Yes, I had that thought as well. The Biosphere is extensive and there are signs along the coastal highway. No idea where it ends, but yes there are some huge dunes out there. Crossed over in a Jeep years back when the coasta highway was still under construction. It is very, very isolated up there so if you go take great care. Getting lsot or disoriented in that area could have very serious consequences.make sure you are out of the park zone.