In the Pacific Northwest, two invasive beachgrasses, European beachgrass (Ammophila arenaria) and American beachgrass (A. breviligulata) were introduced beginning in the early 20th century and dramatically transformed the coastline by building dunes. Today, they are widespread across the coast and, where they overlap in their ranges in northern Oregon and southern Washington, we have detected that hybridization is occurring. Through a citizen science project in partnership with CoastWatch, community members have uploaded over 1,200 observations of the Ammophila parents and their hybrid since the beginning of the project in 2020. Additionally, we have searched over 26 mi of dune and discovered nearly 300 hybrid occurrences across the hybrid’s range, a 155-mile stretch from Pacific City, Oregon to Ocean Grove, Washington, although other opportunities for hybridization are possible beyond this range. Other research findings include that the hybrid shows substantial growth, exceeds its parents in certain traits important for dune building, and is found near and within threatened bird habitat. Overall,
the high abundance of this new beachgrass, as well as its likelihood to spread further in future, indicate that the hybrid is an important consideration for dune management and conservation planning.