 Willapa Bay is known for its biodiversity and much of it, including the entirety of Long Island, has been set aside as part of the Willapa National Wildlife Refuge.The oyster beds help the ecosystem by providing habitats and filtering water, improving the quality of the water.The bay's ecology was threatened in the 1990s by the rapid spreading of Atlantic cordgrass ("Spartina alterniflora"), a non-native species of grass introduced possibly to help preserve wetlands and marsh areas, and possibly simply by accident as packing material in crates of oysters from the East Coast.