unlabelled area. There is nothing special or exclusive about it, its just a beautiful area to visit.