Hello, 
it's an International Nature Park: "the Bourtanger Moor-Bargerveen International Nature Park" or "Internationaler Naturpark Bourtanger Moor-Bargerveen". 
Here are some links about the park and the area:
- https://en.m.wikipedia.org/wiki/Internationaler_Naturpark_Bourtanger_Moor-Bargerveen
- https://www.naturparke.de/naturparke/naturparke-finden/naturpark/bourtanger-moor-veenland/detail/beschreibung.html

Sincerely,
Wiebke