The 11-hectare parcel of land was donated by Joey Caissie of Richibucto-Village.
The Nature Conservancy of Canada says the area is habitat for the nationally endangered piping plover, as well as black duck, wood duck and blue-winged teal.
It says a diverse number of rare plants also grow on the beach and dune, including rare beach pinweed, which is only known to grow at a handful of places on the Gulf of St. Lawrence.
The donated land is next to 41 hectares already protected by the Nature Conservancy.
The Richibucto Dunes Nature Reserve is bordered on one side by salt marsh habitat on the Village Bay, and fronted on the Northumberland Strait by raised dunes and a sandy beach.
The land was donated under the federal ecological gifts program, which provides tax incentives to people who donate ecologically significant land.
Since the program began in 1995, the Nature Conservancy has received more than 272 gifts of land, including 19 in New Brunswick.