Yes, that's snow fence at the beach. It's not that uncommon a sight anymore, but some of you are stuck in ...the center of things, and may not get to the coast that often.
The status of beach sand dunes has changed alot in my young life. As kids, they were just sandy mounds and we loved it when Dad would take us dune riding at the beach. We'd hang out the windows, Mattel submachine guns blazing ala Rat Patrol at imagined Nazi's.
Later as teens, when we usurped our Father's 4-wheel drives, we cruised the beach fishing the surf, surfing the surf, and riding over dunes to see what was over the next one. At night, the dunes were a great place for a little stargazing with your sweetie.
Driving in the dunes came to a screeching halt in the early 1980's as their importance and fragility was publicized and then protected. At about the same time, I became a National Park Service Ranger and wound up enforcing those regulations...which by now had gotten so tight that you could not walk across a sand dune without risking a $25.00 fine, written by yours truly. I did a lot of warning as $25 in the 80's was a fairly steep fine for a tourist from Nebraska or some other oceanless state.
During the 70's and 80's, it was very common to use discarded Christmas trees for dune building and restoration. The Christmas trees were set out in rows and staked down. As the prevailing onshore winds blew sand up the beach slope, the trees acted as a net, slowing the wind and causing it to drop it's loess. This was a popular Boy Scout (never was one) activity until it was realized that the tree skeletons offered habitat to some of the predators of the endangered Anastasia Beach Mouse.
That ended the Christmas tree dune building.
Yankee snow fencing was put in to play after the end of the Christmas tree era and it was very effective. (Does it work on snow?) Working at Fort Matanzas National Monument, a Ranger named Pete and I drove posts and strung snow/sand fencing for hundreds of yards along the ocean side of the park. On the protected lagoon side to the west of the Matanzas Inlet A1A bridge, we strung fence around a low sand flat that a colony of terns had chosen as a creche. The area flooded often, destroying their ground nests, so we took it upon ourselves to string fence along the perimeter.
The fencing in both cases worked like a charm and slowly vanished beneath growing mounds of sand, which were then colonized by sea oats, railroad vine, and dune sunflower.
When I go home, I can walk along the nice boardwalk on the beach side and bore my kids with repeated tales of how I "built" the large line of sand dunes crossed by the walkway. Then, just in case they haven't rolled their eyes enough, as we drive over the Matanzas bridge, I 'll point west to the terns nesting behind the ring of sand dunes and share that story too...again.
Then they start whining...
"You've already dune that story before..."
"Are you dune yet, because I really want to hear the radio..."
"Dune ya know we've already heard how you made the dunes safe for democracy and terns?"
...they get that from their mother.