>The biggest black spot in Western Massachusetts is actually the Quabbin Reservoir

Yes, though there are also lots of large parcels that haven't been inhabited in a century or twp and many of which are now preserved - it was pretty much all farmed at one point, but now only the rich river floodplains and select hilltops are, so there are huge tracts of more difficult terrain that's regrown woods with only old foundations and stone walls. And trails. Lots of trails.