This is an interesting discussion. Although, remembering the North Carolina map, it doesn’t correlate perfectly. Here, for reference, is that map:
Now, the mountains along the western edge include Great Smoky Mountains National Park and the Blue Ridge Parkway, which are major ecotourism draws – the Smokies, especially, are promoted for their extreme tree diversity. So that may fit with the tourism factor being discussed. It is possible that the Outer Banks may experience this effect, too, although beach tourism is less tightly coupled to nature tourism (not all beachgoers are there to look at organisms).
Similarly, the inner coastal plain, although rural, has extensive agricultural areas such as cotton, corn, soybean, and tobacco, and not a lot of public land. This would explain its extensive belt of dark purple color on the map.
The part that needs some explanation is the “island” of green in the center. This is the “Triangle Area” – Raleigh - Durham - Chapel Hill and environs. It is a major urban center, which would suggest fewer opportunities to observe wild organisms; but conversely, it is also the most highly educated part of the state, as the “Research Triangle” attracts large numbers of people in STEM careers and is home to prestigious universities such as Duke. This suggests that it would be interesting to parse out the relative influence of each of Bradley’s factors, and the extent to which there are interaction effects.